You take the bore area times the pressure, and multiply by the barrel length, and you end up with the total FPE that can be produced
Except the barrel length is in feet!.... Maximum FPE = 343 FPE.... and 40% = 137 FPE....The reason being sq.in. x lb/sq.in = lb.... Multiply by the barrel length in ft. to get ft.lb energy ("x" lbs. acting over "y" ft.).... I guess I should have included that, sorry.... I added that to the original post about max. FPE.... Bob
rkr, you are correct that 3600 psi is high, but with 300 bar/4500 psi bottles readily available, it is within reach, even with a regulated PCP.... If you are tethered to, or filling from, an 88CF SCBA bottle that starts out at 4500 psi, you will have 900 psi of "headroom" (pressure available), times the 550 CI internal volume, which even allowing for the VanDerWaals correction should give you about 30,000 std. CI of air available.... An 80 gr. slug at 1000 fps is almost 180 FPE, so at 1.0 FPE/CI efficiency that should give you about 160 shots or so.... Calibres smaller than .257 will of course get more shots (with less recoil as well)....If you scroll up to Reply #7 and look at the chart, the RA4 and G1 BC's are the same at just over 900 fps, so if you checked your BC at that speed, they would have been the same.... The BC(G1) is lower than the BC(RA4) below that velocity, and higher above that....You are of course correct that shooting at the most accurate velocity for your slug is of paramount importance.... By selecting a slug with a low enough SD that I can push it at 1000 fps without having to tune the gun as an "Air Hog" gives me the ability to do so, it is always easy to tune it slower if that is more accurate.... It may well be that shooting a heavier slug slower could produce better results.... Shooting at 950 fps only increases the drift about 8%, which could be made up by using an "equally slippery shaped" heavier slug at a lower velocity.... However, the lighter one, shot at 1000 fps, will have a flatter trajectory than the heavier one at 950.... Sighted at 100 yards, a shot at 300 yards will impact about 10" higher using the higher MV....The change in my thought process just gives me more options.... Previously I was designing and selecting slugs with the idea in mind of shooting them at 900-950 fps.... Now that we are finding that their drag is less at 1000 fps than we thought, I am encouraged to work on lighter slugs as part of my "inventory" of possibilities, which affects both gun and slug design....Bob
....300 yards.... 12.49, 12.35, 12.33, 12.46, 12.72" (lowest drift at about 1015 fps?)400 yards.... 22.63, 22.34, 22.22, 22.31, 22.61" (lowest drift at about 1026 fps?)500 yards.... 36.09, 35.56, 35.27, 35.27, 35.56" (lowest drift at about 1037 fps?)600 yards.... 53.05, 52.20, 51.68, 51.52, 51.74" (lowest drift at about 1048 fps?)700 yards.... 73.71, 72.46, 71.62, 71.23, 71.33, 71.87" @ 1100 (lowest drift at about 1060 fps?)That assumes a perfect match to the RA4 drag model, of course, which is unlikely.... . Bob
.... The SLG1 has a faster increase in drag above 1000 fps compared to the RA4 model…Bob
We discussed Ted Bier's "magic BC" results when driving .22 PCP slugs to 1100 FPS, a while back. As I recall, we assumed his flattering POI drop results had to do with barrel harmonics and scope above bore height, rather than velocity retention. Going back to Ted's video, he zeroed at 50 yards and then looked at the reduced drop at 100 yards. So, perhaps his BC calculations might warrant a second look:
Yes!!!!
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