I figure this is the better place to ask this-- what prompted you to build an AR under the 10in length mark? I see a lot of trash talk about shorter lengths like 8 and 7 but they obviously have a following, and I'm assuming a mission beyond just range toy... especially at the extreme end of 5.56 where velocity takes the biggest hit.

I'm looking to build one and pair it with an frt as a close quarters build. Or am i just kidding myself and should go with the 10.5?

Whats the case for your shorty?

10.5 is the best length imho.

I have a 7 cuz I have money to burn... never use it..
It throws nifty fireballs and sounds like a 338 .. it's pretty worthless.

Not 5.56 (300blk) but I went short in order to fit in this briefcase with a suppressor.

Attached File

IMO, if going shorter than 10.5 one should go larger in caliber.  A 300 will lose less FPS per inch than 223.

300 blk excels with short barrels. 300 blk is mostly burnt by 8 or 9 inches and the round maintains energy downrange better.

Anything under 10.5" is not a 5.56 for me. But I do have fantasies of a 7" 5.56 with a cookie cutter brake.

Personal opinion, I think pistol length 5.56 is a waste.  That cartridge just loses too much.  I mean, the physics don't lie and there are better caliber choices for shorties.  300 Blackout being the obvious choice.  I would also throw 350 Legend in the mix and 458 Socom, or if you really want to go outside the box, 510 Whisper.

What is a shorty good for in general?  CQB, a truck gun, anywhere something smaller is easier to handle or store in limited space.  Also, many pistols tend to get a suppressor stuck on the end as well and that adds another 6-8" to the length.  A 16, 18 or 20 inch gun with a suppressor is pretty unwieldy for those scenarios.

Suppressed pistol lengths usually mean sub sonics and since you have a velocity limit, the only way to get more energy on target is with more mass (i.e. heavier bullet) and to do that, you realistically have to go to bigger calibers.  LeHigh and a couple other makers are starting to come out with big, heavy, effective bullets that work well at sub sonic speeds.

Sure, you can get just about any AR-15 compatible caliber in any length you want, but as the saying goes, just because you can doesn't mean you should.  However, with that said, it is not "wrong" to make an 8" 5.56 and even slap a "loudener" brake on the thing if stupid loud ultra blasty shooting is "your thing", but I just think you need to understand the difference between "useful" and "blingy range toy."

I'm personally a pragmatic person, so I usually don't build range toys just because, I prefer to build something that has utilitarian value.  The problem is, like so many arguments when it comes to guns and cartridges, is that no matter what you build, someone is going to say it useless or a poor choice for X,Y, or Z (in other words, a Dodge, Chevy, Ford argument).  Fortunately, ballistics is rooted in pretty settled science along with the pros and cons for many of the pieces parts and gadgets you can get for an AR.  This is why I will always suggest that someone building an AR do so from the perspective of a defined end goal or use case before you start bolting parts together.  The "lego" nature of the AR, coupled with the capabilities of many of the available cartridges, can easily get configured in useless combinations that is not particularly good at any one thing (and sometimes not even acceptable at any thing).  The example I usually give is the venerable 300 Blackout.  A cartridge that shoots bullets from about 110 grains all the way up to 250-ish grains.  The problems people have is usually because they come to the table expecting an AR to run that full gamut without issues.  That's why you'll see posts  along the lines of "my xxx AR shoots unsuppressed 125 grainers fine, but won't run suppressed 220 grainers, or something along those lines.

300 BLK got an 8.5"barrel for $100, HAD to build a complete pistol around it.

9mm Banshee upper, suppressed.

7.5" 5.56 in a Vltor CASV-M with a KX3.  THE MOST irritatingly loud pistol upper ever! I shoot this on Independence Day.

My reasoning is it teeters into that PDW/Sub Gun realm. You can have a very compact weapon that still has soft body armor defeating capabilities. While I wouldn't own a sub 10" 5.56 gun. Their are cartridges that are at home in said lengths that still offer a significant increase of terminal ballistics over a pistol caliber weapon of the same size. 300blk, 350L, 338 Spectre, are just a couple that come to mind. I feel a 22 TCM could also really wake up in an AR if loaded to 55-62k psi with spitzer style bullets.

Then there's us nutjobs with their wildcats but that a different disease.

Wildcat disease....I have it, but I have to keep it in check at the mental level as my wallet is giving it the big middle finger.  I fear it enough that I won't even contact gunsmiths or bullet manufacturers just to get quotes.  I suspect I will one day because the one in my head just won't go away.

LOL! Sometimes I shake my head and think....damn I could have bought alot of other cool shit with said money....but their is enjoyment in doing something different too! You don't jump down a rabbit hole....You end up in the labyrinth

11.3" is a better option than 10.3/10.5.  With that said, a barrel 10.3" and above is preferred.  I have an 8.5" pistol in 5.56.  It is a lot of fun to shoot.

Oh, and I meant to add...about that "frt", good luck with that, Rare Breed has been issued a cease and desist by the ATF.  Even if not, the things seem to be very problematic.  I know at least 3 people who managed to get one and none have been able to get them to work properly.  One even broke.  I was jazzed when they came out and almost bought one, glad now I didn't.

Get a binary, Fostech or Franklin Armory BFSIII (I went with the BFSIII).  They work and not hard to mag dump.  Just takes a mag or two to "get the rhythm" down.

In 5.56…..outside of a blasting toy, I don’t see much use.   For a few other calibers, it makes perfect sense.

I have many different sized ARs.. get one of each... Or don't.

Cause I can.

all depends on mission

Used to have a 7.5” 5.56 because I thought it would be fun. That lasted about 5min after the smile factor wore off. Then it became an 8.3” 300aac. Haven’t suppressed it yet, but at least it serves a purpose along with being fun and all.

Did somebody say cookie...?

Got a great deal on a 6.5" Olympic. Installed a Liner comp from Black River Tactical, not sure why everyone says they are painful to shoot.
No fire ball, not tooth pain. It is actually quieter than my 14.5" with PWS comp. It is an absolute blast to shoot one of my favorite ARs.

Steve

300blk Sig Rattler 5" barrel.
It is usable as a pistol without the folding stock, or you can add a brace if you want, but don't want to go SBR.
Much easier to carry around than a 10" AR.

Attached File

6.8 works really well in short barrels.  Once the ATF approves the stamps I'll have a suppressed SBR shorter than most people's unsuppressed 10" guns - and it will put more energy on target than 10 or 12" barreled 5.56 guns.

Nice Rattler!  
My MCX is an 11.5" as I stuck with 5.56.

if youre a good builder a 7.5 will work just as well as a 10.5