300BLK or 223/556 for SBR/Pistol?

Discussion in 'Firearms' started by JediWoodsman, Oct 17, 2020 at 12:38.


  1. JediWoodsman

    JediWoodsman Insomnia Monkey

    So, I own plenty of guns, but no AR-Pistols/SBRs. Been looking at getting one, mostly for paper but of course for the off chance of home defense.
    What do y'all think about 300blk?
    I currently have a few 5.56 ARs and kind of like the idea of ammo interchangeability, although I could just get a 300blk upper for those too and change all my ARs over.
    I am one of those people that likes same caliber across multiple platforms. Almost all of the pistols in my home are the same caliber, and I only have two other rifle calibers (223 and 308 if you don't count the dedicated hunting guns).
    Anyway, I am thinking about something with maybe a 10inch barrel that can be used as a truck gun/brush gun for when I am out and about either in town or on the homestead (we have our fair share of wildlife on this property). I am really leaning toward the 300blk but not sure if it is worth it to add a new caliber to the mix.
    Either way I was thinking probably doing a CAN as well as I have heard the short barrels can get pretty loud.

    What do y'all think? Who has both? or just one or the other?

    -JediWoodsman
     
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  2. Ura-Ki

    Ura-Ki Grudge Monkey

    Both! Uppers can be swapped easy, so you can plink with the 5.56 and use the .300 B.O. for S.D!
    I know folks that even hunt with the .300 B.O. so there is that! Plenty of options, it's just ammo availability that's the limiting factor!
     
  3. Seacowboys

    Seacowboys Senior Member Founding Member

    The .300 BO will cycle in any upper without adjusting the gas block, all the powder burns in the first 8" of barrel. 5.56/.223 tends to need the gas block opened a bit before they'll run. All the experts will tell you a bunch of BS about the correct Buffer and spring, etc. but the bottom line with me has always been having to drill a slightly larger gas port to get them to run. if you reload, .300 AAC is easy to build out of .223 brass, just get you at $20 Harbor Freight chop saw and cut the suckers off, size them and stuff em'. .30 bullets cost a bit more that .22 but cast bullets work just fine in sub-sonic loads. BTW, you'll never find a sub-sonic .223 that will cycle your rifle so cans are not much use there unless it's just to protect your ears.
     
  4. Tully Mars

    Tully Mars Metal weldin' monkey

    100% what @Seacowboys said.
    I went back and forth on this as well and ended up with the blkout because it was originally designed for suppressor use vs the issues Sea mentioned with the 5.56. I have a SBR in 5.56 and it runs great, but I don't suppress it. I do use a flash can on it and that helps greatly by forcing the noise/blast forward.
    Also, I'll add that I do 99.5% of my shooting at our own range here so the blast can isn't an issue to other shooters like they can be at a public range/indoor range.
     
  5. oil pan 4

    oil pan 4 Monkey+++

    I don't know about a 5.56 pistol. The muzzel blast seems pretty intense.
    The 5.56 depends on all that velocity to do what it does best.
     
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  6. VisuTrac

    VisuTrac Ваша мать носит военные ботинки Site Supporter+++

    I'd not suggest a 5.56 pistol without some sort of brake or blast can.
    was at the range a few slots down from a guy with one with std flash hider. OMG blast and fire ball was like a mosin carbine.

    I don't think i'd enjoy shooting that one.

    I couldn't imagine touching that off in say a hallway.
     
  7. Ura-Ki

    Ura-Ki Grudge Monkey

    I wouldn't ever run a 5.56 with a barrel shorter then 10.5 in, they really need a minimum of barrel length to get the most out of them, and even then, your still giving up a lot of velocity with the barrel that short!
     
  8. oil pan 4

    oil pan 4 Monkey+++

    I would like a short barrel AR so I will probably SBR a lower, so I can run a stock, pistol brace (unlikely) or just the tube, get an upper in 5.7x28 with a 12 inch barrel that takes the 50 round FN P90 mag.
    I'll do the SBR because the ATF gets weird and reverses their decision on what is an AR pistol and what is an SBR.
    But that's just me.
    This guy explains it very well.
     
    Last edited: Oct 17, 2020 at 16:01
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  9. Ura-Ki

    Ura-Ki Grudge Monkey

    I go ahead and SBR everything, but that way there is never any question!
     
  10. Tully Mars

    Tully Mars Metal weldin' monkey

    Actually the brake won't do much at all for the noise. A short barreled pistol/rifle in 5.56 is gonna be loud. The flash can for me has worked the best as it forces the bulk of the blast/noise forward of the shooter. Which helps you, but may not help the guy 3 stalls away from you;)
     
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  11. JediWoodsman

    JediWoodsman Insomnia Monkey

    Sounds like everyone thinks a short barrel 5.56 is not an ideal set up, thanks for the input. I do like the thought of being able to go subsonic and add a suppressor. I have a few questions on SBR vs Pistol brace, maybe I need to start a thread on that (or look for one probably already out here)
    This isn't something that is going to happen soon, but I am excited at the idea of a new gun, obviously.
    So, no-one worries about having 2 different calibers that relatively fit in each other and run the same mag? Maybe it's paranoia on my part over the internet urban legends (or real but few instances) of errors, but it's also why I don't own a 20ga where I have a 12ga. Probably just overthinking things, but I did recently watch a guy load a 40 round into a 9mm mag and jam his gun so....

    -JediWoodsman
     
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  12. Tully Mars

    Tully Mars Metal weldin' monkey

    Most of those issues can be solved with a bit of foresight and common sense. Many folks use color coded mags for their 5.56 vs 300BO. I personally do not. I keep things organized with ammo cans/weapons separate from one another. Same for pistols/revolvers.
     
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  13. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    I use labeled dust covers on the AR and specific Magazines for each weapon.
    Each Mag or Ammo Can is labeled too.
     
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  14. JediWoodsman

    JediWoodsman Insomnia Monkey

    I did see that Magpul (my preferred mags) makes a mag just for 300blk with differences in texture for ID purposes, but also "optimized" for 300blk PMAG® 30 AR 300 B GEN M3™, 300 BLK
     
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  15. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    If you folks would NOT use 5.56 Rifle Ammo in your AR15 10.5” Pistols, and loaded your Pistol Ammo Appropriately, with a fast Pistol Powder, for the Barrel/Weapon, the Flash issue wouldn’t be a problem..
     
  16. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    One of the reasons I do not have a 5.56 pistol.
     
  17. Ura-Ki

    Ura-Ki Grudge Monkey

    For the 5.56 shorty, I run a CMMG conversion to run .22 LR and feed it 60 gr sub sonics through the can, all you ever hear is the hammer strike!
     
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  18. oil pan 4

    oil pan 4 Monkey+++

    The fastest burning powders I see for "223 handgun" loads is H322 and IMR4198, maybe RE7 for 45gr bullets.
    You could probably work up a RE7 load for 55gr. Max load would probably be around 18gr of RE7.
     
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  19. ghrit

    ghrit Bad company Administrator Founding Member

    If you are going to run experimental loads, do so with appropriate caution. Check EVERYTHING and use a heavy dose of skepticism when loading other than loads published by the manufacturers.
     
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  20. oil pan 4

    oil pan 4 Monkey+++

    That's out of speer #13, but they don't list a RE7 load for 55gr.
    But they do for 45gr.
    It's marginally faster bring than H322 and marginally slower burning than H110.
    I'm sure a safe load could be worked up with RE7 starting with 14 or 15gr.
    My main concern would be does it fill the case more than half way.
     
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