Not much to look at, QB 78s as PCP

[CFH]

But plenty actually for backyard vermin, I get 6 good shots before needing a refill to 1200-1300 psi. Shot count and bone stock save for bulk fill with check/poppit valve, 3x7x20 scope. 1.687fps, 2.685.9fps, 3.679.6fps, 4.667fps, 5.669.3fps, 6. 662fps using Crosman 14.3gr pellets. 14.46fpe.

[Ribbonstone]

Whole lot alike.

Had a 3K PCP tube….had a .25 Mountain Air QB conversion….seemed like they should get together with the QB78S  plastic stock.

DSCN3078 by Robert Dean, on Flickr

[wll2506]

But plenty actually for backyard vermin, I get 6 good shots before needing a refill to 1200-1300 psi. Shot count and bone stock save for bulk fill with check/poppit valve, 3x7x20 scope. 1.687fps, 2.685.9fps, 3.679.6fps, 4.667fps, 5.669.3fps, 6. 662fps using Crosman 14.3gr pellets. 14.46fpe.

Wow so you just filled up the stock 78 tube with air ?

Very cool idea,  I have a bulky 13ci tank to give ? shots at 1100+ psi as I remember in 177 cal.

wll

[singleshotcajun]

Very interesting. I have a AR 2078,a 79 in .22 and a standard.177 78 all bulk fill and bulk filling C02 is getting harder. I do hate powerlets.

[Jonah]

Where did you get the bulk fill adapter? They are hard to find.

[Back_Roads]

 Mine had to shed the poly, and blend in with our 1910 house, fun gun, do plan on adding an air fitting next time I get to tinkering.

[singleshotcajun]

Where did you get the bulk fill adapter? They are hard to find.

I built mine by drilling and tapping 1/8 pipe  with a smaller hole offset to the piercing point connecting to the tube. A small bolt with an O-ring and a spring behind the head to make a check valve. This style works with both powerlets and bulk.

[nervoustrigger]

Nicely done.  As you say, that’s plenty for backyard pest control.  Also would work fine for a woods walk looking for gray squirrels as long as you make your shots count.  I built one up a few months ago in .177 cal along with a new poppet and lightweight hammer, and it manages somewhere around a dozen shots at 11-12fpe on the same 1200psi fill.  Nice lightweight gun for walking around and taking offhand shots when needed.

[Ribbonstone]

Couple of times I got out all the old QB stuff and gave a QB a 4 way test.

NOT that it’s a good idea to high pressure air fill a QB tube, so any “whoops” is all yours to own.

DSCN2112 by Robert Dean, on Flickr


All run though the same rifle, same valve, no changes.  One mod was to remove the piercing pin inside the standard valve (that in order to use “C”)...other than that, was a standard QB valve.

Test rifle  (carbine) was a .177 set up low power.  Made for back yard pest birds shooting, which it does really well (the stock was made for shooting “up”).

A – regular end cap to run 12gr. (only one as I killed the valve piercing pin).
B – bulk fill end cap to run bulk fill co2
C – same bulk fill end cap, but tube filled with 1200psi air.
D – old HiPac unit to use with  higher pressure air.

DSCN2114 by Robert Dean, on Flickr

Using “A” as a base line.

Speed picked up a little from bulk fill...not much, more like 3%.  Just less clutter/restriction in the gas flow.  More gas in the tube, more shots.

Regular tube filled with 1200psi air started little slow, peaked at about 1000psi.  Considerably faster than base line (more like 16%).  About 5-6 good usable shots with this low-tuned rifle.

Useless to run higher pressure, start approaching valve lock at 1400-1500psi.  Striker hit to the valve stem not strong enough at this .   Can be adjusted to do much better, but tested with the original 12gr. tuning.


While no one really wants to recommend it, and I can understand why,  it can be done...may not get a lot of great shots.

Quick target (just a spray paint blob on old moldy sheet rock)...a .22 this time.  Consider it a visual of what velocity variation will do even at 25 yards.

DSCF0488_zpsafbe2c33 by Robert Dean, on Flickr

Can guess about what the volume of a QB tube has to be…..inside of the tube is made 2 12gr long.   That turns out to be about 6.25” of air space length.  Inside diameter is about .74”.   going to work out to about 44-45CC’s (can plus the inside of the valve and call it 50cc’s).

That’s tiny….but enough that if you work at adjusting/tuning, can see where Jason’s 12 shots could happen.

[wll2506]

Mine is a good outdoor hunter, even though it is 17 cal. 3000 PSI with an out of ~1100psi as I remember.



Shooting Monsters in the high 775+ area and 12.5gr slugs are the same .. Downrange energy with the slugs is ~14fpe at 50 yards ;- ) Monsters give me about 10fpe at 50 yards --- not to bad ;- )

The LDC makes this gun "Mouse Sneeze" quiet !

wll

[CFH]

I think there are 17 shots available in that little tube, 1-6 are good, from there the velocity starts to fall off, but if you are shooting cans.... 30 pumps with my hand pump, and they are easy at that (6 or 7 pumps to pressurize the line) But yep, they are not designed for hpa as such, so keep that in mind if anyone trys this.

I bought 4 of these to play with when they hit $58... The stock is kinda ugly, but pretty comfortable, and I love bolt action guns! I am hoping to buy the repeater if they ever become available again.

Couple of times I got out all the old QB stuff and gave a QB a 4 way test.

NOT that it’s a good idea to high pressure air fill a QB tube, so any “whoops” is all yours to own.

DSCN2112 by Robert Dean, on Flickr


All run though the same rifle, same valve, no changes.  One mod was to remove the piercing pin inside the standard valve (that in order to use “C”)...other than that, was a standard QB valve.

Test rifle  (carbine) was a .177 set up low power.  Made for back yard pest birds shooting, which it does really well (the stock was made for shooting “up”).

A – regular end cap to run 12gr. (only one as I killed the valve piercing pin).
B – bulk fill end cap to run bulk fill co2
C – same bulk fill end cap, but tube filled with 1200psi air.
D – old HiPac unit to use with  higher pressure air.

DSCN2114 by Robert Dean, on Flickr

Using “A” as a base line.

Speed picked up a little from bulk fill...not much, more like 3%.  Just less clutter/restriction in the gas flow.  More gas in the tube, more shots.

Regular tube filled with 1200psi air started little slow, peaked at about 1000psi.  Considerably faster than base line (more like 16%).  About 5-6 good usable shots with this low-tuned rifle.

Useless to run higher pressure, start approaching valve lock at 1400-1500psi.  Striker hit to the valve stem not strong enough at this .   Can be adjusted to do much better, but tested with the original 12gr. tuning.


While no one really wants to recommend it, and I can understand why,  it can be done...may not get a lot of great shots.

Quick target (just a spray paint blob on old moldy sheet rock)...a .22 this time.  Consider it a visual of what velocity variation will do even at 25 yards.

DSCF0488_zpsafbe2c33 by Robert Dean, on Flickr

Can guess about what the volume of a QB tube has to be…..inside of the tube is made 2 12gr long.   That turns out to be about 6.25” of air space length.  Inside diameter is about .74”.   going to work out to about 44-45CC’s (can plus the inside of the valve and call it 50cc’s).

That’s tiny….but enough that if you work at adjusting/tuning, can see where Jason’s 12 shots could happen.

[airpuffhunter]

qb´s are amazing, I love mine

[johnbrown]

I really wanted a QB78 for a while.
But I hate CO2 and there are no bulk fill end caps available anywhere.

On the other hand my 2400KT on HPA are great (using the GMAC Powerlet Eliminator).

[singleshotcajun]

I am happy with my QB series rifles with bulk fill. I live near Houston (fourth largest city in the country and full of shooting enthusiast) but no longer can I find a place to fill my C02 24 Oz tanks or sell new ones. One day I will get off my butt and see about a larger tank from a welding or restaurant supply. Years ago when I modified my piercing caps for bulk fill I made a “ tree” to fill my rifles from a standard paintball tank. These days I have gotten into PCP but still very much enjoy the fine triggers and everything else about the QB series. I have never considered the QB for pesting but for fun and maintaining my marksmanship skills. When I was still shooting Service Rifle and 3P Smallbore matches my AR 2078 helped me to improve my Offhand scores by shooting Offhand in the backyard everyday.

[Ribbonstone]

May be I have more use for co2 than most on the dark side...likely it’s more because of a warm climate and uses that do NOT include big-power.  There is also a bit of laid-back-lazy in there as well.

Different ways/parts/etc., but seems like 5 reasons folks want to consider conversions...usually it’s only 2 or 3 of these reasons bundled together.

1. Converted for more power by running on air.

2. Thinking it would be an easy way into air use...which it can be if you already own a QB and count that as “no money”.

3. Remove the expenses of co2 (after all, it’s the only air gun power plant that’s not air... we HAVE to buy as we can’t really make it).

4. Winter use for those out and about in the  harsh winter areas.

5. Bored and want to keep mind and hands busy.



The other side of those 5: (CONSIDER...a whole new PCP can cost less than $200)

1. Yep...certainly can make more power.  Almost all readers will think that’s a good thing, but it does depend on what you use them for.

2. Easy is a retaliative term….it’s not quite as easy as a parts-swap. Seems cheap until you tally up all the costs of doing it from new.

3. Kind of.  If thinking a $50 hand pump, then cheaper in money.  $50 of co2 will run out faster than $50 of pump..everything past that is “sweat effort” rather than “cash money”.

4.  No real counter to that….can use co2 from a nice warm room out into the frozen tundra….just not all that great when wandering around in that snow covered mess.

5. OK...actually a really good reason.


Time passes...an air gun nut will end up with a lot of airguns….and what seemed a good idea then may not be a real useful result later.

Pulled he conversion insert tubes (HiPAc) and readjusted them for co2:

DSCN2734 by Robert Dean, on Flickr

Direct top-swap...keeping it running on co2 as I didn’t want to rebarrel another one to 5mm.

DSCN1436 by Robert Dean, on Flickr


Some plus-points: (which is really an expansion of #5 at the top):

Really do learn the relationships between air and co2,... fill pressure and valve opening force... the balances to get the best air use for the power in order to get a good shot count.

 Ain’t all  plug-n-play fun and games, there is some serious thinking going on.

Over all, by converting them to  efficient air use, what I learned has been worth a lot more than the $ spent.  Somewhat frustrating at times, but if nothinge else, can appreciate a cheap  PCP that came out of the box most of the way there.