Best Investment...
It seems as if the cup launcher that clamps on to the nose cap that I bought for about $20 some 15 years ago may have been one of the better investments I've made in some time!
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It seems that the caliber of the WW-II British grenade (Did they use these rigs in WW-I?) was almost exactly the same as a regulation tennis ball, which I thought was terribly considerate of them.
With a home rolled blank using a dab of shotgun powder and a patch of wool for a wad (they used wool for the powder bags of Napoleonic cannon as it does not smolder / set things on fire after firing) it lofts a tennis ball pretty well - but since it blasts a hole clean through them they aren't much good for anything after that.
I found a mill that turns decorative and craft wood items, and by chance they have hardwood balls in just the right caliber!
Yowie!!!; Don't those things sail?!
Since my wooden balls don't weigh as much as a grenade, recoil is negligable and firing from the shoulder is no problem.
In the old boards some one posted an earlier manual that shows how to launch a grenade out of one of those muzzle-cups attached to the No. 1 Mk. III.
A distinctly different technique.
By and large you'd reverse the rifle (barrel away from you) with the butt planted on the ground, tilted towards target (kind of like the Chinese "Knee Mortar" I suppose) and hang on to the nose cap with the left hand.
There is a vent port at the base of the cup with a sliding gate so that the launch pressure may be adjusted. Once set, a knurled set screw locks the gate in place.
The Mk.III barrel was known to flex under recoil and sometimes blow the handguard right off. That's why they wrapped them and the wrist in wire.
Although this picture shows a mid-forestock grip, apparently Tommy quickly learned that this was not where he wanted to be holding on when the handguard blew off!
Another thing; using light "squib" blanks the report is not all that bad - but if you load them up for serious ball - launching (have yet to find a tin can that really fits well) you will need hearing protection - the "muzzle" of that cup is about level with your ears and will ring them badly if you are not properly muffed up or plugged!
The cup "rings" like a bell for a second or so after firing, which is sort of an entertaining effect.
Since our Government, in all it's infinite wisdom, has decreed that the PVC plastic sewer pipe "Potato cannon" is a "Destructive device" and mere possession of one is now a federal crime, It's probably safe to assume that in any realm where subjects are found to be having too much fun launching golf or tennis balls or other inert projectiles, that they will be verbotten there as well, if they are not already "contrabando".