I have recently acquired a number of magpul stocks (CTRs, STRs and ACSs) for both commercial and mil spec receiver extensions. ALL of the mil spec tube stocks fit tight when the locks are engaged. ALL of the commercial tube stocks fit loose when the locks are engaged. It doesn't matter whether the commercial tube is Bushmaster, RRA or no-name, it's the same lousy fit.  Anybody in the hive know why or have a fix for it?

The several Moe mil-spec stocks I've had the pleasure to fondle all had loose fitment of the extension.  You could slather some JB weld or similar product onto the extension and sand to fit maybe an option.  The one ACS I do have fits perfect on my mil-spec receiver extensions.

Interesting.  I have a CTR, an STR and an ACS-L on commercial tubes (two UTG, one Armalite), and they lock down tight.

What does a caliper show your tubes at? Should be 1.170"

Not that uncommon with commercial.
No clear standard on tube O.D.

Take a look at this...

https://twopackshaker.wordpress.com/2011/12/11/tighten-up-your-magpul-ctr-stock/

I have read where people put a little black tape on the buffer tube. Never tried it as all my mil spec stocks lock up tight.