I have been wrangling over AR10s and AR15s and it appears that some manufacturers use "proprietary" parts that will not easily interchange with other AR15 platform weapons.

Does anyone know which manufacturers are pulling this proprietary boloney so I can avoid them?

Most all 15's as long as they are milspec will interchange with all other parts.

The 10's however have 2 different patterns the AR10/SR25 and DPMS/Most others.

Rock River, POF, and Armalite use some proprietary parts, most others use mil-spec.

Stag, RR, and a couple other 6.8's have non-standard threads for muzzle devices.

Couple use proprietary barrel nuts, but that's not a deal breaker.

Can't really think of anything else off the top of my head unless you're going side-charger or something.

one of the AR15s I saw was a S&W - M&P. The guy bought an aftermarket AR15 barrel (wouldn't work) and an AM charging handle (wouldn't work). The aftermarket grips, forend and suppressor worked though.

So, if that is correct, that would make the "proprietary" list:

M&P/S&W
Rock River
POF
Armalite
Stag

Knights is almost ALL proprietary, although their e3 bolt is the bees-knees

Big issue with the .223/5.56 is with the gas piston models. You prety much have one offs.

My Windham Armory model seems to follow the mil spec standards.

maybe this would be easier to just list who makes the AR15 with all the interchangeable parts (no special proprietary stuff)

Bad levers don't work to well with the Sig 516 patrol.

but good levers work well?

B.A.D. lever is a Magpul Battery Assist Device.

If I were going to advise an ar15 buy, as opposed to a build, I would go with these local:

1. Colt
2. Wyndham
3. DPMS Oracle

Internet:

1. Spikes Tactical
2. Palmetto State Armory
3. Special Ops Tactical

I was trying to make a funny! But thanks for the explanation! =)