Alt to 300 BO

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ADIDAS69

New member
so I am aware of the awesomeness of the 300 Black Out round. That said ammo scarcity and expense keep it well out of my armory. I have discovered some 200 grn subsonic loads for the 7.62X39 round and i am thinking I need an AR pistol in same caliber. The question is with a 1/10 twist what would be the shortest barrel length before a 6" group at 200 yards would be a problem.

http://www.radicalfirearms.com/category-s/2087.htm

these are the ones i am looking at and the company will take the 16" to whatever length I want for an extra $100.

NOTE: i already own an AR in 7.62X39 with a 16" barrel and it performs perfectly as well do the magazines.
 
Do you currently reload? Do you already have a .223 as well? If you do, I don't understand what the problem is. I do reload and have a couple .223's as well, so when my necks start to look a little damaged or dented cases, I just chop them up and re-size to .300BLK. Its a fun little cartridge, just don't rule it out completely.
 
My experience, with all kinds of guns and calibers is that barrel length, in and of itself, has very little to do with accuracy.

Barrel construction, and its condition (and the firearm in general) are more important, as is the vitally important relationship between the barrel and the bullet.

Length alone matters little, and even though things like sight radius, and barrel stiffness do have an effect, for what you are talking about, I don't think it really matters.
 
I am not impressed with the 300 Blackout round, you may want to consider the 6.8 SPC as an alternative.

Jim

Unless you just want a sub-sonic rifle to suppress.
 
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Jim243; wanting a combination of heavy subsonic (to run with a suppressor) whilst also incredibly common. If I was gunna go with a goofy caliber I'd lean into it and go 458 SOCOM or 50 Beowulf. Seriously if I could get a 50 round double drum from Beta Mag I'd have a 50 Beowulf in like two seconds.

SpringOWeiler/AMP44; I'm hearing that RPM would be more relevant than barrel contact?

Mxsailor803; I got kids chief, ain't got time for making wild cat cartridges and kids use a lot of ammo so it's gotta be cheap

Also I know Olympic Arms makes pistol caliber upper but they won't custom length one for me. My dream would be a 10mm or 357 sig with a 10 barrel on the AR platform. Also yes I did see Sig Sauer's newest offering in the pistol cal. carbine arena and of course my dream languishes in the ether cause BATFE doesn't like the built in baffles.
 
It yet another answer to an unasked question. So is the 6.8 SPC. All the stuff in these chamberings are big kid's toys. Mind you, that's not a bad thing.
 
ADIDAS69: "I'm hearing that RPM would be more relevant than barrel contact?"

RPM? We're talking about a semi auto right? Do you mean short stroking on the heavy weight subsonic rounds? Are you planning on using 200gr cast bullets or jacketed?
 
It depends on the length of the bullet but just guessing 1 in 10 is going to be pretty close to the unstable range with a subsonic 200gr bullet.
barrel length is really only important in how it affects muzzle velocity
 
SpringOWeiler: apologies for bad nomenclature "rpm" = twist rate. Yes a semi auto weapon. Also that is an awesome calculator. I was planning on starting with the Sierra 150 grns and seeing if I could work up a successful subsonic load that would still cycle the action. I'm trying to avoid cast/casting bullets; trying to stay as lead safe as possible. I do have a CZ bolt action chambered for 7.62X39 although I'd have to remove the front sight to thread the barrel for a suppressor. I appreciate your help, I'll admit I'm always confused at how a 45 ACP projectile can be stabilized by a 1:16 twist in a 5" barrel whilst a .223/5.56 weighing more than 65 grains has trouble with a 1:12 even through the barrel is 26" long.

T.O'Heir: so...cause I can I should? Agreed, I'll pick up a 50 Beowulf as a Halloween present for me. The neighborhood kids will have to suffer with fun size candy this year instead of full size.
 
I never understood the .300 BLK.

7.62x39mm performance or less than, for triple to quadruple the cost. Oh wait, you can make subsonic loads in .300 BLK. Well you can do the exact same thing with 7.62x39mm.

If anything, .300 BLK cements the excellence of the clasic 7.62x39mm loading as it tries to stuff that round in an AT magazine, and doesn't quite succeed.

But OP, I think you are perfectly well served with your current loadout.
 
I have a few of the calculations i ran for my 7.62x39
With the optimal being 0-2
123grSP Hdy: 4.74
150grSP Hdy: 3.13
174grFMJBT Hdy: 2.17
Now this is with .312" bullets and a 1:9.5 barrel. I didn't have a 200 too measure so i estimated the bullet length at 1.45". I also was loading for max velocity so the numbers will be different for a subsonic round. A quick extrapolation shows that reducing all them to 1050fps from my max loads reduces the stability factor by .6. Thus making them more stable. 200 yards won't be a problem.
I would feel comfortable that the manufacture took the subsonic desires into designing that upper and would be surprised if it didn't work right out of the box. My suspicion is you'll be using the faster end of powders to get a positive recoil impulse. My experience is primarily in Hodgdon and IMR powders so I won't bore you if you don't have those options.
 
IMO, 7.62x39 has been problematic in the AR platform. Sheared locking lugs and bolt issues abound. Less then stellar performance in AR type magazines kills the deal for me.

I can get x39 balistics outta the 300blk and not deal with the finicky nature of X39 in the AR platform. In an AK the X39 is an EXCELENT choice as evidenced by the Millions of rifles out in the world
 
What is your end result/goal/purpose for fire arm might help clarify some responded. People are just gonna promote what they have has been my experience.
 
Sharkbite: I have an Olympic Arms complete upper ( in 7.62X39) mated to an Aero Precision lower with a DPMS lower kit and a Law Tactical folding stock attachment. I've put about 3000 rounds through it; double taps, full mag dumps what have you, with nary an issue using AR Stoner magazines. I quizzed the salesmen RE the issues you mention (when I bought the rifle a couple yrs ago) and he explained that the primary reason for bolt failures was manufacturers taking existing 5.56/.223 bolts and machining them out to fit the 7.62X39 and not properly heat treating them after doing so. Magazine issues, of which I have had none I have no answer . I picked up 5 from midway and a further five from a local retailer. Now I may have gotten, by way of a coincidental cosmos, the only working AR platformed 7.62X39 but I've experienced nothing that recommends against purchasing another. The 300 Black Out is a fine round and I'm more than well aware of all the things that recommend it. I wasn't at all being sarcastic in my original post but similarly in my original post; the round itself is too scarce and too expensive. I'm near a military base and am surround within 15 miles by a total of 12 firearms and munitions retailers and I can't currently (18 sept 2014) walk in to a single one and purchase 300 black out ammo and when I can it's never below $0.90 a round. Conversely I can retrieve all the 7.62x39 ammo I could ever want steel or brass cased from all but 3 of the retailers and spend no more than $0.55 per for the most expensive stuff.

Zen Archery: primary goal of the weapon is an at platformed pistol, originally I was looking at Bravo Company Upper assembly (5.56 NATO). I was tooling around on "yea' Olde interwebs" and found the above online retailer offer the 7.62x39 assembly. I'd previously quizzed Olympic Arms RE making me a pistol length barrel and they flatly refused. I may still buy one of their bolts for reasons mentioned above and the above posted retailer allows you to choose whether or not you'd like a bolt with you order. Given this new opportunity I thought it'd be nice to go subsonic using my suppressor.
 
lots of people here talk about their great experiences with x39 AR's, all the bad things I hear are second-hand. I have 300BLK and really like it, but I agree with your assessment if I didn't reload and make my 300 cases, I would never own a BLK
 
"so I am aware of the awesomeness of the 300 Black Out round"

I'm not overly enthused although I currently own 2 uppers that use that round. I also own 3 in 7.62x39. These are two totally different animals with only somewhat similar expectations.
If you reload, the 300 has several options not available with the 7.62. Brass prices for the 300 are actually lower than for 7.62 and is available in large quantities. If you want to spend the time, it's easily formed from .223/5.56 brass. 7.62 brass on the other hand is fairly scarce since most users shoot steel cased ammo.
Most 300 barrels will handle a wider range of bullet weights than are even available for 7.62 (although you can get creative by using numerous other .311 bullets) due to the commonly produced twist rates of barrels.
The 300 went from a heavy bullet beginning(300Whisper) to lighter supersonics. To reach the same goal, the 7.62 would have to go the other way which IMHO is more difficult w/o special twists.
The 300 functions well through most .223 capable mags while the 7.62 requires round specific mags or followers/springs for internal magwells.
 
Look again, blackout ammo which used to be $1 a round and impossible to find is now available online for 52cents a round (ammo seek). I got the American Quality ammo from cheaper than dirt and its great.

If you reload, blackout uses .223 brass and .308 bullets, both easy to find online and in stores now. Powder for the subsonic (AA1680) is hard to find, however H110 is available and suitable for everything from 110 to the 220 grain behemoths, the only problem is h110 wont cycle some blackout AR's.

If you want a subsonic, well suppressed rifle 30 cal rifle, there is no better choice than the blackout. Every other caliber is going to be harder to find and you will run into problems with cycling. The blackout was specifically designed fro the AR frame and to shoot subsonic and supersonic in the same gun without any problems. Its getting a lot more popular as well as people realize that you don't need the super flat .223 ballistics for most areas in north America. By next year I predict blackout ammo will be the same price as .223.
 
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