Question of the Day: Why Make an SBR?

1. The major disadvantage of the 10″ barrel is the loss of bullet velocity. The relatively small and light 5.56/.223 rounds require high velocity to reach reasonable energy levels. Remember, E=½ mv², where m is bullet mass and v is bullet velocity. With a 55 grain projectile, the 16″ barrel will produce a velocity of ~3000 ft/s, but the 10″ barrel will only be ~2600 ft/s. That’s 15% more velocity, but 33% more energy for the 16″ barrel over the 10″ barrel. The 10″ barrel will also produce more muzzle blast.

   You’ll have to pony up the extra $200 for the tax stamp plus fingerprint and photo fees. You also have to notify the BATFE on Form 5320.20 before transporting the SBR across state lines. This notification is not required for silencers.

   Get the 16″ barrel.

   • I agree. SBRs make sense for Uzis, HK MP5s, FN PS 90s, Sterlings, etc, where the 16 inch barrel is obviously not a part of the original design of the weapon system. On an AR system, these 7, 10, or 11 inch barrels are pushing the weapon design to its limit, and start to really comromise the effectiveness of the weapon. I’m going to SBR my 5.56 Yugo Krink kit when I get it built this summer, but that’s mainly for aethetic reasons.

   • You’re forgetting that you can bypass the fragmentation problem by using soft-point ammunition. No, it probably won’t be quite as effective as a fragmenting M193 round would be, but it’ll get the job done fine.

     It’s not like you need to shoot EXCLUSIVELY with soft point, either… you can always load up on the cheap stuff to plink with, and keep a mag or two of soft point for “real work” (properly testing function with it beforehand, of course).

     For some smaller people, chopping the barrel makes a huge difference in usability for the AR-15 platform. I would not necessarily dump it by the wayside just because M193 and M855 aren’t terribly good in SBRs.

   • not barrel velocity, but its range. i hate it that people dont listen to physics. a shorter barrel will usually increase or decrease only slightly. like 20 fps on the outside. what you lose is distance capabiliy.

     • You are wrong on this one, chief. “Distance capability” is directly related to the velocity of the projectile. A 400fps difference is huge at distance in terms of drop. Remember, this is 5.56/223 – We aren’t talking about a round like the 308win where you can go from 24 inches to 18 inches with relatively minimal velocity loss.

2. Where I think SBRs shine is with the pistol calibers, a 9 inch 9mm makes for some very respectable energy in a light, handy, low recoil package that screams for a silencer.

   • Exactly. Get your multi-caliber marked AR lower SBR’d, then add a 9mm upper and magazine block. Since the upper can be swapped out easily, you can play with a 5.56 (or .300 AAC) upper at some later date if you want.

     Congratulations on your selection of a Sparrow. I was just shooting mine yesterday. The design is extremely clever and does indeed make it a cinch to clean.

3. In my opinion, it would be one of the more useless purchases you could make. I suppose in a doom and gloom scenario, you could use your SBR to fire out of a car as your driver is trying to get you the heck out of dodge. With the shorter barrel, it might make a better home defense AR than a 16″ barrel AR, but not worth the extra hassle just for that. Sure, you might impress your friends, but I doubt it, as all you did was fill out paperwork and wait the requisite time period. The demonization of these weapons such as silencers, SBR’s, and full-auto capabilities plus the extra effort required to procure them is what everyone is counting on to market them to the gun nuts who see and just have to have it. I am guilty of this as well; however, I forced myself to get over it and decided that spending money on better optics and accessories for guns that I already own would be a much better use of funds than to waste money on these items. I think that once your initial excitement of having these items has worn off, you might, just might, regret that you spent the money and went through all the hassle to get them.

   I get the silencer thing. But there has to be something (a rifle or handgun) that would be more versatile for you and fulfill other purposes in your gun safe than an SBR.

4. “Please, give me a reason to justify the purchase.”

   Sorry, I don’t have one.

   Don’t get me wrong, I can understand the utility of SBRs, I just can’t see the upside to taking a super lightweight, super high velocity round and then neutering it by cutting the barrel length in half. I just think that there are rounds better suited to SBRs than 5.56.

   True, 5.56 has the advantage (in overall energy) over pistol rounds in an SBR, but something about being blind and deaf during a DGU doesn’t appeal to me very much. I (me, my opinion, based on limited real world experience and plenty of speculation) would rather have either an SBR in a pistol caliber like 9mm, .40, .45, 10mm or a short barreled shotgun.

5. +1 on the 16″ don’t get me wrong the 10″ is cute but IMO in this case bigger is better.

6. The question is not if, the question is how many. Once you have one, you’ll figure out why pretty quick at the range.

7. Palmetto state armory had a brand new 7.5″ upper that was in stock about 2 weeks ago for ~450 complete. Should be back in stock soon if you check often (it sells out quick).

   Pluses: make more noise at the range or not with a can. Also, night stand rifle? I guess if your night stand is big. Makes room to room navigation easier in a DGU situation. That’s the only benefits I can think of – other than coolness factor.

   • Correction, it’s back in stock for under 500 with a free float hand guard. Slap it to a $130 plum crazy lower and you’ve got a SBR for about $850 including stamp (not counting the lawyer work since that appears to be sunk cost). The question is, why not?

     • Because plastic lowers are a fad that will die out once people realize how stupid they are from an engineering standpoint.

       Also, 7.5″ is too short for an AR; anything under around 10.5″ isn’t long enough to be ergonomically functional, or even cyclically functional.

       • Boy, do you look stupid now. NFA complete lowers rock and other lightweight polymer lowers are following.

       • The AR15 in that picture is mne that I built in 94.
         Its a7.5″ barrel and cycles flawlessly.
         I had problems in the beginning with it letting go of the shells upon ejection, but that was solved with a tuned extractor.

         Today it sports a flattop and slidefire stock.

         I was supprised that the picture popped up on this site years ago.

8. All SBR’s don’t have to be tactical zombie guns, but the same rules apply to lever action rifles.
   I want to put a longer stock (not full) on my Ranch Hand / Mare’s Leg. 12 inch Barrel, but a longer stock makes it an SBR. Longer Stock makes it harder to conceal , but able to be shoulder fired. I just want to extend the stock about 3 1/2 inches.
   Why an SBR?
   It would make it a great light weight brush gun for hog hunting. The Shorter Barrel of 12 inches actually improves the .357 and .44 magnum rounds than from a standard revolver and recoil is much less out of a mare’s Leg than a revolver.

   • Good reason, but unfortunately, no hogs around my neck of the woods.

9. How about an AOW shorty 870?

   • +1

     I would give important parts of my anatomy to SBR my Mossy 930.

10. “Please, give me a reason to justify the purchase.”

    For most of us, the answer is “because I can”.

    • So true

    • +1

11. I respect this site and its contributors alot. So it is with reflection that I state this – I should not be the first person saying “this”. The “this” is – if you are going to go SBR and/or suppressed for your next project then do not go with a gas AR; go with a piston AR.

    You mentioned “uppers” and “lowers” and not much else. Maybe you already (and others) knew that gas impingement AR’s suffer from issues (usually over gassing) when shortened too much? Maybe everyone else knew you were already going piston? If that is the case then I am the douche, wanna be know-it-all. I know there are ways of mitigating over gassing but why not just go piston and be done with it.

    My question for you all is: Where do you all get the money for these projects?

    • “My question for you all is: Where do you all get the money for these projects?”

      Answer: Priorities.

      Who needs cable or hot water when you can have cool toys

      • Methinks the wife and kids might feel otherwise about that.

    • Heh. Where do I get the money? Well, it was a very good year last year for my company. This year? Probably not so much, which is why I have to introduce a little more discretion in my purchases.

    • If the issue you see with DI guns has to do with cycling, then the solution is to get a barrel with an undersized gas port so that you can size it yourself. If your issue is cleanliness, then you’ve never seen how filthy piston guns get when you run them suppressed.

12. I’d buy a complete SBR so you can transfer it on form 4. Form 1 means you need to pay someone to engrave the lower with your complete trust name (since there are no ATF allowed abbreviations). I think a rifle engraved with “LMT” or “Noveske” would look better and hold value better then “The Jim Barrett Trust” (or whatever the formal legal name of your trust is).

    And for why, if you can’t already answer that don’t buy it. It’s like asking why you should buy a machinegun or a Ford Mustang Boss 302.

    • Well, if I had unlimited resources, I would get both the machine gun and the Boss 302. Then while I’m at it, I’d buy a couple hundred acres so I could drive the Boss while firing the machine gun out the window. Course if I did that, I might get one of those coveted (or not so much coveted) IGOTD awards.

13. I’d do it to get a P90, just because P90s are cool.

    Otherwise, you could do it if you wanted an actual carbine length M4 (14.5″) without having to permanently pin a flash hider to the front of the barrel. That’s technically an SBR.

    Of course, this is all theoretical for me, because I’d have to get Washington state law changed first.

    • Honestly, given what I’ve seen Five-seveN pistols do when they blow up, I see no reason risk te same happening to my face.

14. If you are going to get a 300BLK suppressor then I would get a 300BLK SBR so you still have a compact and maneuverable rifle with the suppressor mounted. Adding a 4″ can to a 16″ barrel = 20″, adding that can to a 10.5″ or 12.5″ barrel is IMHO the way to go.

    • I had not considered that. Thanks.

    • This is what I was thinking, without the stigma on class III then the honey badger type setup, way shortBR with suppressor would be an ideal home defense weapon for someone who values their hearing. But self preservation arguments seem to be the most vilified. “I put that on there so I don’t go deaf in the event I have to defend myself” is just as evil to some people as “I was defending myself from an attacker who was trying to kill me” if not more so. Whatever is best for the law abiding is worst for the lawmakers.

15. The Sparrow is an excellent choice.

    As to a SBR:

    5.56 is and excellent choice in an SBR(availability of many 5.56 load options allows you more uses that others). A piston run SBR is best(control of and smoother operation, better running reliabilty, and the ability for use in every environment). As to dollar amount I would say buy the best. Your life and lives others are what is important, as is running a ‘great system’ compared to just a ‘good system’.

    Good shooting

16. No good reason. Just like some people see no good reason to own more than one hand gun. I have Rock River 10.5 in 5.56 because I can and its a second kind of cool. Also when I add a can my over all length will still nice and compact

17. A local gun store (WA) says they confirmed directly with ATF that a short rifle barrel with a permanently fixed suppressor does not count as an SBR as long as the total length is over 16,” and only requires one tax stamp for purchase. Just get one where you can clean it from the front.

    I haven’t seen any direct proof of this, but the store is reputable and I believe their word. Not sure I believe the word of the ATF, but it’s better than nothing.

    • This is the reason for guns like AAC’s 10 22 with a milled-down bull barrel with a baffle stack milled into the front of the barrel. Pop off the shroud (effectively the tube of the silencer) and you can reach everything for cleaning.

18. I really dont see a reason for an SBR. If you need it for self defense then you dont want a 5.56 unless you want one in full auto. If you want one because you have the money to waste then get one. I have friends who have trust funds that will never let them go broke but they dont buy stuff because they can. I am like some of the other posters, for a SBR I would go for 40S&W or 45acp I wouldnt use a bullet that wont be very accurate at beyond pistol range that is that small. I would use something that would stop someone in body armor.

    • Looking to stop someone in Body armor probably means a 30-06 or better. That will defeat everything but Level 4. Then again, I don’t think I want to deal with the shoulder dislocation that shooting a 30-06 SBR would bring even if something like that was possible to build without a room full of metalworking equipment and a hell of a lot more expertise than I have. If I’m facing body armor, I think I’m pretty much screwed regardless.

19. Ever considered an AR pistol? You can even get them registered in CA (although they come with lame single shot sled magazines.) They are simple to register, and once you have a lower, you can pretty easily get barrel lengths from 7.5 – 12″ for uppers. I agree with the 5.56 be very limited by a sub 16 or 14.7″ barrel, but still workable. The MK 318 Mod 0 (Marine Corps) load is still effective, and will still expand out of a 10″ barrel. It’s pricey, though. The 6.8 SPC still works pretty well out of an 8″ barrel (check out Silver State Armory’s info). A .300 Blackout is a hot new round as well, although less energetic than the 6.8. If you really want a cannon, the .50 Beowulf is available with a 12″ upper. I run my 16″ .50 will an H3 buffer so my lower doesn’t get so much abuse. Then there’s the pistol calibers, if you really must put a pistol round in a rifle.

    LWRC makes awesome piston pistols, but they are pricey. Rock River Arms has multiple options as well.

    I always recommend trying a few different configurations before making a purchase. That way, you are less likely to have “range remorse.” That’s what happens when you see someone rockin’ the range with a new AR, optic, etc. that you wish you would have bought more than what you currently have.

    SBR’s, silencers, multiple uppers and multiple calibers, – life is good! Good luck with your search.

20. I’d say ignore all this talk of velocity loss. It’s certainly true but with the kind of shots you’d be taking with an sbr, which is to say very short, it doesn’t really matter. That being said, I agree with pretty much everyone else. If you don’t see yourself shooting out of a car or clearing buildings or playing swat ninja some other way, the sbr is pretty much a waste.

21. I have several 10″ AR-15 SBRs and they work well maneuvering inside a home. The new OTM 77gr (Mod262) and 62gr (MK318) loads the military has developed largely negate the need for speed for proper fragmentation and wounds capacity. I can dump 3-4 rds a second from my rifle and keep easily in a pie plate while moving at 15m. I’m not sure about anyone else but 3-4 rds of 77 gr OTM in someones chest *may* change their channel. YMMV.

22. I read this interesting article about using a NFA item for self defense, and the conclusion was DON’T…
    http://findarticles.com/p/articles/mi_m0BTT/is_168_28/ai_112685749/?tag=content;col1

    To quote from Massad Ayoob’s article (the link above):
    You and I know that Class III holders are the ultimate “card carrying good guys and gals.” That particular card says they have been investigated for six months by the Federal government and been found trustworthy to possess machine guns. Unfortunately, most of the public in the jury pool, and most politically motivated prosecutors, don’t know that. Every self-defense shooting I’ve run across with a Class III weapon, however justified, has at the very least ended with the shooter facing a grand jury. Asked what he thinks would have happened if he’d shot Hamilton with a Remington 870 Wingmaster instead, Fadden replies with certainty, “I would have gone home that night. I’ve told dozens of people since, ‘Do not use a Class III weapon for personal defense.”‘

23. If you need a 10″ barreled NFA rifle for home defense–you need a pistol.

24. I have a RR SBR AR 5.56, a Serbu Super Shorty 12ga, and a Glock-19 with a can on it. I put them on a trust so no pics, prints, or LEO sig required. I know you are eat up with envy and would be even more so if you saw pics of my smoke’n hot wife shooting these puppies. I also bought a Springfield .308 SOCOM and a Springfield Govy target model on their “Dealer Employee Purchase Program”. If you can prove that you work for an FFL they will sell you one of each per year for 21% under dealer cost. I bought both of mine around 2009/10 for $1153 and $714 delivered. 🙂

25. SBR’s definitely have a place in the military special operations, and in law enforcement SWAT teams. A full size AR-15 with a suppressor added, will normally bring the overall length up to 22″. When inches count in close quarters, a 10″ barrel, with a 6″ suppressor would be much easier to maneuver in close quarters. I think an SBR would be very effective for home defense also. Plus they look freakin awesome too! Have you ever thought about building an AR pistol? And attaching a Sig Tac SB15 brace? They say those act much like a stock when shouldering the weapon. Also, I read in an article online about velocities and lethality in sbr’s. The article pretty much says to not get a barrel any shorter than 10″, or you lose all lethality of the .223/5.56 round. I built me a Frankenstein pistol with an 11.5″ barrel and it’s freakin sweet, I’m totally happy with my purchase.

26. Why SBR? Because: They’re fun to shoot. They make suppressed length reasonable and maneuverable. And of course 300 BLK. Nuff said! Forget pistol calibers!

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