What’s the Difference Between a Carbine and a PCC?

First off, I realize that the second ‘C’ in PCC stands for Carbine, so a PCC literally is a carbine, so let’s make she we’re all talking about the same thing.

Definitions

A ‘PCC’ is a pistol-caliber carbine, whereas a ‘carbine’ is a short rifle. Carbine originally meant a shortened variation of a standard rifle, and usually meant for horse-borne soldiers. That was then, and today’s definition of ‘carbine’ is something along the lines of ‘a kinda-short semiauto rifle, generally intended for offensive or defensive purposes’. A PCC is a rifle that is chambered in a pistol cartridge, such as 9mm or .45 ACP. So, where’s the confusion?

What about the M2 Carbine? Its a miniaturized M1 meant for rear-echelon troops who might need more than a pistol but shouldn’t be burdened with lugging an entire M1 Garand during the work as a mechanic, truck driver, cook, etc. The M2 is chambered in .30 Carbine. This one is pretty cut & dry as not a PCC.

Current Standards

The two cartridges that I’ve seen most compared to the .30C is the .30-30 and the .357 magnum. The .30-30 is completely outside this discussion, so we’re going to look at the .357 magnum and the .30 Carbine. Here they are from the muzzle to 200 yds:

.357 Magnum (from a rifle)

Muzle: 1830 fps (1175 fp) – 100 yds 1427 fps (715fp) – 200 yds 1138 fps (458 fp)

.30 Carbine

Muzzle: 1990 fps (967 fp) – 100 yds 1567 fps (600 fp) – 200 yds 1236 fps (373 fp)

So, we’ve decided that a .30 Carbine-chambered rifle is a carbine, and a 9mm rifle is a PCC. So what about .357 magnum? That is absolutely a handgun round, but from a rifle it is on equal footing with the .30 Carbine. So would a rifle in .357 Magnum be a PCC or a Carbine? This is pretty gray area and I haven’t seen anyone really put forth any work on clearing it up, so I’ll start.

First Offering

As I was mulling this over with the other contributors on here, we came up with this possible definition:

A rifle chambered in a caliber that gains significant energy when shot from a rifle barrel compared to a pistol barrel is a Carbine. If the energy gains are insignificant, it is a PCC.

There are some problems with this rule. What is significant? What is insignificant? What energy? Heat? Kinetic? Potential? This ‘rule’ is more of a ‘feelings written down’ than anything that someone can look at and accurately apply, and that’s not good. Lets start to use some real numbers.

Data Collection

I think I’m going to use 5.7×28 to both prove and define the rule. Why? Because 5.7×28 was originally created for the P90 Carbine, which was created for the exact same purpose as the M2 we detailed above: rear-echelon troops who shouldn’t be burdened with an entire rifle but should be given more than just a pistol; yet the 5.7×28 is also commonly chambered in handguns and has been gaining popularity in this role for a few years now.

5.7×28 was created to be shot out of rifles (the P90), and only appeared in a handgun as a way to get more products out of existing R&D. Sounds like it should be a rifle round, except that the energy levels from a handgun are comparable to 9mm. It is both a handgun and carbine round, and it depends on what it is being shot out of. Perfect for defining where the Carbine/PCC line probably exists. I’m going to compare 5.7×28 to 9mm because 9mm is the most popular handgun cartridge in the world, and the quintessential PCC is a 16″ 9mm rifle.

As a point of interest, I’m choosing to use NATO-spec 9mm instead of something else for a reason. NATO-spec ammo is hotter than most commercial offerings, meaning it can leverage a longer PCC barrel more than other 9mm offerings, as I show below.

According to the source listed below, a 40gr 5.7×28 from a 5″ barrel travels an average of 1743 fps (270 ft*lbs) but from a 16″ barrel reaches 2131 fps (403 ft*lbs). That is a 22% gain in velocity and a 49% gain in kinetic energy.

And now the 9mm:

Since I’m both trying to stay consistent I used the same guy for my 9mm data. 124 gr NATO 9mm from a 5″ barrel travels an average of 1113 fps (341 ft*lbs) and from a 16″ barrel achieves 1328 fps (486 ft*lbs). That is a 19% gain in velocity and a 43% gain in kinetic energy.

I did the same analysis on some published data for 147 gr 9mm, and it was interesting. 147 gr 9mm from a 5″ barrel travels an average of 1025 fps (343 ft*lbs) and from a 16″ barrel achieves 1079 fps (380 ft*lbs). That is a 5% gain in velocity and a 11% gain in kinetic energy. 9mm’s grain weight and what pressure it was loaded to greatly impact the performance out of a 16″ barrel, and should be taken into account.

Analysis

Sooooooo, the above data is much more interesting than I initially expected.

First My initial assumption that the amount of increase of energy (or velocity) seems to be correct. 5.7×28 gains more than 9mm gains. I stress the word ‘gains’ because the 9mm KE actually outclasses the 5.7 in both barrel lengths. I’m going to keep the Carbine/PCC rule based on increase, because if we start saying that a weapon’s class is determined by its muzzle energy or velocity, revolvers are going to make things even more confusing than they already are.

Second of all, the NATO-spec 9mm gains a lot more from those 11″ of barrel than I expected! A 43% increase in kinetic energy? And it delivers more energy on target than the 5.7×28 from all barrel lengths? I never expected that! I’ve been sayin for a while that a 9mm PCC is a great option as a home defense gun for those newer to the self-protection lifestyle, and this only reinforces my choice. A 43% gain is basically shooting a bullet-and-a-half of the same stuff every trigger pull. At least, for NATO-spec 9mm.

Conclusion

Getting back on-topic, I think I have enough data to take my qualitative rule and make it a quantitative one. Basically take it from being vague and put real numbers on it. here’s my new and improved rule:

A rifle chambered in a cartridge than gains less than 20% muzzle velocity when going from a 5″ barrel to a 16″ barrel is a PCC.

I hope this clears things up for you, it certainly does for me. If you had no idea that this was even an area of confusion and you’re actually worse off now than before, I apologize.

And if you decide that a PCC is right for you, don’t use standard-pressure 147 gr 9mm. If you’re going to have all that extra gun, you really ought to get something out of it.

Acknowledgements: 9mm rifle & pistol data from here and here, 5.7×28 rifle & pistol data from here, .357 pistol data here and rifle data here