The receivers are exactly the same, it's the hammer packs and the trigger stop under the safety that are the differences. The barrels were identical at the breach and there were no other difference with the exception of length. The barrel sleeve nor the bi-lock touch the receiver. The receiver is made of a softer metal (alum?) and would take damage if they butted up against the receiver. There is a small amount of play between the receiver and the barrel and the barrel is held forward by a strong spring located right behind the front end of the receiver. The reason that the barrel and flash hider need to be "tuned" to a specific ft-lbs is because it is at the end of the threads, not because it's up against the receiver.
Zhur, I hate you and your sexy '90. Let me ask you this, when I go to the range and I take my baby, alot of people will gather around me with anticipation of me shooting or they just want to admire it. Now, being that you SBR'd it, people are naturally think that you have a P90...do you ever get any negative feed back on doing this?