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PostPosted: Tue Jul 24, 2018 12:52 pm 
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Location: Caronport, Saskatchewan
Looks good! Did you glue a rail to the bottle for that bipod?

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PostPosted: Tue Jul 24, 2018 6:41 pm 
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No rail, the single pipe clamp holds the stock, bottle, and bipod in place.

I got a chance to run a full string today. Bad news is that I wildly over-predicted my shot count/efficiency. Closer to 100 shots @ 24fpe from 4200-1350 (efficiency is around 1.1)

The good news is my extreme spread is holding solid, not a single shout outside of 770-785.

Not sure what I need to change to improve efficiency, or if I should just accept that that’s what I'm getting. It’s tuned right to the knee of the curve, I expected a little better maybe.

That aside I’m super pumped about how it shoots,


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PostPosted: Tue Jul 24, 2018 8:57 pm 
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That's great you can get quite a few more shots after falling off the reg, anyway, and that the es is nice and small. Maybe Bob will have some suggestions for improving g efficiency. I need to do a test with mine as well and see if it has lost a lot of efficiency now that I've put a regulated bottle on. I was getting pretty astounding accuracy for my skill level in tuning before, but I'm kind of suspicious that regulating it has dropped mine considerably as well.
Looks good, your setup, congrats on a successful project!

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PostPosted: Wed Jul 25, 2018 8:48 am 
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Here's where I got the new bottle and reg, I got the 200cc/1500psi output...
https://www.aliexpress.com/item/PCP-Pai ... 4c4daWE8Fb

Arrived in a few weeks, finish was good. Regulator works great (I haven't opened it up). I fill to 4200 as I don't want to stress my hand pump to try 4500. From full to set point, the regulator output only varies by about 50psi. It also creeps about 50psi if I let it sit for a while, so 100psi total variance from 4200-1500psi. I'm able to get a 2% shot string from 4200-1350psi, and I'm hardly a tuning pro.

Edit: I should mention the 1500psi regulator came with a 3000psi low-side burst disk. Plan on swapping for a 1.8k.


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PostPosted: Mon Jul 30, 2018 7:16 pm 
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Final efficiency numbers:
4500psi to 1500psi (setpoint) = 143 shots @ 24fpe

Efficiency = 1.36 FPE/ci

JSB 18's average 775fps with an extreme spread of 16fps.


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PostPosted: Tue Jul 31, 2018 12:04 am 
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Nice, that's pretty good! Lots of shots. Pumping to 4500psi would be tough with the hand pump though, at least I think so!

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PostPosted: Tue Jul 31, 2018 6:42 am 
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I think it all depends on your hand pump; it’s only th last few hundred psi that require me to really put my back into it.

Shot three 10 shot groups at 70 yards last night, aside from one flyer they were all under an inch.

I’ve been hoping to try out some field target at some point, this might be the rig. Not sure how light a pellet I’d need to bring it below 20fpe.


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PostPosted: Tue Jul 31, 2018 8:42 am 
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Great shooting! Yep sounds like a great gun for field target, though I know nothing, I'd like to try out ft as well. =)
Have you thought about getting a magazine adapter for it? $59 US can get you a 9 shot magazine with auto indexer, shipping included. =)
Sellers name is Lukas
amerlock@volny.cz

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PostPosted: Tue Jul 31, 2018 10:42 am 
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Location: Vancouver BC
Great project and thread! I've sorted out bent barrel issues with my QB and am ready to do basically the same thing.
I like this setup because I think it's safer to have a flexible connection hose between bottle and gun compared to some rigid connections done with metal fittings.

But that hose is way to long eh?
So I wanted to share this link to a site that sells very short 4, 5, 6 inch hoses.
I haven't ordered from them but these hoses are so cheap I could order two or three sizes to get the best fit.

https://www.ansgear.com/Paintball_Fitti ... _s/117.htm

This 5.5" hose would seem to be a perfect fit.
https://www.ansgear.com/Stainless_Steel ... hose55.htm

These are bare bones hoses, no fittings, no swivels but I think they would screw direct into the bottles paintball valve and the QB's fill cap, no? Of course you could add a QD fitting.

Locally I called around to Paintball shops and then industrial hydraulic shops. The PB shops only had long remote lines and the industrial shops only had huge 1" diameter tubing in the braided steel jacket I'm looking for. This site is the only source I've been able to find with pre-made short hoses.

Whatdayathink? Good way to interface a PB bottle? I'd use it with the the Scope&Ammo fill adapter which has a 45deg inlet hole so I could use the even shorter 4" hose to go between the bottle and gun. I would mount the bottle in the same basic way, steel strapped to the bottom of the stock.


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PostPosted: Tue Jul 31, 2018 11:18 am 
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If you go to the bottom of page 3, there's an updated pic with a new hose. It's 3.75" (4" would probably be ideal), attached to a quick release at the air cylinder.

Since I can't de-gas the rifle, it's convenient to be able to empty the gun without emptying the tank. I can shut off the valve on the bottle fill adaptor, dry fire 10-15 times, and then un-hook the quick connect from the air cylinder. I removed the check-valve from the air cylinder quick release, so once the hose is disconnected I know 100% that the rifle is empty.

From a safety standpoint, I prefer the hose to standard NPT fittings. If anything was going to go "boom" from too much pressure, the o-ring on the quick disconnect should be the first thing to blow. That's on top of the regulator and 1.8k burst disk keeping the rifle pressure in the safe zone.


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PostPosted: Tue Jul 31, 2018 12:43 pm 
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Sorry, missed that pic but yes. Exactly what I was thinking.
Now that I see it a straight filler cap looks better than the 45deg one.
And I'll include a QD too. Great de-gassing tip. Not much left out on this thread.

Where did you source the short hose?

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PostPosted: Wed Aug 01, 2018 7:16 am 
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wesb2007 wrote:
Great shooting! Yep sounds like a great gun for field target, though I know nothing, I'd like to try out ft as well. =)
Have you thought about getting a magazine adapter for it? $59 US can get you a 9 shot magazine with auto indexer, shipping included. =)
Sellers name is Lukas
amerlock@volny.cz

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I keep going back and forth on adding a magazine. I’ve got the scope clearance for it.

Thanks for the link!


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PostPosted: Wed Aug 01, 2018 9:01 am 
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Pushtone wrote:

Where did you source the short hose?


I'm pretty sure I got it from Badlands Paintball. Cheaper options, but they got it here quick.


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PostPosted: Mon Oct 22, 2018 2:53 pm 
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Location: Vancouver BC
I've got all the bits to put together a HPA conversion for my QB78 based on this thread. I'm trying to keep it close to the same setup.
> 0.35L 3000PSI bottle
> 1500psi output regulator
> GMAC Fill adapter from CSS
> Stock hammer spring
> Clipped hammer spring
> I'll be using a hand pump to pressurize the system.

I have the fittings assembled with the bottle secured to to stock in a solid but temporary fashion.
I plan to disassemble one more time to apply teflon tape to some fittings.

QUESTIONS:

Should I clean the insides of the QB78?
This gun was used with Crossman CO2 powerlets that have oil in them and I use Pellgun Oil on the powerlet tips and to lubricate the hammer and trigger. I does not feel oily inside the air tube but the hammer is slick with it.
Is this oil going to explode if I don't clean it out?
Should I clean out the air tube before I pressurize it?
If so, what can I lubricate with after the HPA conversion?

Burst discs; I have a 5k disc on the bottle side and a 1.8k on the output (1500psi regulated output).
Does this 5k on the bottle side sound right? I also have a 3k and 7.5k on-hand.
Should I apply teflon tape to the burst discs?

The regulator's fill port has a brass screen mesh blocking the opening. It's wrinkled and squished in there.
Do I remove this screen?

Should I invest in a water filter/separator to go between the hand pump and the regulator/bottle?
I'm not sure if water buildup is a problem only for compressors or if it can happen with hand pumps?

Thx
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PostPosted: Mon Oct 22, 2018 7:26 pm 
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Location: Caronport, Saskatchewan
Cool =). I'll probably miss some of your questions and someone else could answer. Have you taken the valve out and removed the fiber piece inside it? That'd be a good idea first, before it plugs everything up with the higher pressure blowing through it. You could clean the tube then if you want. With the 1.8 burst disk you shouldn't really need to worry about the Pellgun oil as it is not going to ignite at 1500psi but won't hurt to clean and put silicone oil or silicone grease on the orings for sealing things up. You can buy silicone oil cheap on amazon.
Did you put a bigger transfer port in?
Cheers,
Wes

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