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Thread: Ballistic-only advantages to sticking with 5.56?

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    Ballistic-only advantages to sticking with 5.56?

    I've been doing searches for a while on this thread and others, but I'm not finding anything definitive. This isn't really aimed at parts availability or logistical advantages, it's more aimed at ballistics and lethality.

    I've pretty much lost all wishes to utilize an alternative caliber AR because of how much modification is required, not to mention sketchy reliability and parts incompatibility. The platform wasn't designed for larger cartridges and this has been proven after years of poor results from rounds like the 6.8, 6.5, .50 Beowulf and others. They look great on paper, and they really are, but until someone builds a better rifle specifically for them I personally don't think it's wise to try and fit a family of 5 into a 4-seater. I believe LWRC's Six8 line of rifles are a step in the right direction as far as solving that problem, but until they're released we'll just have to improvise.

    However, the .300 BLK has caught my attention for the same reasons as everyone else: magazine and BCG compatibility. It seems like a win-win with the heavier bullet, negligible recoil and no loss of reliability (Is this accurate? Has anyone heard of feeding/ejecting/magazine problems with the .300 that the 5.56 doesn't have?). However, I have no interest in SBRing or shooting suppressed, so the subsonic advantages and short barrel effectiveness aren't important to me. All I care about is that the round may have superior ballistics when compared to the 5.56. What I want to know is whether or not this is true.

    My question is whether or not the 5.56 can hold its own in a supersonic, power-oriented comparison with the Blackout. Is it truly advantageous to make the switch when the only thing different is the barrel? Does the 5.56 have an advantage when it comes to range and accuracy? Which round tumbles better? Is the recoil still controllable? Perhaps most important of all, are two identical rifles with the different calibers equally reliable? What about in higher capacity magazines such as a quad-stack or drum? If the BLK falls short in this category, it's immediately off the table.

    I think it's also important to add that this shouldn't be looked at from a hunting perspective; I'm talking about a fighting gun. Take all the reasons that you'd want the 5.56 for a worst-case scenario and compare them to the .300 BLK: does it stack up?

    This has been debated in the past, but I wanted a fresh take on it and also wanted to take out some variables like shooting suppressed, short barrels and economic advantages. I could care less if 5.56 parts are more available or cheaper, that's obviously going to be true and not what this discussion is about. If you have any input, please share. I'd like all sides to have a say so I can come to an eventual conclusion.

    Thanks for reading and have a good day.

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    1. I would retract your statement regarding "years of poor results." 6.8 is a BA round and 6.5 has the BC. And Beowulf--I have no reason to doubt the "terminal ballistics" of a 300+ gr bullet.
    2. Some thoughts on 300BLK and 5.56. Pretty good overall. https://www.m4carbine.net/showthread.php?t=100109

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    Quote Originally Posted by nml View Post
    1. I would retract your statement regarding "years of poor results." 6.8 is a BA round and 6.5 has the BC. And Beowulf--I have no reason to doubt the "terminal ballistics" of a 300+ gr bullet.
    I wasn't talking about terminal performance, I was talking about reliability. All 3 rounds that I mentioned (and countless others) have suffered from compatibility issues including but not limited to magazines and pressure.

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    6.8 updated the chamber specs a while ago. 6.5--people do reload and brass needs to be in spec. I do not have a ton of trigger time with Beowulf but found it agreeable (beyond the mag capacity obviously).

    Magazine issues can happen with any caliber when it comes to shitty mags. If your point is the top magazines available for the caliber have issues that is one thing, but I can give you some shitty brand mags that will even choke an AKM.

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    Quote Originally Posted by Tacti-square View Post
    .......
    Does the 5.56 have an advantage when it comes to range and accuracy?
    ........
    I'm certainly curious about this part when it comes to mag length rounds.

    (In July 2002 Sgt Hatcher of the AMU put 20 rounds into a 20 inch circle at 1,000 yards using an A2 rifle (iron sights, 20in barrel, etc). He was using 90 grn JLK bullets)
    Last edited by danpass; 06-03-13 at 23:39.
    Dan Miami, FL

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    The CTTSO TSWG MURG testing for US mil and Fed LE organizations clearly demonstrated that there were NO reliability issues with well built 6.8 mm uppers firing high quality 6.8 mm ammunition from properly executed 6.8 mm magazines over many tens of thousands of rounds.

    For .300 BLK to be fully reliable in self-loading rifles, properly designed projectiles specific for .300 BLK must be used, not generic .30 cal bullets intended for .308/.30-06/.300 Win Mag. Other wise, a nicely built .300 BLK using the correct ammunition is just as reliable as an equivalent quality 5.56 mm or 6.8 mm weapon.

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    Quote Originally Posted by DocGKR View Post
    The CTTSO TSWG MURG testing for US mil and Fed LE organizations clearly demonstrated that there were NO reliability issues with well built 6.8 mm uppers firing high quality 6.8 mm ammunition from properly executed 6.8 mm magazines over many tens of thousands of rounds.

    For .300 BLK to be fully reliable in self-loading rifles, properly designed projectiles specific for .300 BLK must be used, not generic .30 cal bullets intended for .308/.30-06/.300 Win Mag. Other wise, a nicely built .300 BLK using the correct ammunition is just as reliable as an equivalent quality 5.56 mm or 6.8 mm weapon.
    Thanks for the info Doc. What mags were used for the 6.8mm MURGs?

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    Each vendor supplied magazines for use with their rifles. IIRC, magazines from Barrett, HK, and PRI were used successfully. Magazines from another vendor did not work well...

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    Quote Originally Posted by DocGKR View Post
    The CTTSO TSWG MURG testing for US mil and Fed LE organizations clearly demonstrated that there were NO reliability issues with well built 6.8 mm uppers firing high quality 6.8 mm ammunition from properly executed 6.8 mm magazines over many tens of thousands of rounds.

    For .300 BLK to be fully reliable in self-loading rifles, properly designed projectiles specific for .300 BLK must be used, not generic .30 cal bullets intended for .308/.30-06/.300 Win Mag. Other wise, a nicely built .300 BLK using the correct ammunition is just as reliable as an equivalent quality 5.56 mm or 6.8 mm weapon.
    My Barrett 6.8 Rec7 with Barrett Mags has never malfunctioned in over 1000 rounds. I will give you that the mags and ammo are expensive, but the price of 6.8 defensive carry ammo is roughly the same or less than the good 5.56 carry ammo like the 5.56 Black Hills 50gr TSX. The best 6.8 is significantly better than the best 5.56.

    With my purchase of the Tavor, I have become interested in 5.56 ammo again. Ballistically speaking, I don't think the .300 blk offers anything over the better 5.56 loadings with the exception of the subsonic load. I have stated it on here before- I wish someone would factory load the Barnes 62 gr TTSX to mil-specs, i.e., cannelure, crimped primers and primer and case sealant. The barrier blind performance, lower expansion velocity, and excellent ballistic coefficient make this a great choice IMPO.
    Last edited by Swatdude1; 06-05-13 at 17:39.

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    Quote Originally Posted by Swatdude1 View Post
    Ballistically speaking, I don't think the .300 blk offers anything over the better 5.56 loadings with the exception of the subsonic load.
    So if you didn't have a multi-purpose carbine and your choices were the KAC SR-15 and the SR-30, identical in every way except caliber, which would you choose?

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