308 AR15 – Can I Shoot 308 in an AR15?
308 AR15 – When speaking with or listening to less experienced shooters I often hear the expressions 308 AR15 or AR 15 in 308. It’s expressions and the confusion around the AR-15, AR-10, 308 AR, AR308 platforms that was the purpose this site was created in the first place.
Can I shoot .308 Winchester in an AR-15? NO! To shoot a .308 bullet from an AR-15 is possible but it’s in the form of a cartridge called 300 Blackout. 300 Blackout is essentially a .308 bullet in a .223 case neck sized to accept the .308 diameter bullets used in the .308 Winchester cartridge. Obviously 300 blackout is much less powerful than the .308 Winchester.
Update! Since originally writing this page the 308 AR discussion has become even more confusing. Colt has finally released their much anticipated SP901 Modular Carbine aka LE901. The Colt features a modular lower receiver that can be configured as an AR-15 or AR308/308AR. Some times the Colt SP901/LE901 is actually available to buy. It’s rare though. The polar opposite of Colt is DPMS. DPMS has reinvented the 308 AR, AR308 or should I say LR-308. The new DPMS platform is known as DPMS GII or DPMS G2. The DPMS GII is an AR308/AR 308 that is closer in size to the AR-15 and shares more parts with the AR-15. I don’t believe the DPMS GII will replace it’s larger sibling but it will definitely cut into market share. Other 308 AR, AR308 manufacturers have taken notice and are producing their own “GII”. The DPMS GII also occasionally available to buy. Both platforms are in short supply.
Below I will explain in pictures why there in no 308 AR15 or more importantly why you cant physically fire .308 ammunition out of an AR15 or convert an AR15 to do so. There is no 308 AR15.
AR-15 Upper and Lower Receiver vs AR308/308 AR Upper and Lower Receiver – In the picture above it’ quite obvious the the 308 Receiver Set is substantially larger than the AR-15 Receiver Set.
Starting simple, walk in to your favorite gun shop and pick up a box of .223 Remington/5.56 NATO ammunition and a box of .308 Winchester/7.61x51NATO . The first thing you should notice is that the .308 Winchester box is heavier than the .223. That’s because the .308 Winchester cartridge is substantially larger than the .223. Remember despite what you have heard the .223 is a small game and varmint cartridge. In military applications it was originally intended to wound enemy soldiers so they would be come a battlefield burden and liability. It is not the scary cartridge portrayed by the media, on screen, talking heads and general clueless morons with an opinion.
The .308 Winchester is a hunting round for medium sized game as well as humans on the battlefield. The .308 Winchester has performed admirably on all fronts since 1952.
In the first picture you learned the AR308 308 AR Receiver Set is bigger than an AR-15 Receiver Set. Now look at the physical size difference of the .308 Winchester cartridge on the left versus the .223/5.56 on the right. The 223 Remington looks puny compared to the .308 Winchester. Also worth noting while discussing cartridge size is there relative power. The Federal Lake City XM855 SS109 Penetrator Full Metal Jacket which is one of the best ammunition choices for the AR-15 clocks in at 3020 feet per second with 1256 foot pounds of muzzle energy. The .308 Winchester 168 grain Remington Hog Hammer Barnes Triple-Shock X Bullet Hollow Point clocks in at 2750 feet per second with 2821 foot pounds of muzzle energy. The .308 Winchester cartridge has twice the muzzle energy than the 5.56 NATO round! By now it should start making sense as to why there is no .308 Win AR-15.
In the above image a genuine Colt 20 round capacity AR-15 magazine is positioned in front of a factory DPMS LR-308 19 round magazine. Note the height difference. The DPMS LR-308 magazine is much taller than the AR-15 magazine despite holding one less round.
The view above is a pretty representation of not only the difference in magazine heights but goes a long way to show the overall mass difference.
As you can see in the images above while you can force a .308 Winchester cartridge in to a Magpul AR15 PMAG. The cartridge was way too long for the magazine. Aside from the obvious it also means the .308 Winchester Cartridge is too long to fit in an AR-15 magwell and AR-15 lower receiver. See below
The picture above does a great job of showing off the cavernous magwell of the 308AR, AR308. The AR-15 magwell is about 2/3 the size of the AR-10, AR308 308 AR
Remember above I said a .308 Winchester Cartridge is too long to fit in an AR-15 magwell. The 308 Winchester cartridge is NEVER GOING TO FIT in the AR-15 lower receiver.
Now to further reinforce the size and proportion point a Magpul 308 PMAG 25 appears massive compared to the AR-15 receiver set.
The above picture begins to show the upper receiver barrel nut thread difference. The AR308/308AR is much more substantial in outside diameter, inside diameter and thread length than the AR-15.An AR-15 barrel extension will not fit a 308 AR/AR308 upper receiver. it’s too small in diamter and too short in length. The opposite holds true for the AR-10,AR308 308AR.
In the picture above it’s easy to see thread diameter difference. Obviously there’s a substantial difference in barrel nut dimensions.
The picture above does a great job of stating all the differences of the AR-15 barrel and barrel extension compared to the 308 AR/AR308. Look at the chamber, bore, locking lugs, inside diameter, outside diameter.
In the above image Rainier Arms Ultramatch 308AR (left) and Criterion Barrels Inc HBAR (right) barrel extensions are aligned edge to edge. The size difference is obvious. The 308 AR barrel extension is much more substantial.