.172 Build

[rsterne]

"Supersonic" (as in 1200 fps) yes, but 1500 fps with a 25 gr. pill is 125 FPE (and 1600 fps is 142 FPE).... Using my "lofty goal" formula, a .172 cal with a 28" barrel and 4500 psi might get 122 FPE for a single, full power shot.... That is twice the power I am getting with a 28" barrel at 2800 psi, with full bore area porting throughout.... Even if I could manage the same power/pressure ratio (which I know won't happen Supersonic), I would need 5600 psi to get there.... 

Bob

[Taso1000]

We also have a velocity limit to where the soft lead used in slugs will deform and tear or come apart in the rifling.  I'm not sure of the proper term for that. 

Increased leading of the barrel may also happen at higher velocities.

But I am sure both are related to twist rate and velocity.

Thanks,

Taso

[YEMX]

OP wont take a picture without full accessory. keep us in suspense and OP thinks without accessories the gun wont look as good?

OP as in me?  What's the point of taking pictures at this point?  It looks like a normal AF rifle w/a really thick barrel.  My accessory choices don't really have anything to do with looks- the roller trigger is simply (or rather, supposedly at this point) a better trigger, the new trigger guard both stiffens the frame and allows me to us AR grips, and the LDC is to quiet the gun. 

[darkcharisma]

i am actually curious to see how thick it is. isnt that strange? is it green mountain 1” blanks?

[bear air]

LOL, patience is a virtue.

[YEMX]

i am actually curious to see how thick it is. isnt that strange? is it green mountain 1” blanks?

Yessir,  Green Mountain.  I believe it's a 1" O.D. blank.  It's also been sleeved in CF, but that was the machinist's choice.  I assume for looks, as a 1" O.D. steel barrel in .172 isn't lacking in the stiffness department!  I didn't care either way.

The trigger guard should be here in a couple days, and the LDC might be here tomorrow?  Regardless- I should have pictures up this week sometime.  The dovetail to picatinny conversion rail won't be here for another week     

[darkcharisma]

"Supersonic" (as in 1200 fps) yes, but 1500 fps with a 25 gr. pill is 125 FPE (and 1600 fps is 142 FPE).... Using my "lofty goal" formula, a .172 cal with a 28" barrel and 4500 psi might get 122 FPE for a single, full power shot.... That is twice the power I am getting with a 28" barrel at 2800 psi, with full bore area porting throughout.... Even if I could manage the same power/pressure ratio (which I know won't happen Supersonic), I would need 5600 psi to get there.... 

Bob

We hit our limit pretty fast with airguns dont we? you are pretty conservative on not telling people outright that its hard to get there…

[rsterne]

I have learned over the years not to tell people things are impossible, unless they are.... For instance, the maximum possible FPE for an airgun can be calculated by using the pressure (psi) times the bore area (sq.in.) times the barrel length (in feet), and that FPE is the total, including the energy necessary to accelerate the air released by the valve (the biggest loss).... For my "lofty goal", I use half that, to allow for pressure loss during the shot, friction, the air mass, etc.etc.... but that is only an estimate, and a couple of times it has been exceeded by using a very short barrel and high pressure, or projectiles so heavy that the velocity is quite low.... In cases that have slightly exceeded 50%, there was a lower air mass relative to projectile weight.... The caveat to the 50% "lofty goal" I use, is that the projectile weight is such that the velocity is about 950 fps.... I have never managed to reach 50% at 950 fps, about 48% is the best I have done, even with full bore-area porting and large reservoirs....

My approach is to discourage people from wasting their time, trying to do things that are either nearly impossible to achieve, or have good, sound, scientific reasons to be counterproductive.... If they ignore my warnings, there is little downside, but for most it ends up being a learning experience....

Bob

[YEMX]

DonnyFL came in today, and I've got some slugs on order so I can begin shooting this rifle.  I did a preliminary measurement, and the OAL will be around 43.5" 

[bear air]

Excited to see how this gun turns out Tom. It's been a couple years now (at least). I was thinking about making a high speed 177 shooter when you started this project. Bob I have always liked how you approach questions. I really love how you simply line out the data lol.

[YEMX]

Excited to see how this gun turns out Tom...

SAME!!

Okay, slight change.  New estimated OAL are 39.25" w/o the LDC, and about 47" with the LDC.  None of my LDC's will work w/this barrel, because the muzzle threads are a bit too long.  The muzzle touches the baffles on all my LDC's save for 2, and one I'm NOT going to use on this build because I just don't think it'll work well, since it's for a .357.  The LDC I'm going to use is an old NC made for a .25.  SO!!  There's that.  No biggie at all.  I'll simply use the NC, and just take it off during transport.  Or leave it on.  I don't know yet. The rifle case I have for LONG guns can fit 66" rifles.  Doubles as a shooting mat.  Should work out just fine.  It'll definitely be transporting both my AF guns, as they're easily the longest guns in my collection.

NO, I couldn't wait for the dovetail to pic rail adapter to come in (for the bipod), and decided to assemble the rifle.  I had to do some work on the grip, but I'll take pictures of all that tomorrow.  I'm pretty happy with it!  The trigger does feel good.  Definitely smoother than factory.  Is it BETTER?  Eh.  That'll be up to you.  But for a drop in with nothing else done to the trigger components, it's definitely smoother.  I'm really glad the Masterpiece Arms grip works comfortably with this rifle set up.  The other target grip I have (LuthAR) does NOT work w/this set up.

[YEMX]

I forgot to mention, I picked up an Arken 4-14x scope for this build.  It's still in the mail.

[bear air]

Who had the you tube video a couple years ago shooting one of these guns? I think he used to be a member here on GTA.

[YEMX]

Who had the you tube video a couple years ago shooting one of these guns? I think he used to be a member here on GTA.

Cedric- Tofazfou.  He's got 2 vids, his Gen1 build (modified Mrod) and his Gen2 build, which is an AF rifle.  Other than the stock and tank, this is almost an identical copy of his build.

I'm also thinking about switching over to a CF tank...  Slightly larger at 500cc, and higher fill pressure.

[YEMX]

Okay...  She's assembled.  The rifle's still not done though.  Here's a quick run-down of parts again:

Condor frame
.172 Green Mountain 1-9 twist barrel, 25" long, 1" O.D. (not sure if these are still currently available though)
Doug Noble .172 top hat, valve work, and guts
WOK Guard 15
WOK-butt
Masterpiece Arms Enhanced Grip
RMP Airguns roller bearing trigger
CF 500cc 4500 psi bottle

I'm still waiting on the dovetail to picatinny conversion rail for my bipod, and I also got a conversion rail for the scope rail.  I also still need to get rings- I haven't decided what I want though.  Normal rings or adjustable rings...  I'll figure it out.  I've removed the auto-cocking dog from the gun.  Anyhoo, here's a bad pic: 
 



Darkcharisma, this pic is for you.  You wanted to see how thicc the barrel is LOL  It pretty much takes up the entire I.D. of the frame. 



Here's a shot of the WOK Guard, and the RMP Airguns trigger (well, the trigger shoe anyway):



Here's some shots of the Masterpiece Arms grip.  It's kinda hard to make out, but I had to remove some material from around the back "beavertail" section of the grip, and I also installed a locating pin, just like factory AF grips have.  Except my locating pin is steel.  I just used a dremel to do this.  Well, a dremel and a drill press.  No, the grip does NOT touch the tank.   





No, I'm not going to leave it that miss-match of colors, I'm going to eventually give it a coat of paint.  I'm not going to do any real patterns though.  Just different camo colors.  Just kinda spray it around, and have fun with it.

OAL w/o an LDC is 39.5", and w/LDC is 48". 

[woogie_man]

You know the next question that will be asked....... How does it shoot!   

Had to be that guy.

Your builds are always lengthy, but the end product is always worth the wait.

[YEMX]

You know the next question that will be asked....... How does it shoot!   

Had to be that guy.

Your builds are always lengthy, but the end product is always worth the wait.

Dunno! I've got some slugs on the way. 

[bear air]

Nice looking gun Tom. Cedric was who I was referring to. LOL. Couldn't remember his name last night. I seen the one he had done in the marauder configuration.

[YEMX]

Nice looking gun Tom.

Danke!

I picked up some No Limit rings, and I'm going to put my Element Helix on this rifle- I'm going to put the Arken on the 6mm Condor. 

I really want to run the DonnyFL on this rig, so I got some precision shims from McMaster Carr.  .075" thick does the trick.  The rest of the parts will be here around the end of the month.  So I'll update again when the rest of the stuff gets here, and I can mount everything and post a "final" assembled pic for y'all.  Then it's out to the field for sighting her in and getting some groups.

[YEMX]

Main scope rail came in today!

Still waiting on the conversion rail for the bipod

Still waiting on the no-limit rings

Slugs came in today as well- they look fantastic!  I got some cast (solid- not HP), along with some swaged (HP).  I can't wait until everything is together, so I can do some shooting!!