Hi Guys,
I need advice on an Bushy AR15 jam that occured over the weekend. While shooting a match and changing magazines I let my bolt close as usual. When I pulled my trigger, nothing happened. I tried to clear the round from the chamber but could not open the bolt by pulling the charging handle back. The range armorer had to push the bolt back with a screw driver through the ejection port. the round then ejected and the gun worked fine after that. I measured the round in question with a Dillon (go / no go) gauge and calipers checking all dimensions, and could find no problems with the round that was jammed in my gun.  My gun was clean and lubed too. I can't figure out what happened... Any Ideas ?

If you let the gun get hot and are using some of the surplus ammo that is coated there is a chance that this coating will melt and stick the round inside the gun.
just my 0.02 Ron

 Check your extractor, and clean your chamber.  Stuck cases are usually the result of some foreign matter stuck on the cartridge case, 'freezing' the cartridge in the chamber.  If you are using laquered steel case ammo, this will ocassionaly happen due to sticky laquer. If it's all Bushy, it'll probably never happen again, unless you feed it poor quality ammo.

Surplus ammo will jam like that under rapid fire situations.  The same thing happened to me with some south african ammunition after a period of firing.  So what do you do!  Pay a hell of lot more for just plinking or deal with an occosional jam!

Another posibility was that the forward bolt assist was touching the bolt.  Therefore you could not move it backwards.   This happened to me on my M16 twice.  It ended up breaking.   I am now running my 16 without it.   I'll eventually replace it but its not really needed.