Day 2:MROD tuning .22 (better results)

I did some more tuning with my .22 MROD and I shot a pretty good string with the Crosman premier 14.3 The high fpe shot of the string yielded 31.12 fpe @ 990 fps

SP 3100 psi
Hammer spring preload: 3 turns in (halfway) from longest travel.
Hammer stroke : MAX (counter clockwise) Note: any adjustment in with this high of a fill pressure caused the fps to drop significantly…
Transfer port metering screw 3/4 turn in from “wide open”

14.3 CP (brown box)
958
966
957
977
967
965
975
984
985
983
986
987
989
988
990
987
987
986
982
979
978
971
971
967
960
958
960
957
ep 2100 psi
es 33

I decided to give some heavier pellets 21.10 gr Kodiaks a try with the same start pressure, same settings. I think a turn or two on the hammer spring preload will get me into the curve much quicker…and I will try this next time I test….but overlooking the slow climb, the heart of the curve was very nice indeed!

shot #23 yielded 36.044 fpe @ 877 fps
803
804
803
827
821
828
832
836
843
856
850
854
862
862
866
868
869
874
861
860
864
872
877
872
874
873
870
865
862
960
856
end pressure 2100 psi
I tried a fill pressure of 100 to 150 psi less and it gave me an average velocity of 10fps slower than the one above, but it dropped off quickly after shot 26. I’d really like to stick with a 3100 psi fill for the purpose of this tune, so I am thinking some more hammer preload is the answer perhaps with a little transfer port metering screw adjustment.

I am curious to check out my accuracy with this new setting as the shorter hammer spring travel should yield less “hammer bounce”, ie. recoil.

I do have a question for those more familiar with the crosman premier brown box .22: what speed do these pellets prefer to travel for the best accuracy?????? Thanks!

80 Grit