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PostPosted: Mon Oct 22, 2018 7:30 pm 
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Location: Caronport, Saskatchewan
Oh yeah, one of these smaller filters for hand pumps work great. I notice they remove a lot of moisture and it's good to open it up to dry after having a good pumping session, (like when you fill that big tank, lol!) Here is a pic of one I happen to know where you could buy but can't tell, lol. =) Image

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PostPosted: Mon Oct 22, 2018 9:26 pm 
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Location: Vancouver BC
This QB78 is modded with the basics...

> Valve filter and rear piercing pin removed. Setup to use one powerlet.
> 1/4 hose transfer port.
> GMAC stainless extended bolt.

I have a stock hammer spring and a clipped one too.
With one CO2 (at 68C degrees) the stock hammer spring yielded 24 shots at 550fps with 18.34gr.
The clipped spring with two washer shims got me 42 shots at 490fps.
The clipped spring without the shims equaled 80 shots at 400fps.
The highest velocity it achieved with these basic mods was 610fps on a day with 28C degrees temps. That day it was shooting to 40 meters with good accuracy.

My ultimate goal is to add an 'off-center' RVA to range velocity from 500 to 700fps with 18.34gr pellets.

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PostPosted: Mon Oct 22, 2018 11:06 pm 
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That's great, I'm guessing the stock hammer spring should get you to your goal. The rva is handy. Have you modified your bolt for cock on open?

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PostPosted: Tue Oct 23, 2018 12:44 pm 
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I'm going to do a 'off-center' RVA with a 1" long 8-32 set-screw with a hex top.
Drilling and tapping an off center hole seems like the easiest way.

I plan to grind the set screw shorter so the hex head sits flush on the outside when set to 700fps.
It will stick out a bit when set to 500fps. It's a visual indicator.
The hex set screw comes with a black finish so it should visually disappear.

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PostPosted: Tue Oct 23, 2018 1:01 pm 
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At 1500psi, I’m running great at 780ish fps with 18’s. My valve and bolt don’t breathe as well as they could, with a bit more deremel work I’m sure 850+ would be easy.

Even at 1500psi setpoint, I had to trim (slightly) the stock hammer spring to tune anywhere near the knee of the curve.


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PostPosted: Tue Oct 23, 2018 4:42 pm 
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Yeah! It's funny after all these years they still have such a powerful hammer spring for co2. You'd think they'd want to save the few cents on the spring and advertise it as new and improved to make more sales. =)

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PostPosted: Wed Oct 24, 2018 9:20 pm 
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So success! I've added air and with my weakest hammer spring setup I got a consistent 144 shots at 435FPS with bottle psi going from 3000-2000psi.

It took 40min to pump up the bottle from zero to 3000psi.
Hand pumping was interval timed; 2min of pumping followed by 3min of cooling time. The pump got warm allright!

It took 7min to pump from 2000-3000psi. with a single 2min cooling break. (so 5min of actual pumping)

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PostPosted: Wed Oct 24, 2018 11:58 pm 
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I tried it without the bottle and just filled the QB's tube to 1500psi.
With my weakest hammer spring I'm getting 30 shots, amazingly, but...

For the first 5 shots the pressure is too much for this weak hammer spring and it shoots low and slow at 390fps.
Then over the following 10 shots the velocity jumps to 420fps and climbs to around 480fps.
The last 15 shots all came in around 480fps with one peaking t 501.
Then velocity dropped quickly over just three shots making a fart sound instead of a snap.

Shooting with the PB regulator is definitely more consistent.

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PostPosted: Thu Oct 25, 2018 9:17 am 
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That was pretty quick pumping from 2000psi to 3000psi psi with that hand pump. Nice!


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PostPosted: Thu Oct 25, 2018 11:53 am 
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Just did it again! 4min 22sec from 2000-3000 with no break. Getting peck buff ;-)

BUT SOME WATER!
I've pumped up the bottle from zero once and three time from 2000-to- 3000psi; and the QB's tube five times.
After all that about a teaspoons of oily water came out the pumps bleed valve when tilted back.

I'm definitely gonna need to get a filter. I was hoping a hand pump would not generate water thinking that was a compressor thing.

Good thing I have to tear my QB down for the RVA mod today. Good chance to look for water inside.

I blasted air out the bottle (nothing attached) onto a paper towel but no sign of water came through. So thats good.

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PostPosted: Thu Oct 25, 2018 7:34 pm 
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What happens to your FPS when you get below the regulator setpoint? My guess is it climbs over 700fps for a pile of shots.


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PostPosted: Sat Oct 27, 2018 11:11 am 
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Yes it does climb but I didn't get to chrony the effect.

I noticed this climb the most when filling the QB's tube directly (sans bottle)

It was obvious in the scope; hitting low then ontarget, then high, then really high.
With my weakest hammer spring setup I was getting 24 shots with just the QB's tube alone. So I could see the POI string up and down my target.

Ideally, I don't shoot the bottle below 2000psi to keep hand pumping to a minimum.



I have a gauge on the output side of the reg (like yours) and that helped me put together the relationship between the hammer spring and the pressure.
My 1500psi reg is actually 1700psi and I think this is too much. Will order up a 1200psi reg that will probably run at 1400, eh?

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PostPosted: Sat Oct 27, 2018 2:01 pm 
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.

The small gauge on the PB adapter is reading over its 1500psi supposed set point.

Attachment:
1700psi-1.jpg
1700psi-1.jpg [ 113.59 KiB | Viewed 466 times ]



So I tried screwing the gauge from the hand pump into the PB adapter. Now I have a more precise reading of 1700psi for the regulated output.


Attachment:
1700psi-2.jpg
1700psi-2.jpg [ 115.39 KiB | Viewed 466 times ]



Operating at only 100psi headroom is not what I had in mind.

I also had to throw everything I have at the hamerspring to overcome the pressure.
The setup I used for one CO2 powerlet was; weak spring and two washers. That got me 520fps on a hot August day.
With my strong spring and CO2 this moded QB peaked at 610fps
But that setup was still shooting at 435fps on 1700psi HPA.
It took my strongest spring and THREE washers to get it hitting hard! Chrony numbers tomorrow.

Here are some pics of my hammer spring setup.
Attachment:
hamersprings.JPG
hamersprings.JPG [ 403.96 KiB | Viewed 466 times ]

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PostPosted: Sat Oct 27, 2018 7:18 pm 
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I picked up a tin of CHPP from C-Tire for the consistency testing because I didn't want to use my mail-order JSB 18.1 to test with.

Bonus good news - the 14.3gr CHPP, which were intolerably inaccurate at 500fps, are preforming really well with a tad few fliers at this higher velocity.
Probably around 700. I'll find out on Sunday for sure.

Anyway, on my first test I got 110 shots from 3000-2000psi with clover lief hole consistency. Overall, a tighter than 1/2 inch spread shooting standing with a tripod at 12meters 16yrds.
Thats kinda too many shots for one session. I'm liking the idea of 50 shots with three minutes of pumping the bottle from 2500-3000psi. That's eazy.
Pumping it up from 2000 takes 7 min with a break and feels like a real workout.

Sunday is HFT Club day at Mission Rod & Gun Club. Got this together just in time.

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PostPosted: Sat Oct 27, 2018 9:42 pm 
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Nice amount of shots! I hear you on the amount of pumping though. =)
If you got the 1200psi regulator you could pump from 1400 to 2400 and not work the pump so hard and probably get just as much velocity or even more.

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