Be advised, as I was, that if you are going to swap an upper with the full length gas tube onto a lower with a collapsible telestock, you'll have problems with function and wear.
I was very excited about installing the 24" V-MATCH UPPER onto my Pre-Ban Dissipator with the aforementioned telestock, that is, until the guys on the Forum told me what to watch out for, and it was confirmed by Bushmaster.
My solution? I ordered the NEW TeleSTYLE buttstock!!! It looks (almost) like the collapsible one when extended, only the buffer and spring are larger and compatible with either the short or long gas tube. I just test-fired both uppers on the same lower with the TeleSTYLE buttstock and they worked perfectly for me.
I, too, will be ordering a new Post-Ban LOWER at a not too much later date, so I can have a KillerKarbine and a TargetShooter.
Good Luck. The folks at Bushmaster are the best.