The "rifle in your car" thread currently in the rifle section got me thinking.

With the proliferation of AR-based and AK-based pistols with arm braces, we're seeing intermediate rifle cartridges being fired out of relatively short (9" to 12", I believe) barrels. The two popular cartridge options on the market seem to be the 5.56x45/.223 Remington and the 7.62x39.

From what I can find online, it seems that the 7.62x39 will fire a roughly 124 grain bullet at anywhere from 2,200 (for example, the cheap Tula) to somewhere between 2,350 and 2,450 (for example, the Tula-branded 8M3) FPS from a 16" barrel and around 2,200 FPS from a 10" to 12" barrel for at least some standard loads. At "defending yourself with a pistol" ranges, that ain't much of a significant drop.

If someone is shooting from a pistol length barrel, what's the advantage in shooting 5.56 over the 7.62x39?

Commonality of ammo with your M4/AR, possibly.

Accuracy.

Don’t forget 300 BO. It’s effective from barrels even shorter. If I were to build a compact pistol based on a rifle cartridge and needed it as small as possible, it would be 300BO.

literally everything seems better in the AR based on my experience in these. Better options to buy/build what you need, likely way cheaper, less weight, better ammo choices, less muzzle blast, less recoil, better optics mounting, accuracy,better ergo's, etc.
For that you give up some terminal energy in a gun that is certainly intended for short range use and probably gain some reliability (though that hasn't been my actual experience in owning a number of AR and AK rifles)

I'm not sure I follow that comment. We are talking AR in 5.56 and AK in 7.62 which are the native rounds? If somehow the idea of AR in 7.62 and/or AK in 5.56 got into the discussion, I would say for a defensive gun you are nuts based on my personal experience.

5.56/.223 would be the better choice for many reasons as listed above. For me, the biggest points would be ammo cost and availability, projectile variety, and recoil.

I'd prefer to see the platform (whichever one you choose) matched to the cartridge it was designed around.

quote:

Originally posted by hrcjon:
I'm not sure I follow that comment. We are talking AR in 5.56 and AK in 7.62 which are the native rounds? If somehow the idea of AR in 7.62 and/or AK in 5.56 got into the discussion, I would say for a defensive gun you are nuts based on my personal experience.

I think that by default, at least at this point, we have to think in terms of a 5.56 AR and 7.62x39 AK. I'm a big fan of the potential of the AR in 7.62x39, but I'm at least 1,000 rounds and a spare headspaced bolt away from relying on it as a defensive rifle.

I was a huge fan of the idea of 7.62x39 in an AR. I spent several years, lots of ammo and parts trying to make that a reality that would actually be trustworthy. I couldn't.
When I have some time I recently got a CMMG to try and see if that actually runs (this is the model that uses the AK mag) and is AR mostly otherwise.

For me the AK, AR has been Great ! Over 17k rounds across 10 rifle/pistols and so far the only real problem has been a broken extractor. My trunk gun is a 10.5" AR-47, for the exact reason above. Going from a 16" down to a 10" the velocity drop is almost 200 fps. Cheap to practice with and now they make some very good hunting rounds = Damn !

quote:

Originally posted by smithnsig:
Don’t forget 300 BO. It’s effective from barrels even shorter. If I were to build a compact pistol based on a rifle cartridge and needed it as small as possible, it would be 300BO.

That's what I decided on for my shorty. .300B was built to run just fine out of a 9" Bbl.

Well, if anyone were to actually shoot either as a pistol instead of bypassing SBR and shouldering the brace, I’d say the recoil of 5.56 is much more manageable. But we know that’s not that’s happening.

So then there’s the accuracy argument that I think has already been mentioned. But let’s think about that for a second. It’s not like 7.62x39 is a round that just goes spinning off into the nether. It does have a good amount more drop than the pretty flat 5.56, but that’s just a matter of knowing drops and holdovers. The platform? Well, yeah the average AK is probably built with a wider MOA spread than the average AR. But there’s nothing stopping either from being perfectly reasonably accurate.

But now let’s get real. Engagement distances for a defensive shoot are gonna be less than 100 yards. Probably less than 50, or even 25. So how much bullet drop or MOA spread is really gonna come into effect? Oh wait, we’re talking about returning fire, which means receiving fire, shouldering a brace and probably shooting on the move or from odd positions, all while dumping adrenaline. So tell me how important your match grade barrel, ammo, and trigger are when you’re not benching under controlled circumstances.

So really to me, the real consideration between the two is bullet performance against cover. I’m not sure what kind of fight you’re expecting with a trunk gun. Is it aliens landing in a cornfield or a fracas in the Walmart parking lot? Well, the 7.62 will start breaking down a cinderblock wall a fair amount better than 5.56. But either will go through car doors and windows pretty effectively. Just the 5.56 relies more heavily on speed to do damage.

Really truly having a pistol on you puts you leaps and bounds ahead of 95% of people for preparedness. Just having a truck gun puts you in the 99th percentile and you don’t really need to worry about minutia.

Just be sure to drop it after the threat is stopped. You’re gonna look like a bad guy from Heat/North Hollywood shootout to responding cops.

Besides, the answer is obviously .350. That’s the new hotness, right? Everyone gonna throw their panties at this “new” caliber for the next 18 months or so? Maybe not that long...that .224 Valkyrie seems to be fading already.

This message has been edited. Last edited by: BuddyChryst,

Everything Buddy said. Well put, sir!

Also, In most standardized forms, the AK can offer a folding brace. Something the AR cannot.

I’m not advocating either one, but to answer the OP’s question; aside from a specific users taste in equipment, there is no logical reason that the AK pistol would not be as effective or even more effective in this specific configuration. At least in theory, mass still wins.

For a firearm with a short barrel, 223 really isn't the best option. Fluid dynamics -- plus a few cartridge developers who seem to feel they invented the laws of physics -- tells us that highly-bottle-necked cartridges work better with longer barrels. Based on kinetic energy alone, the 7.62 AK chambering has an advantage. In an AR-15 platform, this is why the 300blk is better chambering for SBRs. The kinetic energy from 300blk really is pretty close to that from comparable AK-47s. This is one reason why nobody really claims to favor AK-74s in SBRs.

223 Remy & 300 blackout & 7.62x39 in an SBR all offer more kinetic energy than typical handguns calibers, although true magnum handgun calibers may swing the kinetic energy advantage to the handgun. But it also depends on barrel length.

One challenge with any shorter barrel is how loud they are. In my experience, few people train very much with really loud firearms. Which of course means that their efficacy will be reduced when the time comes to perform under pressure. Adding a suppressor helps, but there are issues for some with suppressors, and suppressors add length to the gun.

***
"Besides, the answer is obviously .350. That’s the new hotness, right? Everyone gonna throw their panties at this “new” caliber for the next 18 months or so? Maybe not that long...that .224 Valkyrie seems to be fading already."

.350 may, or may not, go anywhere. Time will tell. There was notable fanfare upon the introductions of 6.5 Grendel, 6.8 SPC, 300 Blackout, 22 Nosler, and 224 Valkyrie. Each has its own following, each has its own niche where it performs well, and probably none are going away anytime soon. Although I suspect the 22 Nosler is currently having the roughest go of it right now. The press related to the Valkyrie has become somewhat silent recently, but it doesn't mean the people have stopped shooting them. None of the AR-15 chambering variants magically change the platform to the performance level of an AR-10 -- a logic fallacy which I believe causes a number of shooters to jump on the new cartridges as early adopters.

quote:

Originally posted by matthew03:
.300B was built to run just fine out of a 9" Bbl.

Ah, you've read the sales pitch of the cartridge "designers".

300blk was designed to use a .30-cal bullet in a more or less 223 Remy case with minimal changes to the platform. Something that two other similar chamberings had already proven effective, but not gone so far as to get SAAMI standards. The physics properties of fluid dynamics pretty much locked in the ballistics characteristics of the 300blk, once powder capacity and bore size was determined. "Running fine" out of a given AR barrel length is a result of understanding pressure curves, bolt cycling properties, and gas port size & location -- among other things.

This is no different than stating 223 Remy was built to run fine out of a 10" or 14.5" or 16" or 18" or 20" or 24" barrel. Which is why there are pistol, carbine, mid-length, intermediate, rifle, and extended length gas systems. Mate the gas systems to the barrel lengths, and most ARs cycle like nobody's business.

How much do cartridge ballistics come into play in regards to a "car or truck" rifle?

We are talking about a close quarters engagement rifle. I'll take a heavier caliber round out of side folding AK if I need a SHTF car rifle.

I chose a 9mm PCC for my more mobile "long gun". I had tried a couple of short aks and while certainly fun, I just felt there was too much in the way of blast and concussion for me to consider them as viable defensive tools.

It's been mentioned by a couple folks already, but accuracy and ammo cost as well as ability were the primary reasons for me.

It's the same argument with the rifle as it is pistol. It's all personal preference. Both rounds are easy to come by and will get the point across.

Ford vs Chevy... Or in this case, Ford vs whatever a reliable Russian pick-up truck is.

I don't think that either round was designed for SBR stuff. (Well, anything shorter than carbine length) IIRC, the .300BLK was designed for SBR.

Remember, "back in the day" there was rifles, pistols, and Sub-Machineguns. Uzi, MP5's, Mac-10's et al, and they were all in pistol cartridges. (Then there were the chopped down M1 Carbines)


As far as a "truck gun"? hey, if that's what you think you need, go for it. Either will work if it's done right. If you have 8 different AR's all in 5.56 at home, but you now want an AK SBR/pistol in 7.62 just because THATS WHAT YOU NEED FOR A TRUCK GUN, well, go for it.

If you're heavy into your Eastern European Heratage, and the home arsenal looks like Putin's closet, but all of a sudden you yearn for an American weapon system, and that's the ONLY 5.56 with a brace and a 10in Bbl behind the seats? You do what you gotta do.

(I'd suggest a Piston AR in .300Blk. This way, it's everything from both weapons )