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If both are chambered in 7.62?

Is this a trick question?

I thought the difference was the caliber.

Well, no. You can buy uppers for an AR-15 chambered in 7.62, .308 and 300 Blackout. I'm thinking about getting one of those for hog hunting and use the 5.56 for target practice.

Bonus question: Which of those calibers would be the best for large boars?

I don't believe you can get a .308 magazine to fit in an AR-15 mag well??

I did some checking and found this...

First --- Its not a converted AR15 to .308. You have to purchase an AR15 already built for the .308 cartridge. The receivers and uppers are a whole different animal than a regular AR chambered in .223 / 5.56......

As an example -- This DPMS rifle is chambered and built for the .308 Winchester... NONE or almost none of the parts interchange with an AR chambered in .223... You cant just change uppers... The receivers different...

http://www.dpmsinc.com/" onclick="window.open(this.href);return false;

Heres an example of a Rock River Arms.... It isn't a converted anything. Its completely built for the .308....
http://www.rockriverarms.com/index.cfm? ... ory_id=254" onclick="window.open(this.href);return false;
Notice how the magazine well is longer than a standard AR15 for .223?

Can't get an AR-15 chambered in .308 to the best of my knowledge as the cartridge is too long for the chamber/magazine. Of course I could be wrong and it wouldn't be the first time nor the last.

The Colt 901 Modular Rifle is the only AR pattern rifle that can be mounted with either a 5.56x45 or 7.62x51 upper on the same lower. AR-15 pattern rifles can be had in various 7.62 calibers though; 7.62x25, 7.62x35, 7.62x39, 7.62x40. SR-25 or AR-10 pattern rifles are chambered for the 7.62x51/.308 family of cartridges, .243, 7mm-08, 7.62x39, 338 Fed, etc.

The Marshal wrote:I don't believe you can get a .308 magazine to fit in an AR-15 mag well??

Yeah, scratch the .308. You can get 7.62 mags and the 300 Blackout cartridge was designed to fit the 5.56 mags. At least that's my understanding of it.

Carry-a-Kimber wrote:The Colt 901 Modular Rifle is the only AR pattern rifle that can be mounted with either a 5.56x45 or 7.62x51 upper on the same lower. AR-15 pattern rifles can be had in various 7.62 calibers though; 7.62x25, 7.62x35, 7.62x39, 7.62x40. SR-25 or AR-10 pattern rifles are chambered for the 7.62x51/.308 family of cartridges, .243, 7mm-08, 7.62x39, 338 Fed, etc.

Here's the place I ordered my upper from: AR-15 Uppers. They sell 5.56, 300 Blackout and 7.62x39 uppers to fit any milspec lower. I've already ordered a 5.56 upper from them. I'm thinking about ordering a 7.62 or 300 Blackout upper as well. Both to fit the lower I want, which I hope to order soon.

baldeagle wrote:

The Marshal wrote:I don't believe you can get a .308 magazine to fit in an AR-15 mag well??

Yeah, scratch the .308. You can get 7.62 mags and the 300 Blackout cartridge was designed to fit the 5.56 mags. At least that's my understanding of it.

7.62x51 mags only work with AR-10/SR25 pattern rifles.
300 AAC Blackout is very similar to the 300 Whisper which is based on a necked up 221 Fireball.
300 AAC Blackout a cut down 5.56x45 case re-sized to 7.62 and is designed for AR-15 pattern rifles.

I still learn something new everyday!!

I specifically went with the Armalite AR10 and the 7.62x51/.308 caliber. I felt it would be the best all around caliber for hogs, other game, long range target, etc. Some of the guided or semi-guided hog hunts will only allow .243 or larger, so the .223/5.56 would not be allowed, of course on private land it wouldn't matter.

ammo is not cheap though, especially now.

The AR10 is upscaled in every way from an AR15, primarily for two reasons: (A) the beating administered by the 7.62x51mm NATO cartridge, also known as .308 Winchester in civilian form, upon equipment is significantly more thorough than that administered by the 5.56/.223 cartridge, and that requires much more robust parts....and more robust parts take up more room, meaning a larger upper receiver; and (B) the magazine for a 7.62 NATO cartridge won't fit into the magazine well on an AR15 lower receiver. It is too long front to back, and too wide (double stacked .308 cartridges require more width than double stacked .223 cartridges). Furthermore, the .308 cartridge requires a longer bolt throw to pull the case clear and eject it.

Even in basic carbine format, an AR10 weighs an easy 1.5-2 lb more than an AR15.

Colt makes a hybrid AR platform rifle that will mate either a 5.56 or a .308 upper to a modified lower, but neither of the two uppers will fit onto a standard AR15 or AR10 lower, and the Colt hybrid lower will not accept standard AR15 or AR10 uppers.

There is an AR15 lower/upper combination that takes the Russian 7.62x39 cartridge, the same round that the AK fires. That is a true .308 diameter bullet, but it is lighter and shorter than a .308 Winchester bullet, and the ballistics are similar to the old .30-30....which is also a .308 diameter bullet. The magazine well is wider than for a .223 rifle because of the wider case/bullet, but it is roughly the same length as a .223 rifle's magwell.

The standard AR15 lower can also be mated to uppers chambered in 5.7 FN, .300 Whisper/.300 ACC Blackout, 6.8mm SPC, .458 SOCOM, .50 Beowulf, plus others I haven't thought of here. It is interesting that a standard 30 round 5.56/.223 magazine is also a 7 round .458 SOCOM magazine. If they ever pass the magazine capacity limit, you'll be able to buy magazines stamped as 7 round .458 SOCOM magazines and use them as 30 round .5.56 NATO magazines.

Also, not all AR10s have interchangeable magazines. For instance, the Rock River Arms AR10s use FAL mags, while DPMS, Bushmaster, and Remington AR10s use the mil-standard SR15 magazine.

After doing yet some more reading, I'm thinking the 300 Blackout round would be a better choice for the AR-15. Less abuse to the BCG and equivalent terminal ballistics. Plus, if I get really brave, all I would need is the barrel and a barrel wrench (and some brave soul on the forum to hold my hand.)

baldeagle wrote:After doing yet some more reading, I'm thinking the 300 Blackout round would be a better choice for the AR-15. Less abuse to the BCG and equivalent terminal ballistics. Plus, if I get really brave, all I would need is the barrel and a barrel wrench (and some brave soul on the forum to hold my hand.)

If you don't plan on running a suppressor on the rifle I would go with 6.8 SPC over 300 AAC for hunting. YMMV