With a public, successful test firing, now is a good time to talk about the XM913 50mm autocannon, a modern application of the 50mm Supershot (sort of). The rounds are the same overall dimensions as the 50mm Supershot rounds, i.e. a straight-walled version of the 35x228mm cartridge. Since it’s building on an existing cartridge, the XM913 is actually a rather boring gun. It’s just a Bushmaster III with a different barrel. Same feed system, same great electrically-driven “chain-gun” design. The Bushmaster design has proven to be very reliable and scalable, since it’s externally-powered action doesn’t have to be recalibrated to function correctly with a different amount of recoil or gas. Rate of fire is also easy to adjust.

The ammunition in question is rather more interesting. While it has the same overall cartridge dimensions as 50mm Supershot, the new case is 100 mm shorter, at 230mm length instead of 330. Where 50mm Supershot was designed to give more KE power for armor penetration, the new rounds are designed to launch a larger volume projectile, for better airburst and guided options. Current design is for a command-guided airburst round for C-RAM and anti-UAV work. And it should still work with the previous rounds, if more armor penetration is desired.

Ammunition is the same base diameter and overall length as 35x228mm, so we’d expect the same ammunition capacity. It’s about half what you can get with 30x173mm, give or take depending on details.

On to what we think. I’ve always liked the notion of 50mm Supershot. I’m pretty skeptical of some sort of command-guided C-RAM munition, but bigger airburst is better airburst. We’ll see how tests shake out.