MAG-7 shotguns are an example of good idea with poor implementation. Designed for law-enforcement and special operations, MAG-7 were supposed to offer the mobility of submachine gun with versatility and stopping power of pump shotguns.
Initial trials suggested, that standard 12ga shells would be unsatisfactory, due to length (hard to fit into magazine slipped in grip) and too hard recoil for off-hand shooting. Therefore, MAG-7 were designed to accept shortened 12ga shells (60mm long). The downside is that this ammo is very, very hard to get. Centurion, an Italian co. makes 2" shells for Law Enforcement that function perfectly with this gun.
This decision, coupled with short barrel, had limited the effective range of MAG-7 to 40 meters, though it had been proven, that shots maintain lethality on distances up to twice that (80–90 m).
While the range was not of particular issue (It's, after all, a close quarters weapon, not a sniper rifle.), MAG-7 had often received complaints about poor ergonomy. Most often were the complaints about the need to take hand off the slide to switch the safety and poor accommodations for gloves-wearing shooter.
Coupled with the fact, that proprietary shells are fairly hard to come by, although you could cut down regular shells, MAG-7 is more of a curiosity or collectible, then of workhorse weapon. Initially, it was oriented solely at military/security/law-enforcement market, but later, a MAG-7M1 civilian version was developed, with long barrel and fixed stock, to comply with civilian gun laws.