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PostPosted: Wed Jul 02, 2014 12:12 pm 
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Location: Central West River Nova Scotia
I did 2 full strings this morning. first string with the plug removed. hammer out 2 turns.. 200 bar. 15.6 gr jsb. 55 shots. avg speed 832. fpe 24. efficiency 1.25 fpe/CI..
Second string. hammer turned out one turn. 200 bar. 13.4 gr jsb. 70 shots.. avg speed 835. fpe. 20.74 efficiency 1.24 fpe/CI.
The only thing I'm not sure of is where the 9 CI in the calculation comes from. is that the tube volume ?
Anyway. If my calculations are right, then the efficiency from yesterday and the two strings today, are nearly identical, even though there were significant changes in the data. .01 fpe/ci difference. Do you think more efficiency is achievable ? I don't mean small improvements. like .05 or .9 I mean is it possible to get 2, 5, 10 etc, percent more.
Certainly I'm happy with the numbers I got. But the quest for the best is always nagging to be pursued.

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PostPosted: Wed Jul 02, 2014 1:30 pm 
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Yes, the 9 CI is the remaining tube volume (180 cc = 11 CI minus the volume of the regulator and plenum, which is about 2 CI)....

It may be possible to get incremental increases in the efficiency, but I wouldn't expect anything major at that power level and when you already have that efficiency.... You might do better if you back down the power.... Where you are now is pretty darn good....

Bob

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PostPosted: Wed Jul 02, 2014 4:11 pm 
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rsterne wrote:
Yes, the 9 CI is the remaining tube volume (180 cc = 11 CI minus the volume of the regulator and plenum, which is about 2 CI)....

It may be possible to get incremental increases in the efficiency, but I wouldn't expect anything major at that power level and when you already have that efficiency.... You might do better if you back down the power.... Where you are now is pretty darn good....

Bob

I was figuring it must be pretty good considering I change some of the variables and still got practlically the same energy output. Slowing down the pellet speed to nearer 800 fps, might give me 10 more shots, but 10 shots more is not a big deal.
Thank you Bob for your input.
I do have one more question though. The first 20 shots uses up 50 bar, the remainder uses about 15 bar per 10 shots. Is that normal ? For the sake of 20 shots I might as well fill only to 160 bar, which will save me 30 percent or more pumping.

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PostPosted: Wed Jul 02, 2014 4:47 pm 
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Pressure should drop nearly a straight line.

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PostPosted: Wed Jul 02, 2014 4:51 pm 
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I agree Walter but the way this reg is working I loose more air per shot from 3000 psi down to 2000 when I get nearly 1 shot per 1bar. I put the last 3 strings on a graph in excel, but dont know how to post them here.

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PostPosted: Wed Jul 02, 2014 6:51 pm 
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If you start shooting right after filling, without allowing the gun to cool and topping it up, the pressure will drop drastically for the first few shots.... that's perfectly normal....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Jul 02, 2014 8:17 pm 
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rsterne wrote:
If you start shooting right after filling, without allowing the gun to cool and topping it up, the pressure will drop drastically for the first few shots.... that's perfectly normal....

Bob

Thats good to know. Also my pump reads about 2 or 3 bar higher than the gun. but I adjust for that.

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