AR-15 Bullet Length

[varminater]

Can any of you guys tell me what is the longest/ heaviest bullet that can be successfully fed through a 20 round AR mag and rifle? The barrel I will use for my rifle build will be a colt 1 in 7 chrome lined bbl., and I would like to shoot the heaviest bullet possible and get good long range accuacy.,I am referring to 223 cal.) Thanks

 

[ronemus]

The Hornady 75 gr HPBT,not the A-Max) is the highest-BC bullet for mag-length loads in standard magazines, and the 77 gr Sierra is the heaviest. If you want to run VLDs from the magazine, DPMS sells a modified magazine that lets you load to 2.43" with up tp 8 rounds in the magazine; however, they require a modified bolt catch that isn't compatible with standard magazines.

 

[varminater]

OK, lets say I use the Hornady 75gr HPBT in the AR-15. Is the 1 in 7 twist going to deliver optimum velocity and accuracy or would a slower twist do better?

I can get another barrel, however I would like to use the one I already have unless I will have to sacrifice loss of accuracy or velocity.

 

[ronemus]

You could use a twist as slow as 1:9, but probably wouldn't see any significant difference in velocity or accuracy. I use a 1:7 twist for my competition barrels,NRA Highpower and Long Range) and get easy sub-MOA accuracy - typically 2/3 MOA.

 

[kevinbritvec]

1/9 twist may or may not work with a 75 Hornady. I would bet against it. I have a 26' 1/9 Winchester bolt action that shoots them,75's) very well. Most 20' barrels will not. Go with at least 1/8 twist if you want to be sure.

If you want to higher velocity go with a longer barrel. Twist rate will have virtually no effect on that.

 

[spclark]

There's an 80-grain out there but only from one supplier I know of: a place called Fur, Fin & Feather,or something close) and they may not be easy to find. Custom-made for this place by a major,Nosler? Hornady? Not sure...) bullet maker, I know one shooter who's used them for all positions in OTC shooting a few years back.

Other than that I believe,as others have posted) the Hornady 75 is probably your best option. It ought to work well in twists up to 1:8 but I wouldn't go any slower without testing a few, from somebody else's stash, before buying a large quantity.