So Is there any advantage to using 300 bo mags as opposed  to the standard 5.56 mags? I have several hundred of the gen 2 pmags so obviously im good with my 7 rifles lol. however now im seeing actual 300 bo mags is there any advantage to these other than the side says .300 instead of 5.56? writing doesnt matter to me because My 300s are fde and my 556 are black or od to keep em straight.  

From my personal experience, pmags have been fine for lighter weight 300 blk rounds (150 gr and under). Where they seem to occasionally run into issues is with the heavier, usually subsonic, rounds. The fat ogive of 220 gr bullets and the like can cause some feeding issues as they have a tendency to ride against the center rib on the pmags. They still work, it's not a definite failure, but I feel you're handicapping reliability using the heavier bullets. Having at least a few 300 specific mags is good insurance IMO for no more than they cost.

I use the Lancer 300BLK mags. They have a tan baseplate and are marked for 300BLK. I ONLY use Lancer mags for 300BLK to avoid any confusion or potential kabooms.

They have worked great with light and heavy projectiles.

Same here.

sounds like i should get some 300blkout mags when my sandman comes in then.

I do the same thing. I like to use 20s for 300blk but I also use marking bands, just in case the wife needs to grab an ar and I’m not around. trying to make it as idiot proof as possible.

They supposedly have less feeding issues...

My opinion is, buy them IF you need them, not just because you have a .300 Blk.

I have several .300 blk ARs and 95% of the ammo that goes though them is 220 gr subs...  

From everything I read, the 147 gr or the "lighter" stuff is just fine.  
When you get to the heavier gr or maybe longer Projectile rounds, they start having feeding issues.

Myself, I've shot tons of 220 gr and not once had an issue with it.  
All of mine were factory loads, not reloads.

I did pick up 10 or so .300 Blk Pmags, because of well, Marketing.  I have them if needed, but haven't yet.

I do as a personal preference and precaution, either put red tape or those rubber (bracelet looking) bands with .300 Blk embossed into them, around mags loaded with .300 blk and try not to have both .300 blk and 5.56 out at the same time.

JMPO, But, I say, If you are shooting .300 blk in standard Magpul mags and not noticing any issues, keep doing what your doing.
Or maybe just pick up a 10Pk for the hell of it.

yeah Im fine on the supersonics thus far. as i said Im getting a can so when i do i will be using subs i dont see points in using them now without the can.

I use standard G2 and G3 Pmags for .300 and aluminum USGI for .223.  This helps me identify them.  I also have red rubber bands around the Pmag base that says .300AAC and others that say Subsonic.

I run 190, 208, and 220 gr subs with both Sierra and Hornady with no issues.  I also run 125gr Sierra supers.  No issues whatsoever.

I have some Magpul 300 mags and Duramag 300 mags, they've both been flawless. I too use the bright red rubber bands on the mags, as well as wrapped around the handguard on my 300 uppers. Red band mag = red band upper. And I do not even get 300 rounds out of their dedicated ammo can until the 556 guns are put away, and that's only during the rare instance when I take both calibers on the same day. I've only had a couple issues with 300 in regular gen 2 pmags, and that was with some fat 220 reloads.

Lancers and subs. No problems feeding and easy to distinguish by sight and feel.

I use 30 round hexmags, and 20 round pmags that are specific 300AAC models.

I use a silver sharpie to mark my 20 round pmags so that I don't mix them with my 223 mags or guns.

Big thumper bullets get pinched by the forward feed-rails in 223 mags. Which makes the ass-ends of the rounds yaw outward. Which increases friction in the stack. Which sometimes causes big thumper rounds to nose-dive during feeding.

300BLK mags have more-shallow forward feed-rails.

The 300BLK Lancers work great in my gun. They look and feel very different than PMAGS. Hard to mix them up if you are squared away. Still, don’t let others load your mags if you have 300BLK  and 223 at the range at the same time. I am convinced that the IQ of most people drops about 40 points when gunfire occurs. Recoil-tardification.