Keeping non 5.56 ammo out of my 5.56 AR

I know this isn’t much of an answer, but I just wouldn’t. I have three things that eat 5.56 and zero others. I’m to paranoid.

.300BO can, and should, be loaded so it won't chamber in a 5.56NATO, without hammering the bullet into the case. I checked before building my first.

If you're nervous, get. 7.62x40WT or a .30HAM'R.

I'm not aware that 6.5Grendel is a concern.

The only dangerous combination I know of is 300 BO into a 556/223 gun. In my own case 300 BO is a dedicated suppressed gun for me and both of my subsonic loads will not chamber in a 556 even with force. The bullet cannot setback far enough to allow it to chamber due to going solid on the powder long before the bolt can close. I have and use very little super sonic ammo in my 300 BO. In addition I run my 300 BO guns with 300 BO dedicated magazines both for safety and functional reason since my 300 BO hunting load will not feed from a standard 556 magazine.

I have 2 .300BLK guns in all my ARs. Both the BLKs are marked as such with silver sharpies, and I only use 20 round mags for .300 and 30 rounders for 5.56.
Not a perfect system, but it really helps me to keep the guns and ammo separated.

Different colored magazines. For 556, Magpul has two colors and Lancer has 6 colors iirc.



Magpul also has two colors for 300BO and rumor has it that standard Lancer mags run lightweight bullet 300BO really well so the options are many.

if all you have is a grendel and a blackout, trying to fire a 223 wouldn't blow up the guns because the bullet diameter is smaller than the barrel. Also, I don't think the 223 will even chamber in a grendel.

that said, I rather like the 300 hamr, and have no regrets in bailing on blackout in favor of it. it is really only good for subsonic rounds, (for which it is quite good) and compares poorly to every other caliber in the supersonic realm. I do kind of wish I had gone the 277 wolverine route than the 300 hamr route though.

My .300 Blackout wears a LPVO scope and all my other AR's have either irons or red dots, so its quite easy to tell when I intend to have the .300 BO. I also always use a 10-round magazine in the .300 BO and 20 or 30 rounders in the others.

The .300 Blackout is basically setup as a hunting rifle though I rarely take it out (I just always feel more at home with a bolt action out in the field as its what I'm used to).

My AR15 is in the one true caliber.
If I was going to add a 30cal AR I would probably go with 300 hammer, it does not appear that a hammer round will go into battery on a 5.56.

EMT40SW said:

How do you guys keep your non-5.56 ARs marked or separate so they don’t get blown up by mixing up ammo & mags. I have a 6.5 Grendel & I’m thinking about getting a .300 Blackout but I’m alway worried someone will mix up & kaboom my AR. Thought or solutions?

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How often will this person be using multiples of your firearms unsupervised?

I thoroughly enjoy my Blackout. I keep red Lancer magazines just for it, and additionally, label them “Blackout only”. “Not for 5.56!” Would probably be better.

Secondarily, I don’t often have both the 300 and any 22 caliber ARs out to the range simultaneously. Hard to mess them up if they aren’t there to be mistaken.
The truck is right there, just a short walk to put away ‘fun rifles’ and retrieve ‘working ones’.

30 cal AR, 7.62x51 and be done. I don't have to worry about mixing up mags and ammo. Darn fine shooting AR to say the least. Love mine and accurate as can be...

I use mag bands and have one around the mag well on the gun as well, so it is match up the band to the gun. Plain mags and guns are 223, everything else has a different colored band.

https://www.amazon.com/Blackout-Mag...lja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1

I have something along these lines as well, but with 38.

I have a Marlin lever that is in 38/357. I have far more 38 brass over 357, so I load the 38's for that gun darn near at max pressure, The only thing I load like that, I generally forget about that lever when talking about loads. I also have a 1930's vintage colt police positive, not the strongest gun in the world and I shoot some real powder puff loads in it. Those guns never go to the range together. And the boxes of ammo that are hot loaded say all over the box LEVER ONLY YOU IDIOT.

I have not made a mistake yet. They are also the only "red" boxes I have, I actually painted them, everything else is blue or clear.....now that I am thinking about it I might have a green one.

Easy… while I’ve done AR’s in different cartridges for others, every AR I’ve built for myself is 223. Another member said it well… the “One TRUE” AR caliber.. LOL! I like that. Yeah, makes it easy to never have to worry about blowing up your firearm when one isn’t juggling calibers in the same firearms. LOL!

Seriously though. Being attentive and always aware of one’s actions limits chance of accident. Old saying I coined long ago: “Double Check your Triple Check!”

I really like my ARs but its been several years since I shot either of my 556 guns. I shoot 300 BO way more and it serves as my general utility gun working the hunting property in the off season. During hunting season I step up to 450 Bushmaster and 30 Remington AR. 300 Ham'r is intriguing if I wanted a 30 cal super sonic only AR-15 cartridge I think that is one of the best choices out their right now. Will 300 Ham'r feed from standard 556 magazines or does it require dedicated magazines like 350 Legend? But for me 300 BO is my dedicated sub-sonic cartridge for an AR-15 and 30 Remington AR (in all its obsolete glory) is my super sonic 30 cal AR-15 and there is no way you can accidently stuff a 30 RAR into a 556 gun

Magpul makes different colored magazines. I have seen people do things like get the desert tan mags, stencil them 300 BLK, then put desert tan items only on the rifle that is 300 BLK (stocks, grips, and so on) and keep everything black on their 5.56 AR(s). As an added level of protection, you can put the odd mags and ammo in its own ammo can marked accordingly. As yet another level of protection, only have 1 type of ammo out at a time when you are loading mags, as well as on the range, with the gun it is used for.

Good question and I don't have a good answer. I have Grendel-specific magazines that look like aluminum GI mags but that's about it. I 'was' using color coded mags for the .300Blk but that changed. I coordinate my AR's like Barbie dolls so now I have to look at the ammo in the mags to make sure. Since I did a whole lot of reconfiguring in the last year or two, sometimes I even forget which AR shoots which cartridge.

Simple. I only have ARs in .223/5.56.

I use magpul mags for 300 Blackout and metal for everything else. Only the 359 Legend and 450 Bushmaster would chamber something else and it wouldn't kaboom either.

The joys of trying to make something idiot proof, because idiots can be really creative. "My name is moon, and I'm an idiot", from my IA support group.
But PPs have covered the OP's biggest issue; it doesn't seem that he will have any significant problem, and the color coded mags are useful as well. It's still easy to get crossed; headed to the range with a Smith 986, and the Chiappa moon clips.
Reminds me; there is one part box of hunting .45 Colt in the locker; really shouldn't feed those to the Schofield.
Moon

entropy said:

Simple. I only have ARs in .223/5.56.

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Variety is the spice of life! I find AR's so much more interesting in weird cartridges. YMMV.

300 blackout in a 5.56 gun is really the only thing you need to worry about. I don't keep magazines loaded with 300 blackout.

Ummm…the ORIGINAL AR chambering was 7.62 x 51mm NATO so I don’t see where some of you are stuffing any 5.56 into those.

That would be my suggestion however, an AR-10 if you decided to go with “other” to compliment your .22 cal rifles. Beyond that, several good bits of advice above.

mcb said:

Variety is the spice of life! I find AR's so much more interesting in weird cartridges. YMMV.

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I did seriously consider buying a .300BO upper, but it would have been another caliber I'd have to load, and I don't get enough time to do so as it is. I have @ 800 .45 ACP sitting primed, and about 200 .223 primed and ready.

entropy said:

but it would have been another caliber I'd have to load, and I don't get enough time to do so as it is.

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Every time I start an AR (15) build, I always pump myself up... "you should try something new!" But... I don't. Cost and availability... and no small amount of interchangeability... always lead me to another 5.56mm build.

I really, really want an AR in 6.8SPC... maybe next time. But I'm not holding my breath.