Sorry if this has been asked before but I couldn't find it if it is here.  But what is the biggest grain bullet you can reliably feed through the mag/AR system before you may have mag feed problems?

I'll try to attack this...

It depends on if you plan on firing the round and the muzzle velocity you are aiming for.

As long as the round conforms to the standard 5.56 measurement, you can have a pretty heavy round… it’s just that most of the round will be in the case.  The heaviest 5.56mm round I’ve seen is a Black Hill 77gr SMK making about 2800 FPS at the muzzle.  It loaded and ejected fine… but that was out of a 5-round mag in a semi-auto match AR.  Not sure if running 77gr through a M16 will give the same result.

You can probably custom make a heavier grain round…  but it probably won’t have enough energy to push the bullet out of the barrel cause you don’t have enough powder loaded

there was a thread...someone posted a pic of a 80gr bullet (IIRC) but it was too long to go into the mag

Doesn't Sierra make a 90-grain Matchking now?

think bigbore had something in the lines of 100gr.


ammoman sells 80gr. .223 but there is a disclaimer associated with it.

I'm just asking because I thought I saw something in a magazine before about a mag. that feed one round at a time and it was made for competion guns that shot a bigger bullet.  I just thought that maybe I would pick up some 77gr for duty round but before I spent the money on them I just wanted to know that they were not just alittle to big and would catch the lip of the mag or something. Thanks for the replies though.

Ranger99

i have fired 77gr. out of my recon build with no problems using usgi 20's and 30's

I've fired 77gr. SMKs out of 30rd and 20rd mags with 3 different rifles and no problems.

The magazine you're talking about has a single load follower installed so that you can use the 80, 90, and 100gr. bullets.....with 77s this shouldn't be an issue.

IMHO....you can't go wrong with 75gr TAP or 77 SMKs for a duty rifle (if your gun will stabilize them and feed, shoot, and extract reliably).

The 77 grain loads are excellent and work just fine in any quality magazine and 5.56 weapon.
Pat