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Message: <blockquote data-quote="aestus" data-source="post: 1998153" data-attributes="member: 2989">Bullet energy is more than what it's rated out of the barrel, but also how it performs out in distances during bullet flight. This can vary with barrel lengths and powder used and also shape of projectile.  In terms of projectile shape, the 300 blk's ballistically efficient shape will overtake the 7.62x39 out at longer distances.  Right now numbers are reported that about 300 meters, 300 blk will have just under 17% more energy than 7.62x39 with supersonic rounds.  Yes, the video is a bit misleading because he doesn't really mention the specifics of how 300 blk can have 17% more energy than 7.62x39, despite holding less grains of powder, but that's what I believe what he is referring to.  Closer than 300 meters, the difference is negligible and within 100 meters I would say that 7.62x39 would have a slight advantage. Keep in mind that most A/B comparisons are usually with 300 blk out of a short barrel vs .223 or 7.62x39 out of a longer 16" barrel.  300 blk in a 9" barrel has the same energy as .223 out of a 14.5" barrel and because of it's weight and shape can actually have a + percentage in energy than the .223 after about 300 meters or so.  Now this is more due to the larger weight of the 300 blk round, since .223 has a pretty darn effective ballistic shape. The whole point of 300 blk was that it was optimized to be quiet and run reliably out of SBR'.  The round was created as a non-pistol caliber replacement for pistol caliber SBR's like the MP5's and other sub guns that could be quieted down when suppressed.300 blk uses fast burning pistol powders, which is why it's able to achieve almost 100% efficiency in shorter barrels than both .223 and 7.62x39, which both were designed to be shot out of longer barrels using slower burning powders.  It's hard to do apples to apples comparisons because no matter what, you can spin the data to make 300 blk look good. This is what makes AAC's marketing of the round so effective and easy for them.  If you compare 300 blk in 8" barrels vs .223 or 7.62x39 in 8" barrels, then the data weights very heavily for the 300 blk and it's a bit unfair since 300 blk was meant for short barrels. If you compare 300 blk in a 8" barrel vs 223 or 7.62x39 out of 16" barrels, then the fact that 300 blk holds it's own out of a shorter barrel vs the other two rounds in longer barrels is touted as an advantage of 300 blk's capabilities.  Add in longer distances, the 300 blk ballistic efficiency will marginally overtake both .223 or 7.62x39 even out of 16" barrels. The gain is marginal but still can be used as a selling point on it's capabilities.As for the twist rate, 1:7 twist rate is optimized 110gr - 220gr.  1:8 can be used for anything below 200.  1:9 is used for anything below 160gr. Generally, 1:7 and 1:8 twist is recommended and you can shooting anything that it out in the market.  It's no different than .223 rifles (1:7 to shoot 55gr - 77gr with 1:9 recommended if you need absolute accuracy with 55gr or lighter rounds.)The .223 was never meant to run out of short barrels.  You can and they've adapted the platform to perform that role with heavier grain bullets and have addressed reliability with better understanding of gas systems and buffer weights, ect. The fact that we're able to run them in 7" and 10" barrels is icing on the cake. At the end of the day, the .223 was meant to run out of a longer barrel.  The 300 blk was built to be a quiet caliber shot out of short barrels to replace pistol caliber sub guns with a rifle caliber intermediary cartridge.  The use of fast burning pistol powders means it can be shot out of a 10" or less barrel with almost max efficiency and little to no unburnt powder. This makes it a very gentle system compared to .223 when running suppressed and more reliable out of shorter barrels. The fact that you can run supersonic rounds with a mag change, using the same gas and buffer system and still compare with the terminal ballistics of .223 and 7.62x39 is icing on the cake.  Last I checked, subsonic rounds for the .223 are almost non-existant and if you do find them, they're not going to cycle reliably in your rifle without changes to your gas system and/or buffer weights, if not a total overhaul of the gas/buffer system.  Also, I don't recall seeing any special subsonic 220gr 7.62x39 optimized for SBR's for sale either. I'm really not a .300 blk fanboy, but I do like the round for it's purposes.  In an AR platform, out of short barrels suppressed or unsuppressed, it's a great choice. Especially since all that it requires is a barrel change.  Nothing more. Same mags, same bolt and ammo is adequately priced and there's already a decent selection of off the shelf ammo types, with more already being announced for 2013. Are there better rounds / platforms for long range accuracy?  Yes.  Arguably, 6.5 Grendel would be king in an AR platform and I'd pick .308 in a bolt gun for a dedicated long distance target gun.However, in the AR platform, the cost to play vs return is huge with 300 blk when compared to 6.8 SPC and 6.5 Grendel. It just seems like a no brainer, especially if you're looking to stick with the AR platform with SBR or suppressed in mind.I really don't get all the haterz of the round treating it as if it's the Obama of rifle cartridges and that it's prominence will forever change AR's in a bad way and make the venerable .223/5.56 go away... LOLz.This kind of reminds me of .308 vs .223 flame wars that go on.  Just replace .308 with .223 and .223 with 300 blk and that pretty much sums up every argument, heh.</blockquote>

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