B_R QB 78 .177 Safe Pack install / Slug Test Take 1

[Back_Roads]

 Took my QB 78 .177 out of the stock, getting ready for tomorrows Safe Pack installation.
Will be a Sleeper build, here is the test subject as of not anymore 

[nervoustrigger]

Following along.  Assuming this kit lets you run it on a 3000psi fill, I'm curious to see what it will do.  I managed 24fpe (15gr @ 850fps) from the QB79 described here at just 1500psi regulated.  I took the porting out to about 95% of the caliber so that was a big help but the tiny plenum of the 79 is a limitation.  I'm just thinking a bell curve centered around 2500psi could put it over 30fpe without having to go crazy with the porting. 

If you haven't already, you'll probably need to swap the soft OEM poppet out with a hard plastic one (Delrin or better).  At elevated pressure, the soft polyurethane seal will likely flatten out and begin leaking, sooner if not later.  Plus it's so hard to knock open, it may not be possible to develop enough hammer strike to crack the valve adequately at higher pressures.  Let me know if you need one.

[Back_Roads]

 Using one of Froggy's Safe packs, only 2000 psi rated. Most likely will not be high powered, Originally I was going to put this on my .22 QB but had a change of mind before I got to installing.
 Will get back to it this afternoon.

[Bentong]

Got one and prior pressurizing it...no problem going in and out the tube but when I filled it to 1500 it's not going in the tube, had to bleed it out and used sand paper to make it slide it. My tube is probably tight fit or the safepac expanded. Had no problem with safepac for my chaser. As per maker he recommends filling it to 1K and check for leak which is an advantage so you don't chase leaking when installed and filled.

[Back_Roads]

 This one has wiggle room so if it expands that much I might not use it for HPA but rather get into bulk filling

 Well I took the gun apart today, test fit Safe Pack, ran out of ambition, today for now anyway LOL, want to be more alert to measure and machine a few items.

[Back_Roads]

 I measured the twist rate of the .177 QB barrel, I get 1-18 repeatedly +- 1/2" for error seems to have 1/2" of lead in before rifling 
 I may look into alternatives if needed but will give this a go first.

[Back_Roads]

This one has wiggle room so if it expands that much I might not use it for HPA but rather get into bulk filling

 Well I took the gun apart today, test fit Safe Pack, ran out of ambition, today for now anyway LOL, want to be more alert to measure and machine a few items.

Still gathering parts and sorting out options.

[Back_Roads]

 I think I have all the parts together, just reviewing some other builds  and deciding the routes to take. May start on things again this weekend.
 Is there a better barrel band option out there

[mackeral5]

I think I have all the parts together, just reviewing some other builds  and deciding the routes to take. May start on things again this weekend.
 Is there a better barrel band option out there

Tr Robb in the UK used to offer a nice setscrew vs clamping style barrel band for QB'S.  IMO a nice upgrade over the oem unit.

https://www.trrobb.com/product/smk-qbxs-78-metal-a-frame

GMAC made them in brass.

https://gmaccustomparts.com/qb78-barrel-band-brass-9-16

[Back_Roads]

 Thanks for the links 
 Also thanks for the poppet Jason 
Also came up with some QB gold from the GTA Archives. https://www.gatewaytoairguns.org/GTA/library/Charlie_QB-78_Tune.htm

[Back_Roads]

Well I decided I better finish this up so I can do other things, opened ports a bit, don't ask how much, just enough perhaps, LOL .
 Been having a weather migraine as I  call it Lt. Dan has the same, so I'm not 50% today, but figured best to do something took me a few tries to get it together right, then I had it right and took it apart because it looked wrong.
 End results 2000 psi fill, JSB 13.34 gr. 900 fps for 5 shots then drops by 50 fps and out of air. same fill sends 5 NSA 15 gr. slugs at 800 fps and runs out of gas.
 next step would be tether it to an auxiliary tube, such as a medium size HPA filter I have on hand.

 . . .

[Back_Roads]

 So I did some serious crony work today
 ** 2000 psi     **             *            *
NSA 21gr. FB] 18gr. FB]   15gr. DB]  12.5gr.

698                 759          804           871
708                 767          804           875
713                 771          800           878
713                 770          792           860
700                 763          762           864
685                 744          736           818

 It seems to like heavier slugs and perhaps flat base ones at that 21 gr are lasers, followed by the 18, the others can get shot out of other guns I have they love them  The 21gr. edged out the 18gr. in FPE by a small margin 

 Now if NOE will get me a BBT in .178 

[Back_Roads]

 Here is more on the Safe Pack and basic mods I followed, and other things I gathered from various GTA post.

[Back_Roads]

Following along.  Assuming this kit lets you run it on a 3000psi fill, I'm curious to see what it will do.  I managed 24fpe (15gr @ 850fps) from the QB79 described here at just 1500psi regulated.  I took the porting out to about 95% of the caliber so that was a big help but the tiny plenum of the 79 is a limitation.  I'm just thinking a bell curve centered around 2500psi could put it over 30fpe without having to go crazy with the porting. 

If you haven't already, you'll probably need to swap the soft OEM poppet out with a hard plastic one (Delrin or better).  At elevated pressure, the soft polyurethane seal will likely flatten out and begin leaking, sooner if not later.  Plus it's so hard to knock open, it may not be possible to develop enough hammer strike to crack the valve adequately at higher pressures.  Let me know if you need one.

 I hit the 24 FPE with 21 gr NSA slugs, I think that might be the limit with cock on closing system on it now.

[sculbert1]

I have a 79 I'm running a regulated 1100psi regulated Ninja bottle on. I've done some valve porting and the transfer port on it. Shot it over the chrony just now since reading your thread. 12.5 NSA averages 745fps and 10.5 cpum is 815fps. 

[Back_Roads]

 I estimate my max velocity is happening at about 18- 1500 psi.

[nervoustrigger]

I hit the 24 FPE with 21 gr NSA slugs, I think that might be the limit with cock on closing system on it now.
...
I estimate my max velocity is happening at about 18- 1500 psi.

That sounds plausible.  The hammer spring is good for about 1000-1100psi with the soft OEM poppet but the upgraded poppet is easier to knock open so the bell curve is instead centered somewhere between 1500-1800psi.  If you were to decide to nudge it up so the useful bell curve starts at the max fill pressure of 2000psi, the easiest thing would be to shim the hammer spring.  Or for a more versatile setup, convert to cock-on-open by removing the rear cocking pin and tap the end cap for a RVA screw.

[Back_Roads]

I do like the cock on close, just because of how easy the bolt flys open. Will see what a bit of shim does.

[nervoustrigger]

Yeah it mostly comes down to personal preference.  I like the convenience of external hammer spring preload adjustment, and being able to feel some feedback as the pellet or slug is being seated into the leade.

[Back_Roads]

 Another thing I expected is I an still running the OE barrel orings, and get a slight puff from there, I will address that when I add  some shimming. NSA slugs feed smooth so no forward resistance besides the hammer spring.