best barrel length for .243 ?

[Rizla]

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

 

[sinarms]

are you stuck on 243? 243 AI, 6mm rem, 6mm rem AI, 243 wssm, 6-06, 6-06ai, 6mm WSM will all give you more velocity if that is what you are looking for. and I would go 1/7 with a 243.

 

[Rizla]

yeh i'm pretty much stuck on with the 243. accuracy international only make the AW in 243, 308, 300 and 338. the 243 is all i need, i just want to be able to maximise the range i can get out of it.

 

[backwoods83]

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.

 

[Rizla]

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!

 

[backwoods83]

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.

 

[Trickymissfit]

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
gary

 

[Rizla]

correct me if i'm wrong but all the ballistics information i can find on the internet seems to point towards the .243 having less drop and wind drift compared to most if not all of the other 6mm cartridges i have come across. i've seen results showing a .243 115gr dropping 232 inches at 1k. and according to the table at the bottom of the page at .243 Win + .243 AI Cartridge Guide that is noticeably better than the other common 6mm rounds.

is it possible to get barrels with a larger diameter to compensate for lost rigidity in a longer barrel or does this just add far too much weight to bother with? i don't mind having a slightly heavy rifle if it means better performance. its not like i'm going to be doing long stalks carrying it round for hours.

 

[backwoods83]

I think you read to much opinionated info, a 243 is a great round but not the best or fastest 6mm. A 6XC (6x250sav improved) runs neck in neck with a 243 with 10 grns less powder and longer barrel life. Get a 26" barrel, that's plenty. For the record a 6mm rem, 6x284, 6-06, 240 wby, 244 H&H, 240 Gibbs, 240 Hawk and several other 6mms will walk all over a 243 its a 56 year old case design meant to auto feed good, not break any speed records.

 

[Rizla]

haha i stand corrected. i was just reading another thread about the 6mm crusader... that is an impressive round!

1000 ft elevation, 10 MPH FULL VALUE

338 Lapua 300 SMK at 2700 1000 yds 7.9mil Ele, 4.9moa Wind, 1600 yds 17.2mil Ele, 9.1moa Wind

6mm Crusader 115dtac at 3300 1000 yds 5.6mil Ele, 5.0moa Wind, 1600 yds 13.1mil Ele, 9.6moa Wind

i'm starting to think this is the round to go for. it also fits in the accuracy international AW magazine, which is the rifle i want. obviously barrel life is going to be even worse but thats not really a major deciding factor. i'm not going to use a worse round just to have the barrel last a little longer. you wouldnt avoid buying a porsche because of poor fuel economy!

 

[backwoods83]

The 240 wby mag is right on its *** and you can buy brass, no case forming.

 

[Trickymissfit]

I think you read to much opinionated info, a 243 is a great round but not the best or fastest 6mm. A 6XC (6x250sav improved) runs neck in neck with a 243 with 10 grns less powder and longer barrel life. Get a 26" barrel, that's plenty. For the record a 6mm rem, 6x284, 6-06, 240 wby, 244 H&H, 240 Gibbs, 240 Hawk and several other 6mms will walk all over a 243 its a 56 year old case design meant to auto feed good, not break any speed records.

boy you hit that nail on the head! Most of us here fail to look at the whole picture, when looking at case and barrel designs. The .243 design in itself is a poorly designed case that works best with 80 thru 95 grain bullets. Too short a bullet creats all sorts of reloading problems, and too long a bullet puts it deep inside the case body. Then there's the issue of the vortex of the flame path ending up right inside the throat (some folks call this the turbulence point). This is what gives you the 800 round barrel life. There is not a tremendous difference between the standard 6mm Remington and the .243 Winchester at the shoulder in length. The cases are similar in capacity, but one shoots much better. Then we throw in the 6XC and it's clan of derivities into the mix. They don't hold as much powder, but yet shoot just about as well! Even a 6BR can push a 105 grain Amax out to about 3000fps, but more importantly have three times the barrel life! Perhaps somebody is trying to tell us something?

I have owned several 6mm's thru the years, and currently shoot the 6/250AI (very similar to a 6XC improved), and a 6BR. My interests right now are leaning towards the 6BG, as it solves several issues with rounds using the .243 case as a parent. Yet it pushes a bullet as fast as the .243 case with what looks tobe three or more times the barrel life. Does this with about 70% of the powder. The smaller cases allow the use of a shorter barrel, and that's a big plus. My 6BR uses a 22.75" barrel, and is a 14 twist. I shoot mostly 70 thru 80 grain bullets thru it in the 3200fps area with 6 grains less powder than the .243 does while loosing about 75 fps. Will be glad when my 6BG reamers finally show up!
gary