GUN 9mm SBR

Discussion in 'On Topic' started by vwpilot, Nov 21, 2008.

  1. vwpilot

    vwpilot New Member

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    What length barrel should I go for on a 9mm AR SBR?

    My local shop has two in stock, I'm going for one of them. One is a 7" barrel the other is a 10.5 inch barrel.

    I like the look of the 10.5 better, looks more balanced and more AR like to me, the store recommends the 7". Which is the way to go? What pros and cons of each length when using 9mm ammo, will also be suppressed.

    Also, what is the NFA rules on going with a shorter barrel than what is initially registered?

    Since both of these are factory SBRs, they're already registered as 9mm in the length they have.

    If I buy the 10.5" one, would I be allowed to later put a shorter .223 upper on that lower and still be legal? Would it require paperwork? How hard is that to get done?

    Would I be better off just registering one of my other lowers as multi caliber and with something silly like a 5" barrel to be safe?

    I like the idea of an off the shelf SBR since its just marked "SBR" on the lower and dont need to engrave anything else on it.

    Thanks.
     
  2. You're probably going to get more velocity out of the 10.5" one. Of course, when you add a suppressor, it's going to be longer. Since pistols are way shorter than the 7.5 inch one anyways, I doubt it matters.

    That being said, what's the point of a short barreled, pistol caliber carbine? Why not just buy a pistol? It's smaller, lighter, certainly more reliable, cheaper, and you don't have to deal with any NFA issues.
     
  3. yar1182

    yar1182 New Member

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    I'm a big fan of pistol caliber rifles. I plan to build one one day soon. IIRC 9mm maxes out velocity in about 13" of barrel. I would get the 10.5" upper based on what your shop has on hand.

    For me I want a 13.5" barrel and then I would permanantly attach a 3" comp. This way I would have a 16" barrel which is what I like anyway.

    The advantage of a pistol caliber rifle is more velocity, and a more stable shooting platform. I've always thought a PCR would be the ideal home defense weapon as you could fire it one handed in needed as the recoil would be very managable, it has higher capacity than a shotgun, and would be easier for females or kids to shoot if needed.

    My dream PCR would be a 9mm AR-15 with a 13.5" barrel with a pin and welded 3" comp. Comp would be something like the surefire that I could attach a can over if I so chose to. My AR smith says he can ream out a 223 comp for 9mm no problem. Then add a 42mm trijicon reflex scope and a weapon light. Run 30 round c product colt style mags or a 100 round 9mm beta mag.
     
  4. Soybomb

    Soybomb New Member

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    From a defensive standpoint I agree, from a range toy perspective I could see enjoying the low cost of 9mm.

    Now personally I've had a pistol caliber carbine before and won't buy one again, I find it boring but...

    I'd just get whatever you like most. Who cares about velocity, this is toy.
     
  5. vwpilot

    vwpilot New Member

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    I guess you should tell all those guys out there using MP5s and other sub guns they should just be using pistols then. ;)

    I want an SBR in general, once I have the lower I can swap uppers around with just changing the mag block to go from 9mm to 5.56. I think shooting it would just be fun and enjoyable. Hell, with the suppressor on it, a SBR in 9mm might be the ultimate home defense weapon. Small, light, accurate, suppressed so you can hear when the cops come to take you away. :rofl:

    The shop also has a 7" 5.56 SBR, but I think that is a bit short for that. I'd like something more like a 10.5 for that caliber.

    Just thought I'd pose the question to see if anyone had any experience or input on the matter.

    Thanks.
     
  6. yar1182

    yar1182 New Member

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    I've never been a fan of the 223/556 sbr's because there is just not enough barrel to generate velocity. It is a weak sauce rifle. A SBR in pistol caliber is something else entirely. Maximum potential for the caliber.

    We could debate a 223 @ 50% of it's velocity (needs 24" to max out) vrs a 9mm at 100% of it's velocity (needs 13" to max out). Either way it comes down to shot placement.
     
  7. Paul Revere

    Paul Revere OT Supporter

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    ballistics of a rifle > ballistics of a pistol

    if you're using proper ammo it wont be that big of a deal
     
  8. Calhoun Burns

    Calhoun Burns ...and the gunslinger followed.

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    :wavey: I scored a pre-election priced lower yesterday for the express purpose of building a 9mm SBR. Still reading up on which barrel length I want to go with.
     
  9. Soybomb

    Soybomb New Member

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    Actually he's very spot on, the sub guns are kind of dying off in huge le use and being replaced by ar style guns for the reasons he described.

    Shot placement aside, don't you still want to do the most tissue damage per shot possible? I don't think you keep a .22lr for defense because you're the shot placement ninja do you? :big grin:
     
  10. yar1182

    yar1182 New Member

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    What are the balistics of a 223 out of a 7" barrel or a 10" barrel?



    Lets see out of a 10" barrel I estimate a 55 gr 223 is doing about 1500 fps on the high end.

    Is it that much better than a 125 gr 9mm hollowpoint doing a screaming 1475+ fps?

    223 has it's place but I question it's usefulness in anything shoter than a 14" barrel. If doing rifle SBR I would want a minimum 6.5 or 6.8
     
  11. Soybomb

    Soybomb New Member

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    I'd much prefer a 6.5 or 6.8 too but I think for what we're talking about the 5.56 will still win.

    The heavy otm loads (fuck this 55gr business) will fragment reliably down to about 2250fps. mk262 chronos at the muzzle from a 10.5" gun at 2360fps. Loads and other variations aside, I think its safe to say that even with a 10.5" gun you're still going to be tearing people up with a 5.56 gun at 50 yards or less if you use the right loads.

    Adding a few hundred fps onto a 9mm load doesn't really do a great deal to help its wound creation potential, if it was already a good choice to start with at least. We'll assume its already opening to its full potential because its a modern hollow point. It will gain a little penetration depth, but if you picked the right load it should have been enough to start with. It should make a larger temporary cavity too but hitting tissue that will be destoryed by temporary cavitation is an iffy gamble.
     
  12. yar1182

    yar1182 New Member

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    honestly who is going to buy some 5.56 super ammo. I want to know what 223/556 does 2250 in a 10" barrel. I'm having a hard time buying that. I would think it would have to be 55gr or lighter to get up to those speeds. That is unless they are using some powder I'm not framilar with. I'm only able to get 26 grains in a case.

    Most civilians are going to use whatever defensive 223 ammo they can get off the shelves. I don't see any of the stuff doing over 1500 fps especially the heavy stuff.

    That's the reason why I hate this balistic stuff. It's all smoke mirrors and hearsay.
     
  13. Soybomb

    Soybomb New Member

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    There are several varieties of loaded 5.56 otm's that are quite hot, they'll usually be cooking at about 2700 out of a 16" barrel. The more commonly found stuff is a couple hundred fps slower. I would have my doubts that they use anything other than a powder blend that isn't offered to us. I think some people have found they can get reasonably close with tac.

    If people are just running whats on the shelf at walmart I really don't care. Same goes for if they decide to use wwb for defense instead of tracking down some good jhps for their handgun. Personally I'm wanting the best performance possible and will find out what that is and get it. You don't run a walmart ar and optics do you? :big grin: Sure lowest common denominator sucks, but why use that, we're smarter than that.

    Someone send yar a pack of hornady 8126n so he can crono it.

    Just what kind of crappy heavy otm stuff is doing under 1500 fps anyway?
     
  14. Are OTM projectiles really good as a self defense round? I would think you'd get inconsistent fragmentation, since they're not designed to be used against living things.
     
  15. Soybomb

    Soybomb New Member

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  16. Jas0n

    Jas0n Антихрист

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    My understanding is that the uppers aren't controlled, so there's no registration problem... legally speaking, changing one pistol upper for another here wouldn't be any different than swapping out a longer target barrel and slide combo in your Glock or whatever, which is of course perfectly legal.

    So you can swap, in other words, without running into law problems. A pistol isn't regulated in length, to my knowledge. Don't add a stock and you can do more or less whatever. (I'm sure you know that.)
     
  17. Painkiller

    Painkiller Sometimes remembering is better than forgetting

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    I have 9.25" tros 3 lug barrel on my shorty so I can use my evolution 9 on it.
     
  18. Here's some info on .223 in barrels of various lengths. Now, it's a bolt action, but the point is that it doesn't lose nearly as much velocity as one would think as the barrel shrinks.

    http://www.accuratereloading.com/223sb.html
     
  19. Keesh

    Keesh New Member

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    From M4Carbine:

     
  20. Jas0n

    Jas0n Антихрист

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    Oh man.

    Not carefully enough, evidently.

    Fucking nevermind. :uh:
     
  21. yar1182

    yar1182 New Member

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    I'm going to have to chrono some stuff myself. I'm having a hard time believing these numbers. Now I need to find somebody with a sbr.
     
  22. You're having a hard time believing that the numbers that both keesh and I found are valid, even though they were shot by different people, on different days, from different rifles, and they're so consistent?
     
  23. Dumbstixlars

    Dumbstixlars Ron Paul/AR-15/Glock/old car/Scooby/R/C croo OT Supporter

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    Too bad you aren't in Texas, I'd let you chrono my 7" AR, I'm interested to see what it would do.
     
  24. Painkiller

    Painkiller Sometimes remembering is better than forgetting

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    this is mine I made this year.
    [​IMG]
     

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