Has anyone tried shooting 6.8spc out of a 10rd M3 pmag? I want to use it for hunting and will have it limited down to 4rds. Will it feed/function right? I assume the outward pressure from just 4rds loaded in the magazine won't cause the magazine to bulge out. (And I know that the LWRC Six8 Pmags have thicker walls than normal pmags and all that. Just asking about normal 5.56 pmags)

That's exactly what many 68 deer hunters do, myself included. It will feed just fine with 4-5 rounds in the pmag.

Why not just order up a couple of 6.8 magazines from ASC for about $15.00 each in the five round size?  They are the best deal on the market if you can live without using a plastic magazine.

I  own about fifteen of theirs in various flavors plus you can load longer out to about 2.314 or so in the 6.8.  They make a similar sized 223 also BTW

Greg

Just buy a CP or ASC mag for 6.8 and quit screwing around with the 5.56 mags.

http://www.jgsales.com/asc-ar-15-6.8-spc-5rd-magazine,-black-stainless,-new.-p-60053.html

This. I have both and the work fine

It's not about not wanting to spend money on 6.8 specific mags for many hunters, it's that pmags work just fine with 4-5 rounds and provide a bit more stealthiness during the hunt; less noise should you bang the mag against the side of a blind when getting the rifle into a firing position.  You also shouldn't need a ten round capacity when deer hunting. OP's question was whether or not a pmag would work and he wasn't asking who to buy 6.8 specific mags from.

Well I have 2 pmags limited down to 5rds. I just wanted to know if that would work for 6.8 so I don't have to go out and spend $30+ for 2 mags. (I wanted to know if someone else had done it. I knew that someone would get offended when I mentioned pmag & 6.8 in the same sentence. I've seen 5rd mags that are complete piles of shit so I figured I'd ask since I have these 5.56 hunting mags laying around.)
Thank you bobweaver for understanding & answering my question!!!!

Not offended, just don't understand why you wouldn't get the correct mag when they are that cheap and both ASC and CP have been proven reliable.

The honest answer is you are going to have to test them to find out. It's hit or miss.

The follower is designed to present a 5.56 cartridge into the chamber at a certain upwards angle, and towards the center of it. When you load the wider 6.8 cartridges in that mag, the follower will not present the projectile high enough ( though you might get by ), and it will spread the mag, allowing the cartridges to point outwards some. With a polymer mag, you can't adjust the feed lips to fix the issue. Many times the bullets will hit low or outside the feedramps and jam. I would test it with whatever ammo you're going to hunt with, shoot at least 20 rounds and see if it feeds. Nothing worse that having to clear a jam on a follow up shot when $15 ( sometimes less ) would have prevented it.

Add stealthiness to the equation a true 5 round mag has very little showing comparing to a 10 round reduced one.  And a game warden won't look twice at it but may want to inspect your longer mag.

Cdnn has cheap 6.8 mags also.  They occasionally put them on sale for even less if you get their email.

I load longer than 2.26. So, I'm a no-go for PMAGS, besides LWRC.