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The 6.8 SPC could have been a winner if...

Discussion in 'Rifle Country' started by Matt304, Jul 15, 2010.

  1. Matt304

    Matt304 Well-Known Member

    ...If it was a 6 SPC instead. :)

    My thoughts are that the 6.8 SPC is a ballistic failure. Although, it is only a failure when compared to the 6 SPC. It's not too hard to trump a 55 grain .224. The 6 SPC is a potential big winner. Or, was. I don't nag from a typist's position only. I have enough experience with .277 to know that when you are working with light bullets, ~110gr, it is tramped on by the 6mm.

    Here's my frustration. A chance exists to pick any caliber, and .277 is chosen in this day and age? What genius was doing the brainstorming for that cartridge...

    I would chamber my rifle for an SPC, but it surely is going to use 6mm bullets. Heck, even 6.5mm bullets would put a ballistic hurting on the .277 choice.

    And please don't attempt to use the argument that a .277 mysteriously multiplies the damage to the target over a longer, faster 6mm bullet. :neener:
  2. Dionysusigma

    Dionysusigma Well-Known Member

    ... okay... :scrutiny:

    Not that I agree or disagree on any particular point, but... where are you going with this? :confused:
  3. Matt304

    Matt304 Well-Known Member

    You know, just making a random, pointless discussion. Following Rifle Country trends! :D

    I guess you could say I'm wondering if anyone else is scratching their head as hard as I am over this cartridge and its design.
  4. R.W.Dale

    R.W.Dale Well-Known Member

    actually I disagree that it's not the CALIBER that could be changed to offer the biggest improvement but rather the case length

    Lop off 4mm and you'd have opened the door to all kinds of excellent .277 projectiles in much more aerodynamic profiles

    The problem with 6mm is it's just not that much different than 5.56 and to the extent of what the SPC was developed for size does matter with regards to the bore

    As I see it though the SPC is a cartridge that sold it's soul to the velocity devil at the expense of bullet mass, SD and BC
  5. HorseSoldier

    HorseSoldier Well-Known Member

    From an armchair I suppose it's all a puzzler. The round was developed by guys who shoot people for a living and 6.8 was the best performer for what they wanted. I don't think 6mm was even considered as it didn't do anything much better than 5.56.
  6. Matt304

    Matt304 Well-Known Member

    It's all about scale, guys. Things need to match, case size and the caliber.

    The 6BR is a go-to round for efficient, ballistic performance. Why? Scale, which equates to powder capacity and efficiency. The BR case is small, and thus the caliber needs to be.

    Here we have a case not much different in capacity than the BR round. It is just slightly larger than the 223 case, and a bullet slightly larger is what's needed. Instead, they put a bullet mismatched to the case capacity. I guess that's what guys who shoot people for a living do best!

    You could easily make this a 600-700+ yard performer with 6mm bullets in this case size. As it stands, you aren't doing much at all with .277 bullets. This case simply does not have the capacity to drive .277 bullets properly.
  7. HorseSoldier

    HorseSoldier Well-Known Member

    Optimizing a combat round for 6-700 meter shooting is silly.
  8. Tirod

    Tirod Well-Known Member

    Let's see, the SF and AMU worked to make a better, more lethal bullet downrange with the restriction it had to fit the M16 mag well no matter what, and mostly couldn't mess with the bolt face, as it had limits to what size it could accept.

    For the military requirement, better range was good, but more foot pounds of force was also a goal, as that is a lot of what lethality is about. A bullet delivering more energy will be more lethal because it has more penetration and creates a bigger cavity which disrupts tissue and blood vessels. More damage means less fight from the recipient, which is the end goal. PAY ATTENTION: the military isn't necessarily looking for Dead Right There. Nice if you can get it, but remember, the worlds Armies already walked away from the .30, 8mm, etc. There is an effective limit to what works altogether in a package.

    So, the 5.56 has to have more mass to carry more energy, as it's already on the upper limit in ballistic performance with speed. Making it faster will have quickly diminishing returns, like increasing barrel erosion. We already have to chrome it to keep barrel life up.

    In general, bigger is better, but - BUT - only up to a point. You can quickly increase mass to deliver more energy. As the bullet gets more diameter, it also has to accomodate the ogive for streamlining, which makes the bullet seat out further. At that point something has to give - either the case becomes shorter, or the bullet can't get longer.

    Add the mysterious art of cartridge case design, which so many of us seem to be uninformed about, and which is a common subject on wildcat forums. The length, diameter, shoulder, and case to neck ratio all have an impact not only on flame propagation, but also the mechanics of automatic feed, especially from magazines. In this specific situation, the M16 has a STRAIGHT magazine well and DOES NOT accommodate tapered cases very well. Highly tapered cases create a bigger problem in this lower trying to feed them, as the properly curved magazine to do it simply hasn't existed.

    For those who quickly dismiss lethality as any valid reason in cartridge design, the real truth is that many combat cartridge designer test calibers and bullets on LIVE targets. Shooting pigs has been and continues to be a method to verify the assumptions and calculations that otherwise remain unproven. It would be more than derelict to design a cartridge and never actually shoot a live target until the first soldier is lined up in a GI's sight picture. Pigs are considered a comparable and valid test medium, and are used. When you shoot live targets and see a specific condition is met more often in one caliber combination - powder, case, bullet, and twist as a working team, you don't ignore it for another. The results have been achieved.

    Given the existing restrictions - an overall length fixed regardless of whether it's optimum, a straight mag well that limits case taper, balancing bullet diameter and length, and a responsible upper limit on bullet speed, certain combinations get eliminated quickly. One such factor is that extensive military combat studies show the average soldier only shoots out to 400m regardless of the actual effective range of the gun they use. That was discovered when most battle rifles could shoot to 600-800m. Soldiers would not take the shots, and still won't, regardless of the complaints by long range enthusiasts.

    With a 400m effective range "limit," it's a waste of effort to design for longer ranges, and compromises the design when used in shorter barrels - like the ISSUE 14.5" M4. No, the military does not have to comply with BATF rules in that regard - they even use 10" barreled weapons. The cartridge chosen would also need to meet the requirements of that use. The government doesn't need multiple rounds of the same caliber optimized for different length barrels, as the use of +P+ submachine gun ammo in the Beretta proved. If a soldier can get the wrong ammo, he will, even if it's not his fault. The cartridge is required to fit in the operating envelope, not the rifle to the cartridge. Those that complain about cheap low powered ammo not cycling their M4gery should take specific note.

    Rather than complain about what a caliber is good for, it's probably a better perspective to understand how it got to be as good as it does considering all the dimensional and specific requirements it has to comply with. In that regard, the bigger than 6mm cartridges do a better job in the AR platform, and a lot of shooters already know that. The sales figures are right there, and they are winning.
  9. hammerklavier

    hammerklavier Well-Known Member

    They weren't looking to make a long range gun with great ballistics. They were looking for increased lethality out to 500 yards. The requirement was 500 ft-lb or more energy at 500 yards. They tested a 6mm but it didn't make the cut, perhaps due to the terminal ballistics?
  10. Shawn Dodson

    Shawn Dodson Well-Known Member

    Photo of SPC cartridge development:

    More info at: http://www.m4carbine.net/showthread.php?t=19936&highlight=Grendel

  11. Matt304

    Matt304 Well-Known Member

    Thanks for the history, guys.

    That's an eye opener! I was not sure that this round had the amount of homework done that it did, with all of the different calibers being used. But it sounds like they did do their homework on finding the caliber for their needs.

    I personally would not be shooting live targets in combat. So if it were me, I still would be chambering the wildcat, 6mm version for a paper-puncher.
  12. Dionysusigma

    Dionysusigma Well-Known Member


  13. Matt304

    Matt304 Well-Known Member

    Good play of my words! :D

    You know what I meant!

    I have defense firearms covered and ready. From now on, when I buy evil black tac rifles, I want them to, when possible, be able to hang off my 500 yard bench. ;) Since I reload everything anyways, I would prefer to use a caliber with bullets I like.

    Anyways, I just wanted to post what I thought about the 6.8mm and hear some other views like I have here.

    ...Thread tapers to an end.
  14. mshootnit

    mshootnit Well-Known Member

    I totally agree

    In fact I started a thread with this title awhile back. Totally agree that 6mm in that case would be a good improvement, while finding something that would get the 100 grain bullet going 3200 or so while being compact and logistically reasonable would be very lethal. I also like the 6mm OCC.
    6mm's are much better than 22's (more so than most understand)
  15. HB

    HB Well-Known Member

    I agree with the 6mm fans... It seems if you could get it going fast enough, with match style 105 grain bullets it would have enough velocity to reach out and touch somebody out to 600m and still have plently of tumbling effect out to that distance. 6mm Hagar anybody? (Which i believe is based on the .30 rem case as is the 6.8?)
  16. amprecon

    amprecon Well-Known Member

    There is way too much disparagement about the 6.8 spc and I try to figure out why. I think maybe because it was touted as the 5.56 replacement. Many AR fans may of had other ideas of what should replace the 5.56, maybe AR fans didn't want any change at all. Maybe it wasn't AR fans shouting about it the most after all. Who knows, but I don't think I've read so many derogatory remarks about a particular rifle caliber ever.
    Pistol calibers?....sure, there are diehards in almost every pistol caliber camp, but rifle calibers...? Not so much, at least not until the 6.8 spc was introduced.
    All I mostly hear is that it sucks and the 6.5 Grendel is better. It's all rather immature.
    I went 6.8 because I became interested in piston AR design rifles in a more effective caliber than 5.56. After reading about the research and development of the 6.8 and of many successful hunters using it, I was sold. Albeit I didn't go the piston route as they were more expensive, I took a leap of faith and went with a RRA DI rifle.
    The AR platform was readily and apparently moderately easy to modify to accept it, the recoil is sublime, it is accurate and apparently quite effective within its limitations.
    If some people don't like it.......well, I'm fine with that.
  17. Tirod

    Tirod Well-Known Member

    As Barnes and others make purpose built bullets for the 6.8, dimensions and the ogive are being tweaked to improve ballistic coefficient, which keeps creeping up as new bullets are released.

    6.8 is becoming it's own bullet, not just another .277. And as loads are tweaked, users are reporting getting as much as 2970 fps from a 12" barrel, chronographed. Apparently you can push an 85 grain bullet with a military load and keep velocity nearly the same as the 5.56, from an 8" shorter barrel.
  18. Matt304

    Matt304 Well-Known Member

    Constructive thinking is immature? I'm sorry that it doesn't appeal to you, but we all have our different ways of communicating our constructive thinking. It's all for the better, really. Without it, we would just accept everything that a manufacturer hands us, there would be no wildcats, and there would be no progression in the world of accuracy and what is possible.

    I feel like when I think about calibers anymore, I think more "ballistically" I guess you could say than I ever used to. I used to be a fairly common shooter. I was not very intimate with rifles and ammo, and bought my ammo from a hardware store. Back then, I used to think the 270 Win was the best long range cartridge that no one ever realized. It was big, sleek, and shot fast. That was because I owned one, and didn't have a true performing long range cartridge. That was also before I bought a 6.5-284.

    Once I started getting into reloading, and examining the science of shooting a lot more, I realized that I previously had no idea how things really worked. I found that less recoil went a long way on the bench. I found that better bullets gave much better groups, and multiplied those abilities at extended ranges. I guess you could say that I became modernized with the bench, and from now on when I look at things, I have a hard time seeing things through the eyes of people who create rounds for self defense. I always find a way to envision the cartridges in an optimal sense, as in, what could they do if they were tweaked for shooting, instead of shooting + lethality. I find myself ending up wondering if a better shooting bullet might actually make more sense for most people than a bullet with more lethality compared against it.

    One of the problems I have trouble with is knowing that the people who own these 6.8s, taking these rifles to the ranges, don't absolutely need the same requirements as the people those rounds were designed for. The cartridge was designed for human targets. Though it is possible we may someday need to use our firearms to dispatch human targets, we don't do that on a regular basis. Some people like to dress up and pretend they do, but the cold hard reality is that they don't. They are still shooting paper on a regular basis.

    So I ask myself. Why do you want to jump on the bandwagon with the people who designed this round for something different than YOU use it for? Why wouldn't you want to tweak this caliber back to an optimal shooting caliber? It was admitted above in the research that the developers saw the smaller bullets could shoot better.

    So I ask, are you using the 6.8SPC for what it was designed?

    Would your situation most likely follow the average battlefield situation, even if you had to use it for the type of work it was designed for in the battlefield?

    It was stated that the average soldier will not take shots past a few hundred yards. Well, if SHTF, I would like to believe that I am not the average soldier. I promise you this; I would take those 600 yard shots!

    What it boils down to is realizing that I am not the person the 6.8SPC was designed to meet a criteria for. If it is me who needs it, it is most likely a 6 SPC that will work better. I like to believe that most of the people that own a 6.8SPC right now are shooters closer to resembling me than resembling a soldier. They've all got the wrong caliber. ;)
  19. HB

    HB Well-Known Member

    Now thats what I'm talking about! I would think a 6mm that fits in an AR would be an ideal deer round because you can use an expanding bullet. I suppose if you are stuck with a OTM or FMJ, then 6.8 makes a little more sense... To me, its still just an improved 7.62x39

  20. Bigfoot

    Bigfoot Well-Known Member

    The 30/06 was designed as a military cartridge too. I'd better not take mine hunting anymore.

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