Okay,  Here's the deal, I have a spare bolt that I obtained from QPI.  Now will this simply drop in should I ever have a need to, or is there something else I have to do ?  I don't have a problem swapping the parts(yes, I've had it apart several times), just would like it to work correctly when I'm done. Also, can anyone suggest a good Book and/or Video dealing with the internals of The AR. (or in my case the XM)

Thanks
BD
"Strength is in Unity"

Got a dial caliper with a built-in depth gauge?  

Take your original bolt (providing it yielded proper headspace with your barrel) and measure the length of each of the full length locking lugs.  The lugs should be within .002" of each other.  Now measure the depth from the forward surface of the bolt to the boltface where the head of the brass seats.  Subtract the smaller number from the larger.  The result is the distance from the back of the locking lugs to the face of the bolt.

Now repeat this process on your new bolt.  If the new bolt "thickness" is equal to or greater than your original bolt, then the new bolt will be compatible with your barrel and will be no less safe than your original combination of parts.


Waldo is right....no substitute for headspace gages.

Thanks guys,  

J3, It should have read QPC not QPI...Quality Parts Co.  Bushmaster.....Hmmm...wonder if they can make me a field headspace gauge in purple to match my upper...

Thanks again guys....

BD