The PWS MK107 has a long stroke gas piston which is fashioned in the same manner as the AK47. The piston is up in the handguard right under the front sight. The gas system has a 3 position adjustable regulator where 1 is full open for typical conditions, 2 is for normal operation with hot loads, 3 is for using a suppressor with increased back pressure and 4 is for disassembly. The long stroke piston has more mass to retard violent extraction and the adjustable gas system is tunable to minimize stress on the guns internals. The long stroke system is simple and robust and not sensitive to fouling either.
