PDW: 9mm vs 5.56

[H60DoorGunner]

I am not so sure there is just one or two weapons for the car. It really depends on what tasks you want the weapons to fulfill. The shortened pump shotgun is weapon that has been discussed on this forum for example.
It also depends on how much of an outlaw you intend on being and what legal environment you have to contended with as to what you carry. A GI M4 with the fun switch is a weapon I would like to own and carry. But I do not own one and for sure will not in a world still with rule of law be carrying such in my car. But there are some might.

I agree, there are no do-all's. The short pump or full sized shotgun are good weapons, particularly in an urban environment.

OP was talking about traveling in a car. Ostensibly, that entails more driving outside of an urban environment than in. In either case, with the exception of very particular operating environments, a braced glock is still less useful.

The level of outlaw one may or may not want to be is entirely irrelevant in regards to the usefulness of a weapon system. A witsec shotgun is still more useful in the middle of a NYC riot than a 9mm PDW, and both would be illegal there.

[Brightlightman]

If those figures are accurate, it wouldn't seem at the 5.56 has enough velocity to cause rifle type damage. Possibly just small caliber ice pick damage. If a bullet is not travelling fast enough to disrupt the elasticity of the human tissues, it makes a lot of sense to go with a pistol caliber instead of an inefficient rifle caliber. Personally, I'd go for the extra 2" of barrel length to give me better terminal ballistics in a rifle caliber though. In 300 blackout I've even gone to 10.5" .

Guffaw all you want. We can cherry pick data all day, but this is where I am coming from;

A 55 grain 5.56 from an 8.5" bbl is roughly 2100 fps +/-.
A 155 grain JHP from an 8.5 " bbl (contract ammo) is 1350 fps.

Considering that the 5.56 works well @ 3300 fps and not so well @ 2100 fps and the 40 works very well inside that velocity envelope, the longer barrel of the 40 essentially bumps it up to full power 10mm country. It performs very well.

You can't just look at energy figures. You also have to get past the " its a rifle " dogma, because it is only a rifle when fired from a rifle.

Not to mention the port pressure and just how LOUD short AR's are.

[barnetmill]

If those figures are accurate, it wouldn't seem at the 5.56 has enough velocity to cause rifle type damage. Possibly just small caliber ice pick damage. If a bullet is not travelling fast enough to disrupt the elasticity of the human tissues, it makes a lot of sense to go with a pistol caliber instead of an inefficient rifle caliber. Personally, I'd go for the extra 2" of barrel length to give me better terminal ballistics in a rifle caliber though. In 300 blackout I've even gone to 10.5" .

Of course with military and normal commercial ammo the above is true. 2100 fps second in .22 hornet range and so handloads with a fast powder and .22 hornet bullets might preform better in tissue from such short barrels.

https://aussiehunter.org/wp-content/...rnet-Table.jpg

[apamburn]

How does the introduction of high quality hollowpoints in 5.56 ammo alter the optimal velocity for high velocity fragmentation and secondary wound cavity creation?

I've certainly seen some gel tests of 77 gr 5.56 out of 10.5 inch barrels perform pretty well at close ranges, and cause damage not comparable to any handgun round.

And of course, we should take all of this with a grain of salt because getting shot in the face with a 5.56 that is below the "magic number" is still a fight stopper.

[apamburn]

Guffaw all you want. We can cherry pick data all day, but this is where I am coming from;

A 55 grain 5.56 from an 8.5" bbl is roughly 2100 fps +/-.
A 155 grain JHP from an 8.5 " bbl (contract ammo) is 1350 fps.

Considering that the 5.56 works well @ 3300 fps and not so well @ 2100 fps and the 40 works very well inside that velocity envelope, the longer barrel of the 40 essentially bumps it up to full power 10mm country. It performs very well.

You can't just look at energy figures. You also have to get past the " its a rifle " dogma, because it is only a rifle when fired from a rifle.

Not to mention the port pressure and just how LOUD short AR's are.

You're totally right.

This anemic 5.56 at a measley 2100 FPS from 10.5 inch barrel, which did this:

556.jpg

is no match for this unstoppable .40 SW at 1300 FPS from 16 inch barrel, which did this.

40.jpg

7x3 temporary stretch cavity and literally blowing a hole out of the bottom of the target vs poking a 16 inch long .8 inch hole.

[barnetmill]

Here is a sale on fragmenting .223/5.56 bullets. Should work well in short barrels. It is a sale at midway.

Screenshot_2021-01-22 Blemished - MidwayUSA.png