they usually want more threads in a shorter span, and my guess they are not different from the other recent housing screws and either 8x36 or 40...seems the 'old model' (large body,small threads) were 6x40, and I have a few stainless ones setting here, and its half and half?? some screw in BOTH an 8x36 or 8x40 and others will not,but ONLY in the 8x36........
over the years many "N" mounts for scopes also used the 8x40 threads....gun screws are normally NOT the same as good ,old hardware store screws................