Originally Posted by alwaysshootin
Guess you aren't aware of the differences in the 20, and 21. There is more to it than a barrel swap. The fact, that all others, who claim the 4th Gen in other models, is a change from the 3rd Gen, would in fact, make the 4th Gen intro of the 10MM model, a "New" introduction.
Your right, it does need a new slide also. The breech face is a different size and would require a smaller drill bit to cut. But the frame is exactly the same as the G21 frame, which is already in prduction.