GTA

All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: nervoustrigger on March 24, 2015, 02:48:49 PM

Title: QB79 HPA build for GTA member
Post by: nervoustrigger on March 24, 2015, 02:48:49 PM
I wanted to do a little pictorial sequence of a .22 cal QB79 HPA build I have been working on for GTA member UCChris.

Chris wants this gun for 50+ yard hunting duties so the goal was to get over 25fpe and let the shot count fall where it may.  The tank block on a 79 almost butts against the front of the valve, meaning the plenum volume is essentially the valve volume.  With so little on-deck air to work with, that makes it a little trickier to reach the 30fpe level.  But I thought that would be a fun challenge to take on, so off I went.

First up, I knew we would want a fairly high regulator setpoint of 1500psi to achieve the energy goal.  So a bit by experience and trial and error, I assembled a Belleville stack onto a Ninja regulator stem and hit a setpoint of 1550psi according to my precision gauge:

(http://i.imgur.com/vhuMS1U.jpg)

Refer to Bob's detailed thread for info on how to do this:  http://www.gatewaytoairguns.org/GTA/index.php?topic=49648.msg469843#msg469843 (http://www.gatewaytoairguns.org/GTA/index.php?topic=49648.msg469843#msg469843)
Also, if you use a hand pump like me, a very small "tank" makes the trial-and-error process much less of a chore:
http://www.gatewaytoairguns.org/GTA/index.php?topic=73635 (http://www.gatewaytoairguns.org/GTA/index.php?topic=73635)

With that done, time to make some metal shavings!

Rear Velocity Adjuster
Drilled the end cap for a rear velocity adjuster (RVA).  It's a 10-32 x 1.5" screw through the end cap which can be threaded in or out to push against the back of the spring guide, whereby adjusting the amount of preload on the hammer spring.  Making relatively small adjustments to preload has a profound effect on velocity and air usage (efficiency), so the effort to do this mod is well worth it.  Notice it also has a #6-32 set screw intersecting it to lock in the adjustment.

(http://i.imgur.com/xVA0ebn.jpg)

Cock-on-open mod
The cock-on-open mod is another worthwhile change.  The action is more natural I think.  Also, the original cock-on-close action masks certain potential problems like pellets hanging while chambering or fitting too loose or too tight.  This mod makes it easier to detect those kinds of issues. 

First, milled a rear downslot for the bolt handle.  This change allows the bolt to be latched back out of the way to make it easy to load a pellet.  At higher power levels necessitating a fair amount of spring preload, the bolt probe may otherwise push forward into the loading tray, making it difficult to insert a pellet.

(http://i.imgur.com/RRvJsfS.jpg)

The other piece of this mod is to remove the rear pin in the spring guide.

(http://i.imgur.com/om9zG7v.jpg)

Lastly a 0.6" long spacer was added to the shaft of the spring guide.  This spacer is simply a section cut from an ink pen.  Stacking washers on the spring guide would also work fine.  Sorry, I did not take a picture of it.

Securing the barrel
This modification helps secure the barrel in the receiver which improves shot-to-shot consistency.  I located a spot on the receiver behind the factory set screw, in between where two of the barrel O-rings reside, then drilled and tapped a hole for an #8-32 set screw.  An M4 would also be a good choice if you want to stick with metric fasteners.  The scuff marks have since been cleaned up and cold blued with Van's.

(http://i.imgur.com/YWQ0OWX.jpg)

Air flow modifications
Ported the barrel to 0.170", same as the ID of the poly tubing that is used for the transfer port seal.  Then radiused the port inside the barrel to prevent a sharp edge from marring the pellets as they are chambered.

(http://i.imgur.com/1PqVoPV.jpg)

Drilled the nose of the bolt probe out to 0.170" as well:

(http://i.imgur.com/zOZTiKq.jpg)

And enlarged the side opening:

(http://i.imgur.com/H0azLyk.jpg)

Valve modifications
Milled 1/4" wide slots in the side of the valve body and drilled out the center hole.  Reduced the poppet OD from 0.371" ->  0.340" and polished up the brass.  Drilled out the valve throat from 0.194" -> 0.219".  Tapered the valve stem from 0.117" -> 0.077" in the region where air flows around it and up through the valve exhaust.  Also radiused the inside edges of the exhaust (in the throat) to reduce turbulence.  And finally, fitted a conical valve spring from Daniel's (rdsail) group buy, a Century Spring TA-2122.

(http://i.imgur.com/jlBY7Wu.jpg)

Increasing the plenum
Bored out the center of the tank block to increase the volume of regulated air available to the valve during the shot cycle.  I think the diameter was 7/16" or perhaps 15/32", and as deep as I was comfortable drilling so as not to punch through into the holes where the tank block retaining screws go.

(http://i.imgur.com/IajaHiG.jpg)

Before reassembly, I thoroughly deburred and polished things where appropriate, especially where O-rings might get nicked on installation.

Chrony testing
A little twisting of the RVA screw to find the maximum velocity yielded...

23.9fpe with 14.3gr Crosman Premier hollow points:
(http://i.imgur.com/6D8Rv2a.jpg)

26.1fpe with JSB 18.13gr heavies:
(http://i.imgur.com/9EDa0Hb.jpg)

Goal met!  That's running pedal to the floor, so to speak...quite loud and surely using a lot of air.  I would want to back off of that slightly for better efficiency. 

However, wouldn't it be nice if we could hit 30fpe?  As it turns out, there's more energy to be obtained by a rather simple valve modification so that will come next.

[edit]Photobucket can die.[/edit]
Title: Re: QB79 HPA build for GTA member
Post by: Geoff on March 24, 2015, 02:52:19 PM
thanks for the tutorial
Title: Re: QB79 HPA build for GTA member
Post by: Matt15 on March 24, 2015, 02:55:48 PM
Very Cool!!
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 24, 2015, 03:31:57 PM
Thanks guys!   Another update here in a few minutes...
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 24, 2015, 03:35:17 PM
Looking for more energy, I pulled the valve and proceeded to cut away the entire front (aluminum) part of the valve.  I kept only a small ring to retain the -113 valve O-ring.  I failed to take photos so here is a sketch:

(http://i.imgur.com/ToH1dwg.jpg)

Then I cut a couple of notches into it so I could reach down into the air tube and turn the ring to put a squeeze on the O-ring to help it seal.

(http://i.imgur.com/03wIKsr.jpg)

I then took the conical valve spring and stretched it slightly so it would be long enough to rest against the tank block.  The nice thing about the wide base of the conical spring is that it is large enough to straddle the hole bored in the tank block.

Got the rifle reassembled and started pumping.  No leaks!  A victory in and of itself. ;)

With it pumped up a little over 2000psi, above the 1550psi regulator setpoint and enough to get a few shots, here's what we have:

27.1fpe with Crosman Premier hollow points
(http://i.imgur.com/92z6XhU.jpg)

29.9fpe with JSB 18.13gr heavies:
(http://i.imgur.com/PUD8os5.jpg)

31.3fpe with Kodaik 21.14gr:
(http://i.imgur.com/hnUaXR6.jpg)

And lastly, 34.0fpe with Eunjin 28.5gr:
(http://i.imgur.com/TZPKmIr.jpg)

That should do it for the energy goals.

Next up is to fine-tune the RVA and begin pellet testing and accurizing.  It may be the weekend before I post an update on that.
Title: Re: QB79 HPA build for GTA member
Post by: starlingassassin on March 24, 2015, 04:34:10 PM
jason,

very impressive numbers and workmanship!  ;D
Title: Re: QB79 HPA build for GTA member
Post by: LAalex on March 24, 2015, 04:51:20 PM
Nice work Jason.  Looking forward to the finished product.

Scotty
Title: Re: QB79 HPA build for GTA member
Post by: SpiralGroove on March 24, 2015, 05:25:55 PM
Pretty Cool Jason!,
You've got the process down............... and must be related to Bob 8)?
It's a pleasure ;)
Title: Re: QB79 HPA build for GTA member
Post by: rsterne on March 24, 2015, 06:13:15 PM
Good job!.... You don't need the notches in the valve ring, just glue it to the back half using an O-ring for a spacer to get the right gap.... A standard, cheap 70D buna O-ring (or a better one, of course) will seal just the way O-rings are supposed to, by moving into the rear, outer corner of the groove.... same as "normal" valve seal....

Bob
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 24, 2015, 07:01:52 PM
Thanks guys.

Bob, thanks for the heads up about the valve O-ring.  I remembered you saying something about being pleased that it sealed when you documented the $200 PCP so I figured a belt-and-suspenders approach would be worth the 2 minutes it took to grind some notches with the Dremel.  Hissing air is like fingernails on a chalkboard! :D 
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 24, 2015, 07:12:42 PM
Okay, ran some pellets across the chrony to check efficiency and consistency.  Started with a partial fill of 2600psi and shot until it fell off the regulator at 1500psi.  Got 51 shots, all within 2% of the peak velocity for an efficiency of 1.41 fpe/ci.  Extrapolated to a full 3000psi fill, it would yield 69 shots  :o

Equally pleasing is the consistency for a brand spankin' new rifle and newly assembled regulator paired with CPHP pellets from the tin.

Stat summary
No shots:  51 (69 on full fill)
Max:  922fps
Min:  902fps
Average energy:  26.7fpe
ES:  20
SD:  3.59
Efficiency:  1.41 fpe/ci
Title: Re: QB79 HPA build for GTA member
Post by: Rdsail on March 24, 2015, 07:42:23 PM
very nice write up!
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on March 24, 2015, 08:10:46 PM
VERY Cool build thread !
I will be following with great interest and anticipation  ;)  ;D
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 24, 2015, 09:19:58 PM
Did I read that right? Did you say 69 shots? That's with it at 29.9 fpe with JSB 18.1? (I know you tested with the CPHP, but same tune?)

So, you hit 34 fpe with this rifle. Imagine what you could do, power wise, on a 78 with your nifty valve mod!
Title: Re: QB79 HPA build for GTA member
Post by: Tonycalves on March 24, 2015, 09:24:29 PM
Nice job Jason!
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 24, 2015, 11:15:10 PM
Chris, yes that's right.  Same tune.

Put a couple of extra pumps in at the end and call it 70 shots :)  Actually, you should pick up a small number of shots with a heavier pellet anyway.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 24, 2015, 11:35:34 PM
Chris, yes that's right.  Same tune.

Put a couple of extra pumps in at the end and call it 70 shots :)  Actually, you should pick up a small number of shots with a heavier pellet anyway.

I've died and gone to heaven. You have way surpassed my expectations!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Title: Re: QB79 HPA build for GTA member
Post by: SpiralGroove on March 25, 2015, 01:35:18 AM
Hey Jason,
Performance looks fantastic ;).  Can you please ship that gun to me now!  ;D
Kirk
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 25, 2015, 01:40:10 AM
Hey Jason,
Performance looks fantastic ;).  Can you please ship that gun to me now!  ;D
Kirk

I will find you, hurt you, and take it back.

 ;D

But you're welcome to move to Utah and play with it!
Title: Re: QB79 HPA build for GTA member
Post by: Matt15 on March 25, 2015, 09:54:13 AM
Awesome build Jason. 8) Congrats on a fine gun Chris!!! 8)
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 25, 2015, 10:15:59 AM
Thanks Matt! But I'm just the dude paying for it. Jason deserves all the credit possible. He is a master worker on these things!
Title: Re: QB79 HPA build for GTA member
Post by: Matt15 on March 25, 2015, 11:10:31 AM
Thanks Matt! But I'm just the dude paying for it. Jason deserves all the credit possible. He is a master worker on these things!

LOL!! Yes, Jason did a great job!!! ;) 8)
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on March 25, 2015, 11:28:16 AM
Chris,
Purely out of curiosity,
 What was the deciding factor for going with the 79 on this build,... rather than the 78D ?
Title: Re: QB79 HPA build for GTA member
Post by: SpiralGroove on March 25, 2015, 11:45:01 AM
Likely cost (no block needed), less labor for the mods and lighter -> at the expense of even more power in the QB78D & looks.
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 25, 2015, 12:17:34 PM
Thanks for the kind words from all you guys.  I'm really happy for Chris that this QB has turned out so well.  He strikes me as a great young ambassador of the sport, having done such things as donating a gun to Ron's 4H group and taking a slighly misguided youth under his wing and teaching him both marksmanship and ethical hunting practices.

Ron, I can answer the question about 79 vs 78.  The initial plan was a 78 Deluxe but at the time we started the project, it was not in stock in .22 cal.  So Chris and I talked and I agreed to tune a 79 carefully and see if the results were to his liking, and if not I'd transplant all the go-faster parts to a 78 tube.  Chris had already started looking at fitting the 79 to a target stock.   With the numbers it is producing, I think we are going to stick with it.

Chris, feel free to add or correct.
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on March 25, 2015, 12:50:37 PM
All great stuff here!
34 fpe out of a 79 with still a BIG shot count is just flat out IMPRESSIVE in my book, and shows that Jason has certainly done his homework and applied all that he has learned.
BRAVO Jason ! I can practically hear Chris just giggling his head off from 2 states away ;-)
 I look forward to his coming posts once he gets his hands on it.

Did I read that right?  Imagine what you could do, power wise, on a 78 with your nifty valve mod!

Hehe,... Here's a little teaser,... We will soon be finding this out ;-)
and yeah,... that sound you can hear is me giggling too
Title: Re: QB79 HPA build for GTA member
Post by: silent_airman on March 25, 2015, 01:16:12 PM
Nice gun, Chris. I have a QB79 that badly needs some TLC. Right now it's in pieces lol. ::)
Title: Re: QB79 HPA build for GTA member
Post by: Prouzy on March 25, 2015, 01:17:12 PM
Looking for more energy, I pulled the valve and proceeded to cut away the entire front (aluminum) part of the valve.  I kept only a small ring to retain the -113 valve O-ring.  I failed to take photos so here is a sketch:

(http://i779.photobucket.com/albums/yy80/jmneal1/projects/airguns/UCChris/valve%20-%20inlet%20mod%201_zpsgjl2y3nq.jpg)

Then I cut a couple of notches into it so I could reach down into the air tube and turn the ring to put a squeeze on the O-ring to help it seal.

(http://i779.photobucket.com/albums/yy80/jmneal1/projects/airguns/UCChris/valve%20-%20inlet%20mod%202_zpsnxfok9qt.jpg)

I then took the conical valve spring and stretched it slightly so it would be long enough to rest against the tank block.  The nice thing about the wide base of the conical spring is that it is large enough to straddle the hole bored in the tank block.

Got the rifle reassembled and started pumping.  No leaks!  A victory in and of itself. ;)

With it pumped up a little over 2000psi, above the 1550psi regulator setpoint and enough to get a few shots, here's what we have:

27.1fpe with Crosman Premier hollow points
(http://i779.photobucket.com/albums/yy80/jmneal1/projects/airguns/UCChris/chrony%20-%20CPHP%2014.3gr%2027.1fpe_zpsn9wvhoti.jpg)

29.9fpe with JSB 18.13gr heavies:
(http://i779.photobucket.com/albums/yy80/jmneal1/projects/airguns/UCChris/chrony%20-%20JSB%2018.13gr%2029.9fpe_zpsy65kghzi.jpg)

31.3fpe with Kodaik 21.14gr:
(http://i779.photobucket.com/albums/yy80/jmneal1/projects/airguns/UCChris/chrony%20-%20Kodiak%2021.14gr%2031.3fpe_zpskah2vwq8.jpg)

And lastly, 34.0fpe with Eunjin 28.5gr:
(http://i779.photobucket.com/albums/yy80/jmneal1/projects/airguns/UCChris/chrony%20-%20Eun%20Jin%2028.5gr%2034.0fpe_zpsslfcy2jt.jpg)

That should do it for the energy goals.

Next up is to fine-tune the RVA and begin pellet testing and accurizing.  It may be the weekend before I post an update on that.

Jason

Very nice write up, I enjoyed and appreciated it very much!  Im new to modding and wondering if you could explain the reason for reducing the valve body?  Im guessing this has been covered elsewhere, so feel free to tell me to look but any direction is greatly appreciated!

Chris
Title: Re: QB79 HPA build for GTA member
Post by: rsterne on March 25, 2015, 01:26:43 PM
If you change the stock, I would strongly suggest that you inlet the new stock for the tank block and install it with the two screws to fasten the block to the stock... The two screws in the tube are very close to the end of the tube, and in fact the metal between them and the end of the tube can bend on a very hot day just on CO2.... The stock screws provide a significant safety margin should the screws in the tube, or the end of the tube, fail.... If you use a stock from a QB2079 this would already be done.... I recommend that the QB79s not be pressurized over about 1000 psi without the stock in place....

Bob
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 25, 2015, 03:08:29 PM
Ron, I can answer the question about 79 vs 78.  The initial plan was a 78 Deluxe but at the time we started the project, it was not in stock in .22 cal.  So Chris and I talked and I agreed to tune a 79 carefully and see if the results were to his liking, and if not I'd transplant all the go-faster parts to a 78 tube.  Chris had already started looking at fitting the 79 to a target stock.   With the numbers it is producing, I think we are going to stick with it.

Chris, feel free to add or correct.

You're dead on Jason. I wanted the 78D at first, but it was out of stock in .22. We could have added a 78 tube, but I kinda liked the idea of a gun with the COG farther back than the 78D. Turns out it was a fantastic decision!

BRAVO Jason ! I can practically hear Chris just giggling his head off from 2 states away ;-)
 Hehe,... Here's a little teaser,... We will soon be finding this out ;-)
and yeah,... that sound you can hear is me giggling too

Haha, I was quite tickled at Jason's results!

And are you alluding to what I think you are?!  :o
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on March 25, 2015, 04:28:46 PM
Bingo!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 25, 2015, 05:24:32 PM
I'm giggling for you now!
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 25, 2015, 11:02:48 PM
Im new to modding and wondering if you could explain the reason for reducing the valve body?  Im guessing this has been covered elsewhere, so feel free to tell me to look but any direction is greatly appreciated!

Hi Chris,

It's pretty much all about increasing the volume of regulated air available.  In a QB79, normally this volume is pretty much that of the interior of the valve itself...there isn't really an air tube to speak of.

As soon as the valve opens and air rushes into the barrel to expel the pellet, the pressure inside the valve (and air tube) falls.  The larger the volume of air, the less the pressure falls, thus the higher the average pressure during the shot cycle, giving the pellet a higher velocity / energy.
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 25, 2015, 11:21:22 PM
Got home this evening with enough daylight left to commandeer a scope from another rifle--a Leapers 3-12x44--and put it on the new QB:

(http://i.imgur.com/BilXJeH.jpg)

Then put a few pellets through it to get it somewhat zero'd at 25 yards.  For a new barrel with less than 100 pellets through it, it shows good promise.

(http://i.imgur.com/DO8jcfS.jpg)
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on March 25, 2015, 11:40:31 PM
That'll work just fine !
Title: Re: QB79 HPA build for GTA member
Post by: Prouzy on March 25, 2015, 11:44:58 PM
Im new to modding and wondering if you could explain the reason for reducing the valve body?  Im guessing this has been covered elsewhere, so feel free to tell me to look but any direction is greatly appreciated!

Hi Chris,

It's pretty much all about increasing the volume of regulated air available.  In a QB79, normally this volume is pretty much that of the interior of the valve itself...there isn't really an air tube to speak of.

As soon as the valve opens and air rushes into the barrel to expel the pellet, the pressure inside the valve (and air tube) falls.  The larger the volume of air, the less the pressure falls, thus the higher the average pressure during the shot cycle, giving the pellet a higher velocity / energy.

Thanks Jason! So the volume of air(flow) following hammer strike/valve opening is NOT limited to the volume in the valve, that makes a whole lot more sense seeing the slots milled into the body :-) There are so many components to all of this, makes more interesting than I ever imagined.

Chris
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 26, 2015, 12:06:47 AM
So the volume of air(flow) following hammer strike/valve opening is NOT limited to the volume in the valve, that makes a whole lot more sense seeing the slots milled into the body :-)

In general that's right.  In many cases there is a volume of air outside the valve that contributes to what is available during the shot cycle. 

In the QB79, however, that isn't the case.  In fact, I was probably wasting my time milling the slots in the sides of the valve.  It works wonders on a QB78 where there is a lot of volume beyond the valve...
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 26, 2015, 12:41:44 AM
I'm tickled pink with that first group.
Title: Re: QB79 HPA build for GTA member
Post by: rsterne on March 26, 2015, 12:44:09 AM
It makes just as much difference in the QB79.... but getting rid of the front end to increase the volume does both jobs....

Bob
Title: Re: QB79 HPA build for GTA member
Post by: SpiralGroove on March 26, 2015, 09:08:33 AM
Hey Jason,
Nice group by the way :D

Is that a plain muzzle brake on the gun (aka B50/B51) or more of an LDC?
My QB79 is slightly louder than my tuned BAM's, so far I've just put a simple aluminum brake on and got rid of the open sights.
Don't mind a little pop from a gun, actually prefer it to a more silent ping, I think one of my next projects is making a decent LDC.

(http://i113.photobucket.com/albums/n227/kirk_schwarz/Profile_zpszijdfetp.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Profile_zpszijdfetp.jpg.html)

Kirk
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 26, 2015, 10:06:11 AM
Hi Kirk, it is a simple LDC.  The QB is noticeably louder than my B51 at the same power level but is much, much more backyard friendly with the LDC.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 26, 2015, 11:15:17 AM
And backyard friendly is key for me!
Title: Re: QB79 HPA build for GTA member
Post by: Matt15 on March 26, 2015, 11:19:29 AM
So when do you get the gun in your hands Chris?
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 26, 2015, 11:24:39 AM
So when do you get the gun in your hands Chris?

Whenever Jason is done working his magic!
Title: Re: QB79 HPA build for GTA member
Post by: Matt15 on March 26, 2015, 05:04:58 PM
So when do you get the gun in your hands Chris?

Whenever Jason is done working his magic!

LOL! It will probably be worth the wait. ;D
Title: Re: QB79 HPA build for GTA member
Post by: K.O. on March 26, 2015, 05:15:16 PM
Nice work Jason!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 26, 2015, 11:49:06 PM
So when do you get the gun in your hands Chris?

Whenever Jason is done working his magic!

LOL! It will probably be worth the wait. ;D

Amen to that!
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 30, 2015, 10:03:06 PM
I went outside this evening after work to do some pellet testing on the 43 yard target.  Just a light breeze; not much to speak of.

First up, JSB 15.9gr:

(http://i.imgur.com/ckDh3Zb.jpg)

The rifle isn't broken in yet so I didn't expect it to group that well, so a second group:

(http://i.imgur.com/0rUyYRO.jpg)

Okay, not a fluke.  It seems to like those.

Next the JSB 18.1gr batch that shoots exceptionally well in my QB:

(http://i.imgur.com/rbEo8Fr.jpg)

Now that's what I'm talking about!  4 in a tiny hole and one errant shot.

I had some Predator Polymags on the shelf that I never use so figured I'd try them:

(http://i.imgur.com/RRh74r6.jpg)

Haha :D.  Alright, scratch Polymags from the list. 

About that time the light had faded to the point where aiming was difficult but this satisfies me that the gun is capable of being accurate with the right pellets.
Title: Re: QB79 HPA build for GTA member
Post by: Prouzy on March 30, 2015, 11:22:17 PM
Amazed at the performance out of box let alone what you accomplished after tuning for both power and accuracy. Nice work!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 30, 2015, 11:38:43 PM
 :o

 :D

 ;D ;D ;D

To say I'm ecstatic would be a gross understatement!

.45021" is 1 moa at 43 yards. Is it possible you have built a gun that is 1 moa out to 50+ yards? Those 18.1 JSB certainly seem up to the task with a little break in!

Jason, you're my hero.
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on March 30, 2015, 11:48:40 PM
Hey Chris,

I think Jason is getting a little "attached" to it. (I know I sure would be).
You may want to start thinking about how to bribe it out of his hands, LOL!

Very Nice Work Jason !

So lemme get this straight.
 You take a low cost Co2 rifle, that OOTB shoots roughly 450 FPS and only gets around 30-ish shots.

 Then you throw a little bit of cash and some serious "loving expertise" at it, and the results are:

  a 30+ FPE gun,
  chucking heavies at 800+ fps,
  holding dime sized groups at 50 yds,
  and still getting over 50 shots WITHIN 2% !

HMmmm, how could anyone be happy with THAT ? ! ? ! ?
 ;D  ;D  ;D
Title: Re: QB79 HPA build for GTA member
Post by: Monkeydad1969 on March 31, 2015, 12:10:16 AM
Can you say .30 QB78?  With a steel air cylinder and not bottled.

Joe
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 31, 2015, 10:26:45 AM
Can you say .30 QB78?  With a steel air cylinder and not bottled.

Joe

I was thinking along the same lines. A 78D with Jason's touch should be capable of throwing the .25 JSB @ 800 fps or so. We're talking about possibly the most affordable .25 PCP if we could find a way to convert to .25... Heck, with the new valve mod that got my gun up to 30 fpe (and some fantastic efficiency to boot) Jason may be able to get north of 40 fpe out of a .25 conversion!

Hey Chris,

I think Jason is getting a little "attached" to it. (I know I sure would be).
You may want to start thinking about how to bribe it out of his hands, LOL!

DON'T GIVE HIM ANY IDEAS RON!!!!!!!
Title: Re: QB79 HPA build for GTA member
Post by: SpiralGroove on March 31, 2015, 10:41:32 AM
Hey Ron,
Beware of any subsequent threats, California isn't much farther than Washington State  :D
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on April 01, 2015, 10:59:03 PM
Well, it was a hectic day at work today so when I got home this evening, I decided slinging a little lead would be a good stress reliever.  Chris' rifle could use some breakin so I grabbed it and a tin of JSB 18.1gr, and trained a tightly focused LED flashlight on the 43 yard target.  The first group ended up measuring 0.51" and the second 0.39" CTC:

(http://i.imgur.com/Oc5tail.jpg)

There's also a stainless steel rat spinner set up at the same distance, and the QB managed to smack it in the head with authority 6 consecutive times before I decided that was enough.

And with that, the QB has earned a spot tonight at the airgun throne...a place that only trusted rifles may dwell:

(http://i.imgur.com/Q317qWH.jpg)
Title: Re: QB79 HPA build for GTA member
Post by: MEAT on April 01, 2015, 11:16:58 PM
Jason, you are my favorite enabler. Why, you may ask? Because… You are about quality. You are about disruptive innovation, you are producing an effective, simple, rigorously tested accurate machine! And we get to watch!

Surely this is the most fun anyone ever had purchasing a gun!

If you had a company, I would buy stock in it!

P.S. - great shooting!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 02, 2015, 12:41:06 AM
I'm wearing a stupid grin and I'm not even the one shooting it...





yet!!!
Title: Re: QB79 HPA build for GTA member
Post by: Monkeydad1969 on April 02, 2015, 05:53:16 AM
I still say .30 pcp conversion.  Huh, any takers?
Title: Re: QB79 HPA build for GTA member
Post by: SpiralGroove on April 02, 2015, 10:55:51 AM
Yeah Meat,
Bob (rstern), Scott (Motorhead) and Jason (aka The Reaper) are the Three Musketeer's  of Tuning on the GTA.

Knowledge, Experience and Perseverance................ is what tuning is about.
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on April 02, 2015, 11:40:03 AM
Well, it was a hectic day at work today so when I got home this evening, I decided slinging a little lead would be a good stress reliever.  Chris' rifle could use some breakin so I grabbed it and a tin of JSB 18.1gr, and trained a tightly focused LED flashlight on the 43 yard target.  The first group ended up measuring 0.51" and the second 0.39" CTC:

(http://i779.photobucket.com/albums/yy80/jmneal1/projects/airguns/UCChris/JSB%2015.9%2043yds%20no3_zpsjhggwnfj.jpg)

There's also a stainless steel rat spinner set up at the same distance, and the QB managed to smack it in the head with authority 6 consecutive times before I decided that was enough.

And with that, the QB has earned a spot tonight at the airgun throne...a place that only trusted rifles may dwell:

(http://i779.photobucket.com/albums/yy80/jmneal1/projects/airguns/UCChris/door2_zpsx1muny5i.jpg)
AHhhh,... next to the door, charged and ready to go,... just waiting for the donger to speak.
 A coveted place indeed. ;-)
Title: Re: QB79 HPA build for GTA member
Post by: WECSOG on April 15, 2015, 10:21:15 PM
You guys are making me seriously consider (again) getting a QB78! ;D
In spite of repeatedly deciding that there is nothing I could do with one that I can't do with my the 22xx/2300/2400 platform, I'm very tempted!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 15, 2015, 10:38:39 PM
The bb gun in question arrives tomorrow! Buckle up for pictures and first blood!!!
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on April 15, 2015, 11:33:28 PM
The bb gun in question arrives tomorrow! Buckle up for pictures and first blood!!!
Geeee,... do I sense just a LITTLE joyful anticipation? LOL!


Title: Re: QB79 HPA build for GTA member
Post by: Pilgrim on April 16, 2015, 01:44:41 AM
How can you sleep tonight, dude?  Excited for you myself!

The bb gun in question arrives tomorrow! Buckle up for pictures and first blood!!!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 16, 2015, 02:03:16 AM
Who said anything about sleeping?
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on April 16, 2015, 02:19:41 AM
I hope you have the scope and some JSB 18's ready!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 16, 2015, 10:07:26 AM
I hope you have the scope and some JSB 18's ready!

They are sitting right next to me!
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on April 16, 2015, 12:43:03 PM
I can picture Chris now,
sitting there holding a broomstick,
 with his scope mounted to it,

 making Pffft, Pffft, Pffft sounds  ;D
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 16, 2015, 01:44:24 PM
I can picture Chris now,
sitting there holding a broomstick,
 with his scope mounted to it,

 making Pffft, Pffft, Pffft sounds  ;D

You spyin' on me Ron?!

Anytime now would be great!

(http://i836.photobucket.com/albums/zz287/footballplayerchris/IMAG0098_zps0voabgjp.jpg)
Title: Re: QB79 HPA build for GTA member
Post by: SpiralGroove on April 16, 2015, 02:08:10 PM
Hey Chris,
Sweet scope -> you're ready ;)
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 16, 2015, 02:17:03 PM
Thanks Kirk! It's a SWFA SS 12x42 MilQuad if anyone is wondering. It's the nicest scope I've ever had the privilege of using! The QB is more than deserving of it.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 17, 2015, 01:01:32 AM
Well, I came home from work to find a brown box sitting there. Odd, I wasn't expecting a package today...  ;D

I'm exhausted, so I will make a big long post tomorrow about the unboxing and first blood!
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on April 17, 2015, 01:39:43 AM
I like that...
"unboxing AND first blood" !

Congrats buddy, and Great Job Jason !
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 17, 2015, 05:35:28 PM
Here we go! Unboxing and the first hunt! I will let the pictures speak for now!

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0712_zpsmscistmr.jpg)

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0714_zpstmgaqm7p.jpg)

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0715_zpsasgcxldn.jpg)

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0716_zps1fbwmbud.jpg)

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0717_zps9ckowo0u.jpg)

Now to the good part! Here are the 30mm UTG rings that Jason trued.

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0718_zpsbggwmrwf.jpg)

Here is the LDC that Jason made up for me.

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0719_zpskemjplbk.jpg)

The gun out of the box

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0720_zpss3xs8zsu.jpg)

The gun with the LDC attached, along with the scope.

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0722_zpsd71jfko7.jpg)

At this point I had planned to put on a swivel stud and attach the bipod, but I was too excited to shoot it! I pumped it up and did a quick sight in. This is how my first nine shots went...

1) Left - adjust scope
2) Hit pebble at 30 yards
3) Hit wasp at 25 yards

(At this point I headed off to my permission)

4-9) Dead starlings

:D :D :D

Yeah, best first shots ever?

Here is the pic of the last starling. You can see that it is quite dark. The scope is most excellent and lets me see way later than my other scopes have.

Oh yea, I forgot to mention, those six starlings? Yeah, they all went down in under 15 minutes...

(http://i836.photobucket.com/albums/zz287/footballplayerchris/IMAG0099_zpsuosz0izd.jpg)

After getting back from my permission, I mounted up the bipod. Here is the gun as it is now.

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DSCN0724_zpsomq8arkg.jpg)

So, after having shot it last night and some more this afternoon, what do I think of it? Well, my stupid grin probably says enough... But, there are a few key points I'd like to mention. 1) The way Jason has the LDC attach to the barrel is awesome! He drills and countersinks the LDC and then uses the front sight hole to hold the LDC on. It is amazing! 2) The trigger is stupid smooth. I think it is technically a single stage trigger, but the second stage is so light, and there is enough takeup, that it feels like an amazing two stage trigger. I'm in trigger heaven!

Anyway, I'm overjoyed with the gun. It is absolutely amazing. Stupid accurate and she hits hard!
Title: Re: QB79 HPA build for GTA member
Post by: Chako on April 17, 2015, 05:42:53 PM
Looks good, aren't you lucky. ;) :D
Title: Re: QB79 HPA build for GTA member
Post by: grand-galop on April 17, 2015, 06:22:37 PM
Imagine what you can have now with a 22 ci tank on it..  If you take a look at my avatar pic, this is a QB79 with a 22ci tank on it..  I have manage to shoot it 860fps with 14.3 chp and around 90 consistant shot.. At 21 FPE this little baby is grabbing any small game i want at 50yards..
Title: Re: QB79 HPA build for GTA member
Post by: Matt15 on April 17, 2015, 07:41:58 PM
Chris, you mentioned a stupid grin but I did not see any pics?!?!?!?  ;D Nice gun!!
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on April 17, 2015, 08:10:53 PM
Yeah, C'mon Chris,

We wanna see a pic of you holding Helga !  ;D
Title: Re: QB79 HPA build for GTA member
Post by: silent_airman on April 17, 2015, 08:26:29 PM
Ok, so let me get caught up with this new vernacular. So stupid is now a good thing? ??? Must be, because I see stupid being used a lot in a positive way! :P ::) ;D ;)

So in that vein, congratulations Chris for having a really stupid rifle! ::) May we all have equally stupid guns! :P ;D

Title: Re: QB79 HPA build for GTA member
Post by: Matt15 on April 17, 2015, 08:40:13 PM
Ok, so let me get caught up with this new vernacular. So stupid is now a good thing? ??? Must be, because I see stupid being used a lot in a positive way! :P ::) ;D ;)

So in that vein, congratulations Chris for having a really stupid rifle! ::) May we all have equally stupid guns! :P ;D

Read my stupid post and see that I said stupid GRIN not gun.  ;D ;D
Title: Re: QB79 HPA build for GTA member
Post by: Monkeydad1969 on April 17, 2015, 09:37:43 PM
Very nice, Chris.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 17, 2015, 11:14:44 PM
Haha George!

Thanks for the congrats guys! But the true congrats goes to Jason. He's doing some amazing things with these diamonds in the rough!
Title: Re: QB79 HPA build for GTA member
Post by: silent_airman on April 18, 2015, 01:08:04 PM
Ok, so let me get caught up with this new vernacular. So stupid is now a good thing? ??? Must be, because I see stupid being used a lot in a positive way! :P ::) ;D ;)

So in that vein, congratulations Chris for having a really stupid rifle! ::) May we all have equally stupid guns! :P ;D

Read my stupid post and see that I said stupid GRIN not gun.  ;D ;D

Duh, I's stoopid! :P ??? ;D
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 18, 2015, 06:56:57 PM
Here is a 30 shot string that Jason requested I put up on this thread!
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on April 18, 2015, 07:11:30 PM
Holy Cow that is consistant !

SOoooo,... if you were to continue shooting past 30 shots...
 And lets say, keep it within a 4%-5% ES,...

 How many total shots do you figure you could get on the one fill ?
 Just curious.

Now get that pic posted up of You wearing your Chesher cat smile, holding onto Helga  ;D ! ! !
 I love the name btw. (I had a big hen named Helga)
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 18, 2015, 07:59:56 PM
I'm not sure Ron. That was 3000 psi down to 2450 psi. We used 550 psi over those shots. That is 37.9% of the available air. Assuming the psi per shot stays constant, which it should due to the regulator, we can assume that 30 shots is 37.9% of our available shots. That means that, on paper, we should see 79 shots (real number is 79.15 shots) before we go off the regulator at 1550 psi. Now, Jason has tuned this gun to, what Bob describes as, the "knee". This means that we have the potential to get several additional shots, in this "4-5%" range you are looking for, after going off the regulator. However, I bought this gun for the long range capabilities it has. This means that I want to stay within the smallest ES possible. At some point, I am going to have to sit down and throw a fifth of a tin of pellets through the gun to see just how tight the ES will be over a complete fill. These 30 shots has an ES of a mere 0.46%!

Some might ask why these numbers look a little bit better than what Jason posted just before he sent the gun off. My theory is that it is due to the elevation. I'm not sure how it effects things, but I have noticed that, back when I had a Disco, I was getting better efficiency that what I saw posted most of the time.
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on April 18, 2015, 09:31:44 PM
I was out in the shop this afternoon when Chris texted me with the stats from that string:

Code: [Select]
30 shots
High:  857fps
Low:  853fps
ES:  4fps
SD: 1.38

After I picked my jaw up off the floor :o and dusted off all the little metal shavings, I asked him to post a graph.  That is sweet!  Or stupid.  Something like that.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 18, 2015, 09:43:53 PM
Jason, it's stupid sweet! You've really out done yourself with this one.
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on April 19, 2015, 03:00:18 AM
My jaw hit the floor too and I can't seem to find it now. :o
Those are AMAZING numbers !
 MAN, I'm happy for you Chris!

 I was only throwing the 4-5% out as a reference. Naturally the lower the better. At a theoretical 79 shots before coming off of the reg,.... well,... Heck Who CARES after that, Right ! ? ! haha.

Strange, but for some reason I get the feeling that Utah will need to start importing yellowbeaks in the near future  ;)  ;D
 Give Helga all the love she deserves, and it sounds like she will serve you well for a very long time.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 19, 2015, 04:24:00 AM
She is getting all the love she needs! Twelve pest birds between Thursday night and now. One dove, one sparrow, and ten starlings. I am going to make a separate thread on the dove. It is intensely graphic.
Title: Re: QB79 HPA build for GTA member
Post by: silent_airman on April 19, 2015, 10:13:47 AM
She is getting all the love she needs! Twelve pest birds between Thursday night and now. One dove, one sparrow, and ten starlings. I am going to make a separate thread on the dove. It is intensely graphic.

Blood sacrifices to Huntress Helga, goddess of airgun hunting!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 19, 2015, 12:20:15 PM
Two starlings and a magpie down this morning! My Disco was accurate, but I had to work for it. This gun just puts the pellet where it needs to go. Had the gun for three days, 15 pest birds down so far, ranges from 8-73 yards.

Jason, you've made airgunning fun again!
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on April 19, 2015, 01:22:50 PM
Jason, you've made airgunning fun again!

Wow, I am honored you feel that way.  My heart swells to read those words.  That's what it's all about!  Have fun!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 19, 2015, 05:46:31 PM
Well, then you're going to love this post Jason! I'm on top of the world right now!

Do any of you remember that game we played (back in the good ol' days) called Chinese Flyswatter? Gist was, grab any Chinese springer, set up a target of flies 10 yards away, and see how many you can hit. Well, I did it the PCP way. 30 yards instead of 10! Here's the target.

(http://i836.photobucket.com/albums/zz287/footballplayerchris/IMAG0105_zpslde1pfge.jpg)

As you can see, I was able to hit all of them. There's a big hole a little to the right and up of the center, that was a 5 shot group just for fun. Also, see the fly that is two flies diagonally down to the left of the group? The hole in that one looks a little oblong right? That's because I decided to back up to 50 yards and see if I could nail one. Yup, sure enuff!!!

Jason, again, I can't thank you enough for this fine instrument! She will be in my airsenal till the day I die.

Ron, buckle up man. These guns are a hoot!!!!!!!!!!!
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on April 22, 2015, 03:56:38 PM
Chris, that is some fine shooting sir!  Fantastic job putting it all together...the right pellets, well zero'd rifle, the hold, breathing, trigger pull, and follow through.  That is a target to be proud of!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 23, 2015, 12:48:55 PM
It is on my wall permanently!

So, Jason asked me my honest opinion on his homemade LDC that is on the gun. I responded that it worked well, but the sound still had a "sharp" bite to it. However, I need to update my opinion. So far, I have taken back to back birds three times. I don't know what it is, but the sound profile of this gun does not scare off birds. I have been picking off dandelions in my yard and have had a starling land right in the yard. As a test, I shot a pellet roughly a foot off to the side of him. Nothing. Next pellet gave him a headache of course... :D

Anyway, just wanted to post my experiences with the LDC. It has been fantastic!
Title: Re: QB79 HPA build for GTA member
Post by: tronickero on May 16, 2015, 07:43:44 PM
Wow! ..your modification is amazing!!  ;D

 I want to do it, can you show me the tools used to make it? (Air flow modifications, valve modifications )


Regards from Chile, South America

Tron
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on May 19, 2015, 12:09:32 AM
Hi Tron,

The good news is you don't need a metalworking shop to do the modifications.  The most sophisticated tools I use are a drill press and a router table.

Valve
I slotted the sides with a 1/4" solid carbide spiral bit on the router table.  That makes it look pretty but anything that permits air to flow into the valve with less restriction will get the job done.

Drilled the throat from 0.194" -> 0.219" (7/32").

Tapered the valve stem into an hourglass shape by spinning it in the drill press and abrading it down with a Dremel emery wheel.  And reduced the poppet diameter from 0.371" -> 0.340" using the same technique.

Radiused the inside edge of the exhaust port (just behind the poppet) using a 1/8" diamond ball in the Dremel.

Bolt
Used a hand drill to open up the nose to 0.170", stepping up one numbered bit at a time to help stay centered.  Then used a diamond bit in the Dremel to enlarge the side hole into an oval shape.

Barrel
Enlarged the barrel port to 0.170" with a #18 bit, and deburred the inside edge of the hole with a 3/32" diamond ball in the Dremel.

I think that pretty much covers the air flow modifications.  If you have any other questions, just let me know.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 17, 2016, 01:08:35 AM
Jason
I realize this is an old thread but am in hopes it will still get a response.
.
I have followed this thread all the way thru and understand all the mods you did except one which is the RVA mod since the rear trigger housing mounting screw goes all the way thru the center of the reat tube cap in the pics provided at the very first start of the thread it looks like the 10-32 adjustment screw hole is drilled off to the side of the pass thru hole for the trigger/end cap/ breech plug screw securing hole.

If this is how you do it for a RVA so it passes by the triggers rear screw and still pushes on the spring guide then that is easy enough it just was not clear in the picture if it was of to the side to pass by the rear screw or if it was centered and the rear cap threaded to accept shorter larger screws from the trigger and breech ends to hold the tube cap and breech cap in place along with the trigger.

Any clarification would be helpful.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 17, 2016, 02:18:37 AM
Hi Mike, yes you have it right.  The screw is drilled off center as shown here:

(http://i.imgur.com/9QtALX9.jpg)

I also saw your other question regarding a concern that the guide may cant, causing the spring to bind.  I too had that concern at one time but if it were binding, you could expect the velocity to be erratic.  But again and again, the ES is excellent just as we observed with this rifle.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 17, 2016, 02:49:22 AM
Jason
That's what I was wanting to see as I thought it had to be off the side of the retaining hole like it shows and yea if spring is binding on the guide at all is occurring it does not show in the shot string on UCChris's rifle you built him.

By the way very nice work and has given me a lot of clear direction for my build to proceed with much more certainty.  I am not going for a power house just yet but rather a FT gun to shoot JSB 10.34s at 900 fps for 60 plus shot to shoot an entire match plus sight in on one fill.

I have a FDPCP 60C in 22 that I am looking at installing a ninja bottle on it to max it out for the power you got from UCChris's gun as it shoots 15.89s at 900 fps now but has a spread of 860 up to 900 and back to 860 for 30 shots at a 2000 psi fill so while not bad it can be improved considerably with a tank and some more modding IMO.

Thanks for the pic of the RVA.

Mike

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 20, 2016, 07:15:37 PM
As some of you may know, I had to sell this rifle in order to pay for college. However, it is back on its way to me! I'm planning to update the look of this gun, so stay tuned.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 20, 2016, 07:59:46 PM
Chris
Well hate you had to sell it but then glad you got it on its way back as well so it apparently all worked out for the best.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 20, 2016, 08:16:13 PM
Chris
Well hate you had to sell it but then glad you got it on its way back as well so it apparently all worked out for the best.

Mike

Agreed. I owned several guns in the interim between selling it and getting it back, some of them quite nice. But I compared them all to the QB, and they all lost.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 21, 2016, 12:47:07 AM
Chris
Yea I am just on my first QB build and hoping it will turn out as good as all the reports I have read here about them. Got my bolt probe and valve all done modding and working on the cock on open, RVA and tank block mods to be completed and ready for tuning.

I started with a QB 78 and am going for a 177 caliber FT gun shooting 10.34s JSBs at 900 fps so I  can shoot an entire match plus sight in on one fill.

Then I will go after the power house mods if this one turn out as expected. I have a Flying dragon PCP in 22 just begging for the 30 fpe mod with a tank installed to up her shot count over the 30 I get now filling to 2000 psi and shooting JSB 15,89 at 860 up to 900 and back to 860 for 30 shots at 28.89 fpe now but only for about 5 shots on the knee of the curve so only needs a little valve work and the regulated bottle to get the 30 fpe with double the shot count for a nice hunting gun as it is a tack driver now as is just to big a ES for consistent POIs.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 21, 2016, 02:00:50 AM
Chris
Yea I am just on my first QB build and hoping it will turn out as good as all the reports I have read here about them. Got my bolt probe and valve all done modding and working on the cock on open, RVA and tank block mods to be completed and ready for tuning.

I started with a QB 78 and am going for a 177 caliber FT gun shooting 10.34s JSBs at 900 fps so I  can shoot an entire match plus sight in on one fill.

Then I will go after the power house mods if this one turn out as expected. I have a Flying dragon PCP in 22 just begging for the 30 fpe mod with a tank installed to up her shot count over the 30 I get now filling to 2000 psi and shooting JSB 15,89 at 860 up to 900 and back to 860 for 30 shots at 28.89 fpe now but only for about 5 shots on the knee of the curve so only needs a little valve work and the regulated bottle to get the 30 fpe with double the shot count for a nice hunting gun as it is a tack driver now as is just to big a ES for consistent POIs.

Mike

The good news is that you are using a 78 tube, which means you can use a lower psi setpoint to achieve the 19 fpe you are after since you have a giant plenum compared to the 79. I would start at a psi setpoint of 1100 fps. Also, if you can get a half decent efficiency out of the gun, you should get 100 shots or so.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 21, 2016, 03:06:27 AM
Chris
That sounds good as I have a pro SHP reg already set at 1100 psi output. I have opened up the probe to .140" for the port hole and .125" for the probe passage hole and cut away the valve nose with two 3/8" slots down the sides and a 3/8" center hole where the piercing pin was, also replaced the poppet head with and older crosman 2240 brass head that is stepped and uses a delrin seat on the valve seal area and opened up the throat to 9/64' with the valve port angled and rounded.

Next is the cock on open mod and installing the tank block and RVA screw hole but may go with a crosman end cap so I can keep the adjustment screw centered instead of off set. since I have several end caps on hand.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 21, 2016, 03:14:01 AM
Chris
That sounds good as I have a pro SHP reg already set at 1100 psi output. I have opened up the probe to .140" for the port hole and .125" for the probe passage hole and cut away the valve nose with two 3/8" slots down the sides and a 3/8" center hole where the piercing pin was, also replaced the poppet head with and older crosman 2240 brass head that is stepped and uses a delrin seat on the valve seal area and opened up the throat to 9/64' with the valve port angled and rounded.

Next is the cock on open mod and installing the tank block and RVA screw hole but may go with a crosman end cap so I can keep the adjustment screw centered instead of off set. since I have several end caps on hand.

Mike

The more porting the better and it looks like you're on the right track. The better the rifle can "breathe", the less air you are going to have to use to make your velocity goals.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 21, 2016, 03:30:58 AM
That's my goal is to get the power level I want on the least amount of air per shot as I need 60 shots for the match plus 20 or so for sight in before the match. Can always top up before actual match so at least 60 shot on a fill is a requirement for the build.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 21, 2016, 03:39:36 AM
Oh and opened barrel port to .140". Also and will be using 3/16" ice maker tubing as a TP port seal. So now I am just trying to decide on the actual length I want to cut the tube down to for the tank block or if I want to use the factory CO2 fitting drilled out to accept a 1/8" pipe thread elbow and turn the tank around backwards and mold into the stock for a shorter more compact look and feel.

I eventually want to get an AR 2078 stock to put the action in for a better FT platform target style stocked gun so still deciding on some more options at this point as well.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 27, 2016, 06:49:55 PM
She's back in my hands and boy, how I've missed her!

(http://i836.photobucket.com/albums/zz287/footballplayerchris/B579354D-A0BB-4DD3-9836-8626F47BC138_zpsilp1jei3.jpg)
Title: Re: QB79 HPA build for GTA member
Post by: Monkeydad1969 on March 27, 2016, 07:53:35 PM
Looks good, Chris.

Joe
Title: Re: QB79 HPA build for GTA member
Post by: mackeral5 on March 27, 2016, 09:51:05 PM
Very nice.  I can name a couple of guns that got away and I wish I could get them back.  Congrats!
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 28, 2016, 02:39:52 AM
Chris
I like the 2078 stock cut away to fit the 79 action and tank block as I have thought about getting the target stock for my 78 with the tube shortened slightly so its good to see it can be just cut to clear the tank and block. I like the olive drab green paint as well and is it just paint or colored bedliner.

I just got the 79 I traded the disco I got from you yesterday and have shot it some and very happy with it and just need to tune it for a bit more velocity as its shooting 10.34s at 790 fps and I want another 100 fps so going to see how many shims under the hammer spring it has since it has the cock on open mod done and if cannot add any to the hammer spring I will up the tank pressure by 100 psi.

Which do you think is the best route to go add spring tension or output pressure to gain 100 fps over what it shoots now.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 28, 2016, 02:53:29 AM
Chris
I like the 2078 stock cut away to fit the 79 action and tank block as I have thought about getting the target stock for my 78 with the tube shortened slightly so its good to see it can be just cut to clear the tank and block. I like the olive drab green paint as well and is it just paint or colored bedliner.

I just got the 79 I traded the disco I got from you yesterday and have shot it some and very happy with it and just need to tune it for a bit more velocity as its shooting 10.34s at 790 fps and I want another 100 fps so going to see how many shims under the hammer spring it has since it has the cock on open mod done and if cannot add any to the hammer spring I will up the tank pressure by 100 psi.

Which do you think is the best route to go add spring tension or output pressure to gain 100 fps over what it shoots now.

Mike

It's just Krylon camo paint. Two coats of primer, two coats of paint, and I'm still working on the satin polyurethane coats. I just threw it in the stock for a pic.

I'm assuming the 79 is regulated? If it has a power adjuster on the back, I'd screw it in all the way and see what type of speed you can get. If it doesn't and is running the Ninja SHP tank @ 1100 psi, bumping it to 1450-1500 should get you the fps you're looking for. Playing with the hammer spring is ideal though. You want the lowest regulator set point possible for the fps you want. That way you are getting the most shots possible. Ideally, you want the gun to max out at 15-20 fps higher than you want with the power adjuster screwed in all the way. That way, the fps you are going for is on the knee.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 28, 2016, 08:20:37 PM
Chris
I like the 2078 stock cut away to fit the 79 action and tank block as I have thought about getting the target stock for my 78 with the tube shortened slightly so its good to see it can be just cut to clear the tank and block. I like the olive drab green paint as well and is it just paint or colored bedliner.

I just got the 79 I traded the disco I got from you yesterday and have shot it some and very happy with it and just need to tune it for a bit more velocity as its shooting 10.34s at 790 fps and I want another 100 fps so going to see how many shims under the hammer spring it has since it has the cock on open mod done and if cannot add any to the hammer spring I will up the tank pressure by 100 psi.

Which do you think is the best route to go add spring tension or output pressure to gain 100 fps over what it shoots now.

Mike

It's just Krylon camo paint. Two coats of primer, two coats of paint, and I'm still working on the satin polyurethane coats. I just threw it in the stock for a pic.

I'm assuming the 79 is regulated? If it has a power adjuster on the back, I'd screw it in all the way and see what type of speed you can get. If it doesn't and is running the Ninja SHP tank @ 1100 psi, bumping it to 1450-1500 should get you the fps you're looking for. Playing with the hammer spring is ideal though. You want the lowest regulator set point possible for the fps you want. That way you are getting the most shots possible. Ideally, you want the gun to max out at 15-20 fps higher than you want with the power adjuster screwed in all the way. That way, the fps you are going for is on the knee.

Chris
Yes it does have the pro SHP reg on it and as far as I know is still set at the 1100 psi factory set point but I am going to test it and see just what the output of the reg is right now. It has the cock on open mod but no RVA screw in the end cap so the spring would need shimmed for more tension if its not already at max preload. getting ready to check that as well. I have some 2240 end caps that I am thinking of drilling and threading for a RVA screw so it will be in the center of the spring guide block and would rather increase hammer spring preload than up reg pressure to keep the shot count as high as possible. Time to play with settings and see what I can get out of it since I am wanting 890 to 900 fps max from it.

That stock is looking good and should be nice once you get the urethane coats on it to seal it from the elements.

Thanks for the info and will let you know how it turns out.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 28, 2016, 10:08:42 PM
I'm looking forward to seeing how your build turns out. Keep us updated.

As for my QB79, I am working on making an adjustable comb kit to drop into it in addition to having a half shroud made for it. This thing is going to be stunningly gorgeous when I'm done. The half shroud should arrive sometime next week and I'm hoping to have the adjustable comb kit made up by then so I can unveil it next weekend at a group hunt I'm going to.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 29, 2016, 02:11:29 AM
Well the hammer spring was at almost full preload and was able to add one 1/16" shim under spring and it still cock so it will either be what I need or another spring will be required to add more tension or cut the guide rod off about 1/4" to allow more preload. Going to test the reg output pressure tomorrow and if its at 1100 psi and if it is will up it to 1200 to 1300 psi and see what it does for increasing the fps of the 10.34s to get close to 890 or 900 fps.

Not sure why you stated to shoot for 15 to 20 fps above desired fps since with reg it will stay constant to the set fps until it falls off the reg  is that not correct since you really don't have a knee in the curve with a reg until it falls off of it or am I mistaken in my thought process on how the reg should work.

The adjustable comb will be a nice addition to the target stock and as far as the half shroud I have found this one on ebay for 20 bucks that is 3d printed and is a perfect snug slide on fit for the QBs barrel and work very well to quiet it down considerably and adds little to no weight to the gun at all.

http://www.ebay.com/itm/331815546678?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/331815546678?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT)

It shows as sold out but it also shows to be relisted so check it out in a day or so and it should be relisted for sale, I am very pleased with it for the price.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 29, 2016, 02:26:51 AM
Even with a regulator, there is a sweet spot in the tuning process. This is called the knee. You see, if you crank the hammer spring as much as possible, there will be a point where, no matter the force you hit the valve with, there will be a maximum velocity that is limited by the PSI and volume of air allowed into the plenum by the regulator. Other things play into this such as valve/transfer port diameters, medium used in the rifle (CO2 vs HPA vs Nitrogen), etc. But those factors are over my head. Anyway, this maximum velocity is called the plateau.

The only way to get it to go faster is with either a) more air volume (more plenum or longer barrel) or b) more pressure (higher reg setpoint). Furthermore, at some point, the only practical way to increase speed will be with more pressure, since none of use are going to put a 40" barrel on our rifles, nor are we going to put a 500cc plenum in our guns. However, that's not what we're worried about. We're worried about what lies below the plateau.

What you want to do is find the plateau (fastest speed possible with the pressure/volume of air in the plenum) and then back off that about 10-15 fps. That is called the knee in the regulated tuning process. This is where, according to Bob aka rsterne, the regulated gun will be most efficient.

Good find on that LDC by the way. That's a very affordable option for those who are doing these HPA conversions for the money to performance value. I wanted something a little more flashy so I got a 10.5" long half-shroud done with a carbon fiber exterior. That along with the comb adjustment is going to make this gun look much higher dollar than it really is. Though, it deserves to look like a $1500 gun since it performs like a $1500 gun, after Jason worked his wizardry on it.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 29, 2016, 04:29:36 AM
Chris
Ok I see what you mean as its the same as tuning without a reg only the fps variation will be far less since the volume and pressure are more constant in the regulated gun. So I am at max spring preload now without heavier spring or cutting guide rod to allow more preload on current spring. so still need to see what my reg is set at now and shoot some test shots to see how much over the string of 770 to 777 fps for 20 shots I got today from it as received.

If I gains some in fps with the spring set at max preload then I will go up in reg pressure to get it at 15 or so fps above my 890 to 900 goal and then remove one shim from spring to put it on the knee and at the 890 to 900 fps goal. If it all goes as planned and if not then I will add a RVA in the end cap to be able to fine tune to the knee of the curve.

Yea I am like you and want to build my gun to look like a much more expensive gun than it really is and I have a FWB 300s stock that is broke at the knee that I am going to get fixed and inlet it to fit the 79 in so it will look like a 300s from a distance but will be HPA instead of a spring 10 meter gun. I do have two 300s that I use in my FT matches that do indeed make it out to 55 yards quite well since they are tuned up to shoot 10.34s at 590 fps and 8.44s at 675 fps. They are just to heavy for me for the off hand and kneeling lanes and is why I am building the QBs to be able to do better in those lanes.

Thanks Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 29, 2016, 05:23:59 AM
Glad you are understanding what I'm talking about. Sometimes I tend to get long winded and redundant. ;)

I'm headed to the local hardware store at 6 am to get parts for my adjustable comb and buttpad extension kits. There are adjustable comb kits available on the internet, but they range from $35 on up. I may have found a ingenious way to make an adjustable comb kit for a mere $10 of parts.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 29, 2016, 11:10:15 AM
Chris
That sounds good on the adjustable comb and if it works out we need pics so it can be duplicated by those who want/need it.

Got some more done on the 79 last night and going to test and setup the reg today but got to contact Jason to see if he can tell me now much pressure increase one .005 shim provides so I can only have to adjust once or twice since I don't have a manifold made up to keep from having to fill the entire bottle to test pressure instead of just the reg itself.

Mike.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 29, 2016, 11:20:15 AM
I have the extended buttpad setup and I've been working on the adjustable comb. Problem is, I only have a coping saw (yay for living in college dorms) and I've been sawing for an hour and a half and only gotten 1/3 of the way through the comb. I'm going to give a guy in my parent's neighborhood a ring. He does custom canoes for a living and I'm hoping he'll have a bandsaw. I will take pictures of the process.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 29, 2016, 11:46:57 AM
Yea I have a woodworking buddy with a full shop of tools so that's where I will head for my wood work projects. If its mechanical I have a garage full of tools from days as a master mechanic but a body man or wood worker I am not so that's best left to those who have done that for a living.

I believe a coping saw will work if you have enough elbow grease but its not how I would want to do it as a band saw is the way to go for sure.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on March 29, 2016, 12:31:41 PM
Mike, generally you can expect about a 100psi increase from the thin shims (0.005" if memory serves).  I want to say the thick (red) shims measure 0.015" so that would be about 300psi.  Just treat these as guidelines though, actual results may vary depending on the particular spring rate of the stack.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 29, 2016, 03:17:26 PM
Mike, generally you can expect about a 100psi increase from the thin shims (0.005" if memory serves).  I want to say the thick (red) shims measure 0.015" so that would be about 300psi.  Just treat these as guidelines though, actual results may vary depending on the particular spring rate of the stack.

Jason
I just got one regulator set and I ended up with approximately 50 psi per .005" shim which is what Ninja Ray thought it would be but then my dead head gauge may not be that accurate either as it is a small 1 1/2" non liquid filled gauge.

The first test of the reg as factory stock showed it to be 1100 psi as stated by Ninja website with 3 .005" shims installed so I added a red shim which are .020" ( not .015" ) for a total stack of .035" and it now reads 1300 psi on my gauge so I have it where I think I need to be and getting ready to shoot it over the chrony in a bit to see if it has picked up from the 775 fps range it was shooting at to the 890/900 fps I am after.

It has the cock on open mod as well and had two shims on the end of the spring guide that were 1/8" in thickness so I added another 1/16" shim and it is at the point it will just cock so spring is at max preload as well. If I am not at my desired fps I will tear farther into it to see if any valve mods have been done or porting done to improve the flow and if not then look into some work there.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 29, 2016, 05:26:34 PM
Well, I sawed away with the coping saw for a good hour and only got 1/3 of the way through the comb. I'm headed to a friend's dad's house to use his band saw. Got all the other parts cut and finished, so I'm just going to have to cut the comb, drill the necessary holes, and epoxy some stuff together.
Title: Re: QB79 HPA build for GTA member
Post by: GD Giles on March 29, 2016, 06:24:05 PM
Chris I know you're glad to have her back! Looking forward to pics of the comb mod.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 29, 2016, 07:01:58 PM
Got my reg set at 1300 psi output and hammer spring maxed out and filled to 3000 psi and shot a 20 shot string for some numbers and pretty happy with the results as is now.

3000 psi down to 2600 psi for 20 shots at 71 degrees F
Lo = 844.6
Hi = 857.1
Avg = 853.4
ES = 12.50
SD = 3.31

So while not at the 890/900 fps desired it is much better than the 775 it was at with JSB 10.34s and if the shot count is consistent with the air used I should get 80 shots shooting from 3000 psi down to 1400 psi just before it comes off the reg. I am going to mount a scope and see how it groups next and shoot it at this weekends FT match if it groups good at sight in and see if I need to really tune for the extra 40/50 fps or leave it alone and enjoy it.

Mike 
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 29, 2016, 09:07:38 PM
Got most of the work done on the adjustable comb. Just have to drill a couple more holes in the comb piece and do some epoxying. I also turned the power down to 12.84 fpe. It is crazy quiet now and still super accurate. I just need to get the shroud in the mail and finish the comb and this project will be done!

(http://i836.photobucket.com/albums/zz287/footballplayerchris/B5BC2E33-A24D-42EB-BBC6-E4D57A587F9C_zpsftvbqnp1.jpg)

(http://i836.photobucket.com/albums/zz287/footballplayerchris/DAE2B0D1-F874-45D1-89A5-CA0D862E82CA_zps9dk37vhe.jpg)

(http://i836.photobucket.com/albums/zz287/footballplayerchris/6168540B-5C84-4854-BF78-D9A259275A39_zpsda3hh4ss.jpg)
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 30, 2016, 01:06:05 AM
Looking good Chris especially for cutting by hand with a coping saw and should help with the cheek weld when shooting for sure. I want to see the finished project as well.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: Gertrude on March 30, 2016, 01:22:40 AM
looking good so far Chris.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 30, 2016, 03:38:28 AM
Well, I am a doofus. I left the aluminum rod that I'm using for the vertical adjustment bar at my apartment when I went to my parents house. I still got some stuff done on it (the pictures posted above) and when I left my parent's house, I left my epoxy there. Gah!

I couldn't sleep so I decided to drive up there again, this time with the aluminum rod, to pick up my epoxy and cut the rod to size. Got all the parts epoxied and they are setting right now. Should have pics by morning.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on March 30, 2016, 05:44:21 PM
Sounds like me and my mind as I forget it most days and end up going around without it just making like I know what I  am doing. But I have an excuse I am old and feeble minded and retired so I don't have to think unless I want to. HaHa.

I hate when stuff like that happens.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 31, 2016, 10:54:33 AM
Mike,

Did you say that you were going to modify a Crosman endcap to fit the QB so you could more easily use a power adjuster? Do you know what modifications that requires? My adjustable comb idea totally failed, but I have an even cooler idea if I can make a Crosman endcap fit.

I'm talking about part 17 in this here diagram.

http://www.crosman.com/pdf/manuals/BP1K77xx%20&%20BP9M22xx%20EVP.pdf (http://www.crosman.com/pdf/manuals/BP1K77xx%20&%20BP9M22xx%20EVP.pdf)
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on March 31, 2016, 02:11:34 PM
Here you can see how my comb was setup. The rod was simply epoxied into the comb, then a hole was drilled in the buttstock with a tee nut used as a threaded collar for a set screw.

(http://i836.photobucket.com/albums/zz287/footballplayerchris/84F322AE-6C09-457F-B798-EBEDFDFE69FD_zpsgwjc0jnr.jpg)

Simple, nice design, but when the set screw was tightened, the epoxy failed and the tee nut detached itself from the stock.

So, in a fit of rage, I did this.

(http://i836.photobucket.com/albums/zz287/footballplayerchris/A1F3CB31-ACE9-4027-873E-38309EFCB05B_zpsue9l21iy.jpg)

Not actually in a fit of range. I've decided to try something else. Hopefully this next idea works, lest I waste a $95 stock...
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 03, 2016, 02:14:59 PM
I hope your project is going well Mike. Inquiring minds would like an update!

Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on April 04, 2016, 04:20:56 AM
Chris
Got under the weather for a couple days and then had a FT match Saturday that is an all day affair and was just worn out so rested most of the day today.

But on your adjustable comb its a shame you hacked the end of the stock off as I could have told you what to do to remedy the set screw and threaded insert from coming loose. They make threaded inserts like a heli coil for repairing stripped thread in metal for use in wood. It is as simple as drilling the proper size hole in the stock and threading the insert into the stock to sit flush with the surface and the insert has the inside of it is threaded for a machine screw or set screw to go into so that it would have tightened down on the rod to hold the comb at whatever height you needed. If you can drill the stock and piece you cut with holes that can have wooden dowels inserted into the halves and glued in place to effectively make it one piece again it a simple modification to install the inserts for the set screws to hold the comb in place. See the link for the inserts from McMaster Carr below

 http://www.mcmaster.com/#standard-threaded-inserts/=11txmqn (http://www.mcmaster.com/#standard-threaded-inserts/=11txmqn)

For the power adjuster yes the disco end cap is one of the end caps that can be used to place the adjuster screw in the center of the end cap for a RVA in a QB and the other is for a 2240 but it requires drilling and threading the cap for the RVA screw so the disco part is a simple bolt in and buy a threaded screw to fit the threads already in the end cap of the length required which I have figured to be 50 to 60mm long. To install the end cap you just need to drill a hole thru the top of the breech 180 degrees opposite the hole that the trigger screw that hold the breech plug in place with now. Then measure the length of 8-32 thread screw you need to put in the top of the breech that will thread into the hole in the disco end cap and another one for the trigger side as well so the end cap will be held in with two screws from the top and bottom instead of the one screw it uses now. The disco end cap is threaded 8-32 in the two holes that the screw for the QB end cap passes thru now so the center is open with no screw blocking it. You can drill the top hole in the breech big enough so that using an allen head screw would allow the screw head to sit against the breech plug and not the breech itself and leave it sunken in the breech somewhat so it would not interfere with scope ring mounting. The threads in the QB breech plug do not need to be drilled out as the 8-32 screw will pass thru the plugs threads easily without issues so you can always go back to the stock end cap it you decided to. Or just buy the screws that hold the disco end cap on the disco and they should be the right lengths but the trigger side is a flat blade screwdriver head with a square middle driver head that tends to get buggered up easy with repeated removal so I prefer allen head screws plus you can get grade 8 screws instead of the cheap unknown grade crosman screws. The crosman screws are numbers 26 and 27 in the attached schematic. If you use the lengths given in the schematic to get allen screws from your local hardware store you should be good for a nice fit in the QB but may require some custom fitting of the lengths so they don't protrude into the RVA screw cavity of the end cap.

Hope this helps and sorry for the late reply as I wish I had caught you before you cut that stock UUGH.

http://www.crosman.com/pdf/manuals/BP1K77xx%20&%20BP9M22xx%20EVP.pdf (http://www.crosman.com/pdf/manuals/BP1K77xx%20&%20BP9M22xx%20EVP.pdf)

Mike     
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on April 04, 2016, 04:37:21 AM
Chris
Forgot the update on my 79. you saw the chrony numbers I posted with max hammer spring tension with just using the cock on open mod the gun came with from you know who with the spacer and shims inside behind the spring guide so have not installed a crosamn end cap RVA as of yet but did play with reg pressure some and found that upping the pressure from 1300 psi that the numbers were shot with to 1350 psi and it only gained me 10 fps and was using much more air. So now going down to 1250 psi to see if I loose fps or stay the same at 850 fps average it was at 1300 and if so will gain some efficiency with less used air but if fps drops will go back to 1300 for the time being  until I can get my RVA made and installed so I can add some more spring tension as I tried adding a spacer that fit inside the hammer cavity but it bound up the bolt on closing and caused a loss of fps due it creating hammer drag.

So as it is now have to fill and shoot a string at 1250 psi to see if I have lost fps or stayed the same and then do some grouping sight in to see if it even likes that velocity before I try to increase it because if it groups well out to 55 yards at 850 fps with JSB 10.34s then I don't see a need to up the fps at this time until I shoot some matches to see if it is an accurate FT gun. I am basing my goal of 900 fps on my Mrods velocity with those same pellets and its accuracy in FT matches but it does not mean the QB will like shooting them that fast so just still in the testing stages.

But at 1300 psi and with a 20 shot string I am happy with a predicted 80 shots per fill and still not be coming off the reg since matches are 60 shot max per session.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 04, 2016, 04:40:51 AM
Thanks for the updates Mike! Don't stress about the stock. I found a different way that is going to be every bit as awesome. I'm on my phone which makes typing out replies a royal pain, so I will write up a better reply tomorrow when I get back to my computer.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on April 04, 2016, 04:52:23 AM
Chris
Ok cool but it just pain me that I did not get on the forum to see the issue you had so I could direct you to the threaded inserts that would have solved the epoxy letting loose issue. but keep me updated on the newer stock and I will keep you updated as well.

On the disco end cap the threads for the RVA screw I believe are going to be 12-28 but not sure as its actually there in that end cap to degass the gun by threading a long screw into push the hammer open against valve pressure so it was not intended to be an RVA hole but works very nice for one.

Tomorrow will be a busy day so not sure if I will get any testing done or not but will see if I can since I am eager to see how it groups.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: BigTinBoat on April 04, 2016, 10:16:40 AM
Chris
Ok cool but it just pain me that I did not get on the forum to see the issue you had so I could direct you to the threaded inserts that would have solved the epoxy letting loose issue. but keep me updated on the newer stock and I will keep you updated as well.

On the disco end cap the threads for the RVA screw I believe are going to be 12-28 but not sure as its actually there in that end cap to degass the gun by threading a long screw into push the hammer open against valve pressure so it was not intended to be an RVA hole but works very nice for one.

Tomorrow will be a busy day so not sure if I will get any testing done or not but will see if I can since I am eager to see how it groups.

Mike

Disco end cap is 10-32
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 04, 2016, 11:04:16 AM
Correct, the center threading is 10-32 and the two retaining holes are 8-32.
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 04, 2016, 12:08:34 PM
(http://i836.photobucket.com/albums/zz287/footballplayerchris/A2886C3F-2E1B-4CE4-B181-FEBECD8CDF9E_zps394h4mbt.jpg)
Title: Re: QB79 HPA build for GTA member
Post by: AmBraCol on April 04, 2016, 12:39:56 PM
That pistol looks like quite a handful!   :o

Looking good!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 04, 2016, 12:47:19 PM
Thanks, Paul. It's a sweet shooter. Won't be a pistol for much longer!
Title: Re: QB79 HPA build for GTA member
Post by: AmBraCol on April 04, 2016, 12:52:43 PM
Thanks, Paul. It's a sweet shooter. Won't be a pistol for much longer!

I figured as much from your posts.  This build looks interesting indeed.  Looking forward to seeing how you finish it out! (are these builds ever, truly, finished?  ;D )
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on April 05, 2016, 03:37:34 AM
Chris
Ok cool but it just pain me that I did not get on the forum to see the issue you had so I could direct you to the threaded inserts that would have solved the epoxy letting loose issue. but keep me updated on the newer stock and I will keep you updated as well.

On the disco end cap the threads for the RVA screw I believe are going to be 12-28 but not sure as its actually there in that end cap to degass the gun by threading a long screw into push the hammer open against valve pressure so it was not intended to be an RVA hole but works very nice for one.

Tomorrow will be a busy day so not sure if I will get any testing done or not but will see if I can since I am eager to see how it groups.

Mike

Disco end cap is 10-32

Rob
Chris has it right as the ones that hold the end cap in the tube are 8-32 and like I said I was not sure on the one for the RVA screw and thought it might be 12-28 but is in fact 10-32 so thanks for the correction.

Chris you got it looking better with the end sanded and painted red ( not my favorite color ) but it looks cool but I bet its a handful as AmBraCol stated. So waiting to see what you have in store next.

Did not get a chance to do any work or shoot today as just got busy and ran out of time and tomorrow is not looking good either so just going to play it by ear the next few day and hopefully will get back to it by the weekend.  When our next cold front hits and drops the temps to the low 30s in the am which is not normal for april in Alabama at all, it should be 60s in the am and high 70s in the pm. I thought the gopher did not see his shadow and it was going to be an early spring. Just cannot trust mother nature anymore. LOL.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: Monkeydad1969 on April 05, 2016, 10:00:01 AM
Nice Chris.  Looks like a Ruger Charger.  ;)
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 05, 2016, 12:09:55 PM
Nice Chris.  Looks like a Ruger Charger.  ;)

Thanks! The red stock was actually inspired by your Nail Gun. I don't usually prefer red, but when I saw the tank cover on your Nail Gun, I wanted to try it out.
Title: Re: QB79 HPA build for GTA member
Post by: Monkeydad1969 on April 05, 2016, 02:09:46 PM
Very cool... 8)

But I am sure the QB is the better build, just because of the work put into it.  Now, show us the finished shooter!  ::)
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 05, 2016, 02:41:38 PM
Very cool... 8)

But I am sure the QB is the better build, just because of the work put into it.  Now, show us the finished shooter!  ::)

Unfortunately, now that I'm living at college, I have to travel to my parents' house to use my dad's tools so I can only work on my airguns once a week on my day off of work. Which is probably for the best; my grades couldn't handle me being able to tinker daily. What it amounts too is that I won't be able to post pictures of the finished gun until Thursday.
Title: Re: QB79 HPA build for GTA member
Post by: Gipper on April 05, 2016, 09:25:05 PM
Chris,

Nice job shaping that pistol grip....she looks great.  Look forward to seeing it finished.

Brian
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on April 06, 2016, 03:28:03 AM
Is it Thursday yet LOL.

I got my errands all done today and have the QB filled and ready to test the lower reg pressure tomorrow to see if its still at 850 fps or has lost a little bit so will know then if I have to go back up to 1300 psi or can leave it at 1250 psi and just sight in and enjoy. Will keep you posted.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 06, 2016, 03:50:49 AM
Is it Thursday yet LOL.
Mike

Tell me about it. Only 33 hours until I get to finish this project up. Figure 10 more hours of work and 6 hours for sleep and I only have to survive 17 more hours!
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 07, 2016, 01:45:08 PM
Well, I'd love to post pictures of the rifle all finished, rave over how awesome it is, and create a new thread in the hunting gate about me taking it out after finishing it.

BUT


My boss nixed my day off for the next two weeks...

But

it wouldn't have mattered anyway. The Ebay listing I bought the stock adapter from said the guy had two on hand and would be to my place between April 2 and April 6. Well, he decided to ship on April 6th. So the stock adapter isn't even at my place yet. I'm going to go up to my parents house on Sunday and hopefully knock this project out.
Title: Re: QB79 HPA build for GTA member
Post by: AmBraCol on April 07, 2016, 01:48:37 PM
Life.  It throws curve balls.

We're "glued to the  tube" waiting for when it comes together for you!
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on April 07, 2016, 02:13:58 PM
Chris
Don't you just hate when your bosses pull that "got to work on your days off" stuff on you like you don't have a life and plans made for your days off already. So this stock adapter you are waiting on what is it and how does it work, got a link to the eBay page for it.

Well finally got to shoot my 79 today for some numbers and had to go back up to 1300 psi reg output since the 1250 psi setting only yielded an average 815 fps from the JSB 10.34s instead of the 853 fps with the reg at 1300 psi. so 1300 psi it is and got to mount the scope after the wife's doc appointment this afternoon and sight it in and enjoy it for now.

Eventually I will tear in to it and do some valve work and install my 2240 RVA end cap so I can adjust hammer spring tension from outside the gun without disassembly and fine tune it to 900 fps for my FT matches.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: mackeral5 on April 07, 2016, 02:46:01 PM
I'm thinking the stock adapter is similar to this one:

http://www.ebay.com/itm/Crosman-2240-22xx-Custom-Stock-adapter-for-Tippmann-stocks-with-power-adjuster-/152038139885?hash=item23662de7ed:g:HeQAAOxy3HJTIKAR (http://www.ebay.com/itm/Crosman-2240-22xx-Custom-Stock-adapter-for-Tippmann-stocks-with-power-adjuster-/152038139885?hash=item23662de7ed:g:HeQAAOxy3HJTIKAR)

Already has a hidden RVA built in, could be converted to ssg.  I've got a little 22xx/QB Franken gun project that is using one.


Chris
Don't you just hate when your bosses pull that "got to work on your days off" stuff on you like you don't have a life and plans made for your days off already. So this stock adapter you are waiting on what is it and how does it work, got a link to the eBay page for it.

Well finally got to shoot my 79 today for some numbers and had to go back up to 1300 psi reg output since the 1250 psi setting only yielded an average 815 fps from the JSB 10.34s instead of the 853 fps with the reg at 1300 psi. so 1300 psi it is and got to mount the scope after the wife's doc appointment this afternoon and sight it in and enjoy it for now.

Eventually I will tear in to it and do some valve work and install my 2240 RVA end cap so I can adjust hammer spring tension from outside the gun without disassembly and fine tune it to 900 fps for my FT matches.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on April 07, 2016, 03:25:57 PM
Yup, just like that one. The Tippmann 98 style stock slips in and is held by set screws.
Title: Re: QB79 HPA build for GTA member
Post by: Michael Loar on April 08, 2016, 02:18:50 AM
Got it and yea that would work quite nicely and allow for spring adjustments and a SSG as well and fix the missing butt stock that seems to have been decapitated by accident in a moment of uncertainty.

It should look good but are you still going to have the action in part of the left over wood stock for a forearm and pistol grip or just go bare framed for the skeletonized look.

Mike
Title: Re: QB79 HPA build for GTA member
Post by: imadunatic on September 03, 2016, 10:40:30 PM
Jason/Chris,

Any long term issues with the hour-glassed valve stem?
Title: Re: QB79 HPA build for GTA member
Post by: nervoustrigger on September 04, 2016, 12:07:15 AM
Slimming the stem is a technique that has been used on many different pneumatics with a knock-open valve.  For example, it's a popular modification with Crosman guns...MSP, PCP, and CO2 types alike.

I've never had a stem to fail.  For example, mine has probably 7000 pellets through it and is still going strong.

I'm sure it could be a problem if carried to the extreme but taking it from 0.118" down to 0.080" or so is fine. 
Title: Re: QB79 HPA build for GTA member
Post by: UCChris on September 04, 2016, 04:45:19 AM
Mine had at least the same 7000 or so pellets. Still functions flawlessly.
Title: Re: QB79 HPA build for GTA member
Post by: imadunatic on September 04, 2016, 09:53:14 AM
Great to know,  thanks guys. I'm adding it to the list.
Title: Re: QB79 HPA build for GTA member
Post by: grand-galop on January 21, 2017, 07:57:21 PM
Any update on this build???  I taught it was ADEQUATE to bring it back to life since there is so many questions that can be ansewred with this topic... ;D