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Old 01-22-2017, 10:58 PM   #2
Clifford
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Join Date: Oct 2012
Posts: 86
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Attempting to find my solution I ordered a super hat from Airguns of Texas. While I was waiting for it to arrive jward sent me a link to a TAG thread where an oring was used to reduce the TH throw. I just happened to have the o ring here so I installed it and began my testing again.

o-ring size used: 1/4"x 3/8"x 1/16" (found in the HF nitrile o ring set)

In the TAG thread a TH spacing of 0.09" was initially used but I started higher based on using heavier pellets. I'll spare you some extra failures here and just suffice it to say that 0.09" is a decent starting point when using the o-ring in .25 caliber. At 0.09" I was shooting a decent curve at 915fps with the 33.95gr heavies. Still too hot for my liking. At this point I knew I only needed a slight reduction and coins with stacked feeler gauges can only get so accurate. From here I turned the TH down 1/8th of a turn.

TH 0.090"-1/8th turn PW 3
875
869
869
876
868
889
893
876
880
887
887
890
893
890
889
890
885
887
887
888
881
879
882
880
881
881
881
880
877
873
872
871
865
863


The shots in bold are what I have "trimmed" the string to. I will have better fill pressures when I get a more accurate gauge but for now I'm hand pumping and neither the hand pump nor the AF gauge seem very accurate. On the AF gauge this string was from somewhere around 2800psi to around 2000psi. The hand pump gauge and AF gauge are within 200psi of each other.

25 shots within the 20fps ES range averaging 884fps. Average FPE comes out to 58.9fpe.

I feel pretty happy with this curve. At least enough to mount the scope and do some shooting.
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