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Web Clavin Extraordinaire
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posted
Are the 300 BLK mags on the market a real necessity to shoot the caliber in an AR? Are there actual feeding issues caused by using 300 BLK in a 5.56 mag?


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Educating the youth of America, one declension at a time.
 
Posts: 19016 | Location: SE PA | Registered: January 12, 2001Reply With QuoteReport This Post
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Absolute necessity, no. Preferred, yes. The main issue with using 5.56 magazines is the strength of the magazine spring. 300BLK will wear out a 5.56 spring relatively fast due to the additional weight of the bullets, especially so when using subsonic loads that can have projectiles that are close to 4 times the weight of the typical 55gr bullets that are used for XM193, for instance.


-MG
 
Posts: 621 | Location: The commie, rainy side of WA | Registered: April 19, 2020Reply With QuoteReport This Post
Freethinker
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As everyone probably knows, AR magazines have stiffening ribs on the interior surface of the mags. Because of the larger diameter of 300 Blackout bullets, they contact the front ribs that were designed for 0.224" bullets and that don’t touch the ribs. That causes the bullets of 300 BLK cartridges to be pushed at a slight angle toward the center of the magazines rather than being absolutely parallel with the barrel bore. The dedicated 300 BLK magazines I’m familiar with have lower/less prominent ribs and they don’t push the cartridges off line to that degree. I believe that may be why 223/5.56 mags hold fewer 300 BLK rounds than the cartridges they’re designed for.

In any event, I and the other people I know who have 300 BLK ARs use 223/5.56 magazines without any functioning problems.




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Posts: 43387 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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I'll just leave this here... Wink



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Posts: 4274 | Location: New Hampshire | Registered: October 29, 2011Reply With QuoteReport This Post
Freethinker
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quote:
Originally posted by nhracecraft:
I'll just leave this here...


Thanks. That pointed out the ribs I was referring to. I haven’t done too much with the heavier subsonic loads from full magazines and wasn’t aware of the slow feeding issue.




To argue with a man who has renounced his reason is like giving medicine to the dead.
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Posts: 43387 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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My Rattler came with a Lancer 5.56 mag and I bought some extras. Due to the ammo situation I haven't shot the thing yet though. Not sure if they have the same issue as the Magpuls in the video.

A lot of the reason for dedicated 300BLK mags is to avoid mixing up your ammo and putting the wrong mag in.

Local shop had a 5.56 upper that someone accidentally put a mag of 300BLK in, getting mixed up at the range when their friend/relative was shooting 300BLK. Not a mistake you want to make.
 
Posts: 2557 | Location: Indiana | Registered: December 28, 2004Reply With QuoteReport This Post
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I prefer the Lancer dedicated 300 BO magazines.

I have a few GI mags that have a modified spring and feed lips that I am going to try this weekend. (a friend did the mods so we will see)
 
Posts: 3105 | Registered: April 20, 2010Reply With QuoteReport This Post
Age Quod Agis
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The best reason for a dedicated mag, or a different color mag is that a .300BO will chamber and fire in a 5.56 AR, and the results can be catastrophic. Sometimes you get a really long swaged bullet, and sometimes you get a complete and violent disassembly of the rifle. Neither is good.

A friend of mine who has both has black magazines and kit for his 5.56, and FDE magazines and kit for his .300BO to avoid this very problem.



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Posts: 11292 | Location: Central Florida | Registered: November 02, 2008Reply With QuoteReport This Post
Freethinker
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I haven’t been able to find the magazines I like in different colors, and I don’t like painting them, therefore my 300 Blackout mags have identification bands. There are at least a couple of different types:

https://www.amazon.com/Sightho...arking/dp/B07MVFMN8T
https://www.ammobands.com/




To argue with a man who has renounced his reason is like giving medicine to the dead.
— Thomas Paine
 
Posts: 43387 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
Old Air Cavalryman
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quote:
Originally posted by Lefty Sig:

A lot of the reason for dedicated 300BLK mags is to avoid mixing up your ammo and putting the wrong mag in.

Local shop had a 5.56 upper that someone accidentally put a mag of 300BLK in, getting mixed up at the range when their friend/relative was shooting 300BLK. Not a mistake you want to make.


Better feeding and preventing mix ups.

This is what a .300 b/o bullet looks like after traveling most of the way through a 5.56 barrel:





"Also I heard the voice of the Lord saying who shall I send, and who will go for us? Then said I, here am I, send me."




 
Posts: 7437 | Location: Georgia | Registered: February 19, 2005Reply With QuoteReport This Post
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^^^ Damn that's like a cartoon effect.
 
Posts: 2557 | Location: Indiana | Registered: December 28, 2004Reply With QuoteReport This Post
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My only .300 BLK is an FDE colored Tavor X95. The only FDE colored magazines I own are those used with this firearm and loaded with this ammunition. It really avoids confusion.



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Posts: 9394 | Location: The Free State of Arizona | Registered: June 13, 2007Reply With QuoteReport This Post
semi-reformed sailor
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I only use my black pmags for 300BO
My USGI mags are for 5.56



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Posts: 7958 | Location: Temple, Texas! | Registered: October 07, 2006Reply With QuoteReport This Post
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I follow the same practice - FDE mags (or FDE MagPul magazine pulls) on magazines loaded with .300 Blackout.

Lancer recommends their 5.56 magazines for supersonic .300 Blackout and their .300 Blackout magazines for subsonic.
 
Posts: 588 | Registered: March 08, 2006Reply With QuoteReport This Post
Alienator
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I use ETS mags for my 300 blackout, and pmags for 5.56. Very easy to identify.


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Posts: 6006 | Location: NC | Registered: March 16, 2012Reply With QuoteReport This Post
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quote:
A lot of the reason for dedicated 300BLK mags is to avoid mixing up your ammo and putting the wrong mag in.



Easily done by specialized markings.

My local shop laser engraves Magpul magazines with the caliber.

I also use a bright yellow electrical tape around the magazine to differentiate them.

I've shot quite a lot of ammo, both sub and supersonic using a standard GI and Magpul magazines with zero issues.


Richard Scalzo
Epping, NH

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Posts: 5544 | Location: Epping, NH | Registered: October 16, 2004Reply With QuoteReport This Post
Web Clavin Extraordinaire
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I'd just put colored electrical tape on them to differentiate. I put red tape around my range/training/beater mags, and I have some blue tape I haven't used yet, which I can put on 300 mags.

I'll probably pick up some of the Lancer mags. I generally prefer them to Magpul.


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Chuck Norris put the laughter in "manslaughter"

Educating the youth of America, one declension at a time.
 
Posts: 19016 | Location: SE PA | Registered: January 12, 2001Reply With QuoteReport This Post
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I’ve got elastic bands marked 300 BO wrapped around the lower part of each mag.
 
Posts: 2329 | Location: South FL | Registered: February 09, 2007Reply With QuoteReport This Post
hello darkness
my old friend
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I have had feeding issues using 556 mag with 300BO. I bought magpul mags for 300 ad they have been flawless.
 
Posts: 6914 | Location: West Jordan, Utah | Registered: June 19, 2007Reply With QuoteReport This Post
Web Clavin Extraordinaire
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Just ordered 4 Lancer mags.

Would have gotten more but I was primarily ordering 7.62 ammo and, well, I don't even have a 300 BLK AR setup yet. Just preparing for the future....


----------------------------

Chuck Norris put the laughter in "manslaughter"

Educating the youth of America, one declension at a time.
 
Posts: 19016 | Location: SE PA | Registered: January 12, 2001Reply With QuoteReport This Post
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