What is the Optimal Barrel Length and Caliber Combo for Sub-Compact Autos?

[Powder_Burn]

I'm in the market for a plastic sub-compact and am trying to determine the optimal barrel length and caliber combination. I am familiar with the pros/cons of common pistol designs and calibers but I need to better understand how a short barrel influences overall effectiveness.

For example, some sub-compacts have 3" barrels while others have 3.5" barrels and I am curious as to whether this makes a meaningful difference in velocity. Also, do any particular calibers reach their optimal "working" velocities faster than others? I want to avoid caliber/barrel combos that result in velocities too low to reliably expand hollow points. Appreciate any clarification or corrections around this.

Ultimately, I am looking for the caliber and barrel length combination that delivers the greatest velocity and energy in a sub-compact package. Preferred calibers would be 9mm & .45 ACP just so I don't have to start stocking another caliber. Many thanks for your help!

 

[FEG]

The range of possible loadings in a cartridge like .357 Magnum or 10mm makes this sort of discussion moot. No pistol is so superior that it can afford to ignore the load...

 

[Powder_Burn]

So taking the 10mm example, can an over the counter hollow-point load reach it's "working" velocity in 3" or 3.5" barreled gun? If no, what calibers are capable of doing so? Don't want to end up w/a pistol that basically ends up shooting ball ammo no matter what I feed it! As an example this is known to happen with pocket .380's.

 

[loop]

Regardless of what some people will say, there is no such thing as reliable expansion in pistol ammo unless you are shooting a very high-velocity round like the .357 or .44 mags.

Plus, there are far too many variables that can affect expansion. Shooting through a leather vest or jacket will tend to plug most HPs and prevent expansion. A pocket protector will plug a HP. A Band Aid will do it too, as will a nylon windbreaker. Layered clothing can plug an HP and prevent expansion.

I carry a .45 and load one HP in the chamber and fill the mags with hardball. The hardball may not expand, but it is going to make a .45 hole no matter what. If a 9 gets 30 percent expansion it will be the same size as a .45, but will weigh half as much.

I've done a lot of experimentation shooting loads that had previously been chronographed into water. Under optimum conditions the minimum velocity to get all rounds to expand was 980 fps. This included bullets made by Speer, Sierra, Hornady, Winchester Silvertips and Remington Golden Sabers. All rounds were handloaded so I could bump the velocity up a little at a time until all of a five-shot group expanded.

In a .45 I couldn't get a 230-grain bullet up to 980 and therefore never achieved consistent expansion.

The general rule of thumb is you lose or gain 100 fps per inch of barrel. With factory ammo you cannot believe what the maker says about the velocity. Because of the way commercial powder is made there can be great variation within the same batch and even more between batches.

Further, unless you know the test barrel length and type, their velocity statement is meaningless. Some makers may test out of a standard gun, but some test out of a special barrel with a sealed breech. The maker may say the load is rated at 1,116 fps, but you might find that was out of an 8-inch barrel with a sealed breech. Meaningless if you have a 5-inch barrel.

Unless they say it was fired from this type of gun with this length of barrel, the number means nothing.

With auto loaders, the shorter the barrel the more there are reliability issues. I'm not aware of any 10mm in a 3-inch barrel. I think the logistics of making a functional 10 in that length are overwhelming. Plus, you won't get much of the benefit in that barrel length. 10s use relatively slow-burning powders for the most part and require more time to achieve their velocity.

I have a number of very reliable 45s in 3 1/2-inch barrels. One in particular also is one of my most accurate guns. I don't have any in 3-inch, but of the ones I've seen at the range most had some reliability issues. But, they were also using factory ammo. Many reliability problems can be overcome by hand loading specifically for that particular gun.

Because of reliability issues I would recommend the 3 1/2. It isn't much bigger than a 3, but it is enough bigger that there are far fewer reliability problems.

If you really want the best performance out of any gun start reloading. You can get everything you need in terms of equipment in a kit from Lee for a little over $100. Buy $30 of powder, $10 of primers and a couple hundred bullets for $20. Your first bullet costs you $160. I buy in bulk and my .45 ammo runs me $8.20 per 100 rounds. Plus, every round is tuned to the gun.

 

[Powder_Burn]

So in the above example a velocity of 980 if required for expansion in ideal conditions. Taking that into the discussion, the key question is which rounds can reach 980 in a 3 or 3 1/2 inch barrel. I haven't found sub-compact chrono data that I need to make a decision. Unfortunately, I'll be using only premium factory loads so I can't tweak the ammo. Thanks.

 

[Northalius]

Speaking of 10mm in sub compact (well, a little bigger), the Glock 29 has a 3.78" barrel, and does spectacular according to gel results from DoubleTap. Even better with expansion in gel compared to the Glock 20, since the Glock 29's shorter barrel makes less velocity, and thus doesn't frag up like from a 4.6" Glock 20 barrel. The rounds fired from a 4.6" barrel Glock 20 were bending back a little, but still the 165 gr. Gold Dot from DT expanded to over an inch in diameter; so I'm assuming the Glock 29 did similar or better.

The 10mm has similar or faster speeds than the .357 Magnum, so it's going to expand reliably compared to the average weaker "service caliber."

 

[Z-Michigan]

.41 AE with 3.873434" barrel.
2nd choice: .500 S&W with 2.9995544" barrel.



On a more serious note, I've tried to figure this out myself, and have found that there is not a consistent relationship between barrel length and velocity, even though you would think there should be. It is not uncommon for a shorter barrel to be consistently faster than a longer barrel in a different brand/model of gun.

I would pick whatever you like that is quality and practical to carry, and focus on ammo selection. The Speer short barrel ammo is a top pick.