Smyth Busters: AR-10 vs AR-308 - What's the Difference?

Brownells Gun Techs Caleb and Steve are sharp as new thumb tacks and even more adept at bursting balloons of firearm misinformation. Today they tackle the notion that any AR-type rifle chambered in 7.62 NATO or .308 Winchester is an AR-10. Many people who think they own an "AR-10" actually have what's generically called an "AR-308". The AR-10® is a specific rifle made by the Armalite® company, which owns the AR-10® name as a registered trademark. So ONLY that Armalite rifle can be legitimately called an AR-10®. ("AR-15" is a non-trademarked, public domain designation for the smaller rifle usually chambered in 5.56 NATO or .223 Remington.) The big deal for an AR-308 owner is that AR-10® parts are NOT necessarily interchangeable with parts for the DPMS LR-308 or other AR-308 rifles. Significant differences include the upper receivers, barrel extensions, handguard mounts, bolt headspacing, gas tubes, and buffers. The fire control groups, dust covers, pistol grips, muzzle devices, and receiver extensions (buffer tubes) WILL interchange, as will the magazines (except for some very old AR-10s that used FN FAL mags). If you own an AR-10®, Armalite will be your main source for parts, though some aftermarket parts makers do offer AR-10® specific handguards and the like. One problem is that some makers of AR-308 components are careless and say their parts are for the "AR-10". Have you had compatibility problems with AR-10 vs AR-308 parts? Tell us about it in the comments!