Qb79 25 cal repeater on hpa

Qb79 25 cal repeater on hpa

Joined: January 1st, 2008, 5:25 pm

November 1st, 2010, 1:09 pm #1

Had a chance to do a little shooting and testing this weekend. The Qb79 at the bottom of the picture has a JRA Quickshot breech and 24" Lothar Walther.25 cal barrel.
The transfer port is .160" diameter and polytube was used from valve to breech. A Rich from Michigan modified valve is used. I shot at 2 pressures so far. Ammo selected was JSB Kings 25.4g. The first pressure was 680 PSI and and muzzle velocity was 615 f/s. The 2nd test pressure was 1060 PSI and MV was 715f/s. I will probably push this one to 1400 PSI with a custom gas tube. More pressures to come as well as shot count.
.

.
Accuracy was 1 hole at 20 yds as you would expect with the Lothar Barrel. On this caliber an internal o-ring groove is machined in the barrel to seal the bolt. No problems indexing. This caliber takes a bit more pressure on the bolt to seat the pellet. The .177 and .22 cal version of the Quickshot do not require the internal oring groove. As you can see from the picture the Quickshot breech family is growing and now includes the Disco (top Pic) There is a posting with more info on the Disco Quickshot on the Benjamin/Discovery section of the Yellow.

Jay
http://qbmags.com
Reply
Share

Joined: March 4th, 2003, 8:31 pm

November 1st, 2010, 1:18 pm #2

and I look forward to reading more about your conversions. Great work Jay.
Reply
Share

Joined: August 11th, 2010, 10:53 pm

November 1st, 2010, 5:28 pm #3

Had a chance to do a little shooting and testing this weekend. The Qb79 at the bottom of the picture has a JRA Quickshot breech and 24" Lothar Walther.25 cal barrel.
The transfer port is .160" diameter and polytube was used from valve to breech. A Rich from Michigan modified valve is used. I shot at 2 pressures so far. Ammo selected was JSB Kings 25.4g. The first pressure was 680 PSI and and muzzle velocity was 615 f/s. The 2nd test pressure was 1060 PSI and MV was 715f/s. I will probably push this one to 1400 PSI with a custom gas tube. More pressures to come as well as shot count.
.

.
Accuracy was 1 hole at 20 yds as you would expect with the Lothar Barrel. On this caliber an internal o-ring groove is machined in the barrel to seal the bolt. No problems indexing. This caliber takes a bit more pressure on the bolt to seat the pellet. The .177 and .22 cal version of the Quickshot do not require the internal oring groove. As you can see from the picture the Quickshot breech family is growing and now includes the Disco (top Pic) There is a posting with more info on the Disco Quickshot on the Benjamin/Discovery section of the Yellow.

Jay
http://qbmags.com

That is a killer looking rifle..... as usual.

Everyone should have one of these risers! I love mine. The bolt knob you have on the one, what is that? And what is the current cover on the bolt handle made of, and how would one remove it?


Keep up the great stuff man....... You should try and make a nice bullpup with one
Reply
Share

Joined: January 1st, 2008, 5:25 pm

November 1st, 2010, 5:43 pm #4

Thanks,

The 25 is fun to shoot. Probably more power than I need. Those kings leave a big hole.

The current knob is black delrin and is a tight press on the handle.
The larger knob is black nylon I believe. Check the new products section of the website.http://qbmags.com


Jay
http://qbmags.com

Reply
Share

Joined: October 21st, 2001, 3:36 am

November 1st, 2010, 6:32 pm #5

Had a chance to do a little shooting and testing this weekend. The Qb79 at the bottom of the picture has a JRA Quickshot breech and 24" Lothar Walther.25 cal barrel.
The transfer port is .160" diameter and polytube was used from valve to breech. A Rich from Michigan modified valve is used. I shot at 2 pressures so far. Ammo selected was JSB Kings 25.4g. The first pressure was 680 PSI and and muzzle velocity was 615 f/s. The 2nd test pressure was 1060 PSI and MV was 715f/s. I will probably push this one to 1400 PSI with a custom gas tube. More pressures to come as well as shot count.
.

.
Accuracy was 1 hole at 20 yds as you would expect with the Lothar Barrel. On this caliber an internal o-ring groove is machined in the barrel to seal the bolt. No problems indexing. This caliber takes a bit more pressure on the bolt to seat the pellet. The .177 and .22 cal version of the Quickshot do not require the internal oring groove. As you can see from the picture the Quickshot breech family is growing and now includes the Disco (top Pic) There is a posting with more info on the Disco Quickshot on the Benjamin/Discovery section of the Yellow.

Jay
http://qbmags.com
but you knew that already.

Reply
Share

Joined: January 1st, 2008, 5:25 pm

November 1st, 2010, 9:40 pm #6

Had a chance to do a little shooting and testing this weekend. The Qb79 at the bottom of the picture has a JRA Quickshot breech and 24" Lothar Walther.25 cal barrel.
The transfer port is .160" diameter and polytube was used from valve to breech. A Rich from Michigan modified valve is used. I shot at 2 pressures so far. Ammo selected was JSB Kings 25.4g. The first pressure was 680 PSI and and muzzle velocity was 615 f/s. The 2nd test pressure was 1060 PSI and MV was 715f/s. I will probably push this one to 1400 PSI with a custom gas tube. More pressures to come as well as shot count.
.

.
Accuracy was 1 hole at 20 yds as you would expect with the Lothar Barrel. On this caliber an internal o-ring groove is machined in the barrel to seal the bolt. No problems indexing. This caliber takes a bit more pressure on the bolt to seat the pellet. The .177 and .22 cal version of the Quickshot do not require the internal oring groove. As you can see from the picture the Quickshot breech family is growing and now includes the Disco (top Pic) There is a posting with more info on the Disco Quickshot on the Benjamin/Discovery section of the Yellow.

Jay
http://qbmags.com
Pumping the tank pressure up to 2000 psi gave me 2 clips or 16 shots with a 500 psi drop in tank pressure so I am still on the reg.I'd go higher but my pump is failing. At 3000 psi fill pressure this looks like a pretty good shotcount for 29 ftlbs. The groups weren't bad at 50 yds in some wind. Still not used to that long barrel yet and the trigger is a bit heavy for my liking.

Jay
http://qbmags.com
Reply
Share

Joined: November 17th, 2006, 3:51 am

November 1st, 2010, 11:24 pm #7

..so if you're getting about 16 shots for 500psi, with 1500 psi to play with (3K to 1.5K)m would expect about 48 shots per fill.
Reply
Share

Joined: January 1st, 2008, 5:25 pm

November 1st, 2010, 11:38 pm #8

Hi Robert,
That's what I have seen as well on .22 and .177 but didn't want to get too happy. I'd like to shorten the barrel, increase the pressure and shoot in the low 800's. If I got 4 clips from the 13ci tank at that
MV I'd be thrilled. Whats's the 25 cal MROD getting as far as shot count? Thanks for the input

Jay
http://qbmags.com
Reply
Share

Joined: November 17th, 2006, 3:51 am

November 2nd, 2010, 1:17 am #9

Converted a full length tube (QB78) with a QB79 tank block to get a larger volume between the valve and the tank (more "on deck" regulated air). Wanted to use a larger volume of 1200psi air rather than use higher pressure. Running at 1200PSI, could move Kodiaks at 680fps. 20gr. pellets made it to 805fps.

Made for a louder gun. Long blast of lower pressure air makes for higher gas exit pressure (and volume), and that makes noise. Would get about 45 good shots per fill, but I tend to stop a bit before hitting regulate pressure (usually stop at 1500 for a 1200 regulator / 1000 for a 900 regulator).


Recently stepped down from 1200psi to 900psi, readjusted the internals, which dropped the speed of everything by about 100fps. think I can get half of that speed back at this pressure with a couple of ideas...may not, but its fun trying.
Last edited by gubb33ps on November 2nd, 2010, 1:18 am, edited 1 time in total.
Reply
Share

Joined: August 16th, 2006, 10:39 pm

November 2nd, 2010, 3:27 am #10

Hi Robert,
That's what I have seen as well on .22 and .177 but didn't want to get too happy. I'd like to shorten the barrel, increase the pressure and shoot in the low 800's. If I got 4 clips from the 13ci tank at that
MV I'd be thrilled. Whats's the 25 cal MROD getting as far as shot count? Thanks for the input

Jay
http://qbmags.com
shots 16

Min 859.50
Max 883.80
Average 875.20
Median 877.65
Extreme Spread 24.30
SD 7.47
Last edited by critter99 on November 2nd, 2010, 3:28 am, edited 1 time in total.
Reply
Share