LR-308 AR10 AR15 Platform Cross 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 2012 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.
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
- Eagle Arms
- Noveske N6
- Aero Precision
- Aircraft Armament
- Iron Ridge Arms (DPMS also)
- CMMG (DPMS also)
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
- Barrels - While the barrels are the same the barrel extension and the threads of the barrel nut are not.
- Bolt Carrier Group - The bolt carriers are interchangeable if used as a complete unit. You cannot interchange the bolts by themselves.
- Magazines - Magazines are not compatible. Furthermore If you have a LR-308 based platform from a manufacturer other than DPMS you need to be certain what magazines your lower receiver accepts. There are variations that accept FN FAL, H&K G3 and possibly other magazines.
- 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 here
- 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.