just got the finishing touches done on a mod 700 with 28" barrel in 22-243 Win. It is a nine twist designed with the 75 grain A-MAX Hornady in mind. I would like to use imr 4064 powder as I have plenty of it on hand already. The builder recommends 44 grains of reloader 19 behind this bullet but he isn't against trying other formulas. One of the computer loading programs (loadpro I think it's called) recommends 36 gr of 4064 as a max but this seems a little low. Anyone got any ideas about 4064 in this round?
Thanks, Drake

22.243 is a magnum ratio case for 224 bore , powder under 4350 burning rate are too fast , best is to go with 4350 as starting powder .

22.243 is a very fine easy hight velocity 224 cal but if you want to get real hight velocity caution to over pressure and use only slow powder .

good shooting

Drake, I do not own a 22/243, but I have used numerous 224 wildcats that have a case capacity of 50 grains or more.

I assume that water capacity of your case would be between 52 and 54 grains. This is a little more than the 49.7 grains of the 22/250 AI, that I am currently using.

I believe that IMR 4064, which was my powder of choice with the 55 grain bullet in an earlier 22/250, and 22/250AI,is much to fast for use with the 75 grain bullet. It would leave considerable airspace in the case, which in my opinion is not conducive to good accuracy.

I will give you a better perspective of the usable case capacity of your 22/243. In my 22/250AI to fill the case with powder to the base of the neck, it takes 43.5 grains of a long extruded powder such as IMR 4064 and 7828, 44.5 grains of a short cut extruded powder such as Re22, H4831sc etc, and about 46.5 grains of ball powder (WIN WMR). Your 22/243 would probably take 2 to 3 grains more.

I have just finished testing and chronographing the 69 grain Sierra HPBT with various powders in my 22/250 AI, with 1 in 10 twist barrel. I tested IMR 4831, IMR 7828, H4831sc, Re 22, WIN WXR, WIN 785, WIN WMR, Viht 165, and Viht N560. I achieved sub .5moa groups and 3,300 to 3,400 fps with all.

I would recommend starting with powders such as Reloader 22, Viht 165, or WIN WXR. Also you might just have enough case capacity for H1000 and Reloader 25 to work well with the 75 grain Amax. Good luck, Brian.

Thanks for the input, looks like I'll have to explore those ideas. Thanks again, Drake