Why all the ultra short AR barrels?

[Jim Watson]

16" was arbitrary in 1934 and still is.

Nitpick alert: In 1934 it was 18". Rifle minimum length was later reduced to 16".
You can still find Mauser and Mannlicher carbines with rings welded on the muzzle to splice them out from 450mm (17.7") to 18" before that.

 

[DustyGmt]

I've been scratching my head as to why every one is going in the direction of ultra-short AR pistol builds. I understand the whole pistol brace situation, but don't you think the short barrels are seriously handicapping the velocity and accuracy potential of the weapon? Just to make it a little bit shorter? To me, the trade off isn't worth it. What are your thoughts? Thanks!

I didn't even look twice at AR pistols or SBR's and thought pretty much the same as you in terms of velocity and ballistics, etc... but I took my wife and daughter out shooting one day and thought they would be good to go with my carbine, figured it was light and short enough for them both to shoot well and they didn't. It was too cumbersome and heavy. So I built a KISS 10.5" pistol with a mind for keeping it as small and light as possible and they did much better with the Subcompact AR. I think they are great for smaller statured individuals and those with some handicap or for somebody who just wants something small and potent in the pickup. The 10.5" is lights out accurate at 50 yards although I prefer my carbines. I can see the merit of them. I used to think the lil Draco AK pistols were just silly. But with the braces now I definitely see their utility.

 

[12Bravo20]

I have read and always heard that the early M-16s purposely had a slow twist of 1:12, to just barely stabilize the 55 grain bullet. The combination of high velocity, and a barely stabilized bullet was the goal. Upon impact, they would immediately start tumbling, creating massive wounds, while still using FMJ ammo.

Actually the very first M16 rifles (not M16A1) were 1-14 twist. They were later updated to 1-12 twist.

 

[Mars5l]

Are we talking the guys making ones with 2-3" barrels? I think most of those are being made just because they can. Some owners said they went short as Its easier to carry in a regular back pack or hide better in your vehicle

 

[browningguy]

but the FMJ 5.56 relies on high velocity

But who would use FMJ in a home defense weapon is the question you should really be asking. I've got 55 and 62 gr. SP's and some 50 gr. JHP's that shoot really fine out of my 10.5" AR, I'd use any one of them over an FMJ.

 

[marksman13]

Nothing to do with fads or groupthink, but I do like short barreled ARs. I shoot all of my rifles suppressed and being able to shave 6” off the total length by going with an SBR is a big plus. I have plenty of 16”-24” barreled rifles and they serve their purpose, but for killing pigs and deer out to 200 yards, I see no need in carrying the extra length and weight. It’s not the best solution for the person with one rifle, but I have options and most of my rifles are tailored around a specific task. Why carry a 16” 6.8 SPC or 300 BLK when a 10” rifle will do the job just as well and be more maneuverable in and out of the truck or side-by-side?

 

[Fatelvis]

Unfortunately the benefit of a short barrel for suppressor use doesn't apply to me, because I am a mere peasant who is not allowed to use one, because I live in Illinois (insert puking emoji)

 

[Mike .45]

They are fun. I collect guns because its fun. Some of the stuff I have I bought just because I thought it would be fun.

Sometimes we just get too wrapped up a guns specific use or purpose. Not everything has to have a specific purpose and be the best at something or everything to be useful.

AR`s are fun and can be shot fast. Shorter barrels can be shot faster and moved around faster. Set up a bunch of targets grab a couple friends and a shot timer. Loser buys lunch.
Good times!

 

[Goosey]

SA makes a 5.56 with a barrel not even half a foot long. That's just dumb.

 

[adcoch1]

I have a personal preference for ar barrels around 10"-12". They just feel right on my SBR lower, but 10.5 is the shortest I will go in 5.56. I have built two shorter and neither were enjoyable. For 5.56 I personally like 11.5". MY shortest ar upper though is a 3.5" 9mm that will have a suppressor someday, and it is just ludicrous as is. My most used ar15 upper though is a 10.5" 300 blk with open sights. It goes with me on every camping trip, and it has truck gun duty the majority of the time I need/want a truck gun. It just balances perfectly.

 

[entropy]

I have read and always heard that the early M-16s purposely had a slow twist of 1:12, to just barely stabilize the 55 grain bullet. The combination of high velocity, and a barely stabilized bullet was the goal. Upon impact, they would immediately start tumbling, creating massive wounds, while still using FMJ ammo.

Bunch of horse hockey. They changed the twist from 1:14 to 1:12 to accommodate ball powder, vs. the IMR powders used with the original 1:14. And do you know why it was originally 1:14? Because that's what the AR-10 was, the gun the AR-15 (and subsequently, the various prototype M16 models) was based on. They changed the twist rate to 1:12 with ball powder because it stabilized the 55 gr. FMJ better. Fast rates of twist were not a thing back then, except with varminters, and even amongst them, 1:10 was considered enough..It was NOT designed to create 'massive wounds', even though they occasionally happened. The terminal ballistics with M193 ammo are mostly connected to what it hits.
I had a Drill Sgt. spout that "maximum wounding" crap in Basic, and even though I paid in pushups for it, I corrected him right then and there.

 

[jmorris]

Unfortunately the benefit of a short barrel for suppressor use doesn't apply to me,..

That would explain why you scratch you head at folks decisions that do not have the same restrictions you do.

I've been scratching my head as to why every one is going in the direction of ultra-short AR pistol builds.

Wouldn’t need to do a “pistol” build with a barrel 16 inches or longer. I’d have to scratch my head if 24” pistol builds became popular.

 

[TTv2]

Try some CQB training with a 16" and you'll see why 10" are popular with SPECOPS, though they often top those with a can, as FL-NC says. Keeps it at the same length, and doesn't cause loss of hearing when fired indoors.

I understand CQB, I think for home defense CQB should be the top thought when someone is going to rely on a long gun over a pistol for home defense. This is why my next autoloading rifle is going to be a bullpup and not some braced 10 inch pistol. There is really no negative to running a bullpup for home defense over a braced AR pistol and don't bother mentioning those "poor" bullpup triggers, we're not talking about some critical 300 yard shot, we're talking maybe 20 yards at most for a possible home defense situation. Not exactly something that requires a $200 two stage trigger made by Norse Gods.

 

[entropy]

As long as you don't have tons of training already with AR, that makes sense. I still think the ergonomics and reloading on the ones I've shot are awkward, but with enough practice, a bullpup would be fine.

 

[TTv2]

Have you ever handled a 9” barreled SBR or Pistol? They are great to handle due to the mass of the firearm being that much closer to the body of the shooter without all that barrel weight forward.

All the more reason to go with a bullpup, the action is closer to the shoulder than any AR.

Don’t know where you got the idea that longer barrels are more accurate but that statement isn’t necessarily accurate (no pun intended). Yes, they would have a longer sight radius but most AR’s are utilizing a red dot, scope or other optic for sighting. The shorter length barrel has more rigidity which would aid in its accuracy if anything else.

It's not about accuracy, it's about terminal effect. At the muzzle the velocity from a 7" AR is about equal to where it would be if fired from a 16" barrel at 200 yards. That means at 200 yards the projectile from the 7" barrel is moving as fast as if it were at 400 yards from a 16" barrel, which is around .22 Magnum levels of power.

The 10 inch barrels are not great compared to a 16 or 20 inch, but they can hold up out to 200 yards well enough.

 

[BreechFace]

All the more reason to go with a bullpup, the action is closer to the shoulder than any AR

I’m not a fan of bullpups, ergos suck, triggers generally suck and having my head right next to a 60k psi explosion doesn’t sound appealing.

But if they work for you great!

 

[entropy]

All the more reason to go with a bullpup, the action is closer to the shoulder than any AR.

It's not about accuracy, it's about terminal effect. At the muzzle the velocity from a 7" AR is about equal to where it would be if fired from a 16" barrel at 200 yards. That means at 200 yards the projectile from the 7" barrel is moving as fast as if it were at 400 yards from a 16" barrel, which is around .22 Magnum levels of power.

The 10 inch barrels are not great compared to a 16 or 20 inch, but they can hold up out to 200 yards well enough.

I'm pretty sure if you read all the posts that talk about 7" AR's, most, if not all, agree 7" is too short. (at least in .223) I had to build one to find that out, even with a linear compensator, it was pretty nasty. They don't seem very popular with silencer owners, either.

 

[TTv2]

As long as you don't have tons of training already with AR, that makes sense. I still think the ergonomics and reloading on the ones I've shot are awkward, but with enough practice, a bullpup would be fine.

So long as one is using a 30 or 40 round mag, I don't think a reload is likely to be needed unless reanimated corpses are busting down your door looking for brain food.

As a Sub 2000 owner, I can say after shooting that, there are no ergos on a rifle I can't work with.

I'm pretty sure if you read all the posts that talk about 7" AR's, most, if not all, agree 7" is too short. (at least in .223) I had to build one to find that out, even with a linear compensator, it was pretty nasty. They don't seem very popular with silencer owners, either.

10 inch is where I draw the line, but if this is strictly a 10 inch AR discussion, I still think a Bullpup is superior for distances under 200 yards and CQB home defense.

 

[entropy]

As a Sub 2000 owner, I can say after shooting that, there are no ergos on a rifle I can't work with.

I had one, too. 100% agreement there!

 

[12Bravo20]

And for us lefty's a bull pup is out since left handed bull pup rifles are either very expensive or made of unobtainium. I have used military rifles and carbines ranging from 10.5" barrels to 20" barrels. I'll take a shorter barrel for clearing structures or climbing in and out of vehicles all the time. And a 10.5" barrel works well for HD too.

It is well documented that 10" barrels or longer are reliable. Once you get to 7" or less, you can run into reliability issues with 5.56/223. Pistol calibers and 300 Blackout work better with the shorter barrels.

And living in a free state, I can carry a loaded AR pistol concealed in my vehicle just like any other pistol.

 

[entropy]

That's why I have one.

 

[cfullgraf]

I built a 300 Blackout AR-15 pistol with a brace 4 or 5 years ago. It just never lit my fire. A novelty at best with limited usefulness in my opinion.

At least I can comment about an AR-15 pistol from a point of experience.

A legal SBR is a different matter but a subject for another thread.

I ordered a 300 Blackout rifle length barrel for the back in May, 2020 that finally arrived today (12/29/2020). Gee, you got to love the shortages in 2020.

So, I’ll be rebuilding the gun to a rifle in the coming days. I’m done with AR-15 pistols.

 

[Jim Watson]

Bunch of horse hockey. They changed the twist from 1:14 to 1:12 to accommodate ball powder, vs. the IMR powders used with the original 1:14. And do you know why it was originally 1:14? Because that's what the AR-10 was, the gun the AR-15 (and subsequently, the various prototype M16 models) was based on. They changed the twist rate to 1:12 with ball powder because it stabilized the 55 gr. FMJ better. Fast rates of twist were not a thing back then, except with varminters, and even amongst them, 1:10 was considered enough..It was NOT designed to create 'massive wounds', even though they occasionally happened. The terminal ballistics with M193 ammo are mostly connected to what it hits.
I had a Drill Sgt. spout that "maximum wounding" crap in Basic, and even though I paid in pushups for it, I corrected him right then and there.

The horse hockey endures.
The rifling twist was changed from 14" as in the .222 et al to 12" because while it was fine for a 50-55 gr flat base spitzer, it would not stabilize a cheap 55 gr FMJ boattail in cold dense air. As Jeff Cooper said of a different gun; it gets cold in Germany and rumor has it that it gets cold in Russia.
The grade of powder has nothing to do with the twist rate.
The AR 10 is a .308/7.62 and has a 12" twist because that was standardized for the caliber in M14 and Winchester commercial, nothing to do with a .223.

Still faster twists were used in a few oddball wildcats, but the first military use I know was a 10" twist in some USMC match rifles, trying to squeeze a little accuracy out of that cheap 55 gr FMJ.

I don't know what the twist rate was in a .22 Newton or .22 Savage for their 70 grain bullets but if they were as blunt as the 70 gr Speer that shot just fine out of my 14 twist .22-250, it did not have to be real fast.

 

[35 Whelen]

I've been scratching my head as to why every one is going in the direction of ultra-short AR pistol builds. I understand the whole pistol brace situation, but don't you think the short barrels are seriously handicapping the velocity and accuracy potential of the weapon? Just to make it a little bit shorter? To me, the trade off isn't worth it. What are your thoughts? Thanks!

Like all things AR-15: Fad.

35W

 

[Phaedrus/69]

I've been scratching my head as to why every one is going in the direction of ultra-short AR pistol builds. I understand the whole pistol brace situation, but don't you think the short barrels are seriously handicapping the velocity and accuracy potential of the weapon? Just to make it a little bit shorter? To me, the trade off isn't worth it. What are your thoughts? Thanks!

I suppose it's because our nation has continuously been at war for the last two decades so images of the troops and stories of MARSOC guys kicking doors and taking down terrorists have been all over the media. Gun folks have long taken cues from the military and to a degree, the police. Once the M9 was adopted by the Army you saw lots of civilians wanting one. Since the M4 is so widely used by military groups around the world it's not surprising to see civilians getting as close a copy as they can. And since many of the SPECOPS teams have SBRs (often HK416s) it's kind of natural for civilians to want to get as close as they can. The "pistol build" with a "brace" is the easiest way to replicate the looks of an SBR without the tax stamp and associated rules.

Personally I can see the utility to the point where I am wanting to SBR at least one lower and maybe a Scorpion, too. With .300 Blackout you can get pretty good velocity in 8" barrels. With 5.56 even 10.5-11" still gives you enough velocity to be effective (with the right ammo) at least within a 100 meters. Rifles for home defense is a topic many have strong opinions about, but it's a fact that even at 10.5" a 5.56 round still has a lot more KE than a service pistol round.