What speed does the 44.75gr JSB pellets like out of the Impact?
Just grabbed a 700mm barrel!
Just grabbed a 700mm barrel!
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Speed for .30 cal Impact w/JSB 44.75gr
- Thread starter HavocX
- Start date
I don't think you can get to the speed that the 44.75gr JSB's get unstable with a stock Impact, even with the 700mm barrel. I would tune it up to max and then do some groups to see if backing off helps the accuracy, but on mine it didn't-- 3-shot groups under 1"/40 yards even at max hammer spring, 150 bar reg pressure. The smaller cal JSBs are good into the low/mid 900 fps range, and these heavier 30 cal versions are likely to be even a little more stable into transonic from what I've been hearing.
Mark 2 Impacts are rated for 865 fps in 30 cal with the 700mm barrel, but you should be able to exceed that without much trouble, especially after a couple hundred pellets fired. Mine is a bit faster than that even with a 600mm barrel, but I'll have more data after this weekend when my new chronograph shows up (knocked my old Caldwell over on its tripod and it's on the fritz :- O ).
Mark 2 Impacts are rated for 865 fps in 30 cal with the 700mm barrel, but you should be able to exceed that without much trouble, especially after a couple hundred pellets fired. Mine is a bit faster than that even with a 600mm barrel, but I'll have more data after this weekend when my new chronograph shows up (knocked my old Caldwell over on its tripod and it's on the fritz :- O ).
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