Major Robert Henry Cain VC did this at Arnhem. From Dickiebo:

When Cain joined the battle the Staffords were under heavy attack by tank and heavy guns. By firing mortars at almost point blank range towards the Germans, the British were able to hold their ground. Cain and Major Jock Buchanan assisted Lieutenant Georges Dupenois in repelling the tanks by drawing fire and providing him with ammunition for his PIAT gun (low-tech anti-tank gun). Although no tanks were destroyed they were held back until Cain’s forces were ordered to retreat.

Hat Tip: MP.net

1″ long and 0.710″ high.

More photos here.

CU_Cannon built the “Nano-mortar”. It fires .177″ BBs. The bed it sits on is 1″ long.

Click to expand the images.

The Nano-mortar

Here is a video of it in action

Blueprints

Cal.45 built a 3mm mortar called the “Pico “Mortar”

The “Pico Mortar”

The pico mortar was build solely with a drill-press, some files and emery paper. It fires 3mm shot pellets (0.118 inch diameter) and has a maximum load of 0.2 grains of blackpowder. It has a barrel length of 8mm (0.315″) and can fire 6 meters (20 feet)

Anyways. I started with a load of about 0.2gr Swiss #2 but this did just a sizzling sound, so from the next shots on I used Swiss #1 (which is even finer in granulation: about 0.011 to 0.015 inch) which produced a nice snapping. Cheesy.

The touch hole is 0.5 millimeters = close to 0.02 inch (that makes it about 16% of the bore diameter (if one may still call it so).

Priming was done by filling the touch hole granule by granule; sweaty hands help maneuvering these tiny particlesin place.

First I wanted to enlarge the touch hole to fuse diameter and keep the rest at the smaller diameter (to keep some pressure) but the wall thickness is that small, that this wasnot possible.

Ignition with a lighter proofed to be better than trying to do it with a match: the flame produces soot but therefore does not function (kept them as size reference on the photo though).

Whatever. At first I thought that the shot would barely leve the muzzle: wrong!

Firing from the kitchen table I shot dimples into the door! This was 2.5 meters (8.2 feet) away! By the trajectory (angle of the mortar and height of impact) this means an estimated firing distance of 6 meters (about 20 feet): I would never have guessed this to be possible with a piece that has a barrel length of just 8 millimeters (0.315 inch).

The “Pico Mortar” being fired

“Pico Mortar” blueprints

Rickk built the “Nano Cannon”

The “Nano Cannon”

Now I know what only the others who have made one know… what the tremendous roar they make sounds like Grin

Bore is 3/16 (.186), so it will take a BB. Fuse is 5/64, so it will takes 1/16 fuse.

Trunions, as well as cascable, are 3/16 inch steel rod pressed into shallow 3/16 holes and then brazed in place.

All the work was done on my drill press, with some help from an angle grinder and a file for shaping.

It needs a pit more polishing, but I just couldn’t wait to fire it ! Total time into is so far is about 2 hours.

The “Nano Cannon” with carriage

I found the smoldering paper towel pieces about 15 feet away, and the gun recoils back about 6 inches!

BTW, for BB caliber, Q-tips make excellent cleaning rods.

Terry C. built the the very first micro-gonne. A hand gonne is a hand held cannon. It fires #4 buckshot.

the micro-gonne

The micro hand gonne being fired. Note the wooden rod attached.

Victor build a bigger scale hand gonne: