SuperShortBoi AR types were all the rage at one recent time juncture. It was a race to make them shorter and shorter while keeping them running (enough) to still be fun guns.
What everyone shortly discovered with these shorties was… well. They came up short in several aspects.
This didn’t negate their fun factor, just practicality.
Mike covers the HK53 in the video.
I’m going to discuss shorty 5.56’s in general down below.
Velocity is King. Size is about movement.
The two reasons to reduce the overall length of a weapon are ease of transport and ease of use in confined spaces. Both are important considerations.
Your “enemy defeat” capability in a Low Mass High Velocity (LMHV) Projectile comes from its speed first. Speed is arguably the most potent factor in generating a desired kinetic effect on target since kinetic energy is velocity squared multiplied by half the mass.
In simplest terms, increasing a bullet’s speed by 10% is more beneficial than increasing its mass by 10%. Taking a projectile that is 100gr and traveling at 1,000 feet per second and making it go 1,100 feet per second gives you the same effect at the muzzle as making the projectile 121 grains (mass increased 21%).
This is an oversimplification since terminal ballistics are a complicated science, but that is how the raw kinetic energy works out.
It also works the same in reverse. Every foot per second you lose has a substantial effect on what the round ends up at the target with the ability to do. Unless you are shooting paper or steel you aren’t hitting the target just to hit it, you are firing to disrupt it and might being needing an immediate effect to save your life or someone’s life.
Going from about 3,100/fps out of an M16 with it’s 20″ barrel to about 2,300/fps out of the HK53, or any number of other popular personal defense/personal security detail type firearms, drops your energy at the muzzle by 45%.
This is not going to make it ineffective inside 50 yards, 100 yards, maybe even 150 yards, but it will bring that drastic decrease in effective terminal ballistics ‘line’ much closer to you behind the trigger. The range at which the 5.56 or 5.45, the two most prominent LMHV types, lose enough velocity to stop doing all the extra tissue disruptive things that they can do gets brought in closer with every bit of lost speed.
This will also influence the effect on armor and cover. Your ability to tackle intermediate mediums is also challenged by slowing down the rounds. At 2,900/fps that little car might not be great cover. But at 2,300/fps it might be a lot better. An AR500 steel armor plate can stop 2,300/fps all day (sorry AK47). It’s a lot more challenging a stop at 3,250/fps (M16+M193=what plate?)
Blinded by the light…
Muzzle blast is a thing. It becomes a much more uproarious thing the less barrel you give powder to burn in, especially when you drop out of the optimum powder burn zone for a give round.
That optimum zone will give you very consistent velocity increases and decreases for every inch of barrel gained or lost. 5.56×45 is generally happiest in about 12-20 inches of steel and 5.45 seems to be as well. You see sharp decreases as you go shorter and anemic increases as you start going too much longer. This is often subject to the powder too, but we’re talking commercially available generalizations.
We are EZ mode covering a complex series of physics equations.
All that extra powder that wants to burn nicely in that optimal zone is still going to burn, it is just going to do so in the open air and give you that spicy Hollywood special effects muzzle flash…
It turns out that is very distracting behind the trigger… and downright brutal to teammates or other people in close proximity. Now put that inside the confined space of a vehicle or a hall and you have yourself a legendarily rung bell.
Okay… it isn’t that, bad in my opinion, but it is far from pleasant. The little PSD LWRC I have that mimics the size and capability of the HK53 is louder than my SCAR17.
So you’re saying we should…
Be aware of what you are buying and why. Your compact little HK53 pistol has a lot going in the portability and ease of movement categories, no doubt about it. But it gave up effective range of increased terminal effects (if you need it for this particular firearm) and got noisier and more disruptive to yourself and those around you, be they friend or foe.
Are we done talking practically?
Short guns are fun. Period.