I would like to replace the 4" barrel with a 4.25" barrel
in my MP9 M2 Compact 4".
It seems to fit just fine.
However, I saw another forum says the barrels are flared and will not lock up with the slide (maybe P.C. guns).
Another oddity. Seller measured the barrel as 4.22". I believe they forgot to include the bullet case in the measurement. But sure enough, the barrel sticks out only .22" in front of the slide?