In 31.5 years of AR15 ownership, assembling, shooting, and trading (I've had a remarkably high number of ARs pass thru my hands) I've have yet to see or experience a single lower receiver failure. I did have an EXTREMELY low quality cast lower in the early 1990's that was grossly out of spec....but it still worked.

This is why I've sold my extra complete rifles. I bought two spare LWRC uppers as replacements for the couple of complete rifles I kept. I have no worries about wearing out the complete rifle lowers, but the uppers I could eventually wear out.

OK. MY Colt AR15A3 Tactical carbine is as follows:

Marked Colt AR15A3 on the lower receiver. Below that is
SN BD002915 (only thing I can find is this/ BD000134 and Below - Pre-Ban (AR-15A3 Tactical Carbine - very rare model).

On the barrel is marked CMP (I THINK) and 5.56 Nato 1/9 Hbar.

It also has the flat top forward assist W/case deflector.

I THINK it is model 6721, but there isn't any other markings on it that I can find.

Oh and it does have the detachable carry handle as well.

I read your post again Gary and Mine DOES have a flash hider. It is VERY similar to this one, but the bottom side is solid with the slots only along the sides and top.

http://www.midwayusa.com/product/343064/dpms-flash-hider-a2-1-2-28-thread-ar-15-matte
AND mine also has the bayonet lug. JJ sent me a bayonet for it and the "Lock up" rattles a little due to the "Ring" being to large but other than that it fits nicely.

YUP, this looks like what I got. AND I bought it somewhere late 1994-early 1996.

The AR6721 HBAR model.

http://www.colt.com/Catalog/Law-Enforcement/Products/Colt-Tactical-Carbine
Click on the Tech Specs section under the picture.

I've had a 6721.

Your rifle is fine for someone wanting a HBAR DI. You have a very good Colt that would address most peoples' AR needs.

I'm not a fan of: Carbine length gas systems, HBARs, fixed front sights and DI guns. However, that's just my opinion.

ETA: if it works for you don't worry about it.

Regarding the fixed front sight....

I PREFER them if I don't plan on using an optic. I always coupled them with a LMT fixed A2 rear sight. However, I equip all of my social rifles with an optic and UBER PREFER the uncluttered FOV of a flip down front sight.

Today's high end optics are of such quality and durability to actually render flip sights as true "back up" status.

Wouldn't own a rifle without METAL BUIS.

If I planned on running an AR with iron sights only I strongly feel the best option is the fixed front with A1 Rear. I hate that Colt "upgraded" the 6420 from an A1 rear to a A2 rear and renamed it the 6520.

The super lightweight 6420 was the perfect DI KISS Carbine at 5.6#. The 6520 is the same but with unnecessarily complicated and more fragile A2 sights. I have no illusions of shooting 500 meters with the 6520's super LW barrel profile. Let's face it, the 5.56 has ballistic limitations anyway.

Thanks for the info Gary. Yeah I figure that this will serve me well for MANY more years to come.

After training with them I will take static 45deg offset sights all day long over pop ups. As you said Arch less complicated (read failure points) and always ready if needed.

I've only had one set of 45d offsets, and didn't keep them long enough to form an opinion. I like the idea and should explore it further. I'd also like to try a 45d T-1 sistered with an ACOG.

greaser, are your sights fixed or flip?