[kdogg]

One important thing to keep in mind is that somewhere along the lines, Systema changes inner barrel diameters from time to time.

For example.

I have two PTW guns here. Both M4-A1's. We will call them PTW A and PTW B.

PTW A's inner barrel fits into PTW B very easy. However PTW B's inner barrel wont fit into PTW A. After trying to tap PTW barrel B into gun A, I had to use a rod and a hammer to get it back out destroying the brass barrel.

Cough cough... Take that for what you will.