Hi to all! I'm currently building up a couple of post ban AR's using VM HY-TECH lowers and DPMS A3 uppers, I'm waiting for some Bushmaster barrels to complete the projects. I have had great luck with all the manufactures mentioned, and have settled on this combination for any future projects.... but, I have encountered one slight problem, it is not serious, but I would like to make it as right as possible! I am using AR hammers that, it is obivious, were origionally M 16 hammers... the auto sear knob was ground off, but the anti doubling notch on the top of the hammer face was not ground in at the same time. So, I had the notches ground in, and I have been testing them to see how they interact with the bolt carrier, firing pin for correct function... and, I found out that there is quite a varience in different manufactures AR-15 firing pin dimensions... The upper to lower fit is tight, no slop or drop...  so you can barely feel the hammer catch on the major dia. of the firing pin rear spool... When the disconnector fails, is the hammer supposed to catch on the hammer strike knob of the pin, or the larger dia. part of the spool?? What is the dia. of larger part supposed to be?? If the firing pin is out of spec., I'll modify that, if it's ok, I'll revisit the hammer.... Thanks to all! till...later...GT