Hi All,
I got my hands on an old Colt Lightweight Sporter.
I can't for the life of me figure out why the bolt won't stay open in any situation.  For example:
Empty mag, pull charging handle and the bolt slams forward all of the way.
If I press the bolt catch to be up where it will stop the bolt, it feels lie it slides over it with a little bit of a catch.

I've been comparing this with my other AR and I can't seem to figure it out.  I have swapped magazines and the problem stays with the Colt.
The bolt catch appears to be good as well.

What I can tell is the bolt on the colt does not pull as far back as the other AR.  In fact, it seems like it isn't pulling far enough back for the bolt to stick on the bolt catch.

Has anyone seen this before?

I think  I sorted it out.
This Colt has a 3rd party buffer tube.  The buffer is shorter than it should be.  It is a 3 position tube and is around 1/4" short.

GGGRRRRRRR!!!!!!!

Wow

I bought a new rock river and have the same problem. Buffer tube is only 6 3/4" deep....1/4" short

Seems like alot of dealers are buying parts and passing them off as complete rifles to make a buck with todays market.

really f'ing pisses me off that they cant even do a simple check to ensure that everything operates correctly.