AR10 vs AR15 Compatibility;AR15 vs AR-10;AR15 vs 308 AR;308 AR15

308 AR LR-308 AR10 AR 15 Platform Cross Compatibility

308 AR Parts Compatibility

The large platform AR rifles are a great source of confusion and mystery for folks looking to get into the .308 AR world. The number one question being are the parts from a standard AR15 compatible with the Armalite AR10 and DPMS LR-308? Well if only it was a simple yes or no question. The fact of the matter is the LR-308 and AR10 aren’t even completely interchangeable. Hopefully in the paragraphs that follow we can sort all of this out.

Update: As we head in to 2014 there are simply too many brands and variations to list on this page. While i will use it for the most basic of questions I suggest visiting the forum for up to date information.

AR10 vs 308 AR LR-308 Manufacturers

Before we dive into the compatibility its important that you determine the platform your rifles lower receiver is based upon. Below I will group the big names you will come across when looking for parts. It will by no means be a complete list

Click for Massive Updated List of AR308 and AR-10 Manufacturers

Armalite AR10

• Armalite
• Eagle Arms
• Noveske N6
• Aero Precision
• Aircraft Armament
• Iron Ridge Arms (DPMS also)
• CMMG (DPMS also)

DPMS LR-308

• Too many to list

.308 AR Pattern Compatibility Frequently Asked Questions

• Can a Rock River Arms LAR-08 .308 Upper be used with a DPMS LR-308 Lower – No, the upper is longer than a DPMS unit. View image below
  

  LAR-308 vs LR-308

• Is an Armalite barrel and barrel extension compatible with a DPMS LR-308 Upper Receiver? – Yes, Dimensionally the measurement from the back of the lugs to the breach face is within .001″-.002″ on the Armalite and DPMS bolts. Note: You must use a properly headspaced bolt that matches the barrel extension type. This means you need to use an Armalite Bolt in an Armalite Barrel Extension and likewise for DPMS.
• Can a Rock River Arms RRA two stage trigger be used with a DPMS LR-308? – Yes, but some times the hammer needs to have some minor filing or stoning to prevent it from dragging on the bolt carrier while cocked.
• Magpul MIAD pistol grip doesn’t properly hold the rear takedown pin – Magpul addresses this with an adapter called MIAD AR-10/SR-25 Grip Wedge.

LR-308 vs AR-10

For the most part I will point out what’s incompatible rather then list every part.

• Upper Receivers – This is the most significant difference. They are not compatible for the most part. There are cases of folks modifying them to work together but the results are unacceptable and unsightly in my opinion. Click on the images below to view them full size. Images courtesy of AR15Barrels.com

AR10 vs DPMS Upper

Armalite AR-10 Upper, DPMS LR-308 Lower

AR15 vs .308 AR

• Free Float Tubes and Handguard’s – Most not compatible due to the barrel nut size difference

Can I Mix DPMS and Armalite Upper and Lower Receivers

While you can make it work the contours and profiles are completely different. I’m going to call this a NO

Can I Shoot .308 Winchester Ammunition 7.62×51 Chamber

NO. Note: Others will disagree

The cartridges are slightly dimensionally different and do not headspace the same. The .308 Winchester Cartridge operates at considerably higher pressures than the 7.62.51 NATO. The two should not be used interchangeably. My rule of thumb is to shoot the caliber stamped on the barrel. If you are not sure what your weapon shoots consult the original manufacturer.

Can I Use a .308 AR or AR-10 Upper Receiver on an AR-15

NO, The lower receiver is not large enough to accommodate the .308 Winchester/7.62×51 Cartridge

Can a Rock River Arms LAR-08 .308 Upper be used with a DPMS LR-308 Lower

No, the upper is longer than a DPMS unit. See top image