Re: 243 AI ?
First off Varget is a bit fast for bullets in that range , it can be used but you'll end up with a case thats nowhere close to being full and that will generaly not give the best accuracy. I found VV-165 and VV-560 to be great choices for this round (the VV-560 is a high energy powder and burns hotter so that will reduce barrel life) Also 4350 and R-22 are fgood choices for this case with bullets in that weight class.
As far as speed , 3000fps is fully realistic , maybe 3200fps depending on the bullst barrel make and brass used , but I'd say anything higher than 3200fps out of a 24" pipe would be a hot load.
I have noticed that most match type bullets don't like being pushed hard anyway and I have also found that 2800-3100fps is a good nich for accuray with match bullets in just about all calibers
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