Looking to pick up a good all purpose AR and was looking at the M400 elite. Possibly for 3 gun later in life. The Tread is at a great price ($729 shipped) and looks good in reviews, etc. but I have no idea in real life how it is and, most importantly, can't seem to find the answer to a rather stupid question - am I limited to Tread accessories only or will I be able to add anything down the line I'd like? Thanks. Any thoughts and opinions are appreciated.

If you want to have access to the full suite of AR components, just build an AR out of AERO stuff and go that direction.

The farther you get from the standard AR platform, the more you are locked into a propriety platform.

Whether that's important to you or not, is up to you.  (I'm not saying anything "bad" about the rifle in question).

(this is just a general rule of thumb).

I agree, but this needs to be a complete one as a gift to a family member (that will be made legal through all local, state, and federal laws...) so it's a lot easier this way than giving them a build or parts kit and building with them.

Can't seem to find if the Tread is locked into just Tread accessories (I wouldn't think so, but...) or not.

Quite frankly, I would opt for the M400 Elite rather than the Tread. For a GP type AR, the stainless steel barrel of the Tread would be a "no go" for me.

It's not really proprietary, all standard type AR parts.  The handguard takes M-LOK accessories, whether they're the Sig made ones or other brands shouldn't matter.  Any standard iron sights should be fine (you'll need an M-LOK Picatinny rail to mount the front sight).

Thanks, that's what I thought but couldn't confirm. And we've all bought things at one point or another that only used proprietary equipment, so thanks. T do think however, the barrel is a good point. Don't know how i missed that one, so thanks.

And Pmags for stocking stuffers!