I was wondering what brand of barrels and upper recievers the millitary uses?  I know they use colt m4, but do they use dpsm and bushmasters also.  Are all the m4 Colts?  thanks

Colt is the current supplier of M4 carbines to the U.S. military and FN supplies the rifles.
 

I thaught for some reason that they also used Bushmasters also.

For the first Gulf War I heard that they made a run of about 10,000 M4 carbines, but Colt threatened to sue them for infringement on their patent rights. I don't think Bushmaster has made anything for the U.S. military since then. It didn't stop me from buying mine though.[:)]  

Bushie got their contract thru political pull (remember where the Bush family has their summer home?)and the owner is a big Republican doner. Last I heard, tho, all of their production pieces had been farmed out to other federal outfits like the Border Patrol, BATF, etc., and the Army wasn't actually using any of them. In fairness, tho, that is an unsustantiated rumor, and I don't know it for sure.[:D]