Any real advantage to these mags from a reliability standpoint? I've been using pmags and lancers without any real problems. Is there any merit for these, perhaps when using non typical bullet weights or designs?

I love Magpul products, but this seems like a gimmick.

I don’t even know how many 300 blk rounds I’ve fired, but it’s a whole lot...and I’ve never used a specific 300 blk mag. The whole point is that a 300 blk mag IS a 556 mag.

Also, in the product description it says since it has 300 blk written on the mag and a distinct texture that you won’t load a 556 into a 300 blk Gun with “catastrophic” results.

Maybe it’s just me, but I’ve tried to chamber a 556 in a 300 blk Gun many many times and never was able to do it.

I think these mags are a total waste. I’m a big 300 blk fan and would never buy this mag.

Some USGI style mags didn't particularly like .300 BLK because the front stiffening rib on the metal magazines intruded too much into the internal space of the magazine. With the fatter .300 BLK bullet, the jacket would rub on the inside the magazine.

This should never be a problem for a straight-walled magazine like the PMAG, so I kind of think the benefit is labeling, not strictly reliability.

Side note: I don't know what happens if you try to chamber a 5.56mm in a .300 BLK barrel (seems like it should fit), but you can chamber a .300 BLK in a 5.56 with catastrophic results if the trigger is pulled.

You were able to get a 300 blk round to go into battery in a 556?

I’ve never been able to get a 300 blk to go into battery in a 556 gun and visa versa.

I’ve tried it numerous times. I was paranoid about this issue when I first got into 300 blk. I tested all kinds of mags, ammunition and guns (I have an X95 in 300 blk as well as several AR’s.)

Never once got a gun to go into battery with the wrong ammo type.

As for mags, I haven’t found one yet that won’t feed 300 blk.

I may be wrong but I believe the purpose of the dedicated 300 blk rounds is aimed more at the sub sonic market place. I believe you become limited in bullet profile and set back due to the magazine rib.

As a side note I purchased some of the Lancer 300 blk mags at the same price as their offering for the 5.56 variant. Figured I’d give them a shot especially since I’ve been itching for some Lancers for awhile. Haven’t had a chance to use them yet though unfortunately.

quote:

Originally posted by esdunbar:
You were able to get a 300 blk round to go into battery in a 556?

I don't now how into-battery the round finally sat, but I've seen what happens to a barrel and upper receiver after it happens. Not pretty.

I’ve been using 20 round Magpul 5.56 mags with my subsonic 300blk ammo for years with no issues. Feeds and functions fine. Suppressed and unsuppressed and semi and full auto.

If I see a Magpul 20 round mag in my house it is 300blk. If I see a Lancer 20 round mag I know it’s 5.56. I’m pretty much Magpul is 300 blk. Lancer 20 rounders are 5.56. D&H 30 rounders are 5.56.

The 30 round Magpul 5.56 has been fine for my supersonic 300blk.

quote:

Originally posted by LDD:

quote:

Originally posted by esdunbar:
You were able to get a 300 blk round to go into battery in a 556?

I don't now how into-battery the round finally sat, but I've seen what happens to a barrel and upper receiver after it happens. Not pretty.

You’ve seen it happen in person, or on the internet?

I ask because I don’t see how it’s possible. Something would have to be waaaaaaay out of spec for it to happen/fire.

I just don’t see it as possible unless you tweak your gun to make it happen or have a gun so out of spec it will kaboom with the right ammo too.

quote:

Originally posted by esdunbar:

quote:

Originally posted by LDD:

quote:

Originally posted by esdunbar:
You were able to get a 300 blk round to go into battery in a 556?

I don't now how into-battery the round finally sat, but I've seen what happens to a barrel and upper receiver after it happens. Not pretty.

You’ve seen it happen in person, or on the internet?

I ask because I don’t see how it’s possible. Something would have to be waaaaaaay out of spec for it to happen/fire.

I just don’t see it as possible unless you tweak your gun to make it happen or have a gun so out of spec it will kaboom with the right ammo too.

I've seen in person, the upper receiver and barrel, after the fact. The erstwhile combination was brought into my shop, the person who brought it in touched it off--he had no reason to lie.

quote:

Originally posted by esdunbar:
I love Magpul products, but this seems like a gimmick.

Also, in the product description it says since it has 300 blk written on the mag and a distinct texture that you won’t load a 556 into a 300 blk Gun with “catastrophic” results.

Maybe it’s just me, but I’ve tried to chamber a 556 in a 300 blk Gun many many times and never was able to do it.

The problem isn't 5.56 rounds in a 300 BLK chamber, it's 300 BLK rounds in a 5.56 chamber. Which with some bullet profiles and seating depths CAN happen. So, just picture what happens when you try and fire a 30 caliber bullet in a 22 caliber barrel. It aint pretty.

It's also why ALL of my 300 BLK magazines are the Magpul Sand color and all of my 224/5.56 magazines are Black.

Since we're on the subject. What is your preferred supersonic load?

I added a couple of the .300 Blackout mags from Brownell's to reach the $20 off and free shipping over $200 threshold (discount code M8Y)...they ended up costing about $1.00 each on the overall order after knocking off the $20...the molding pattern is slightly different on the body between the .300 Blackout and .556 magazines...as far as feeding, I have nothing to compare one to another...I have only used the .300 BO mags and they worked perfectly...

I use Troy mags for my subsonics because it's the only mag that fits the bullet profile. I use these and the round nose doesn't fit in the bullet tip grooves in the Magpul .223 mags. I've had feeding issues and since switching to Troy mags everything feeds and works as expected.

thanks for the heads up guys. I probably tested 5 or 6 different brands of ammo in both sub and super and couldn't get a 300 blk round to chamber in a 556 gun.

It's good to learn that it can happen though. Appreciate the info.

Ended up just using my DD 32 round mags, I had 5 sitting here for a full loadout. Aside from labeling the mags, I'll know that any other mag i have that isn't DD will likely have 5.56 in it. All the DD mags are stored in a bag with the rifle so mixing should be a non issue

I make all my own 300BLK brass and after stuffing a 300BLK mag into a 223 gun I gave it all to a buddy and I only use nickel plated cases now and I don't get them mixed up any more!

Also, I don't mess with super-sonic 300BLK ... If I want to shoot something in the 308 caliber supersonic I just shoot 7.62x39

But then I'm just out shooting for "fun" ...

quote:

Originally posted by kimberkid:
I make all my own 300BLK brass and after stuffing a 300BLK mag into a 223 gun I gave it all to a buddy and I only use nickel plated cases now and I don't get them mixed up any more!

Also, I don't mess with super-sonic 300BLK ... If I want to shoot something in the 308 caliber supersonic I just shoot 7.62x39

But then I'm just out shooting for "fun" ...

What's your sub load?

Link to original video: https://youtu.be/5UwILeYXZlI

Where did all the FDE mags go???

drabfour -- Thanks for posting that video on the Pmag differences. It makes sense.