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Old August 17, 2013, 10:10 AM   #1
tank1949
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300 AAC

I am considering purchasing a 300 AAC Blackout upper or just barrel/assembly. I have an extra AR-15 flattop upper with bolt assembly that I'd prefer to simply attached a 300 barrel, tube, etc. But. I don't know if this would be possible. Or, does the 300 require special upper and upper hardware?????
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Old August 17, 2013, 03:21 PM   #2
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The only difference between a 5.56/.223 and a 300 Blackout is the barrel.
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Old August 18, 2013, 05:58 PM   #3
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It will work fine.
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Old August 19, 2013, 06:33 AM   #4
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You'll also need the gas system and handguard. Gas block and tube to fit the port location on the barrel. I built one using a carbine port position but there are some with a "pistol" port position. My purpose was for super sonic ammo only which is a factor in barrel choice also.
Plan on loading your own since the available ammo I've seen is overly expensive. There seems to be more brass showing up lately so that makes loading easier.
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Old August 19, 2013, 08:50 AM   #5
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Resizing 300

Is it difficult to size up brass from 5.56 to .300 BO?
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Old August 19, 2013, 12:39 PM   #6
velillen
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It's a fairly simple process.

Cut down the 223/556 at the shoulder

Lube and run through sizing die

Clean brass and trim.

After that its normal loading.
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Old August 19, 2013, 01:02 PM   #7
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The ammo is relatively easy to make - and you will have to do that. I built one 6 months ago and still haven't found any decently priced (<$1) commercial ammo for it. Remington used to sell UMC brand for $13/20, but that seems to have disappeared.
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Old August 19, 2013, 08:27 PM   #8
tank1949
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Best barrel twist to shoot supressed loads

I plan on making this rifel quiet and I have been told that I must work with slower heavier 308 220 grain bullets. What is best twist rate for this application?
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Old August 19, 2013, 10:39 PM   #9
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For best results with heavy subsonic loads I'd recommend 1:7 (all AAC 300 Blackout barrels are 1:7). Lightweight supersonic loads might be a bit over-stabilized with 1:7 but most should still work pretty well. If you still want good stabilization of subs but also want a little better accuracy from supers, you can go with a 1:8 twist instead.
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Old August 23, 2013, 09:51 PM   #10
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Threads

Anyone know the best threads needed on Muzzle for silencer????? I suspect standard that come on rifle barrel?????
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Old August 23, 2013, 10:53 PM   #11
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The standard US thread pattern for a 30 caliber rifle is 5/8x24. Every 300 Blackout barrel I've ever seen was threaded in 5/8x24 and all 30 caliber cans I've ever seen either come standard with this thread pattern or have it as an option for either a direct-thread or a muzzle-device mount.

And many 9mm cans have pistons or direct-thread mounts for 5/8x24 specifically used for threading onto a 300 Blackout; with subsonic loads you're not going to get quieter than a 9mm can.
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Old August 26, 2013, 07:00 PM   #12
tank1949
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Can????????? Have no idea what you are refering to?
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Old August 26, 2013, 08:37 PM   #13
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can = silencer to you

The whole point of the 300AAC is suppressed (silenced fire) which requires a can ie noise suppressor and a projectile at subsonic speed.
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Old August 27, 2013, 09:42 AM   #14
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Quote:
Originally Posted by tank1949
Can????????? Have no idea what you are refering to?
"Can" is a common term for a silencer or suppressor.
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Old August 27, 2013, 10:23 AM   #15
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Quote:
Originally Posted by 20thru45
The whole point of the 300AAC is suppressed (silenced fire) which requires a can ie noise suppressor and a projectile at subsonic speed.
You're completely right, except you don't HAVE to use subsonic rounds; supersonic rounds are still quieted considerably by a suppressor.
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Old August 27, 2013, 11:00 AM   #16
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The 300blk has its place.....

Rule1.

You must reload

Rule2

See rule1

The promised cheap ammo is an illusion

Check gunbot....... Occasionally there is cheaper "remanufactured" ammo , but usually its $1.25 per round and up


I have been researching it for awhile. (I went with another caliber because I wanted longer ranges to hunt)

I think at some point I will get one because it appears the 300 blk does very well in a suppressed SBR role

The bullet gets up to speed quickly in short barrels.

Having the abilty to use cheap brass to reload also helps


In summary

If you reload its a decent choice

If you want to SBR, its a decent choice

If you want to run suppressed, its a decent choice


If you want a hunting bullet for mid size game to 150 yards, its an ok choice

If you want to hunt to 300 yards there are better choices
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Old August 27, 2013, 12:01 PM   #17
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Quote:
The whole point of the 300AAC is suppressed (silenced fire) which requires a can ie noise suppressor and a projectile at subsonic speed.
Not at all true.

Let's compare the 300 BLK to the 5.56. A 125 grain bullet at 2200 fps has more power and shoots flatter than a 224 62 grain bullet at 2950 fps. The 300 blk powder charges are a bit lighter but the bore is larger so the 5.56 will probably be a little less noisy suppressed.

But it is true that subsonic is what really makes the 300 blk shine. It is less noisy and more consistant than a subsonic 308 winchester.
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Old August 27, 2013, 09:22 PM   #18
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Need More data

I plan on shooting handloads and heavy, heavy bullets and surpressed. So what is best barrel length and a generally good barrel. I don't want to spend another fortune on Kreiger. If I can get 2" group at 100 yards (surpressed), I'd be happy. I have a bunch of Blc2 and prefer H4895, but either powder is becoming like finding an honest politician. What is a good handload combination? NO SUPERSONIC STUFF!!!!!!
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Old August 27, 2013, 10:09 PM   #19
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I prefer magnum pistol powders for subsonic rifle cartridges. H110 works well for jacketed bullets but I'm finding some unburnt powder in the bolt when used with cast bullets. Start out with about 10 grains and work down. An 11 inch barrel and longer will work well.

You will need to use a chronograph or you will not get the right load.
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Last edited by Lark; August 28, 2013 at 07:04 AM.
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Old August 28, 2013, 04:02 AM   #20
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Technically you don't have to reload for 300BLK, you just have to be willing to pay for commercial ammo since its expensive. Right now they are about $30 per 20rds. Before the panic they were around $13/20rds.

You should reload if you want to shoot a lot with your 300BLK and have a wide option of ammo between sub/supersonic.
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Old August 28, 2013, 02:36 PM   #21
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Quote:
Originally Posted by Lark
Let's compare the 300 BLK to the 5.56. A 125 grain bullet at 2200 fps has more power and shoots flatter than a 224 62 grain bullet at 2950 fps.
You might want to double check that. In no way does the 125gr 300bo shoot flatter than the 62gr 223. in fact, the drop of the 300bo is almost double.



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Old August 28, 2013, 04:28 PM   #22
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http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
I used a BC of .151 for the ss109 on the above calculator. That is what I shoot in my 5.56. It gives a drop of 104" at 500 yards with a flight time of .98 seconds. I used a Sierra 125 gr with a BC of .338 for the 300 blk. That gave about a 93" drop and .93 seconds flight time.

I can't find any Berger .224 62 grain bullets listed on their website. I used a 600 yard zero for my calculations in the previous post, but I know that bullet BC makes a huge difference.
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