BIG brain fart while shooting today. Thought I had my 5.56 A2 AR but actually grabbed the 7.62x39 A2 Colt uppered AR by mistake.

Fortunately no injuries (except my pride), etc. Had to use a rod to push the casing out to a "***?" moment when I saw that case. After pondering the weird bulge in the case and asking some fellow shooters, the word "chamber" was mentioned... and then IT HIT ME!

Lesson learned: Two nearly-identical-looking A2-uppered ARs need to be tagged to differentiate calibers. That will happen first chance I find a tag or dust cover marked "7.62x39"

Now you know what this deal looks like. Thank you for looking at my foolish mistake!

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Available at Midway.

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The best I can with what I got

All of my 5.56 AR's have black cases, black slings and black rail covers. My 7.62x39 and 300 Blackout AR's have tan cases, tan slings and tan rail covers. My 6.8 SPC AR's have green cases, green slings and green rail covers. I NEVER take 2 different caliber ARs to the range at the same time. Not a perfect system (we all have brain farts at times) but I wanted to try to reduce the possibility of caliber miss-match as much as possible.

I mark all my AR uppers with a silver sharpie. Had the same thing happen to me years ago when someone I really trusted sold me a nicely sporterized 6.5 Arisaka. Told me it was original 6.5 Japanese. Fired it and found out it had been modified to 6.5 Roberts. Checked first case fired like I always do, looking for a backed out primer or other bad headspace indicator. Well, to say the least, we had words, I got an apology, and was given the choice of a full or partial refund. I took the partial and kept the rifle. I already had a 6.5 Bob, so ammo was already in stock.

I keep it simple at my place. The only two rifles I own in 7.62x39 are the Chicom Norinco SKS and an Arsenal SGL21-61 (Russian Saiga AK clone). The AR rifles I own are all in 5.56 or .223 Wylde. AR mags are all loaded with .223 or 5.56 and AK mags are loaded with Russian 7.62x39.

All my ARs are 5.56 except my .224 Valkyrie. The 4-12 sitting on top is a giveaway. Oh, and the wooden stock and grip.

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The best I can with what I got

It could have been worse. At least you didn't load a 300BO into a 5.56 chamber like my nit-wit buddy did....

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SIC SEMPER TYRANNIS

Yep, you're not the first one, and I'm glad no one was hurt. I've found all sorts of "interesting" cases along those lines at my public range, but never one bulged in the middle like that. That'd make a nice addition to a cartridge board.

I think about this EVERY time I get the 300 BLACKOUT out to play,,

Heck, I would probably get rid of the BLACKOUT,, if it was not one of my most fun guns,,,

I wonder what course the bullet took. I guess the case didn't rupture because the instant the bullet left the case a lot of pressure disappeared down the barrel, rather than pushing the bullet.

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Release the Kraken

I know a dullard who had a lapse of attention and loaded .308 into a 30-30. It sucked. No damage done, because it would not chamber, but a lot of cussing and most of a shooting day was spent doing stupid mechanical stuff.

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NHI, 10-8.

I have found several .40 S&W cases which had obviously been fired in a .45 ACP chamber. I once fired, accidentally, a cylinder full of .32-20 rounds in a .38 Special revolver. No damage done to anything except the fired brass. And I really didn’t notice anything was amiss until all shots had been fired and I extracted the fired cases. The hazards of firing two M&Ps in different calibers at the same time.

I once deliberately fired some .44-40 and .38-40 cartridges in a .45 Colt revolver to fire form the cases to .45 Colt. The undersized bullets actually hit the target I was aiming for.

I see I'm very late to this party. I was going to suggest tagging both with an unmistakable markings and everyone here has given you many ways to do that.

My shooting buddy has 3 identical looking uppers. A 5.56x45, a 7.62x39 and a .300 Blackout. Each has a different color Picatinny rail. (aluminum)

Another friend just paints parts of the uppers of different calibers.

You don't have to spend the money on rails. Just think of something that will work for you or use one of the suggestions posted here.

I'm glad the lesson was learned without injuries or broken guns. Thanks for posting this, it's a good reminder for everyone.

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Freedom is never free!!
SWCA #3437

Back during RVn you would hear dipsticks saying Charley could shoot or 5.56 in their AK. There is a lot of cartridges that can be “detonated” in wrong gun but as long as bore is larger diameter the bullet, bulged or split case is all you are going to get.
Several years back a local kid inherited a Rem 721 in 300H&H. I offered to trade him a 700 3006 or similar for it. He wasn’t interested but was to tight to buy a box of Ammo for it. Then one day he came in with a box of Winchester 300H&H in the old Yellow box. He said he wanted me to look at it because bullets looked to fat. Sure enough they were some kind of short 35 cal built on 300H&H brass. They were short enough they would chamber. Kid was lucky he was smart enough not to touch it off. I told him not to buy anymore handloads at shows. That could have been fatal.

I'm trying to figure out what in the world would fore a 300 H&H cartridge necked up to..35 Cal but I can't think of anything. Maybe it was some kind of a wildcat? Of course I don't know everything about cartridges, anyone have a guess as to why someone would neck up a 300 H&H to .35 Cal?

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Freedom is never free!!
SWCA #3437

Shortened and fireformed, 300 H&H brass can be used for .350 Remington Magnum.
The old yellow Winchester ammo boxes were, I believe, used around the time Remington introduced the models 600 and 660.

That’s pretty much where I’m at now. I’ve got AR’s in 5.56x45, 7.62x51, 7.62x39, 5.45x39, 9x19, & .22LR but I don’t shoot them together on the same day. It’s just easier that way (and you just can’t be too careful).

Ah yes, the old Vietnam myth "They could fire ours but we couldn't fire theirs."
Bought a used barrel for my Browning HP, wondered why accuracy was so lousy. Then I realized i was firing 9MMP out of a 40 S&W barrel....

We all have "lapses" at times. A couple months back I took some folks out to the range. Brought .22's, 9mm, and a 1911. Inserted a mag in the 1911 and hit the slide release. I thought "Why the heck did a live 9mm cartridge appear on the ground at my feet?" Dropped the mag and yep, chock full of 9mm ball. I was talking when I should have been paying attention to loading. Joe

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Behavior Creates Destiny

Years ago I had a Weatherby Vanguard 270 and a Remington 700 in 30-06 and took them to the range at the same time, with a buddy.

I was very careful to keep the ammo with the correct firearm. But, there's always a but huh?

While being busy running my yap to my buddy I picked up the 270 ammo with the 06 on the bench. Loaded the rounds into the 06 and for some reason my mouth shut up and my brain kicked in and I said to myself, ummmmm??

I checked again and didn't fire. But I learned a valuable lesson about two very similar rounds at same shoot.

Glad no one was hurt with you.

At the time I looked it up and I think found it in PO Ackley’s book on cartridges. There was a whole raft of .358 cal Wildcats. I think it was a Durham series cartridge, don’t remember the full name.
There are thousands of Wildcats and reasons for them are varied and some defy reason.
I had a couple Rem 600, 350mg back in 70s. Never had them long
enough to shoot any game with it. Used them for emergency backups in case I had problems with my primary shooter. Both ended up residing north of the border, my PR program.

I can personally confirm that .38-40 fired in a .44-40 revolver will hit the target, but just not in the grouping you are expecting.

I decided to make an obvious and explicit warning regarding grabbing/loading the correct gun and ammo combination.

It makes a great learning visual and conversation piece too

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Rather a unique way of fireforming your cases.

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USMC 69-93 Combat Pistol Inst.

my 7.62x39 upper is a side charger. pretty obvious. As are the heavily curved 7.62x39 magazines. But with short 5 or 10 rd magazines, I could see it happening.

None of us who shoot together have 300 BO.

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NRA RSO