Where does the 6.5/6.8/300blk fit in the 5.56/7.62 argument?

Where does the 6.5/6.8/300blk fit in the 5.56/7.62 argument?

This is a discussion on Where does the 6.5/6.8/300blk fit in the 5.56/7.62 argument? within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; Anyone care to learn me about the 6.5 grendel, 6.8 spc, and the 300 blackout? I'm not up to speed on these "newer" calibers and ...

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Thread: Where does the 6.5/6.8/300blk fit in the 5.56/7.62 argument?

  1. #1
    Member Array ak74's Avatar
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    Where does the 6.5/6.8/300blk fit in the 5.56/7.62 argument?

    Anyone care to learn me about the 6.5 grendel, 6.8 spc, and the 300 blackout? I'm not up to speed on these "newer" calibers and am curious where they fit in with the 5.56 and 7.62x39 arguments. Do any of the three surpass the the 5.56 for range and accuracy? Do they beat the penetration level of the 7.62? How about recoil? Ideal barrel lengths? General info and comparisons like that would be great, thanks.


  2. #2
    VIP Member Array jonconsiglio's Avatar
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    All else being equal, they fall roughly between the 5.56 and 7.62x51, generally speaking. I have a 6.8 and a few buddies have the 300, which shines at short, subsonic suppression, but loses much of its effectiveness as well. I like the 6.8 for 8" barrels. The 6.5 is quite nice for longer range. I don't know enough about them and I'm perfectly content with my 5.56 and 7.62x51. I could do without my 6.8 as well.
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

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    The .300 Blackout is the cartridge of choice right now for a couple of reasons.

    The super sonic Blackout pushes a 125 grain bullet at speeds that make it equivalent to the AK or SKS.

    As such, it penetrates cover much better than the .223 and it works just as well out of the shorter barrelled rifles that the 5.56/.223 give up much too in the way of performance.

    In the subsonic/suppressed mode, it is superior to most other cartridges due to using a 220 grain bullet with a much better ballistic coefficient than most pistol rounds previously used. It is more accurate, hits much harder and can be very quiet with the right combination.

    It can be used on any AR with few if any modifications.

    With a bolt action rifle and a suppressor, it can be very,very quiet, with the bullet impact being the loudest sound. Although it is subsonic and it only good to about 300 yards due to its rainbow trajectory, it is very predictable and penetrates amazingly well with the ability to still shoot through a deer or a hog at that range.

    The .300 BLK is a true dual use cartridge, thus its acceptance by many.
    I would rather stand against the cannons of the wicked than against the prayers of the righteous.


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  4. #4
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    300 Blackout is the most interesting of them all. I've never shot anybody and I'm not a ballistics expert, but I don't see any huge benefits of 6.5 or 6.8 over 5.56 if the correct ammo is used. I'll say I think the 6.5 or 6.8 is technically a better performing round on soft targets, however, IMO, it's like arguing 9mm vs. 40 vs. 45. Sure they all differ, but all in all, the differences are negligible. I find the 300 Blackout to be a good option because of it's sub-sonic, suppressible qualities, but unlike the smaller calibers, it's still has the weight on it's side to provide good penetration. Also, if needed you still have the ability to shoot the high-speed stuff.

  5. #5
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    The 6.8 spc falls about halfway between the 5.56 and .7.62X51. It seems like a great round but ammo is so expensive that I quit looking at it. 7.62X51 was much cheaper. If at some time in the future ammo gets more mainstream and prices fall then it would be worth while.

    The 6.5 Grendel is great for long distance shooting and would have great terminal performance. BUT it is a wildcat/proprietary round and hard to find/expensive. It's like the 6.8 in that it's just not main stream. It's pretty much that you buy from Alexander Arms or you don't buy at all.

    I have not studied the 30 blk so I will bow to others knowledge.

    ETA: After much study and ado about different calibers I went with a 5.56. In the AR platform there is nothing that comes close to it in availability/price/performance. In the AR the 5.56 is where it's at.
    Last edited by atctimmy; January 24th, 2012 at 10:47 AM.
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    All the exotic rounds ,I beleive,will eventually fade away,my 5.56 serves me well,if the need were to arise,a Armalite AR-10,18" barrel will suffice.

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    VIP Member Array jonconsiglio's Avatar
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    Here are some comments on the "intermediate AR calibers" from "Ask The SME's" subforum on m4carbine.net. Jason Falla specifically states that military testing has been "less than positive" though the TSX is a nice step forward.

    Ask The SME Subforum - Ask the SME - M4Carbine.net Forums

    Posts in reply to "Intermediate AR Calibers"

    Jason Falla (SAS/Blackwater) - M4Carbine.net Forums - View Single Post - "Intermediate" AR Calibers

    Kyle Defoor (Navy Seal and DevGRU) - M4Carbine.net Forums - View Single Post - "Intermediate" AR Calibers

    Pat McNamara (SFOD-D "Delta") - M4Carbine.net Forums - View Single Post - "Intermediate" AR Calibers
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

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    On numerous occasions I have generated positive results with the current load
    Now that is some very sneaky wording right there. In other words "I have turned a bunch of BGs into fertilizer with the 5.56".
    It is surely true that you can lead a horse to water but you can't make them drink. Nor can you make them grateful for your efforts.

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    I need to check out the .300 blackout; but if you like the Grendel after some research, check out the 6.5 MPC from SSK - based on a .223 case, only a barrel swap needed, and only 150 fps slower than the Grendel. No need to change bolt and mag make it a big plus for me.

  10. #10
    VIP Member Array jonconsiglio's Avatar
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    Quote Originally Posted by atctimmy View Post
    Now that is some very sneaky wording right there. In other words "I have turned a bunch of BGs into fertilizer with the 5.56".
    Coming from a former member of Delta, it's pretty clear what he's saying!

    I like this one too...

    Quote Originally Posted by Mac1 View Post


    I will tell you however, and you will have to read between the lines on this one, I do not have an issue with the current 5.56.

    Mac is a wildman, I would really like to attend one of his classes.

    http://youtu.be/w69N5gsxvpM
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

  11. #11
    Senior Member Array Landric's Avatar
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    I know the question was about where these rounds fall as compared to 5.56mm NATO and 7.62x39mm, but it is really more valid to compare them to the 5.56mm NATO and 7.62mm NATO rounds. The way I see it, this is much the same as the .40 S&W advent between the 9x19mm and the .45 ACP. Much like the 9 & 45 , the 5.56 and 7.62 represent two schools of thought. The three cartridges here split the difference.

    This is how I see it, 6.5 is the .41 AE of assault rifle cartridges, good try, good overall cartridge, but not interchangeable enough. The 6.8 is the 10mm Automatic, better design than the .41 AE for the intended purpose, but still expensive and not as modular. The .300 Blackout is the .40 S&W. It offers 7.62x39mm performance at supersonic velocities with a 125 grain bullet, and fantastic performance (for a suppressed subsonic) with its 220 grain bullet. It uses readily available projectiles, 5.56mm magazines and bolts, and only requires a barrel swap to be functional.

    Assuming ammunition stays available, I think the .300 BLK will shine. Probably not in service with our military, I think they are far to intrenched in the 5.56mm NATO to ever consider a wholesale change to a different cartridge. However, in more specialized circles, I think it is the best option between the 5.56 NATO and 7.62 NATO.
    -Landric

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  12. #12
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    Something else about the Blackout that some people aren't aware of...

    Its pretty much the same thing as the .300 WHISPER, a cartridge that Spec-Ops has used for years for the sole purpose of shooting people that needed to be shot quietly.

    AAC came out with the Blackout and got it SAAMI approved, something that the WHISPER was not, because it was patented by J.D. Jones the inventor.

    When AAC did that, they allowed any one that could access to reamers and head space gages where as the WHISPER was pretty much proprietary. To get around that, the .300 Fireball,.30-221 and .30-223 came into being. It was basically the same thing, just called different names. The main problem with the cartridges was that they were pretty much wildcat rounds and they didn't have standards.

    One might be 1.350 OAL, the next might be 1.400 OAL and even the loading data used had the lengths all over the place.

    The Blackout uses an OAL but it is with a large tolerance so that it is possible that other rounds may be used. Most Blackouts will accept WHISPER ammo, but not necessarily the other way around.

    Another thing that made the Blackout such a hit was that Remington picked it up and has a couple of different loadings. That turned it from a wildcat to something that you can buy off the shelf,which just about guaranteed it to be successful. Hornady jumped on the bandwagon and others are sure to follow.

    The Blackout is popular because it works. If you need stealth, you put a can on the gun with a subsonic round and shoot. If you need range and noise matters not, you slip a supersonic round in there and shoot. Its as simple as changing cartridges.

    For the naysayers out there that don't think that a subsonic round that is below the speed of sound is powerful enough to be of any account, the many deer and the hogs that have been killed from it are proof that it works. Most shots will be through and through, meaning that even the tough hide of hogs is no match.
    Bark'n likes this.
    I would rather stand against the cannons of the wicked than against the prayers of the righteous.


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