For all those who swap out & shoot different upper receiver assemblies on a given lower - Do you use the same bolt carrier and charging handle or do you have a carrier assembly specific to each upper? It would seem to the purist that having a carrier/bolt assembly specific to each upper might be better as they would wear evenly together, etc. What do you have and what are your thoughts? Any aromrers / smiths care to chime in on this one please jump right in. I have both a Colt 20" & a Bushmaster shorty and will soon be getting a 24" bull flat top, will probably use with the Bushy lower - THANKS

The only interface that really wears in is the bolt-to-barrel extension. You could get away with swapping several bolts on one carrier and moving over the charging handle, but after a while you will get tired and buy one set for each upper. There is a little wear along the rails inside the upper receiver, but not enough to matter over the near term.

If money is tight you won't get into trouble by using just one carrier and CH, with a bolt head for each barrel. Then save and buy the pieces as you go.

I bought the complete upper with bolt. It's not that much more money and you'll always have an extra back up carrier if needed.