There are several issues with suppressing the .380 pistol. This, of course, does not apply to the MAC M11 originally built in .380.

First is availability of obtaining extended barrels that are or can be threaded. Usually the wall thickness is not adequate for successful extending with an adapter.

Second is that the weapon is usually a simple blowback and is designed to cycle as an unlocked breech weapon. This includes the recoil spring, slide mass, etc. being designed to handle the time under pressure (dwell) of the bullet in the barrel. A suppressor will increase the dwell, which results in increased opening slide velocity. There are two net effects: first, there is more residual pressure in the bore when the chamber opens and ejects the cartridge (more ejection port noise). Second, with increased rearward velocity, there is a bounce against the slide stop and increased forward bolt velocity with the result that the magazine spring doesn't get the next cartridge in place for the both face to catch the rim. Frequently, the bottom edge of the bolt face will pull the next round out of the magazine by catching it forward of the rim.

There is a cure in that machining a tiny ring (groove) mid chamber will slow opening by having the brass momentarily expand into the groove. The trick (which varies with the weapon), is to have the ring deep enough to do the job with the suppressor attached and continue to have reliable functioning when the suppressor is not used. Of course, the eject brass left on the ground at the scene then looks really wierd and makes it easier for the police to identify the weapon.

There are no aftermarket barrels that I know of with ringed chambers. This is a trial and error process.