Lots of testing today.... I used my new adjustable inline regulator and tethered the gun to my SCUBA tank.... I started out at 2400 psi, with the hammer travel set at 0.9", which gives me about 0.15" of lift available before the hammer hits the bumper on the back of the valve.... I tried four different pellets at every hammer spring preload setting from coil bind to 8 turns out.... Here are the results....



The velocity curve with the JSB Kings is exactly what I have come to expect.... a plateau (at just above Mach 1), and then rolling over the knee of the curve into a nearly linear decline.... As the pellet weight increased, the knee moved slightly to the left (to higher preload), and eventually at maximum preload it started to drop again.... I had concluded previously that this is because at high preload the hammer is bouncing off the bumper on the back of the valve, shortening the dwell.... Why this seems more pronounced with heavier pellets I am not sure.... To check this, I reduced the hammer stroke 0.1", which increases the maximum lift that can occur by 0.042" (so the hammer doesn't get to the bumper).... I retested the lightest and heaviest pellets and the drop in velocity with the heavy pellets at maximum preload was gone.... I then reduced the pressure to 2000 psi, and then to 1600, and repeated all the preload settings at each pressure for the JSB Kings and EunJin Points....



I don't recall ever doing a chart quite like this before.... It actually is pretty interesting.... The point at which the curves cross over is where the velocity is the same at two different pressures.... Where the 1600 and 2400 psi curves are crossing, and the 2000 psi curve is just above where they cross, is a potential tuning point for a bell-curve.... I set the gun up for that point with the Kings, fine tuned the RVA and the fill pressures slightly, and got my first shot string....



There are only 7 shots, but they average over 60 FPE, are within a 4% ES, and only use 750 psi of air.... That works out to an efficiency of 1.00 FPE/CI, not bad for a first effort.... Before I started this round of changes to the gun, I used to get 11 shots within a 5% ES, but at only 45 FPE, and using 900 psi of air, for 0.96 FPE/CI....

Here is a summary of the results to date....

3000 psi:
25.4 gr. JSB Kings - 1219 fps (83.8 FPE)
30.9 gr. Baracudas - 1158 fps (92.0 FPE)
35.2 gr. EunJin Domes - 1115 fps (97.2 FPE)
42.4 gr. EunJin Points - 1055 fps (104.8 FPE)

2400 psi:
25.4 gr. Kings - 1160 fps (75.9 FPE)
30.9 gr. Baracudas - 1100 fps (83.0 FPE)
35.5 gr. EJ Domes - 1045 fps (86.1 FPE)
42.4 gr. EJ Points - 986 fps (91.6 FPE)

2000 psi:
25.4 gr. Kings - 1087 fps (66.7 FPE)
42.4 gr. EJ Points - 933 fps (82.0 FPE)

1600 psi:
25.4 gr. Kings - 1004 fps (56.9 FPE)
42.4 gr. EJ Points - 854 fps (68.7 FPE)

I'm very pleased with these results, particularly at the lower pressures.... The increase in performance over the previous version is very satisfying....

Bob