Since I entered into the world of building ARs I joined as many forums as I could. I went to these forums for ideas, potential sales and just to chat with other enthusiasts. But there is one thing I noticed about forums as I became much more versed in building of ARs and that was the amount of misinformation being put out there. There are thousands of posts asking about certain laws or information on certain parts. The most amount of misinformation I see beyond laws is the information on AR10/LR308.
The AR10 is something that many hear about but don’t think about it being any different than the AR15. First and foremost, there is no standard for AR10 parts. If a company claims to have milspec AR10 parts then they are just using buzzwords to draw you in to buy it. There are two platforms that are available to build an AR10 off of. That is the Armalite pattern and LR308 pattern.
The Armalite pattern is the original pattern but it is the most restrictive for parts. For the current AR10 lowers made off the Armalite pattern today there is a no issue with magazine and which ones you choose to use. But be careful for which lower you buy. Some of the older ones will not take a Magpul magazine, or any magazine except the Armalite steel magazine which are extremely expensive ranging up to $90 a magazine. There is also a significant angle where the upper and lower meet at the back where the buffer extension is.
The LR308 pattern is much more common and looks much more like an upscaled size version of the AR15. The buffer extension is at at a much more acute angle, this is the easily visible difference between and LR308 and the Armalite AR10 pattern. The LR308 is also known at the DPMS high pattern. The reason behind this is because the picatinny rail on the upper receiver sits significantly higher than the AR10 pattern.
What makes the AR10 so easy to work with outside the stripped receivers is the parts they use. The trigger, most of the lower parts kit minus the take down pins work with the AR10 lower. It will use the same buffers and stocks and the same pistol grips. The upper is a bit different, if it has a forward assist it will use a standard AR15 forward assist. The BCG is much larger than the standard AR15 but there is no variance between an LR308 and AR10 BCG, they are the same. The charging handle is bigger and much stouter when compared to the AR15 charging handle.
Now there are companies like Matrix arms who have taken a step to remove this confusion by combining the platform. Their upper and lower are shaped like the AR10, but the picatinny is set for DPMS high. This is the platform I have decided to use as it has a bit more custom options and I like the angled buffer extension.
