So, upon being thoroughly educated that .223/5.56 is in fact a Varmint Cartridge, I've found myself seeking an alternative chambering which may be better suited for general purposes including Big Game Hunting as well as Personal Protection, preferably one which an existing AR-15 can be converted to with a simple swap of the Upper.

However, there are so many choices available that it has my head spinning, so I thought it would be best to take it to the experts and get your insight on the subject.

So what in your opinion is the optimal chambering for an AR-15?

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Shooting Comfort is bilateral.

Kind of a loaded question so to speak. Anything can be a varmint cartridge. You have to look at cost and availability of ammo/brass/bullets.

I have a 6ARC that I am hoping to take a deer with this year. Got it on a whim but, have grown to really like it. Using an 85gr Lehigh Controlled Chaos and Benchmark powder. Only going 2600 FPS +/- but, it is fun to shoot. I am using a CMMG and a Burris scope. I customed the load so the 2600FPS is giving me sub MOA at 100yrds.

I was able to get a bunch of ammo included with the purchase of the CMMG so all I had to do was shoot the over the counter Hornady and then find a good load. some of the other calibers might be easier to find but, might be more expensive.

"General Purpose" = 300 Blackout, IMHO...

Cheers!

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Sit Reloader Sentiret

Not sure what the OP considers "Big Game". While I believe you could reasonably use all of the above on Whitetail Deer, it gets iffy using a number of those cartridges on anything bigger, say Mule Deer or Elk. A lot also depends on what state he is in and the expected shot distance.

For self defense, 300 Blackout is a good compromise when it comes to hitting power and capacity, and gives you the flexibility to go subsonic and suppressed.

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Release the Kraken

This is a "purpose driven" decision. What do you consider "big-game"? Are we talking deer and hogs, or bears and elk?

What is the longest distance you plan to shoot game with it? .300 blackout and .350 Legend are good within a couple hundred yards, but both drop pretty quickly after that.

6.5 Grendel is a great longer distance cartridge, but ammo can be hard to find.

By general purpose I assume you want one weapon to defend your castle, get rid of pesky varmints, put meat on your table, and enjoy shooting at the range for fun. I'd pick 300 Blackout of those listed based on availability alone. Everyone has this round in stock

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What could possibly go wrong?

P.S. With the possible exception of 7.62x39, 300 Blackout has far the best selection & availability for factory ammunition choices...

Reloading is also much more "user friendly" as brass & bullets are widely available.

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Sit Reloader Sentiret

I voted 300 Blackout but unless you are going to use it for hunting would stick with 5.56/223 for an AR. They were designed for 5.56 and I have always had the best results buying guns in the caliber they were designed for.

My experience with 45 ACP 1911s has been very positive, 10mm and other calibers not so much. Same goes with 9mm guns rechambered for 40 S&W when it first became popular. That's not to say such guns cannot be reliable, they just don't have the long track record of a 5.56 AR.

The 300 BO isn't much more powerful than 5.56 but offers the ability to shoot heavier and bigger bullets. I am not a hunter so I will leave how much that helps with hunting to those that have actual experience except to note it would be legal in states with some sort of .243/1000 ft-lbs lower limit for hunting cartridges.

If you want 7.62x39 consider getting an AK style rifle.

If hunting is a theoretical consideration and your main use will be personal protection don't worry too much about 5.56 being considered a varmint cartridge. A lot of the concerns about how well it will perform in that role have to due with how it performs at 100+ yards which isn't much of a concern for most self defense situations. The ammo is less expensive and any rifle round will be much more effective than handgun calibers.

I'd be looking at an AR10 if large game is on the menu.

If you're looking for an alternative cartridge in an AR, you'll be limiting yourself to those cartridges with dimensions that will fit in the framework of an AR. Maybe it would be best to consider a bolt-action design where there are no such limitations and cartridges with much better performance can be used.

The souls of a few people in the SE Asia area thought it was a good round.

Déjà vu?

I’ve never thought the 223 or its nato equivalent an adequate big game cartridge. They’re fine for coyotes but not for our Mule deer, elk or black bear.

Likewise, I don’t like the AR platform well enough to buy one. Here in Colorado, you can’t hunt big game with a rifle that holds more than 5 rounds. The AR platform creates problems shooting from prone (the pistol grip won’t let you get low enough to the ground).

If I was in the market for one rifle for home defense and big game hunting, I’d be unlikely to buy an AR. I’d be much happier with a bolt action rifle in 30-06 or a lever action in 30-30.

In free states I don't understand why anyone would use the weenie 300 blackout or 9mm legend.......Lots better cartridges avail for an AR. My favorite AR Hunting cartridge is the 7.62x39. Using Hornady SST ammunition I have killed 14 deer with it in the 22-23 seasons.

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S&W Accumulator

300 blk is basically a pistols round made to shoot out of an 223/556 AR mag with a short barrel AR15 subsonicly. If I have to grab a rifle I want rifle ballistics with rifle damage. 300blk ain't it.

What about those other three that you could POTENTIALLY harvest...?

Cheers!

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Sit Reloader Sentiret

.308 hands down. Versatile, available, affordable…

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Some Might Say.

Uh, the OP said "... for an AR-15?"...

Cheers!

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Sit Reloader Sentiret

I understand that- but IMO I’d easily trade a pound or two for real versatility of .308 (not 7.62x39 vs .300 Blk). The pros far outweigh the cons for a cartridge like the .308 that can do almost anything.

ETA- I guess I’d the options I’d go for 7.62x39 simply because of availability.

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Some Might Say.

The 7.62X39 is fully equal to the 30-30. Even betters it out at 100 yds because it uses pointed bullets that retain velocity much better. No body complains about the 30-30 as a deer ctg.

Maybe not fully equal to the .30-30, but close. You're right, no one complains about the .30-30 as a deer cartridge because they accept it for the short-to- medium range cartridge it is. Spitzer bullet or not, the 7.62x39 is not a long range cartridge either, just like the .30-30.

I have a 6 ARC and I like the cartridge for target shooting. I haven’t hunted with it, but my brother and nephew have borrowed it and taken whitetail deer, and liked it enough to build two more uppers for themselves.

The whole idea of 300blk is sub Sonic loads with suppressors. That was the driving force behind its development.

If you want to maximize output from an AR platform I’d go with the AR10 in 308. There’s never been a better deer cartridge.

Forte, anyone suggest that you opened a can of worms?

In the beginning, the M16/AR15 (plus the AR180) were built around the .223/5.56 (derived from the 222 Remington) with a 55gr FMJ pushing a good 3200+ fps out of a barrel with a 1:14" twist. Times, rifles, and ammo have changed!

Look to the target shooters that have made the M16/AR platform a competitive platform. Gone is the 55gr FMJ (aka: M193) in a 14" twist barrel, replaced by 69gr/75-77gr HPBT/78-85gr HPBT bullets in barrels with a twist as fast as 1:7".

While the 223 bullets may still tumble if they hit a leaf on branch like the M193, they don't react like a pinball machine, entering a shoulder and exiting from the back of a knee, as the old lore claimed! Plus, today's hollow point bullets tend to be a bit heavier constructed.

Personally, I still see the 223 round more as a varmint or PDW round. I built a 224 Valkyrie upper, which showed great potential at the 1000 yard line (until the state of Delaware effectively banned semi-auto rifles with detachable magazines). I don't have enough experience to comment on the 300 BO, and I haven't really looked into the 7.62x39.

Personally, if I wanted an AR platform as a varmint/ PDW/hunting rifle, I would look at an AR10/SR25/Mk110 in 7.62x51, and build a backup upper in either: 6.8x51, 6.5 CM, or maybe even 7-08. (Note: the 6.8x51/277 Fury is on deck as the new service rifle round, ensuring a degree of future availability!)

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Judge control not gun control!

Maybe I'm missing something here...is there some hidden advantage to semi-auto fire and a large magazine capacity for hunting varmints or game? That's not a Second Amendment anti-gun question for those wholly consumed by such, it's a simple question regarding hunting.

Depends on what you are hunting. For deer and similar game, it isn't much of an advantage.

For hog eradication or coyote hunting, that larger magazine capacity and faster follow up shots can be very valuable.

I've hunted both with a bolt-action rifle; more than adequate.

I didn't do the poll because IMHO the 5.56 is optimum for a AR-15.

But, OTOH, an AR-15 is not suitable for big game, so the question is moot.

I personally hunt deer with a single shot Encore in .308 Winchester. That's quite suitable. If I was inclined to use a bolt rifle, it would be a .30-06. But a 12 ga. with a rifled barrel will do just fine as well.

A 223 with a 70gr TSX Barnes bullets can take down thin skinned game the bullet diameter is legal. Beyond that the 6.5 Grendel is good to 350 yards

OR by a bolt action that is better suited to hunting game

Very good response. A practical one.

12ga slug gun……….spoken like a true NY deer hunter. Get ready Jim it’s 10 days away !!!!!

Who is hunting deer with an AR10? I see the AR15 as "assult rifles." Not many who own .223/5.56 AR15s care about hunting or long range shooting with a 22 cal bullet. Most American are never going to take that long of a difference shot for self-defense (legally) or hunting. The OP asked about a backup caliber aka alternative for a .323/5.56, so I do not understand all the hunting, etc talk.

When we're talking about the best alternative round to .223/5.56 for both self-defense AND maybe hunting on an AR platform, x39 is both the most plentiful, cost effective, and best performing round.

I thought he mentioned a hunting use in the original post; despite that, this seems to be a "stir the pot" type thread rather than one intended to be productive.

My vote would be for the 7.62 x 39..
For factory ammo availability the 300 Black out is probably a better choice.
The 7.62 x 39 for a hand loader will out perform the Black out, and is an easy cartridge to load for.
Opinions, will vary...

Still hunting till Jan 1st.......Didn't mention bks killed with other rifles.

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S&W Accumulator

Yeah, I know. For clandestine people work. Not deer. Think JD Jones developed the same thing called the 300 Whisper.

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S&W Accumulator

For hogs yes. When I deer hunt with 7.62x39 I use a ten rd. magazine. It's only sticks out the receiver about an inch.

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S&W Accumulator

I went other, Ditch the AR 15 and go with an AR 10 in 308 Winchester for big game.

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Front sight and squeeze

You didn't have the new kids on the block listed, 35 Legend and 6ACR.

But I have to say I'm surprised with all the 7.62x39votes. And guess what the Grendel is, an improved 7.62x39. Guess which caliber I voted for?

All this discussion just proves the AR platform is verisitile and can be used for numerous applications.. What ever your hearts desires.

The 7.62X39 is a short range deer cartridge but it can do double duty as an alternative to the 5.56 in a light weight AR carbine . It is a true 300 yd rifle ctg. for military use or SD in rural areas. That's something the 30-30 can never do. Tests done by the US Government have shown that the common FMJ bullets of the widely available 7.62X39 ammo will penetrate the test steel plate used at 300 yds 100% of the time. The Spitzer bullets give it usable trajectory for large varmints two or four legged at that range. It really is an outstanding compact round and very affordable in bulk. Probably a good choice for US adoption but we'll never know.

The OP started the talk about hunting, and yes, I've read about people who hunt with an AR-10 with a 5-round magazine where such use is legal.

I suggested 300 Blk because the supersonic stuff is almost up there with 7.62x39, but almost may not be close enough for some.

Just a heads up, but we usually avoid using "their" language on the board when referring to the AR platform. General view is that if it ain't full auto capable, it's not anyone's assault rifle.

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Release the Kraken

P.P.S. I happen to have a couple PA-10s (in 308, of course!), although I still prefer the ol' M77 Ultra Light in 270 WIN for any hunting activities...

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Sit Reloader Sentiret

The 458 SOCOM gets my vote.
Might call it a mini-458 WinMag.
70+ grains of 4198 launches 300gr JSP Sierras at Mach 10
in a No.1H, and the SOCOM would be a fun companion.

The AR15 with a 7mm bullet might be useful.

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Have Fun/Stay Safe

Few have a need to penetrate steel at 300 yards (or any other distance). 7.62x39 ballistics are quite puny in comparison to many cartridges commonly used for hunting. Certainly adequate power for small varmints, but bullet drop would be significant. More of an inhumane stunt for hunting use than something practical.

I suppose if you used FMJ bullets in a .30-30, the same arguments could be made. Other than cheap cost, is there any real use for FMJ bullets in rifles and carbines for civilian use? If soft point and HP bullets were cheaper than FMJ, that's what almost everyone would be using. Most FMJ bullets, unless they are expensive target bullets, provide inferior accuracy to costlier hunting bullets.

Please do not tell me what language I can or can't use, or lecture me in nomenclature. I respectfully said what I said and meant it how I said it.

Next, the 300blk even at supersonic near the performance of 7.62x39. They appear close on paper, but performance wise, x39 is the much more powerful and better penetrating round.

Here's just one of many examples.

I know several ranchers son's who use AR 10's for deer, elk and bear. Just as their fathers grew up training with bolt actions, they trained and used AR's.

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Front sight and squeeze

The big draw of the AR is the ability to swap uppers with optics and mags and you have a completely different gun. For a big game short range I’d go with one of the big .45s. For a midrange deer cartridge a x39 would be my pick and for small game and fun a .22. I would add one more upper in a 9mm or .45acp for self defense and pcc competition. Here are a couple .22s, three 45acps and the bottom is x39.

Attached Images

IMG_0629.jpg (96.9 KB, 10 views)

When it comes to hunting, shooting out of SBR, barrier penetration, energy, power, etc, x39 beats and is better than 300blk by a noticable margin. .


I don't know anyone, never seen anyone, and don't recall anyone mentioning they use an AR for hunting. Good to know, and thanks for the information.

I like the 300 BO and 6.5 Grendel. Don't know why, just do.

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213th FBINA

I have one AR lower and three uppers, 5.56, 6.5 Grendel and 7.62x39. Of the three the 6.5 has been the most frustrating, I just cannot get that upper to group. Of the three for what you're describing I would look at the 7.62x39. Lower ammo cost for practice and still able to find ammo suitable for deer at close to medium ranges.