Hey, this is my niche! This article is not very good - think of the last article you read about the internet betting a series of tubes, and your Steve Jobs is a brilliant coder.

The rifle design objectives are pretty poor, but there's some interesting innovations in there nonetheless. Unfortunately, it's mostly academic; modern symmetric warfare places less emphasis on small arms than ever before, and asymmetric warfare suffers huge diminishing returns from small arms investment.

In short, the AR15/M16 family will be around for a while, and that's fine.

This like many "this is the future of weaponry" articles doesn't say what specific this is to fix. There is no problem it is trying to solve it seems like. It is designed to be different without a clear overarching purpose. What is the purpose of having a 4 barrels? This was touched on but never fully examined or defined. I feel like this is slated to just disappear into the annals of "weapons that solved no problem".

Yeah this can be an episode of “Forgotten Weapons” in a couple decades.

overheating

This is nothing other than a novelty.

If you want portable bullet count, you use an automatic M4 (750+ rounds per minute).

If you want less portable bullet count, you use a M134 Minigun (2,000+ rounds per minute).

If you want single-shot spread, you use a M500 shotgun.

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Compare Metal Storm's prototypes, which used stacked charges to increase bullet count (but decades later have yet to see practical implementation).

Metal Storm's prototypes would be OK as active defense for a tank. Active defense systems are expected to destroy incoming RPGs, missiles, and possibly bombs or artillery shells. An example of a currently deployed system is one that fires a grenade-like thing upward and then has it explode with shrapnel going mostly downward. Metal Storm's prototypes would fit right in to this role.

Another use is as a replacement for the Claymore mine. It's a minor upgrade. The advantage is increased safety for friendly personnel in the non-target directions. Likely disadvantages are cost, weight, and bulk.

For conventional small arms, differing muzzle velocity due to different effective barrel length killed Metal Storm's accuracy. Eg, the top round in the stack may travel down 6" more of barrel than the bottom round; in a 5.56 gun, this could be a 500fps+ difference (https://rifleshooter.com/2015/12/223-remington-5-56mm-nato-b...).

How in the world do you keep something supplied that shoots 250 rounds per second? Is this a Mass Effect 1 rifle where you just slam a block of tungsten in the back?

It feels like we've mostly converged on the ideal form of a general purpose battle rifle over the past fifty years.

Single-shot spread with sniper range.

Unfortunately, aligning different bores is very difficult. Putting them in the same chunk of steel prevents them from diverging over time, at least, but doesn't solve the original issue.

They'll diverge as the gun heats up and the inner bores stay hotter than the outer ones. Both short term as you use the gun and the barrel warms up, and long term, when the bores wear differently for the same reason.

Good point! Hadn't thought about the bore wear - if they don't force successive shots to cycle through the barrels, that would be a huge issue.

Maybe. I'm skeptical that multiple simultaneous discharges wouldn't adversely affect the accuracy.

This is way too detailed, but describes how barrels behave while a shot is being fired: http://www.the-long-family.com/shock%20wave%20theory%20summa...

Based on this, it seems like multiple barrels probably wouldn't affect each other in different ways, leading to shot consistency as long as there aren't significant differences in ignition time or velocity.

Almost forgot: while not simultaneous, the AN-94 did not have issues with ultra-fast RPM in one barrel (https://en.wikipedia.org/wiki/AN-94).