A few years back when AR-10's were scarce, I had a LMT build going and a Larue OBR 7.62 on back order. It took over a year for the Larue to come in. I had forgotten about that order. In the mean time, I picked up an excellent SCAR 20S that became available from an online dealer.

Long story short, I ended up with 3 excellent AR-10's over time. They all shoot sub MOA. The LMT shoots closer to 1/2 MOA. They all function flawlessly. I can't bear to part with any of them.

Pros and Cons of the three (my opinion):

Larue 20" 7.62 OBR

Pros:
- Accurate
- Reliable
- Selectable gas block for suppressed shooting.

Cons:
- 100% Larue proprietary on every single part (even suppressor/muzzle device) and those parts are not available.
- Not modular at the user level unless you have Larue proprietary armorers tools.
- Oversize fluted chamber pretty much ruins brass for reloading.

SCAR 20S

Pros:
- Accurate (even with chrome lined barrel) sub MOA.
- Reliable. Shoots all varieties of 308/7.62 ammo
- Selectable gas block for suppressed shooting. Currently running a common Surfire Warcomp and Surefire RC2 suppressor. Improves accuracy.
- Modular at user level. Barrel changes are easy.

Cons:
- Proprietary parts but, readily available.

LMT MARS MWS 7.62

Pros:
- Accurate (stainless steel barrel) near 1/2 MOA.
- Reliable.
- Currently running a common Surfire Warcomp and Surefire RC2 suppressor. Improves accuracy.
- Modular at user level. Barrel changes are easy. I have 3 barrels including a 20" 6.5 Creedmoor.

Cons:
- Ammo must be suited for AR-10 service rifle platform.
- No selectable gas block for suppressed shooting.