I am planning on getting a custom accuracy international AW .243 which will be used primarily for long range targets and also a bit of deer and goat hunting. I want to use 115gr DTACs and want the max possible velocity and accuracy for optimum range, but not so long that I start to lose velocity. I have heard that a twist rate of 1:7 or 1:7.5 is best..?
weight isn't really an issue so I want the barrel as good as possible.
I would appreciate any help. thanks
The 115 DTAC will stabilize in a 8 twist but if you can't find them and have to use some 115 bergers they won't do so well. With cut rifling I'd have a custom 7.5-7.8" twist then the 105s won't be spun up to hard if you find that you want to try them or the 107SMKs. But as stated I'd go 243AI or 6mm rem for the extra 1-150fps with like a 26" NBRSA heavy varmint contour 1.150" tapering to .925" @ muzzle.
how much would it cost to get the chamber enlarged for a 243 AI? that would be the simplest improvement. would this give a noticeable decrease in barrel life or is it not that bad?
what is the advantage of having a tapered barrel? surely it would just be less rigid than a straight one..?
and how much of a velocity increase would you get with a longer barrel, and when does it become so long that velocity decreases?
thanks for your help so far!
Having a slight taper ( atleast .050" is actually better harmonic wise) with a 6mm cal anything past 28" is just extra weight. If you want to keep it simple, use a standard 243 with an 8 twist at 26-27" and use 105 amaxs, 105 berger vlds, or 107 SMKs and it'll do all you need. I have seen 6x47 lapuas with a 26" 8 twist and 105 bergers shoot 2.5-8" groups at 1k.
a 51mm case needs nothing longer than 25" with the right powders. But a 24" would be much better due to harmonics alone. A #7 contour at 24" ought to be nearly twice as stiff as a 28" barrel in the same contour. It's obvious that the action length won't take a longer case, and thus your stuck with that case. I'd be looking for something completely different than the .243; yet somewhere close to that length. A Dasher or a 6BR would be high on my list. Myself, I'd order in a 6BG reamer and build that one or else a 6BR