I shot out a lot of 243 barrels on Chucks, p. dogs, jack rabbits, and Coyotes. My primary load in custom and Rem 700 barrels was 39g+of IMR 4064 with an 80g Sierra single shot pistol bullet(no longer made). Just at the point where you see the very mildest pressure with this load, is where the best accuracy is. The velocity ran 3400 fps on custom 12t, zero freebore, 26" barrels. This
IMR 4064 and Varget are rough on barrels, and so is R#15, 4895s, and 8208. I measured the OAL to the lands every 100 rounds. When loading up several hundred, I would always seat the bullets .100 long, then adjust the seating depth to what the barrel liked.
Almost without exception, the best accuracy is where the bullet was just .003 or so off the lands, and I am talking about 3/8" accuracy and MUCH less.
If your climate permits, AA2700 is the coolest burning powder to use, it is accurate and fast, with Win 760 being a great second choice with cci 250s taking the SD down below 10 fps.
In my custom 243's, the 60g Sierra HP, 70g Ballistic tip, and the 80g Sierra are instant Killers with amazing accuracy. We also had fantastic accuracy with the 65-75g Benchest bullets I made off of J4 jackets working excellent on p. dogs, chucks, and coyotes.
As your throat keeps getting longer, you keep seating your bullets out, then go to a bullet with more bearing surface to maintain accuracy, and look no further than a 100g Hornady btsp, 100g Speer btsp, 90g Speer, 95g SST, and Hornady 87g V max. Sierra .243 bullets are rare and since they are not available, I did not mention any of them. Nosler bullets are also not available.
R#26 with cci 250 primer will push the 100's at 3200 fps in the 243 unless you are running a short barrel.
ON all my custom barrels, I start off with zero freebore for varmint rifles, and this has worked fabulously on all bullets 80g and less.
AA2700 and Win 760 are fantastic powders for the 243 unless you are hunting in super cold weather.
On our p. dog hunts, I carried a 5-gallon bucket full of neck-turned 243 and 243 AI. I saw .070-.110 leade growth per bucket fired, depending on how hot and heavy the shooting was. We shot Max Heavy Varmint contour barrels that started off with 5" of straight on 12 twist barrels. The AA2700 and 760 was gentle enough on the barrels to where we could set the barrel back twice as 243 or AI, then the third chamber became a 6 BR at around 24". We did not let the leade get completely shot out before we set the barrel back, and by doing this, we got 10,000 rounds on Hart SS barrels. Kriegers may last longer, don't know. My hunting partner and I ordered Hart barrels ten at a time, as we were shooting 20,000 rounds a year and some years more.
