Weird numbers?

[Laz]

Hey guys, after trying a few hammer bolt adjustments on my Concept, I thought I had it figured out. When I set the the bolt to 4.5mm protrude, it averages 12 or so shots at 750 fps with 21.14gr pellets. The shot curve looked okay too, with a less than 20 fps Extreme Spread for those 12 or so shots. 

So I thought, if I lengthen the hammer bolt, therefore shortening stroke, I'd see a loss in velocity but a few extra shots and mayber flatter curve. So I turned the hammer bolt  to about 8mm. Results are horrible.

What I'm asking is,what can my gun's valve/hammer set up possibly be doing to produce such wild numbers?? Any advice or info much appreciated!

Here is the awful, wild shot string, from 190 Bar. Same pellets, 30 shots.
766.8 
721.9
720.7
722.5
725.7
726.6 - 1 clip
728.6
735.3
731.8
732.3
740.2
731.4- 2nd clip
769.2 
767.6 
766.4 
729.1
731.4
766.4  - 3rd clip
725.1
721.9
722.6
761.3 
762.6 
753.1-    4th clip
723.0
717.8
717.7
718.0
708.0
708.1- 5th clip, shot number 30, 100 BAR left in the tank.

As you can see, after I tried lengthening the hammer bolt/shortening stroke, it seems to want to average 720-740ish, down from 750s avg, but now has wild shots in the 760's?! 

[Laz]

Any ideas why the velocity jumps around so drastically?