I'm starting to build a LR-308 and want to avoid the AR-15 receiver extension system with its smaller/lighter buffer, and wanted to buy POF's 7-position 308 A5 receiver.
Looks like they stopped selling it and now have a 6 position "Evolution buffer tube" for their 5.56 sized 308 rifle. It's a proprietary buffer tube,
so I have no idea if it will fit a typical 3.25" buffer and a rifle length spring. Called their tech support, and he said it's an "A2 format" which kind of confused me?
The only thing I could find on their website is this, which isn't that helpful other than showing the buffer tube being .500" inches longer than a typical AR-15 carbine buffer tube.

https://imgur.com/a/Zw7o3Zh

When I was building a few large frame AR's, I was debating on using that extension.  Never heard anything bad about it but I ended up going with a regular tube.