Noob efficiency quesiton

Last night was the most I have shot my FX Royale in one sitting. While not a lot, this did equate to 5 magazines or 60 shots. All 48 shots were on high-power and with JSB 18s. My initial fill pressure was 220 BAR (gun gauge) and I shot it down to 151 BAR. According to Sikes' calculator this gives me avg 0.97 FPE/cuin per shot (17 psi used per shot at 32.5 fpe).

http://www.calc.sikes.us/1/index.php

start psi = 3190
end psi = 2190
gun tank volume = 480 cc
pellet weight = 18.1
total number of shots = 60
avg fps = 899

Again, I'm a noob with this rifle still. My hammer spring is 3 turns out from fully screwed in. My thoughts are to try backing this out little-by-little until the accuracy drops off.

Any thoughts or suggestions would be appreciated!
 
Thanks for the info guys.

Menttaliist - You're right. I do see a discrepancy of 10 bars between the gun and my tank. My rifle reads 10 BAR lower than the tank. So I did fill to 220 on my gun which showed as 230 on my tank.

Tom - Thanks I'll give those velocities a shot ;-) I had a s510 before and enjoyed shooting it on low at like 20 yards. That was a ton of fun. I am hoping to do the same with the Royale too! I ordered some 14 grain jsbs just for that!