I have just nearly completed (awaiting the carbine stock wrench) a 16" carbine. I also have a 20" barrel I am planning to use for something else. The 20" came off another rifle, and came with a Colt 1/2 circle semi carrier.

Currently the carbine is wearing the Colt 1/2 circle carrier with a new CMT bolt.  

Anyway, I have two bolts, one carrier and two uppers, and a third upper on the way. So I need to start making some decisions.

The original Colt bolt goes with the 20" barrel...but regarding carriers:

Was planning to get CMT shrouded units.

Any mechanical/technical reason to use a 1/2 circle/light carrier in a rifle or carbine versus a full-weight carrier? Is there any mechanical advantage to having extra weight in regards to gas tube lenght, in/re reliability or function?  Or should I not worry 'bout it?

thanks for your thoughts.

Don't mix used bolts and used barrels.  The "shrouded unit" would be good if you want to do rapid fire/bump fire since it keeps the hammer from hanging up on the BCG.  The heavier carrier will smooth out the recoil a little.  Otherwise it makes no difference that I know of.

Shok

Quoted: Don't mix used bolts and used barrels.  The "shrouded unit" would be good if you want to do rapid fire/bump fire since it keeps the hammer from hanging up on the BCG.  The heavier carrier will smooth out the recoil a little.  Otherwise it makes no difference that I know of. Shok

Thanks - my intention was to keep the used bolt and barrel together (they came off the same Colt) but there seems to be no reason to do the same with the carrier itself.