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PostPosted: Tue Jun 14, 2016 11:32 pm 
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Joined: Tue Oct 13, 2009 1:27 am
Posts: 2514
Location: Vancouver
Well that's good I suppose, but I lack a clear notion of just how I'd find where it was off-reg. My normal shot strings without the bottle, from about 1,300psi down to 900psi, look like 748, 735, 725, 716, 708, 699, 692, 684, 675... at which point I'd stop. I did manage a few variations on the tuning where there was more of a peak in the middle than a straight drop, but since I was aiming for the quietest shot (least air wasted) at just under 700fps none of those tunes worked out. Seems now that somehow the bottle is dropping below regulator setpoint... which I didn't think was possible. Doesn't it take pressure in the bottle equal to or higher than the setpoint to open the regulator seal enough to sip air into the main cylinder? But when I put the pump to it, after those 2 extra shots beyond the 125th shot, the pump gauge showed just over 900psi before it stopped filling the hose and started moving air into the bottle. Again I seem to be misunderstanding air and spring behaviour.

If I completely discount the main cylinder volume and take a wild guess at where it dipped below 1,200psi, I'd say it was around shot 120. If I plug that into Sikes I get an efficiency of 1.41fpe/ci. Which is cheering, and not such a big leap to get beyond 1.5, and explains why the air dump seems considerably lower than at any other setpoint above or below 1,200. Just not sure if counting 213cc as the volume and 3,000 to 1,200psi is 'fair' math.


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PostPosted: Mon Jul 25, 2016 3:21 pm 
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Joined: Tue Oct 13, 2009 1:27 am
Posts: 2514
Location: Vancouver
'Final' report on this build I guess, in the sense that at last I got to take it out for an HFT session yesterday in Mission. Shot two rounds and scored 28/32 and 30/32 with a few standing shots but mostly seated on a tripod folding camp stool, the low sort, elbows rested on thighs. My misses were all me. At HFT distances the thing can't miss if I do my job. And it's consistent enough down to a reading of 1,000psi on the gauge that I just shot until that level then pumped up, didn't have to count pellets. About 130 shots before pumping.

Also did the 75 yard thing from the same position on the stool, but much worse groups, I think mostly because I like using the simple crosshair reticle of my Leupold 2-7x VX-1 for shorter ranges but hadn't really thought about the benefit of mildots for longer distance shooting. The 75 yard target made it clear that if I ever do decide to do more long range stuff I'll have to get myself a mildot scope. Guessing at 3x the length of the thin reticle line down into the thick one gets a bit hard in terms of concentration, trying to think about that exact proportion while maintaining horizontal alignment seems like too much to think about while getting the shot gone. A nice little dot to align on the paper bullseye would be so much easier. But for HFT distances it's not an issue so for now I'll stick with the VX-1, which offers all the clarity I need and easy holdover estimation for out to 45 metres.


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PostPosted: Tue Sep 13, 2016 7:15 pm 
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Joined: Sun Jan 17, 2016 1:38 pm
Posts: 113
Very Nice.


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