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Posted: 7/21/2026 7:41:29 PM EDT
| I'm stuck. I'm really wanting a 300 BLK for super and sub suppressed. It may be used for close range hunting deer or hogs...maybe...but, I mainly want a short defensive weapon to use with a Huxwurx 30 cal Flow Ti. I've done a ton of research and know most owners go for a barrel around 8". I understand a longer barrel will offer more velocity, but the 300 doesn't get the benefits other rounds do from extra inches. That said I suspect a 12.5" would be a handy length for general use and not too unwieldy with a can. But, a 9" barrel will obviously perform very well, so I'm stuck. Anyone out there with experience with "middle length" barrels , 11"-14", in 300 Blk? I'd like to hear from anyone who has used one. FYI, I'm eye balling a BCM Mk. 2, which is available in 9" and 12.5". Thanks! |
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If you're not worried about squeezing the supers for every yard of hunting range you can get, I would go for the 9". I'd probably call 175yds my limit for whitetails. I have a 12.5" BCM and I love it. You're right, it's not too unwieldy with a suppressor, but a 9" just feels handy and will do the job on game. |
| I sold my 12.5" and bought another 9". With a can the 12.5" was front heavy and felt more like a pendulum. The 9" is just about perfect for me for a home defense, truck gun use scenario. A titanium suppressor will help the nose heavy feel but it still puts the overall length similar to a 18" to 20" rifle. 300blk isn't a long range round so it didn't make sense to me to sacrifice portability and maneuverability to gain a couple hundred FPS. I don't hunt. Plus 12.5" can push some borderline subs to supersonic, which was also counter productive to my intended use case. |
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Originally Posted By Voland: I have a 9" and with a can, its just about perfect. I didnt see the point of the 12" when I built mine. I like the 12"ers with my Sure Fire SPS300 Can the best... Its just short enough to not be long and unwieldly like my 18"s with Cans, but yet long enough to me to get a great purchase/Grip. At 6'4"or so, I kinda have some Gorilla Arms. The shorter barrels aren't horrible, but I think the 12" shoots/feels best to me. This is all personal preference, for me. So, if someone else has others, I get it. Its your rig, run it how you like. Myself, I just don't like to be too bunched up. I would not be mad if my AR9 and my MP5 had a bit more arm length to them. |
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Originally Posted By Boom_Stick:
""AKs are for villagers you have to tell not to shit in their water supply.""
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Originally Posted By Boom_Stick:
""AKs are for villagers you have to tell not to shit in their water supply.""
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| 8-9 ish is perfect for me. Going with 300 Blackout means I'm focusing on compactness, and also want subsonics which don't care about barrel length. |
It was not preached to the crowd,
It was not taught by the State.
No man spoke it aloud,
When the English began to hate.
It was not taught by the State.
No man spoke it aloud,
When the English began to hate.
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I just have a DD PDW, only have run it with supers, suppressed and not, 100% function. HUXWRX Flow 7.62, 4-5 brands of ammunition. Zeroed with Sig SBR all copper rounds. Surprisingly the then AAC loads were very accurate and zero on with the Sig stuff. When I was in Va, hunted with a Sig pistol, red dot and Barnes 110 tipped, awesome set up. |
| Thank you, all, for the sincere responses. I'm kinda tall, at 6' 2", so understand the need for some forend length. I plan to mainly shoot suppressed, but don't believe the extra 3.5" of barrel will negatively effect that, but also know it won't be quite as handy with a can. Thanks again, gents! |
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I have the spectrum of 300blk barrel lengths out there (16", 12.5", 10.5", 9.0", 8.5", 8.3", 8.2", 8.0", 7.5" and 6.0"). I don't (can't) have a suppressor, but I do have bigger flash cans/linear comps. There is a 12.5" on my bolt action right now, but it may get a different (shorter) barrel. I would put it like this. Pros of longer barrels *Small increase in supersonic velocity (compared to more natural supersonic cartridges) *Reduced recoil *NAS3 rounds made for 8"-12" barrels. *Increase room on rail. - This is the biggest benefit to me. Cons of longer barrels *Weight/length obviously *No increase in subsonic capability *Loss of "advantage" over more natural supersonic cartridges. This is the biggest con for me on longer barrels for 300blk. It isn't that they are bad or useless, it is that the they start to play in the barrel range that other cartridges live in (or go down to without becoming inefficient flash bangs), and those cartridges usually have way longer legs, or more power, or both (and sometimes more accuracy as well). It all comes down to what you want it do. Full disclosure I'm also a bit biased on shorties. I've gotten to the point where my SHTF 10.5" 300blk with a comp looks like a musket to me. My .22LR AR has a is listed as 9"'s, but it is really more like 8.2" in rifle calibers. When I got my airsoft rifles for me and my son, I got us CQB versions which have 8" rails and would be 9" barrels if rifle calibers. I swapped out my 9" HD 300blk upper for an 8" version. I go back on forth on this. One is a 8" barrel with an 8" rail, the other is a 9" barrel with a 9" rail. The extra inch of rail space does make a difference. That 8"-9" barrel range is great. My 7.5" barrel was great when it had an 8" rail, but I now have a 7" rail on it and it feels super cramped. (A majority of my rails are the same...MI Combat). |
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I bought a Noveske 10.5” Blackout barrel and built it into an upper. I shot that for a while until I shot my friend’s 8.5” Blackout. I then sent my 10.5” barrel to have it chopped to 9”. I’ve put many rounds down that 9” tube. Within the past couple years I built an 8” Blackout, and the 9” barrel will be for sale soon. I’ve seen shorter barrels, but those lengths aren’t suitable for my can. Blackout subs are fairly inexpensive to shoot, if, like I do, you reload. But Blackout is a compromise cartridge. |
Knight of Blunder - Fogo '21
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If you have another, preferably higher back pressure can, I recommend you use that instead of a hux can. Itll be loud and you may have issues cycling subs. Everyone that comes into my shop usually has issues with a 762 ti when running subs, or doesnt like the sound performance. (Or both) I own three 300blks. All 9" or shorter. One is even a bolt gun. No need for anything longer than 9", IMO. |
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Go 9". My main hunting rifle is a 12.5" Grendel. With a full size can, it's a pretty good sized gun. It's not at all a compact HD sub gun type thing. I recently built a 10.5" 300 BO for a back up hunting upper. I researched ballistics a good bit. There's not going to be much practical difference between a 9" and a 12.5". You'll be inside 200 yards with any of them, and better off stopping around 100, IMO. I wouldn't get wed to one can ahead of time. Suppressing subs well with 300 BO isn't demanding. You can use a smaller can on that 9" barrel, keep the overall size down, and still get excellent results. If hunting predominates your supersonic use, you also can get flexible on the can since it's low volume fire. Just some things to consider. |
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If I’m going with strictly supers with a 12.5” barrel, my personal choice won’t be a .300BO but in 6.5 Grendel which is a much superior supersonic chambering. With the .300BO, I’m going 10” or less to be able to use subsonic if I have to. But for my needs, supersonic will be what I use. As usual, suppress all things. |
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| I’ve been wanting to get a noveske 12.5in barrel to build an upper around but haven’t been able to pull the trigger quite yet. I bought some Phantom Defense 120gr rounds to use for some eventual white tail hunting. I was hoping a used barrel would show up on the EE but it hasn’t yet. After reading a lot of Sobchak Security’s articles on the capabilities of NAS3 300blk supers I’ve been wanting to try out a “longer” barreled set up than my 6.75” MCX. |
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The platform was built around an 8-9” barrel. That IS the sweet spot and honestly the point. You buy 300BLK to do things 556 doesn’t do well - short length, for one. My 300BLK rifles are all 8.5/8.3” because that’s the point. I gain next to nothing going longer than that, I only lose. 762 cans are bigger, longer and heavier - the shorter the barrel, the better. Anybody doing long 300BLK builds is bench shooting vs actually running around using / hunting / HD etc. |
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https://sobchaksecurity.substack.com/p/125-6-arc-vs-125-300-blackout-for Here’s an article for the benefits of a longer barrel. Note that he’s talking about the benefits of a longer barrel when using higher pressure loads. |
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I went down the 300 Blk rabbit hole a long time ago. One thing I found out, more than concern over barrel length, is trying to get one rifle to shoot both super and subs consistently and reliably without having to resort to all sorts of trick parts. You have to keep in mind, the AR gas system is simple and asking it to do both extremes reliably can be a tall order. Some folks work it out pretty easily, others have struggled with it. I put together my first 300 SBR using a PSA 7.5" nitrided upper. What I discovered was that it will cycle both supers and subs without a can. Hmm. That tells me it is way over gassed. If I put my can on it, then of course it cycles and is quite reliable, but that also means with supers, it is beating the living crap out of the internals. Recoil is noticeably sharp since the BCG is bottoming hard in the buffer tube. I decided at that point that I should complete it to be either a sub shooter or a super shooter. I went with subs since I have the can and I like the quiet. Even then, I still had to put an AGB on it to tame it and get it tuned. I could probably run supers now comfortably by turning the gas down more, but to what end? I would say that if you don't mind having to change parts to tune it and maybe fiddle with your gas block when switching between subs and supers, I'd opt for a longer barrel simply because it'll giver you better muzzle velocity with the supers. I've since swapped out my buffer tube, spring and buffer for a different reason (but it's still well tuned due to the AGB and I don't shoot supers). |
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My two favorite blackout builds run supers and subs reliably with no special or trick parts. -Rosco Bloodline 8.2" with standard gas block, carbine buffer and spring, folding stock adapter, milspec BCG. People sometimes say the Roscos are undergassed. I initially had a few failures to lock back on the last round with a generic nitride BCG, but after swapping it out for a decent and efficient milspec bcg I have had 100% reliability. -BKF (Ballistic Advantage) 9" with pinned standard gas block H buffer and carbine spring, Toolcraft BCG. Has been a sewing machine from day one. YMMV. |
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Originally Posted By Urimaginaryfrnd: I don’t think it makes a lot of difference both are fairly short. This. I have 4 or 5 different lengths. Go with what’s comfortable. |
17 And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name.
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If hunting is on the menu, I would pick 12.5" over 9". More rail length for hand stop, light, or other stuff. I have only chono'd 2 barrels in 300blk, but my 10.3" BA barrel gets 2200fps with 110v-max hand loads. Our 16" Wilson combat barrel will get 2400+ with the same load. So ~35fps/in from 10"-16" is relevant in my opinion. 12.5" barrel will get you to ~2300fps with 110 supers. My longest kill with my 10.3 is only 120yd, but it worked fine. Though those stubby bullets only have a 50% chance to exit when hitting a shoulder. They pancake pretty quickly but do a lot of damage. Great defense load as well I would expect. I bought a 16" rosco to work up a 125gr SST load for short range hog hunting. It was going to be a gassless straight pull bolt action sub shooter, but then I realized how dumb it was to have the 10" shooting supers and the 16" dedicated to subs, so I'm going to swap it around. Though within the next year I might move to a 300Ham'r. Not sure why since the blackout has been killing hogs just fine, but ... you know, the black rifle disease... |
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