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Posted: 2/16/2017 1:13:10 PM EDT
[#1]
The challenge with the Blackout is keeping it subsonic, so I wouldn't recommend anything longer than 8".
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Posted: 2/16/2017 4:41:50 PM EDT
[#2]
Someone on Weaponeer has proposed a blowback action for subsonic Blackout, and venting the bbl in case a supersonic round is accidentally chambered.
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Posted: 2/16/2017 5:28:02 PM EDT
[#3]
Most barrels I've seen (but in this day and age you can get anything you want) are pistol length gas systems no matter length (not all though). I'd stay between 8" to 10", that would also depend on how you are going to stamp or are stamped (sbr w/can or pistol w/can). I went 10" just to give longer sight radius for irons and still waiting to see about HPA before getting a can, since the wait is so long.
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Posted: 2/16/2017 5:47:00 PM EDT
[#4]
All powder is burned by 9" in 300 BLK. So many consider 9" the optimal length for 300 BLK. While you may get slightly higher velocities from a longer a barrel, it's not going to be huge difference since all the powder is already burnt at 9". Just search "optimal barrel length for 300 blackout" on Google and you will find plenty of forums, articles, etc. about this and the "consensus" is 9".
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Posted: 2/16/2017 6:13:17 PM EDT
[#5]
Quote HistoryQuoted:
All powder is burned by 9" in 300 BLK. So many consider 9" the optimal length for 300 BLK. While you may get slightly higher velocities from a longer a barrel, it's not going to be huge difference since all the powder is already burnt at 9". Just search "optimal barrel length for 300 blackout" on Google and you will find plenty of forums, articles, etc. about this and the "consensus" is 9". I don't think it has anything to do with propellant being burnt. According to Quickloads most popular subsonic loads, W296/H110 and Lil'gun are still burning at 16+ inches under a 220gr bullet. Even the favored super sonic load of 110gr TAC-XT pushed by H110 is still burning at 16 inches. 9 inches may very well be a good compromise length for both super and sub sonic, but it's not because all the propellant is all burnt. |
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Posted: 2/16/2017 6:56:40 PM EDT
[#6]
Quote HistoryQuoted:
I don't think it has anything to do with propellant being burnt. According to Quickloads most popular subsonic loads, W296/H110 and Lil'gun are still burning at 16+ inches under a 220gr bullet. Even the favored super sonic load of 110gr TAC-XT pushed by H110 is still burning at 16 inches. 9 inches may very well be a good compromise length for both super and sub sonic, but it's not because all the propellant is all burnt. Quote HistoryQuoted:
I don't think it has anything to do with propellant being burnt. According to Quickloads most popular subsonic loads, W296/H110 and Lil'gun are still burning at 16+ inches under a 220gr bullet. Even the favored super sonic load of 110gr TAC-XT pushed by H110 is still burning at 16 inches. 9 inches may very well be a good compromise length for both super and sub sonic, but it's not because all the propellant is all burnt. Yes it is. This is well established. Article There is, however, a point of diminishing returns. Once all of the powder in the case has been burned, there’s no more fuel to add to the combustion and the gasses are at their maximum energy. Adding more barrel length after that point might still increase the velocity a bit, but the added weight isn’t always worth the extra dollop of velocity.
For 5.56 NATO, that point is 20? of barrel. For 300 AAC Blackout, that point is 9 inches of barrel. That number comes from multiple conversations with the people who designed the 300 AAC Blackout cartridge, did the initial testing, and who continue to design guns around that caliber. AAC Comment on YouTube Video: You Tube (see AAC Comment) Advanced Armament Corp5 years ago
@1IdeaAhead It is made possible by a couple of factors. 300 AAC Blackout Ammunition was designed to be used in a 9" barrel, meaning you get a complete powder burn in shorter barrels. Also see this thread: 300 Blackout Barrel Discussion 9" is enough length to burn all powder for 300 blk, so 9" = no flash. |
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Posted: 2/16/2017 11:07:40 PM EDT
[#7]
Quote HistoryQuote HistoryQuoted:
Quoted:
I don't think it has anything to do with propellant being burnt. According to Quickloads most popular subsonic loads, W296/H110 and Lil'gun are still burning at 16+ inches under a 220gr bullet. Even the favored super sonic load of 110gr TAC-XT pushed by H110 is still burning at 16 inches. 9 inches may very well be a good compromise length for both super and sub sonic, but it's not because all the propellant is all burnt. Yes it is. This is well established. Article It may be well established but that article did not establish anything. Quickloads predicts that most of the loads I indicated are still burning past 16 inches. They are well into the regressive part of the burn so not doing as much work but still burning. If you have actual data to say otherwise I will be happy to look at it. |
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Posted: 2/17/2017 9:22:51 AM EDT
[#8]
While there is nothing to gain from bbl length for subs there are substantial gains for supers. The fact that the powder is burned or not doesn't really matter because velocity is a result of pressure and time. Just because the powder is consumed doesn't mean the pressure is no longer sufficient to accelerate the bullet.
If OP intends to use it for supersonic hunting the fact that many available bullets have a limited expansion thresholds at 300 velocities might make a few inches of bbl a good trade-off depending on what ranges he hunts at. 
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Posted: 2/17/2017 9:48:05 AM EDT
[#9]
Quote HistoryQuoted:
It may be well established but that article did not establish anything. Quickloads predicts that most of the loads I indicated are still burning past 16 inches. They are well into the regressive part of the burn so not doing as much work but still burning. If you have actual data to say otherwise I will be happy to look at it. Quote HistoryQuoted:
It may be well established but that article did not establish anything. Quickloads predicts that most of the loads I indicated are still burning past 16 inches. They are well into the regressive part of the burn so not doing as much work but still burning. If you have actual data to say otherwise I will be happy to look at it. I'm going by what AAC themselves said about development of the 300 BLK round: 300 AAC Blackout Ammunition was designed to be used in a 9" barrel, meaning you get a complete powder burn in shorter barrels. This is straight from the people who developed the 300 BLK. I'm also going by what most people consider to be the optimum barrel length of 300 BLK: 9". Read any forum discussion on 300 BLK barrel length and most people will say 9" is optimum. The real world shooting demonstrates that shooting 300 BLK out of 9" barrel gives no flash, meaning complete powder burn has occurred. Personal experience and that of others. [The blast and flash are caused by the combustion products of the gunpowder and any remaining unburned powder mixing with the ambient air outside the barrel. Are there loads that aren't completely burned in a 9" barrel? Of course. But the round was developed to have complete powder burn in a 9" barrel. EDIT: I stand corrected (see mcb post above and below). It seems that "all powder is burned by 9"" is one of those internet memes that someone said and it took on a life of its own and was repeated everywhere with nothing to back it up. Apologies for perpetuating that incorrect information. |
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Posted: 2/17/2017 10:16:31 AM EDT
[#10]
Quote HistoryQuoted:
While there is nothing to gain from bbl length for subs there are substantial gains for supers. The fact that the powder is burned or not doesn't really matter because velocity is a result of pressure and time. Just because the powder is consumed doesn't mean the pressure is no longer sufficient to accelerate the bullet. If OP intends to use it for supersonic hunting the fact that many available bullets have a limited expansion thresholds at 300 velocities might make a few inches of bbl a good trade-off depending on what ranges he hunts at. http://img.photobucket.com/albums/v726/abinok/412260_343799122333216_617473682_o.jpg From the chart it looks like 9" to 11" is the sweet spot for the 300 blk. You are still adding 40 to 50 fps up till around 11". From 11" to 15" its around 30 fps and closer to 20 fps after 16". 16" is about the max, even though their are small gains after that. Anything less than 9 you are giving up a good bit. |
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Posted: 2/17/2017 10:51:05 AM EDT
[#11]
Quote HistoryQuoted:
I'm going by what AAC themselves said about development of the 300 BLK round: 300 AAC Blackout Ammunition was designed to be used in a 9" barrel, meaning you get a complete powder burn in shorter barrels. This is straight from the people who developed the 300 BLK. I'm also going by what most people consider to be the optimum barrel length of 300 BLK: 9". Read any forum discussion on 300 BLK barrel length and most people will say 9" is optimum. The real world shooting demonstrates that shooting 300 BLK out of 9" barrel gives no flash, meaning complete powder burn has occurred. Personal experience and that of others. Are there loads that aren't completely burned in a 9" barrel? Of course. But the round was developed to have complete powder burn in a 9" barrel. Every publish load on Hodgdon's site and a few others I dug up on the internet when simulated in Quickloads result in a load that has not completely burned in a 9 inch barrel. Most are still burning at 16+. AAC can claim what ever they want that does not make it true. And just because there is no muzzle flash does not mean the powder is fully burnt either. Given the lower pressure of sub sonic 300blk you can have partial burnt powder grain ejected from the muzzle producing no muzzle flash because they simple stopped burning do to the low pressure/temperature at muzzle exit. Again 9-inch might be optimal barrel length to get good performance from both super and sub sonic rounds but the idea that sub sonic rounds are burning all the powder in 9-inches for must published sub sonic loads is just not true. Maybe Remington is using magic pixie dust powder that us lowly hand loader do not have access to... |
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Posted: 2/17/2017 8:13:05 PM EDT
[#12]
Quote HistoryQuoted:
The challenge with the Blackout is keeping it subsonic, so I wouldn't recommend anything longer than 8". 0 problems with my 10.3" staying sub. Really not hard staying sub with a 16" with heavy enough bullet. Longer is actually better if you want to cycle subs without suppressor (pistol gas). To o.p.: I personally like a 10" (have 10.3 BA hanson barrel) very accurate and gives a bit more than a 9", more than 10" to 11". notice chart above post. I hunt with mine, so this was my biggest factor. super on deer, subs on hogs. Im thinking about making a 7" upper for HD. Seriously, suppressed sub is dreamy. " |
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Posted: 2/18/2017 8:38:14 PM EDT
[#13]
Quote HistoryQuoted:
Every publish load on Hodgdon's site and a few others I dug up on the internet when simulated in Quickloads result in a load that has not completely burned in a 9 inch barrel. Most are still burning at 16+. AAC can claim what ever they want that does not make it true. And just because there is no muzzle flash does not mean the powder is fully burnt either. Given the lower pressure of sub sonic 300blk you can have partial burnt powder grain ejected from the muzzle producing no muzzle flash because they simple stopped burning do to the low pressure/temperature at muzzle exit. Again 9-inch might be optimal barrel length to get good performance from both super and sub sonic rounds but the idea that sub sonic rounds are burning all the powder in 9-inches for must published sub sonic loads is just not true. Maybe Remington is using magic pixie dust powder that us lowly hand loader do not have access to... Quote HistoryQuoted:
Quoted:
I'm going by what AAC themselves said about development of the 300 BLK round: 300 AAC Blackout Ammunition was designed to be used in a 9" barrel, meaning you get a complete powder burn in shorter barrels. This is straight from the people who developed the 300 BLK. I'm also going by what most people consider to be the optimum barrel length of 300 BLK: 9". Read any forum discussion on 300 BLK barrel length and most people will say 9" is optimum. The real world shooting demonstrates that shooting 300 BLK out of 9" barrel gives no flash, meaning complete powder burn has occurred. Personal experience and that of others. Are there loads that aren't completely burned in a 9" barrel? Of course. But the round was developed to have complete powder burn in a 9" barrel. Every publish load on Hodgdon's site and a few others I dug up on the internet when simulated in Quickloads result in a load that has not completely burned in a 9 inch barrel. Most are still burning at 16+. AAC can claim what ever they want that does not make it true. And just because there is no muzzle flash does not mean the powder is fully burnt either. Given the lower pressure of sub sonic 300blk you can have partial burnt powder grain ejected from the muzzle producing no muzzle flash because they simple stopped burning do to the low pressure/temperature at muzzle exit. Again 9-inch might be optimal barrel length to get good performance from both super and sub sonic rounds but the idea that sub sonic rounds are burning all the powder in 9-inches for must published sub sonic loads is just not true. Maybe Remington is using magic pixie dust powder that us lowly hand loader do not have access to... you can lead a horse to water but you cant make it drink . this conversation goes on all the time . mcb you are correct , but you might as well forget arguing this point . |
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Posted: 2/19/2017 9:37:05 AM EDT
[#14]
Quote HistoryQuoted:
Every publish load on Hodgdon's site and a few others I dug up on the internet when simulated in Quickloads result in a load that has not completely burned in a 9 inch barrel. Most are still burning at 16+. AAC can claim what ever they want that does not make it true. And just because there is no muzzle flash does not mean the powder is fully burnt either. Given the lower pressure of sub sonic 300blk you can have partial burnt powder grain ejected from the muzzle producing no muzzle flash because they simple stopped burning do to the low pressure/temperature at muzzle exit. Again 9-inch might be optimal barrel length to get good performance from both super and sub sonic rounds but the idea that sub sonic rounds are burning all the powder in 9-inches for must published sub sonic loads is just not true. Maybe Remington is using magic pixie dust powder that us lowly hand loader do not have access to... I stand corrected. It seems that "all powder is burned by 9"" is one of those internet memes that someone said and it took on a life of its own and was repeated everywhere with nothing to back it up. Apologies for perpetuating that incorrect information. |
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Posted: 2/21/2017 9:19:30 AM EDT
[#15]
Quote HistoryQuoted:
While there is nothing to gain from bbl length for subs there are substantial gains for supers. The fact that the powder is burned or not doesn't really matter because velocity is a result of pressure and time. Just because the powder is consumed doesn't mean the pressure is no longer sufficient to accelerate the bullet. If OP intends to use it for supersonic hunting the fact that many available bullets have a limited expansion thresholds at 300 velocities might make a few inches of bbl a good trade-off depending on what ranges he hunts at. http://img.photobucket.com/albums/v726/abinok/412260_343799122333216_617473682_o.jpg Just to add a bit here, the chart abve mirrors my experience with 300BLK velocities and with 3 barrel lengths. 2115 fps from 8.25 in barrel 2380 fps from 15 in barrel 2400 fps from 16 in barrel |
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Posted: 2/21/2017 9:24:16 AM EDT
[#16]
I forgot to mention, those longer barrels are sub moa at 100 and have no problem ringing 8 inch steel plates at 525 yds.
I have never accuracy tested the shorty....usually about 2 to 2.5 moa at 100. It was not built in the name of precision. Subs are subs....but depending on barrel length the loads will change. |
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Posted: 2/21/2017 12:19:42 PM EDT
[#17]
Quote HistoryQuoted:
Yes it is. This is well established. Article AAC Comment on YouTube Video: You Tube (see AAC Comment) Also see this thread: 300 Blackout Barrel Discussion Quote HistoryQuoted:
Quoted:
I don't think it has anything to do with propellant being burnt. According to Quickloads most popular subsonic loads, W296/H110 and Lil'gun are still burning at 16+ inches under a 220gr bullet. Even the favored super sonic load of 110gr TAC-XT pushed by H110 is still burning at 16 inches. 9 inches may very well be a good compromise length for both super and sub sonic, but it's not because all the propellant is all burnt. Yes it is. This is well established. Article There is, however, a point of diminishing returns. Once all of the powder in the case has been burned, there’s no more fuel to add to the combustion and the gasses are at their maximum energy. Adding more barrel length after that point might still increase the velocity a bit, but the added weight isn’t always worth the extra dollop of velocity.
For 5.56 NATO, that point is 20? of barrel. For 300 AAC Blackout, that point is 9 inches of barrel. That number comes from multiple conversations with the people who designed the 300 AAC Blackout cartridge, did the initial testing, and who continue to design guns around that caliber. AAC Comment on YouTube Video: You Tube (see AAC Comment) Advanced Armament Corp5 years ago
@1IdeaAhead It is made possible by a couple of factors. 300 AAC Blackout Ammunition was designed to be used in a 9" barrel, meaning you get a complete powder burn in shorter barrels. Also see this thread: 300 Blackout Barrel Discussion 9" is enough length to burn all powder for 300 blk, so 9" = no flash. Powder burning happens mostly inside the case/chamber area. You aren't burning propellent down the barrel. This is one of the biggest misunderstandings of internal ballistics in the shooting world. |
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Posted: 2/21/2017 12:55:18 PM EDT
[#18]
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Posted: 2/21/2017 1:25:42 PM EDT
[#19]
Quote HistoryQuoted:
http://www.ar15.com/forums/t_6_20/475070_Suppressor-residue-.html That's a lot of unburned powder. |
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