I just took my new 9mm, new to me that is, all factory Colt  out for a test run.  No problems feeding and digesting 3 different types of ammo, in two different magazines.  There were few occasions when the rifle fired a 2 or 3 round burst when the trigger was pulled once.   I tried to replicate the occourance by using different trigger pulls and such, but it seemed to occour randomly.  I cleaned the weapon before taking it out, and this occoured after about 175 rounds went through the gun.  I fired a total of about 300 rounds last night and this occoured maybe 3-4 times.  While it was sorta cool, I'm concerned of any impending problem.  Any ideas?
Thanks,
Tony

it could be crud making the firing pin stick.  blow backs are dirty.  

Thanks for the dirty firing pin suggestion advntrjnky, however I don't think that's it.  It really doesn't look that bad, however I'll clean the entire rifle again and take it out over the w/e.

David,
I tried what you suggested and I can't budge the hammer from the disconnector.  There is no foward movement and very little laterial movement.  I inspected the hammer pin and that is intact also.  Any other suggestions?

Thanks again,
Tony