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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.



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  1. I have the colt 901 but the price is right on this. I may have to pick one up when they get the other calibers released and it will give people time to see if the mags work

  2. I’m not sure why the comment section as already filled in with this info as I am not htis poster, but thought I’d bring it to light.

  3. I’ll never understand this convertibility schtick. If you have to replace 50% of something, you’re not really getting much. Now, if you could shoot 5.56 and 7.62 from the same rifle without changing the barrel then you’d have something. Otherwise, don’t waste my time.

    • The 50% in this case is the part that has most thins that you interface with – the trigger, the safety, the stock etc. Having one set up exactly the way you want and usable with different uppers can be convenient.

      • Yeah it’s also the “firearm” according to the gov’t. That has various advantages now that you can run lots of uppers in lots of calibers on this. You could SBR the one lower and have the option of .300 BLK, 5.56, .308, and even 9mm (with an AR magwell block, assuming they’d work in here) short barrels and long barrels plus long barrels for really legit target and hunting calibers like .243 and .260, plus plans for .300 WSM and/or .270 WSM and others. All while retaining your same nice trigger, grip, stock, and other parts and with only purchasing a single “firearm.” Any uppers and other stuff can ship right to your door.

        I asked Brian if he thought their uppers were legitimately accurate enough to take advantage of and do justice to a caliber like .260 Remington, and he was highly confident that they are. He said he’d be more than happy to send me both a .308 upper and a .243 or .260 upper for testing, and encouraged me to put it on a really solid rest with my 6-24x Lucid scope and pattern it at at least 100 yards.

    • Just FYI, since it looks like the comments are un-effed for now, none of the other posts under Tex300BLK in this thread (or most of the others from today) are from me, just thought I would mention that since this one isn’t as readily obvious as the others.

    • That is really weird that it put someone else’s name on my post. It’s trying to do it again here. I even see his email address. Sorry, Tex300BLK. I have your email address now (but I’m not writing it down).

  4. I am not Bill but I love that I can see his email address… good reason not to trust websites like this with anything real.

  5. Some conversion kits make sense, like .22 conversions made sense when you used to be able to FIND .22 ammo. You could shoot a lot more .22 cheaply and recoup the cost of the kit.
    If I am reading this correctly you have to buy a 5.56 upper to convert, as well as non standard magazines for .308, with AR platforms at a historic low this would only make sense if the 5.56 upper was part of the kit.
    Perhaps in places that limit how many firearms you can possess this would be a great idea.
    I wish Oly good luck and while the concept is interesting, one suspects it will end up along with Trounds as a footnote in firearms design.

    • Personally I think it would be a huge mistake to include a 5.56 upper with it. I’d hazard an assumption that nearly every single person considering purchasing this .308 already owns at least one AR-15. Additionally, even if you don’t, since this lower accepts any standard AR-15 upper you might as well pick or build the one you want. There are a bazillion of ’em out there and I think it’s really cool that since this thing doesn’t require anything proprietary in the upper they aren’t forcing you to buy an Olympic Arms one just ‘cuz. Maybe what they should do is offer a discount on an Olympic Arms 5.56 upper with your purchase of this convertible .308 system. But I, for one, wouldn’t be buying that solely for the fact that I already own an AR-15 upper that I like a lot.

  6. I owned an OA AR15 once. Right at about 1000 rounds it fell apart. The idea is solid, however, I will never buy another Olympia Arms product again.

    • Out of curiosity, was it their rifle or just their lower? It was mentioned to me that OA sold thousands of stripped lowers to other companies, which assembled them into rifles for sale with whatever parts they chose. This was an obvious mistake and I guess OA is working hard to repair hits to its reputation that resulted from this, as many or most consumers thought they were buying an Olympic Arms rifle when it was really just an OA stripped lower that some third party had filled with various parts, etc…

  7. I personally think this is a really great idea. Instead of paying for two complete lowers, you save the cost (which can easily top $300-$500 if blinged out) of one of them and then splurge on a high end trigger pack.

  8. 300 WSM…..THAT has my attention!!

    If someone is looking to have just one AR in safe this would be a good option. Not everyone wants a whole bunch of guns in the safe. That’s the beauty of the whole AR system, something for everyone.

  9. I am in the market for a 308 then I saw this. Good thing I did not buy one yet. I already have an ar15 upper now I can use this 308 lower with my ar15 upper. By the way I live in CA so I called OA about the Mag release. I was happy to here that the lower internal parts are all standard, so I can switch out the mag release button with a bullet button. Now I have to find a dealer.

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