300 AAC Blackout Barrel Questions...

[blacksky]

I'm going to convert one of my AR'S to the 300 AAC Blackout.

Any barrel recommendations?

Length 16" to 20"?

What twist rate?

Which is the most accurate out to 300 yards?

[taylorce1]

Barrel length doesn't really affect accuracy much between a 16.5" and 20" barrels. If you aren't using optics then the longer barrel should provide slightly better accuracy. The AAC BLK is designed around a 1:8 twist barrel, since the heavy bullets are moving so slow you need a faster twist to stabilize the bullets.

[rjrivero]

The "new" 300 Blackout barrels are going 1:7 Twist for the subsonic 220+ bullets designs that will expand at subsonic velocities.

Personally, i don't see any benefit with going longer than 16" in this caliber.

[Palmetto-Pride]

Good luck finding a barrel longer than 16" for the 300 Black Out.

[RT]

I believe th BLK is optimized for a SBR so 16 inches should be plenty.

[blacksky]

http://www.tacticalammunition.com/300-AAC-Blackout-Black-Hole-Weaponry-Mid-Length-Barrel-TA88-0330.htm

16" to 24" barrels with 1-8.5, and 1-11 twist rates???

http://www.tacticalammunition.com/300-AAC-Blackout-Black-Hole-Weaponry-Rifle-Bull-Barrel-TA88-0334.htm

[rsilvers]

A 16 inch 300 BLK has as much energy as a 24 inch 5.56mm. There are velocity gains past 16 inches, not it is diminisning - Daniel Horner used a 20-22 inch:

http://bulletin.accurateshooter.com/2011/10/horner-wins-tactical-optics-divison-at-multigun-nationals/

That being said, I would go with 16 as it is the sweet spot.

[Toxdoc]

18" barrels with 1-8.5, and 1-11 twist rates

Those choice will likely limit you to supersonic ammo, although the 1:8.5 would probably be ok. It is definitely a non-standard twist rate.

AAC recommended a 1:8 and is going to a 1:7 as noted above.

For that kind of money, you can get a barrel from Wilson Combat: http://shopwilsoncombat.com/300-AAC-Blackout/products/397/

[Nitesites]

Congrats!

[taylorce1]

I had to check on the twist rate and it seems to be more of a stabalization issue in SBR's than getting bullets to expand. The 220+ bullets are stabalized better at longer ranges out of a 1:7 twist in SBR barrels. From the littel I was able to research on it it seems that the 1:7 twist might not be of any benifit in a longer barrel. The SAAMI specs (http://www.saami.org/PubResources/CC_Drawings/Rifle/300%20AAC%20Blackout.pdf) are still a 1:8 twist and I doubt anyone will get that changed anytime soon.

[rsilvers]

No one is going to attempt to change the SAAMI suggested twist rate - there is no need to as it is just a suggestion.

[blacksky]

No one seems to have any 16" in stock??? :mad:

[blacksky]

So there is no advantage to a longer barrel with a 11-1 twist rate? What about a 24" barrel? I would think that the 11-1 twist would stabilize the bullett while adding increased distance to the range... :confused:

[taylorce1]

With the .300 Blackout there isn't going to be any advantage to a longer barrel out to 24". You can't cram enough slow burning powders into the case to take advantage of the length, and fast burning powders will be used up before the bullet exits the barrel. Anything over 16-20" isn't going to gain you anything.

For example my little 6mmX47 (6-222 Rem Mag) with a 20" barrel is only 25 fps behind the Sierra manual loads out of a 26" barrel. That tells me I didn't need a 6" longer barrel as I wouldn't gain anything. So I got a lighter and better handling rifle by going with a shorter barrel.

[rsilvers]

A longer barrel has more velocity. But a 16 inch 300 BLK barrel already is sucking the juice out of the cartridge as much as a 5.56mm does with a 24 inch barrel.

So if you are the type of person who wants a longer-than-24 inch 5.56mm barrel, then you would also want a longer than 16 inch 300 BLK barrel.

[rsilvers]

300 BLK does gain velocity up to and past a 30 inch barrel.

http://img211.imageshack.us/img211/7426/300blk.jpg

Barrel length has virtually no effect on which powder to use to get the most velocity. I know it is commonly believed to be the case, but it just does not really work that way. It does a little, but primarily whatever powder gives the most velocity in a 6 inch barrel with probably also give the most velocity in a 24 inch barrel. This is because the powder that reaches peak pressure and velocity for any given bullet weight does so within the first inch of bullet travel.

300 BLK will gain about 65 fps per inch at around 9 inches, 43 fps per inch at around 12 inches, 28 fps per inch at around 16 inches, 21 fps per inch at around 20 inches, 17 fps per inch at around 24 inches, and 12 fps per inch at around 30 inches. You just need to decide where you want to stop.

[Justice06RR]

1:8 is standard for 300Blackout, but damn I can't find any 16in barrels in stock. Its better to just buy a complete 300 upper instead. Somehow they are not making these barrels fast enough?

[blacksky]

Like I said in the first post, I am blind here... So there's no difference in velocity and energy between 16" to 20" other than additional barrel weight? Will the 300AAC reach out to 300 yards with enough energy to hunt with? If so in what configuration? If not what is the max effective range? :confused:

[Abel]

Like I said in the first post, I am blind here... So there's no difference in velocity and energy between 16" to 20" other than additional barrel weight? Will the 300AAC reach out to 300 yards with enough energy to hunt with? If so in what configuration? If not what is the max effective range?

I would think that this round is kin to a 30-30 in performance. In other words, its more of a 200 yard deal. If you want to get out to 250+ yards with flat trajectory, a 220gr projectile may not be what you want. So, a 1:9" or 1:10" would stabilize a smaller projectile, say 150gr or 165gr.

[taylorce1]

Yes the .300 BLK will reach 300 yards, as to having enough energy to hunt with you'll have to decide.

125 grain Sierra OTM bullet
MV 2200 fps, velocity at 300 yards 1536 fps energy 656 ft-lbs.

240 grain Sierra MK bullet
MV 1000 fps, velocity at 3000 yards 922 fps energy 453 ft-lbs.

At 300 yards the 240 grain bullet would be like shooting a deer with a muzzle loader. I wouldn't hesitate to take a deer with either at 300 yards but I would prefer much closer. I do like the fact that the heavier bullet doesn't even loose 100 fps in 300 yards from the muzzle, so maybe a 165 grain bullet like the Accubond would be a great compromise, loose a little MV but pick up more energy out to 300 yards.

[rsilvers]

"So there's no difference in velocity and energy between 16" to 20" other than additional barrel weight?"

2400 fps vs 2491 fps.
1403 ft-lbs vs 1515 ft-lbs.

"Will the 300AAC reach out to 300 yards with enough energy to hunt with?"

Yes - energy and bullet performance is fine at 300 - but the drop at 300 is about 11 inches from a 200 yard zero - so if you want to shoot beyond 300 yards - you will have to start to do scope adjustments or holdover.

If you want to hunt long range - 308 is the way I would go.

"If so in what configuration?"

A 9 inch barrel is good for up to 300 yards for hunting based on bullet performance. A 6 inch barrel I would limit to 200 yards.

"If not what is the max effective range?"

For hunting I would say 300 yards. For military use and by M4 standards based on hit probability, it is 440 meters from a 9 inch barrel and 460 meters from a 16 inch barrel. This is because those are the ranges for which the wind drift and drop matches the M4 at its stated max effective range.

[blacksky]

I can get 16" to 24" in either .750 or .920 diameter at the muzzel,
with 8 - 8.5 -11 to 1 twist rates.

I'm trying to squeeze as much out of this conversion as I can.

I already have a M24.308 5R and just got a .338 WINMAG for long distance.

I have 2 AR'S that will ring steel at 600yards and I'm wanting a 300AAC BLK with all I can get from it. :eek:

[rdmallory]

Check Midway. That is where I picked mine up from.

Doug

[blacksky]

Out of stock! :mad:

[Doug76]

Pegasus Defense has a 16" .300Blk barrel. I recently bought one, and will be getting another.

http://www.pegasusdefense.com/store/products/512/pegasus-defense-16-300-blackout-nitride-barrel

I see this is a fairly old thread, but I posted the info anyway. Maybe it will prevent someone from having to ask the question again, and then it will provide the info they need.

[JD0x0]

Shorter is probably better for subsonics, to keep the weapon compact, especially with a suppressor attached. If you're going to shoot supersonics, extra barrel length will help velocity a bit but gains will be fairly small due to this cartridge's efficiency in shorter barrels.

[Mobuck]

The 300BO burns about the same amount of the same powder as does the 357 mag. While a 20" barrel may increase velocity slightly, I don't see that increase as putting the BO significantly ahead of what you get from a 16". Matter of fact, I'm looking at a 12" "pistol" upper because I feel that's a more appropriate barrel length for my expectations of the cartridge.

[mavracer]

I went with a alpha sports 16" 1 in 8" twist melonited barrel for my blackout and am very happy with how it shoots.

www.shop.ar15hardware.com

[skizzums]

Masdefense.com has lots of in stock barrels, cheap and quality.

[skizzums]

Oops...too late