Is 80 grain A Max a touch much for 1 in 8 twist

[tmjohnson]

I have a Smith and Wesson M & P15T with barrel twist of 1 in 8 and 5R rifling.
I have bunch of 52 grain BTHP that it shoots ok, so today I picked up some Hornady 80 grain A Max, but after looking at the bullets they seem really long.
Will they stabilize or are they too long?

[XC700116]

1:8 should get them stable, 7 may or may not be better, but 8 should get it done unless they are freakishly long for their weight and dia.

But there's really only one way to find out for sure.

[J]

The big problem you are going to have is COAL. The AMAXs almost universally like being set 0.010 off the lands. With a factory cut chamber I doubt you will be able to get anywhere close to that and still have them seated to mag length. Good luck though, let us know how they do.

You may even have trouble getting that bullet to fit in a mag at all without seating too deep and spiking your pressure. Let us know on that too. If they fly good for you I may have to try some, and if they don't fit in my ARs I'll have to try them in my bolt.

But to answer your question: I bet 1:8 stabilizes them. I'm a big fan of 1:8. I've never seen 1:7 outperform it yet with any bullet (maybe some day I will), and the slight bump in velocity plus the slight drop in pressure make good sense to me for my uses. To be honest, I have 1:7, 1:8 and 1:9 and all of them shoot lights out with everything I've tried. Granted that was only up to a 75grs bullet. Will have to try with an 80grs at some points.

[tmjohnson]

What if I trim the polymer tip off, that would give me some room to adjust COAL

[sportbikeco]

I would like to try those in my bolt action.

You plan on shooting them one at a time with your ar? Can you even seat one properly to fit in a mag?

[J]

Uhhh, sure, I guess. Not sure how it will fly without it. They designed that tip as part of the ballistic structure.

If it doesn't fit with the tip on, might as well try a few trimmed. You already have the bullets so I say give it a shot. Worst case scenario you learned something and can share it with others.

Even with that mod I still bet on a 5.56x45 factory chamber you are still jumping 0.075 to 0.150 to the lands, instead of the 0.010 that the AMAX really likes

[Hoser]

They are not designed to be loaded at mag length in an AR.

You cant get there from here.

You can single load them, lots of High Power shooters do exactly that. I use the 80 gn Sierra and 82 gn Berger. About the heaviest bullet you can stuff in mags is the 77.

[unsuperman]

Hoser is right. 77s generally are it for mag length.