Lets start over: how do you design a GPC?

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  • #16
    The .260 Remington is a niche long-range rifle cartridge, that lacks something the .308 has in strides: barrel life. While the .260 Rem has great barrel life compared to 6.5x284, .300 WM, and .338 LM, it is still too short for a military general issue weapon, and is still in the battle rifle size class, since it is a necked-down .308 Win.

    The performance of the .260 Rem is definitely advantageous for a sniper or DM, but way more than a rifleman needs. It is possible to get .260 Rem performance from an AR15 action, but you need a fat case in excess of the diameter of the .308 Win., which is a non-starter for military use. I also don't want a 140gr high sectional density projectile exiting a rifleman's muzzle at 2700fps within close quarters from a high pressure chamber. That is a bad thing from a practical perspective in my opinion, for a number of reasons:

    * disorienting effects of muzzle blast and overpressure

    * muzzle climb and recoil on a lightweight weapon

    * effects of high pressure on barrel, bolt, receiver, and reciprocating parts life

    For COAL, once you start getting to 2.500", you're pushing the limits of the intermediate cartridge concept towards something that is significantly heavier, and will occupy more space on the soldier's load.

    With what I've observed of the existing 6.5 Grendel's performance with 123gr OTM, I see no need for more velocity. The question then becomes how to mass-produce a military projectile with a BC of .510, while still being able to achieve 2350fps from carbines, and 2500fps from a Light Machine Gun.

    Even a 12.5" Grendel carbine can push a 123gr to 2300fps, if not 2350fps with canister powder and the right components. I think Variable is able to get 2179fps with the 123gr A-MAX from his 10.5" Grendel.

    The real area that needs improvement is the current status of our belt-fed, Squad Support weapons, and the decision has to be made whether or not a new caliber should be exclusive to it, or should it share a chambering with carbines/rifles. I personally think the performance requirements of the LMG are different enough to warrant a separate chambering, but one that could be common with Semi-Auto Sniper Systems (SASS), as well as DM carbines, but that goes against the General-Purpose Cartridge concept, which prioritizes logistics over performance.
    Last edited by Guest; 06-30-2013, 06:01 PM.

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    • stanc
      Banned
      • Apr 2011
      • 3430

      #17
      Originally posted by LRRPF52 View Post
      The question then becomes how to mass-produce a military projectile with a BC of .510
      Worth repeating.

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      • bwaites
        Moderator
        • Mar 2011
        • 4445

        #18
        Originally posted by stanc View Post
        Worth repeating.
        I really don't understand why this is a concern, it's harder to consistently make a polymer tipped bullet than an FMJ bullet, and several different companies make polymer tipped bullets in bulk without problems. On top of that, multiple piece bullets, i.e. steel 2 piece with copper jackets are harder, but those also are made in bulk.

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        • stanc
          Banned
          • Apr 2011
          • 3430

          #19
          Originally posted by bwaites View Post
          I really don't understand why this is a concern...
          Perhaps because a high BC is vital to the GPC concept, and no one has yet proven that the necessary BC can actually be achieved in a military ball projectile of the requisite diameter and weight.

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          • KentuckyBuddha
            Warrior
            • Oct 2012
            • 972

            #20
            I don't see how it is rocket-surgery, you make a long pill with good aerodynamics, shove it hard, and you are made in the shade. Only way to get that work done is with a short fat case within the constraints of the lowers we have. I just don't see how there is more than one way to do it.

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            • #21
              I listened to a discussion by Bill A. awhile back that helped illustrate Stan's concern. Paraphrasing:
              • The current 5.56 ball projectile started out being a rather accurate and reasonably well streamlined bullet.
              • The specs written by the government, however, allowed the manufacturer to relax the dimensional tolerances of several key features to allow for minimum cost fabrication.
              • This they did, resulting in increased profits and a comparatively inexpensive bullet that meets minimum performance standards.


              My take away:
              1. We will get what we pay for.
              2. Comparing the best shaped and finished 6.5 slug against the M80 is indeed an apples to oranges comparison.
              3. Make the comparisons between comparable bullet types, e. g., a 150 gr .308 Sierra Matchking for for the 'super M80' and your favorite 6.5 SMK or your favorite 6.5 Lapua against the 150grain-class LockBase, and so on.

                Folks have done this off and on. My own assessment suggested that the Grendel still fares well, just not as dramatically as one might expect with a 144 gr Lapua vs the standard M80.

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              • mongoosesnipe
                Chieftain
                • May 2012
                • 1142

                #22
                Originally posted by Trooper View Post
                If we merely wanted to out perform the 7.62 NATO, the 260 Rem (6.5x51) does that now using the same case. The 260 Rem might be the starting point for comparisons. Then the process would be creating a smaller case that has similar performance. One might want to have a bullet that is similar to the M80. Maybe a FMJ lead core for comparison tests.

                Also there is a need to have something other than a brass case as it is just too expensive to leave on the battlefield. So part of the design is a plastic (polymer) case.
                polymers melt in hot chambers which causes problems, at least that was the problem with past attempts maybe some new wonder polymer is in the works...

                aluminum is not suitable in high pressure application as it has a tendency to fail if i recall they tried aluminum high power rifle cases in the 50s it didn't work out

                titanium cost more than brass beyond the fact that it is difficult to work with...

                steel works and is cheap but its it can be harder on equipment
                Punctuation is for the weak....

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                • SHORT-N-SASSY
                  Warrior
                  • Apr 2013
                  • 629

                  #23
                  Just a dash of light-hearted humor, in this otherwise serious Discussion, if you will.

                  Reviewing the Replies to this Thread, as well as the two related Threads, Military Round Comparisons and Third Generation Battle Rifle, I'm reminded to a couple of cartoons I came across, recently (http://www.cartoonstock.com/director...tion_gifts.asp): Image 1, "Innovate, or die," is relevant to most industries, today --- the Electronics Industry, an outstanding example, while Image 2, "Your proposal is bold and innovative, but we are a traditional corporation. I would prefer changes like the ones we've tried before," certainly is true, here, and in the gun industry, as a whole. And, I think the Objections, in the "Objections and Responses" Section, at the end of Tony Williams' comprehensive web article, The Case for a General-Purpose Rifle and Machine Gun Cartridge (GPC),, for the most part, represent yet another example of this "traditional" (read: brickwall) mindset.
                  Last edited by SHORT-N-SASSY; 07-01-2013, 05:00 AM.

                  Comment


                  • #24
                    Originally posted by SHORT-N-SASSY View Post
                    Just a dash of light-hearted humor, in this otherwise serious Discussion, if you will.

                    Reviewing the Replies to this Thread, as well as the two related Threads, Military Round Comparisons and Third Generation Battle Rifle, I'm reminded to a couple of cartoons I came across, recently (http://www.cartoonstock.com/director...tion_gifts.asp): Image 1, "Innovate, or die," is relevant to most industries, today --- the Electronics Industry, an outstanding example, while Image 2, "Your proposal is bold and innovative, but we are a traditional corporation. I would prefer changes like the ones we've tried before," certainly is true, here, and in the gun industry, as a whole. And, I think the Objections, in the "Objections and Responses" Section, at the end of Tony Williams' comprehensive web article, The Case for a General-Purpose Rifle and Machine Gun Cartridge (GPC),, for the most part, represent yet another example of this "traditional" (read: brickwall) mindset.
                    The brickwall is coming from the military, or elements within the military, dating back to post-Great War with the .276 Pedersen experience. That was actually driven by the Army, where they had determined that the .276 Pedersen would be the new service rifle cartridge, until MacArthur squashed it.

                    Then we had a similar thing happen with the 7.62 NATO vs. .270 and .280 Enfield. US Army Ordnance Corps couldn't put the .30 cal booze bottle down, when offered some nice Gin from England in the 1950's.

                    Since the 1950's, we have stockpiled 7.62 NATO to the point that we have 11yrs of it at current demand, as well as 5.56 NATO. If a unit properly tailors its TO&E for the AOR it's in, 5.56 and 7.62 NATO complement each other quite well at the Squad and Platoon levels. Using one caliber exclusively has been proven to be a failure when it's tried like 7.62 NATO M14/M60 system, and 5.56 M16/SAW system in Afghanistan, although you do have 7.62 belt-fed weapons at the Platoon level.

                    The more you look at this with a clearer picture, the more you realize it's a TO&E and training issue, not a caliber issue. Sure there are more ideal calibers that would work really well in certain AOR's. I know I would rather carry a 16" Grendel than a 16" 7.62 NATO SASS, because I can kick-in doors with it, and reach out to the same effective range as a 7.62, with 50% of the recoil, and more ammo capacity for less weight on my gear. I would still need the logistics footprint to support it though.

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                    • #25
                      Originally posted by KentuckyBuddha View Post
                      I don't see how it is rocket-surgery, you make a long pill with good aerodynamics, shove it hard, and you are made in the shade. Only way to get that work done is with a short fat case within the constraints of the lowers we have. I just don't see how there is more than one way to do it.
                      More than one way, at some point there will be a new platform because existing platforms aren't strong enough or big enough for larger cases that a true GPC will need . A green high BC bullet may be the toughest problem to solve. Could be less BC, more speed, longer smaller dia case with longer action length or longer same dia case with longer action length.
                      Less weight and recoil than the 308 but beat the 308s exterior ballistics with military LIKE projectiles.

                      Comment

                      • KentuckyBuddha
                        Warrior
                        • Oct 2012
                        • 972

                        #26
                        Green and that will meet the agreements we have made in the Geneva Convention will be a fundamental difficulty in accomplishing that design for sure, but if we are to keep the M-16/M-4 lower...you have to have a long pill and a short fat case to make the long pill possible. No?

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                        • stanc
                          Banned
                          • Apr 2011
                          • 3430

                          #27
                          Originally posted by KentuckyBuddha View Post
                          Green and that will meet the agreements we have made in the Geneva Convention will be a fundamental difficulty in accomplishing that design for sure...
                          The latter is no problemo. We have a JAG who has demonstrated he will approve virtually any bullet design the military wants to use. Examples:

                          - Sierra MatchKing hollow point bullet (7.62 M118LR, 5.56 Mk262)
                          - Barnes TSX expanding hunting bullet (5.56 "Optimized")
                          - ATK SOST expanding, fragmenting hollow point bullet (5.56 Mk318, 7.62 Mk319)
                          ...but if we are to keep the M-16/M-4 lower...you have to have a long pill and a short fat case to make the long pill possible. No?
                          Depends on the bullet diameter. AR Performance developed a 6x41mm round using a slightly shortened SPC case that could be a potential candidate to upgrade 5.56 weapons.

                          Of course, there is no requirement to stick with the M16/M4 lower.

                          Comment

                          • KentuckyBuddha
                            Warrior
                            • Oct 2012
                            • 972

                            #28
                            True, there is no requirement to keep the lower...but there is always the desire to save a few bucks, and reduce the need for new training and new components/parts for as much as you can.

                            The JAG folk said that was kosher as long as we were not shooting at Geneva Convention signatories no? Besides one JAG guy might say this the next might say that...next thing you know you are sitting in a box in the Hague or worse you are like those German soldiers at Malmedy, Belgium in the winter of '44 (the were just lined up and shot in the field for wearing the opfor uniform). I knew about the SOST (and I have some) but I was not aware the others were cleared.

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                            • stanc
                              Banned
                              • Apr 2011
                              • 3430

                              #29
                              The only JAG ruling I have personally read is the one giving the okay to use Sierra MatchKings. It declared SMKs lawful for use against any opponents, whether signatories or not.

                              Yes, a future JAG could render a different ruling. Up until 20-plus years ago, only FMJ bullets were lawful for combat.

                              Comment

                              • KentuckyBuddha
                                Warrior
                                • Oct 2012
                                • 972

                                #30
                                Sadly, there is no Supreme Court of JAGS where the precedent is established law. Kinda makes it hard to be a soldier these days I reckon. But, yhea I get the reasoning...we had a deal with those countries and these lot were not part of it. Though to be completely Boy Scout about it, I really don't see the greater humanity of being shot with a FMJ versus a polymer tip or SOST. If I were picking, and hopefully I never will be, I would pick varmint grenade to the dome for sure, but I am sure there is a very good reason nobody asked me. : )

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