I have one of these attached to my custom upper. It's been good so far, but I'm wondering, is there anything the other Colt lowers offer that the HBAR doesn't?

Quoted: I have one of these attached to my custom upper. It's been good so far, but I'm wondering, is there anything the other Colt lowers offer that the HBAR doesn't?

In short......... No

Other than different rollmarks.

The HBAR model was more a reference to the barrel used on the rifle - a Heavy Barrel.

A standard A2 lower.

Except for the rollmarks the only thing I noticed that are different is that some lowers have the hole for the detent pin for the takedown pivot pin, some don't have the hole.

No big problem if it doesn't have a detent hole, a gunsmith could put it in.

I also have a Colt Match Target HBAR model MT6601 lower receiver that I'm using on my Colt M16A2 upper, it's been good so far it runs like a sewing machine.