The M203 is a good system - however it is being eclipsed by more modern designes - and Deimaco's M203A1 mount is an abortion if I have ever seen one - anyone wonder why the Ski tems uses Colt M203's with KAC QD mounts...
However in the CQB environement IF I can keep the grenadiers out of the house (at least clearing I will) even on the C8SFW the M203 is awkward to manuever in close shooting.
The Masterkey set up is another cumbersome item - however unlike the M203 where no effective (key being effective) standalone setup existis for it - the breaching shotgun is an excellent stand alone system.
I have used the KAC Masterkey on a M4A1 and I must say I found it extremely wanting - awkward and tough to aim at a lock (I have several scars on my legs from Kevin's learning the hard way with shooting doors) - the offset for the barrel makes shooting close in tgts very hard.
The pictures Brit put up of the Mosberg/Serbi Super Shorty are an IDEAL breacher - that does not get carried away with any other role.
Less lethal: We where not allowed to use less lethal items in Afghanistan to do certain provision of the Rules of Landwarfare (or JAG interpretation of them) and the Chemical Weapon Provisions :

- Unlike Canada where I support the use of less lethal methods - if some asshat overseas is acting up - he is getting a few 5.56mm rounds and the story is done.
Para - IF I get my shory breacher finished - youl be the first to see - it is a very similar setup - as soon as I can get the business to finish it - I will have a 7" 870 with pistol grip (registered as a pistol) with 3+1 capacity with 2" breaching rounds - or 2+1 with 2 3/4 shells.
You can put a single point on it - or tuck under the cumberbund of a RAV (or similar vest)