At the suggestion of a fellow air gunner that has many tunes under his belt, I adjusted for a slightly higher fpe than my target, then backed off the transfer port a smidge to get down to my target. I did this on the Akela by replacing the hammer spring with one that is exactly 2.57", then adjusting the transfer port. The spring in the gun was only .10" shorter, but it made a difference.
Here is what I have seen:
1st 14 shot string - FPE Avg. = 14.32 ---2.47" spring. transfer port wide open. hammer adjust 1.5 turns IN
2nd 14 shot string - FPE Avg. = 16.52 --- 2.57" spring, transfer port wide open,
3rd 26 shot string - FPE Avg. = 15.18 --- 2.57" spring, transfer port ~15% closed, hammer adjust fully out.
My original target was 15fpe.
It is all subjective, but the report seems to be a little softer right now than when shooting at 14.32 fpe, certainly no louder. Also, since this is my first ever tune, I am surprised at how much a diff. made when the spring was lengthened a 10th of an inch!
Here is the final (so far) shot string and the numbers. I don't think I will fill the gun to 2900 PSI and shoot until it comes off the reg. Earlier I got to about 150 shots before that happened, so at this point I don't care if it increases or decreases 10 or so percent.
