Brian, the owner of Olympic Arms, walked us through the unique features of their new AR-10-style rifle. This .308 uses a proprietary, 10-round magazine and proprietary upper. However, if you want to shoot some 5.56 you can slap on any standard AR-15 upper and the magwell accepts AR-15 (STANAG) magazines without any adapter or magwell block needed. It looked pretty slick and is supposed to have an MSRP in the $1,100 to $1,295 range depending on options. I’m hoping for a T&E sample when production units are ready. Photos and details follow. . .

One pivot pin moves between two locations — the bottom for the .308 upper and the top for your AR-15 upper. The detents are captive and easily pulled back by hand so you can move the pin.

Seen below with the single-stack, .308 magazine installed. Mags and uppers for other calibers such as .243 and .260 are planned.

The same magwell, magazine release, and bolt catch work with standard AR-15 magazines from PMAGs to GI spec. Seen with AR-15 mag installed below.

The buffer system is certainly a trick piece. When running an AR-15 upper, the bolt carrier only cycles the inner, black buffer section seen below. When running Olympic Arms’ .308 upper, the carrier cycles the outer one (I’m not sure at this time if it’s only the outer one or if it’s both, and I’m also not sure if there are two springs — one for each buffer — or if it’s just a weight thing).

Also seen in the video is Oly Arms’ .22-250 AR-15. It’s a semi-auto with a 5-round mag. It will also accept a standard AR-15 upper, but you have to swap out the bolt catch for a standard AR one.