I ordered a custom barrel, sent off the bolt for headspacing, 3 dummy rounds and put in a request for .100" freebore. Having a uni-throater in that caliber I can/could add more freedom to it if necessary........................here's the question...................is .100" reasonable or too much? I'm probably not going to shoot any Barnes, but could be a plethora of other possibilities (Sierra, Nosler, Hornady, Lapua, PPU, Norma, Speer, Swift, Berger). Mono's is possibly a no, but this is a 26cal 8 twist. Seems like most of what other members shoot on here are Hammers with a faster twist per caliber? If my accuracy is under 1/2moa then that's fine, but under 1 will work for me as this isn't a precision built purpose rifle. This is the 3rd custom barrel I've ordered, but the 1st custom AR barrel of the 3.
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- Thread starter ARlife4me
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Your 8 twist barrel will easily handle all but two of Hammer's 6.5 bullet offerings.
MagnumManiac
Well-Known Member
Running long bullets, such as 142g ABLR or 150g ABLR as well as Berger 156g you are going to be needing a throat of .200" at least.
My custom 264WM, 1:8" twist 29.5" barrel has .200" free bore and the 156g could easily add .020" to that length, but seeing as I can't get them, the .200" throat works for everything else just fine.
What is your max magazine length? I understand you will be limited in max cartridge length, but a long throat may still be beneficial.
Cheers.
My custom 264WM, 1:8" twist 29.5" barrel has .200" free bore and the 156g could easily add .020" to that length, but seeing as I can't get them, the .200" throat works for everything else just fine.
What is your max magazine length? I understand you will be limited in max cartridge length, but a long throat may still be beneficial.
Cheers.
It's for an AR10 in 6.5prc and coal 2.830", but haven't measured ctbo. What I've done in making dummy rounds was using the heaviest bullet with the longest ogive for ctbo.
Are these averages based upon the range of bullet weights?
not really bullet weight but more about bearing surface length and max mag length. the .130 will serve you well for most bullet weights 120-140gr. the heavies will be pushed back deep into the case to maintain coal. bullets with a long hybrid nose will also be pushed deep into case to get coal. long nose bullets will be jumping a fair amount and some will have the ogive close to case mouth just to get the needed coal for mag length so if that type of bullet is desired you can shorted the freebore but then you handicap other bullets.
it is all about a balance for max performance at a short 2.830 oal.
it is all about a balance for max performance at a short 2.830 oal.
What I've done to make choices on bullets and not just weights is having the boat-tail just inside the shoulder and not any deeper if possible. A few 130's will have part of the bearing surface protrude into the shoulder area, but none into the body (except a wee bit of boat-tail at most). Berger 135 classic hunting and Lapua 144fmj are the only 2 that'll be heavier than 130's. Even the Lapua 144fmj's boat-tail isn't protruding inside the case body based on measurements I've taken ( it could vary by a few thou).
