That is a pretty good spread. But to tighten it up, I'd find the knee of the power curve. First max out the hammer adjuster and power wheel. Then slowly measure power output at one pressure setting or another till you find what pressure peak power output is at. The pressure gauges arent all that accurate, sadly. So I can't tell you what that pressure is. Once you find the most powerful regulator setting, dial it back 5-10 bar.
Repeat the same process for the hammer tension adjustment. Find peak output setiing, and dial it back a little bit.
The hammer tension on my FX is set at the precipice where power starts falling off HARD. That way, when I do turn it down, I've got a huge range of adjustment. This is also a very efficient spot to be in. In regards to very low valve dwell time for relatively high power output. Muzzle report should be pretty tame as well as a result of low valve dwell.
For more consistency you want to dial the power up a hair from here, so the gun is still under peak output, but is not all that much lower. The power curve will be a good bit flatter here.
But the other variable is harmonics... if you're searching for supreme accuracy. Without an oscilloscope, it's a game of try and see. Slug type/weights, and power level adjustment experiments, until something works. Honestly, though, my latest go at tuning for slugs was anticlimactic. New liner, new barrel, did carbon fiber bond the liner. 21gr LDC .218s, and it just worked. Max power, no adjustments. Just a sight in.
Red bar here indicates my tune, on the left side of the curve. Green bar would be a little less efficient, but more consistent.
