Terminal Ballistics in Pistol Caliber Carbines

General Firearms Terminal Ballistic Information
1

I seem to recall seeing something about how launching a projectile too fast can actually be detrimental to its terminal ballistics.

I’m interested in getting a non-SBR 9mm carbine (Sub 2000, most likely) and I’m wondering if certain loads are better than others to fire out of said carbine. Obviously, I’m familiar with the recommended loads in the stickied thread, but I’m wondering what provides the best overall combination of a flat trajectory out to a distance and best terminal ballistics when the round hits. Kel-Tec says they recommend a 124gr loading, preferably in +P. I understand that would give a good trajectory, but how would it perform in terms of terminal ballistics? What would be the velocity gain as opposed to being fired from a pistol-length barrel? I have a good stock of 147gr HST +P stored up - would that give a good combination of flat trajectory and terminal ballistics?

I understand that training is paramount and as long as I’m getting good hits under pressure that’s all that really matters. Getting the best 9mm round for a PCC isn’t going to keep me up at night. Regardless, I’m just kind of wondering what the best answer is for ammo selection of out a longer barrel.

This is a lot of questions, and I suppose it could all be boiled down to saying: school me up on how firing pistol ammo out of a longer barrel (16") effects your ammo selection. I’m interested really in both terminal ballistics and external ballistics.

Thanks!

2

Defense pistol bullets are designed for controlled expansion within a particular velocity range. Drive them faster than that window, and many will over expand, and under-penetrate.

I don’t have much experience with 9mm out of a 16" barrel, but my hunch would be the lighter weight +P’s would be the worst performers, at least at closer distances, as most of them already penetrate less than the heavier bullets. I’d also further guess that a bonded, heavier round, would end up being a better choice, since I’ve seen some of them perform well in a wider velocity range. I’m sure Doc has run across the subject, as many LE agencies played with pistol caliber carbines, (including my own), in the early days before 5.56/.223 became mainstream for patrol use.

And as far as recommendations on defense ammo from gun manufacturers, I’d take that with a large grain of salt. Most of them don’t have a clue about terminal performance, and just parrot what some gun writer told them, or wrote in an article about their gun.

3

I recently did some chrono testing with 9mm rounds from a 3.5", 5", and 16" barrel. I’m not at home so I don’t have the results handy but if I remember right the .355 bullets were the same velocity out of a 16" 9mm carbine as they were out of a 5" barrel .357 Sig. So basically, a bullet that works well in the .357 Sig handgun should perform well out of the 16" 9mm carbine. I’ll give you hard numbers when I get home and can look up the data.

4

Remember that bullets can vary with caliber, regardless of weight or style of bullet. The bullet they use in 9mm may be different construction than the one in .357 Sig, even if they have the same name.

5

If you ever manage to get ahold of a ammunition developer for a major ammo company, they will tell you that they test their ammunition under a wide range of velocities and design them to work in many barrel lengths. Usually, there is a problem if you use a barrel that is too short, not really if you use one that is too long.

The two core elements of terminal effects with a handgun cartridge are, penetration and permanent cavity diameter. Every caliber has its own expansion threshold. There comes a point where it has a peak expansion, and after than the petals of the mushroom will simply fold back and hug the trunk of the bullet. A 9mm/.357 simply cannot equal the capabilities of a .40, and a .40 cannot equal the capabilies of a .45. Even when velocities are cranked up such in the case of Double Tap ammo, there isn’t an increase in expansion because of the expansion limitations of each caliber…just an increase in penetration:
https://www.m4carbine.net/showthread.php?t=26026

Now, some loads such as Remington GS, Federal HS, or Winchester SXT will shed their jackets during higher velocity impacts. However, increased velocity means increased momentum, and even though they have shed their jackets they still tend to penetration as deeply as they were designed to in the factory. If jacket separations concerns you, then use bonded bullets like Speer GD or Winchester RB.

6

They design pistol projectiles to work under a wide range of pistol/submachine gun velocities. Even the longer barrels of sub guns caused some terminal performance issues with 9mm when they were first introduced into LE. Bullets were redesigned with that in mind. I’m not aware of much in the way of testing any of them have done with 16" barrels and their increased velocities. I’d be interested in anything you have seen from them.

All true, and the thread you refer too is about a bonded core round, which as I said, do perform better through a wider range of velocities. I don’t think that necessarily translates to lighter constructed hollow points penetrating deeper at increased velocity, and that’s not what I’ve seen. Some of them not only lost their jackets, but even fragmented at hyper velocities, causing reduced penetration. Granted, I’m talking a few years ago, and bullet construction has certainly improved.

7

Good point. While they are both .355" bullets the manufacturer could alter the jacket design to change the expansion rate (and the velocity window). Unless handloading, it would be best to check with the manufacturer to see if they use the same bullet.

8

Except for .44 Mag, I detest pistol caliber carbines w/long 16" barrels. With such an abortion in 9 mm, you might wish to stick with the 147 gr loads, although it depends on engagement ranges. If your likely use is at longer 50+ yd ranges, the projectile will have slowed and act more like a handgun hit at close range.

9

Doc, are you saying that if one uses a 147gr loading, that the round will have slowed to typical pistol velocities past 100 yards or are you saying that any given 9mm round will do that?

I would want to be effective to 100 - 150 yards (150 yards being a low percentage of the time and an absolute long shot). And when I say “effective,” I’m more concerned about my ability to make good hits with adequate terminal effectiveness (ie: necessary penetration) than getting top terminal effectiveness. So I guess I’m really more concerned about the external ballistics than the terminal ballistics. That said, I’d still rather use a good JHP round than can expand and do a lot more damage in close than a FMJ round. I guess my first concern is good external ballistics to hit out to around 100 yards, and my secondary concern is good terminal ballistics.

Also, since you mention not liking PCCs with 16" barrels, about what barrel length do you reach your “point of diminishing returns” with PCCs in 9mm? I certainly want an SBR PCC, but for various reasons, it’s not practical for me at this time. Even a PCC with a 16" barrel fills a niche that I need right now.

10

Just out of curiousity what is the niche? Do you want a very compact carbine that uses the same ammo/mags as your sidearm?

That is my guess since you mentioned the Sub 2000. If you need something that compact with ammo/mag compatability then I see a purpose but as Doc pointed out, if you are going with a long gun a true rifle round will give you substantially better external and terminal performance than any pistol caliber.

11

12

Altair, I own several rifles, to include and AR and an AK. The long gun with pistol mag compatibility, the ability to fold the weapon up small enough to stick in a backpack, the low cost for the weapon itself and ammo, low recoil, less flash/blast/noise when used indoors, lightweight… all these things make it a good way to have a long gun handy in places where no rifle can be. Even if it shoots the same round with relatively poor “stopping power” as a handgun, it still offers a far faster and more accurate way of getting that round on target. Put simply, you can get more rounds on target at a longer range with a PCC than you can with a pistol.

It would certainly not take the place of a rifle. I love rifles and I am a big believer in Jeff Cooper’s statement that they are the queen of personal weapons. If I am going to fight somebody else, then I want a rifle in my hands, but there are simply certain things a rifle can’t do.

I would much rather have an SBR PCC than a long-barreled PCC, specifically an Uzi/mini Uzi, for the same reasons outlined above (ability to have a long gun in places/at times you can’t have one as well as less blast/noise/flash when used indoors), but for various reasons, that’s not a realistic option at this time.

Plus, I just want one. I’m a very practical person when it comes to what guns I get. For a “gun person” who grew up in a family of “gun people”, I have a very sparse collection; if I legitimately have no use for something, then I generally don’t want it. That said, I do enjoy guns and I enjoy shooting them. I’ve handled and shot Sub 2000s before, and they are fun, neat little guns to own and shoot. I’m a military man who is looking at law enforcement as a follow-up to my time in the Marine Corps, but guns are as much of a hobby to me as they are work. Sometimes you gotta have some fun. :wink:

Hope I didn’t come across as defensive and/or pissed off, I just wanted to answer the question asked of why I want a Sub 2000.

Thanks for all the info so far. Doc and Molon, you have been most helpful as per usual.

13

I don’t think you have to defend anything about your use of a pistol caliber carbine. Where the rub comes in, is folks that think because it’s the size and weight of a rifle, that they’re carrying a rifle.

14

Here are the velocity differences from my G19 and my SUB2000, as measured by 5 shot groups from my Oehler 35P 10 feet from the muzzle.

147gr Rem Golden Saber
G19- Avg vel, 953fps.
SUB2000- Avg vel 1111fps.

125 gr. Montana Gold fmj, 4.5 gr. 231 reloads
G19- Avg vel, 1068fps.
SUB2000- Avg vel 1161fps.

So velocity increases around 50 fps on 147 gr. and around 100fps on 124 gr. at the muzzle. To me, it’s not a significant difference at all.

Also, if you can make hits on an 8" target at 150 yards with factory sights on a SUB2000, I’ll buy you a bottle of Blantons.

I’m not insulting you, I have a SUB2000 for the same reasons as you but with it’s trigger and sights I am working hard to keep it in a 4" circle at 40 yards from a rest. I had to do some creative work on the front sight to get it to zero elevation-wise at 40. As a working carbine it sucks. As a folding rifle that I can take canoeing, kayaking and backpacking along with my handgun, it’s OK.

Gringop

15

You didn’t come off as defensive, nor did I intend to make you defend anything. I was just curious what your application was. I own a Sub2000 and it is a fun little carbine. Having it folded and packed with a pistol and 6 mags that fit both makes for a very light handy combo so I understand where you are coming from. I just wanted to know what you wanted to accomplish.

As for the Sub 2000, I’ve had no reliability problems at all but there are a few things I don’t care for. The front sight assembly is delicate and rudimentary at best. It is hard to get adjusted properly and if you aren’t careful you will strip the plastic thread (you know how I know). That said, Kel-Tec was helpful and mailed me a replacement for free, no questions asked, so I can’t complain about that. I also don’t like that there is no way to attach a muzzle device. The front sight is attached right at the end of the barrel and has to be for it to fold properly, so there is no real estate left for threads. The trigger isn’t great either, but for the application I don’t mind it much.

On the plus side: it runs reliably with ball and duty ammo, is easy to shoot, rediculously light, and accurate enough at pistol ranges (out to about 100 yards) once you get the sights dialed in. The recoil is minimal, though it is less comfortable to shoot than my wife’s Beretta CX4 Carbine in 9mm.

16

See… I really like the design of the Cx4. If it took Glock mags, I’d be all over it. I could go with something like that for now and then SBR it later. Still, it wouldn’t be as easy to fold up and throw in a backpack as something like a Sub2k. I’m pretty much set on getting a Sub2k, and now it’s more or less a matter of deciding on a Glock 19 or a Glock 17 model. I carry a Glock 19, but the G19 model Sub2k has a 2-finger grip. Of course that would be easy to remedy if I stuck some Glock factory +2s on my 19 mags, but we’ll see… I’ve definitely heard about the crappy front sight. Maybe I’ll be able to find a BFG one floating around somewhere or use a Hi Point sight instead. That would be handy. Also, I’ve heard mixed things about the trigger. A lot of people I talk to say they have no trouble hitting a pie plate out to 100 yards, but others say that the trigger is terrible. Only one way to find out.

Hmm… we seem to have gotten off the topic of terminal ballistics. Regardless, I think a PCC has some value. To get back on topic somewhat, just like I asked earlier: is there a point of diminishing returns when it comes to increasing velocity from a longer barrel with pistol rounds? It seems as though a 100 to 150 FPS increase on average is seen between a 5" and a 16" barrel. Is that increase a uniform one, or does it go up by about 100 FPS between a 5" and 8" barrel and then only go up 50 FPS between 8" and 16"? Also, it seems like that 150 FPS jump shouldn’t be enough to actually cause problems with terminal effectiveness, but I don’t know what I don’t know. Does anyone have a concrete answer on that?

17

The only pistol caliber carbines that made any kind of dent into LE were the HK94 and the Ruger Police Carbine, neither of which are in production anymore. As far as terminal performance testing, unless LE is using it, data is hard to come by. Most of the public seems content with listening to what famous gun writers, and charlatan book writers tell them.

18

Chrono numbers I promised:

Round…3"…5"…16"

WWB 115gr…1123…1214…1402

PDX1 147gr…924…970…1114

19

I don’t have an 8" or 12" barrel to test this theory unfortunately but I wonder if pistol caliber rounds are similar to the .300 Whisper subsonics. The .300 Whisper subsonics with a particular load are actually faster in a 10.5" barrel than they are in a 16". It runs with a very low powder charge with a large bore to case diameter ratio with fast burning powders, just like a pistol. The gas expansion runs out of steam around 10"-12", making any extra barrel after that actually slow the bullet down with friction. That’s one of the reasons you have to be careful working up subsonic loads to not get one lodged in the barrel.

20

I agree that pistol caliber carbines are pretty ridiculous when the same size firearm can be chambered for a cartridge that provides greater power, range and flexibility, not to mention terminal effects.

Nonetheless, I did observe a friend of mine shoot a snowshoe hare with one of those abomination Ruger .40S&W camp carbines (the ones that use Ruger P89 pistol magazines). The rifle was loaded with 165 grain Speer Gold Dot ammo which had been loaded for a law enforcement agency. I wonder if they were a bit hotter than the off the shelf civilian version.

The hare was running at about 20 yards. The bullet entered high on the butt and exited the abdomen, taking most of the small intestine and some other stuff out of the exit wound with it. I would estimate the total penetration from entrance to exit as 4 to 5 inches. It appeared that the bullet provided fairly good results (for hare hunting).