On Friday I had my new PP Impact tuned by some local FX gurus. This is my first tunable rifle, and they saved me a ton of time experimenting with adjustments. Thank's guys! I thought some here might be interested in the results.
FX Impact MKII Power Plenum .25/700mm. 580cc bottle. JSB King Heavy MKII 33.95gr unsorted. The tune ended at 140 bar reg and an average of 956 fps. I shot the gun from 235 down to the 140 reg pressure to get shot count. I stopped at the 140 and got 66 shots which is about 1.44 bar per shot. That's three magazines easily with a 250 bar fill, and I could probably get another ten+ shots before the fps starts to drop significantly. The spread was 41, with a 941 average. That was lower than expected so after a few texts, I was armed with some tweeks to try. The gun did have about 400 pellets through it, so I cleaned the barrel. There was a lot of black gunk in there so I ran a few Ballistol patches through, then pulled dry patches until clean. I shot two magazines through today and shot string was still all over the place. I opened the VS adjuster about 1/8 turn, and that tightened the ES to 9 fps with a 956 average fps. Another slight turn of the VS and the shot string below was the result. I will be doing accuracy testing at this tune, but at 956 it was stacking pellets at 35 yards. I will be doing more fps testing to get a better idea of how much of a fluke this was.
Shot count: 16
Low: 956
Hi: 960
Avg: 959
STD Dev: 1.6
Spread: 4.0
956
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FX Impact MKII Power Plenum .25/700mm. 580cc bottle. JSB King Heavy MKII 33.95gr unsorted. The tune ended at 140 bar reg and an average of 956 fps. I shot the gun from 235 down to the 140 reg pressure to get shot count. I stopped at the 140 and got 66 shots which is about 1.44 bar per shot. That's three magazines easily with a 250 bar fill, and I could probably get another ten+ shots before the fps starts to drop significantly. The spread was 41, with a 941 average. That was lower than expected so after a few texts, I was armed with some tweeks to try. The gun did have about 400 pellets through it, so I cleaned the barrel. There was a lot of black gunk in there so I ran a few Ballistol patches through, then pulled dry patches until clean. I shot two magazines through today and shot string was still all over the place. I opened the VS adjuster about 1/8 turn, and that tightened the ES to 9 fps with a 956 average fps. Another slight turn of the VS and the shot string below was the result. I will be doing accuracy testing at this tune, but at 956 it was stacking pellets at 35 yards. I will be doing more fps testing to get a better idea of how much of a fluke this was.
Shot count: 16
Low: 956
Hi: 960
Avg: 959
STD Dev: 1.6
Spread: 4.0
956
960
956
960
960
960
960
958
960
960
958
960
958
958
960
956
awesome job!, I tuned mine 910fps same pellets 480cc bottle reg 125bar 70 shots on 250bar-125bar. similar spred. I have had my Impact since December 2016? (losing my memory) I'm loving the power and shot count, rekindled the romance with my impact.