Grendel LMG

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  • RangerRick

    #31
    Originally posted by stanc
    Sounds good.

    Cool. By chance did they give you a delivery date?
    Not yet, but the money is gone from my checking account so it better be soon!

    R

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    • #32
      Originally posted by RangerRick View Post
      I would disagree with this if you can't fire the LMG rounds in the rifle and vice versa. If you have different rounds, the zero would be different and that would negate the whole point of ammo commonality.

      I know I've stripped rounds from 7.62 belts for M-14 sniper rifles when we ran out of sniper ammo. I also know of guys who gathered up expended links and assembled belts for the machine guns when they only got rifle ammo resupply.

      Things can get chaotic sometimes...
      You make an interesting point. I think we are almost on the same page. One could visualize that a Grendel used by a sharpshooter or sniper would likely be shooting long range precision ammo with ballistics similar to those desired for the LMG.

      This would be different than using M855A1 in an M4/M16 when the sharpshooter runs out of Mk262 but more or less equivalent with your description of the M14 and general purpose MG.

      And yes, things get chaotic and there are times when the ammo you got is the ammo you use...
      Last edited by Guest; 09-02-2011, 02:49 AM.

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      • stanc
        Banned
        • Apr 2011
        • 3430

        #33
        Originally posted by JASmith View Post
        Since we're already pretty sure the Grendel doesn't quite get the needed energy density to punch the same plate as the .308, we should be surprised if it does any better against the Russian round.

        Why test when one is reasonably sure the outcome isn't what you want?
        To gain knowledge. Without testing, we do not actually know what the outcome will be. If nothing else, test data for the current bullet would give us a baseline to guide improvements.
        One more time -- Inappropriate testing is likely to be harmful to keeping the momentum going.
        Momentum? What momentum??? Momentum implies movement. How are we any further along than we were in 2005? Did some momentus development occur while I slept last night?

        Comment


        • #34
          Originally posted by stanc View Post
          ...Without testing, we do not actually know what the outcome will be. If nothing else, test data for the current bullet would give us a baseline to guide improvements...
          I am beginning to despair of finding the words to communicate a basic truth:

          Absent a federal contract we are guaranteed to have tests that won't be credible except for those people who want to denigrate or destroy the Grendel.

          This truth should not keep us from seeking tests but it should absolutely keep us from doing tests that we can reasonably expect to produce disappointing results.

          Comment

          • stanc
            Banned
            • Apr 2011
            • 3430

            #35
            Originally posted by RangerRick View Post
            The 7.62x54 is more powerful than the 7.62x51 NATO. It is closer to the 30.06. So the comparison would favor the x54.

            The idea is that you can have a light machine gun of acceptable power with much less weight and ammo commonality with your rifles. The comparison should be the RPD in 7.62x39 and the RPD in Grendel.
            I disagree. As I read it, the proposal by LRRPF52 is for a Grendel LMG "to provide the same downrange benefits as 7.62 GMPG's such as the PKM and MAG58." Since he also notes the potential for a one-caliber system using 6.5 Grendel, that means it would have to be good enough to not only replace 7.62x54R in the V4 armies, it would have to be good enough to not be outranged by the PKMs used by the Russian army (the threat for which the V4 nations created a military alliance).
            You could do the x54 comparison for reference, but no way will the Grendel match it, even at long range.
            I don't know if it's necessary to match terminal performance, although the closer we can get to equal performance, the better. More importantly, I think it's vital to match effective range, for the reason noted above.
            You can demonstrate the weight difference, though. The Grendel ammo will be much lighter than the x54.
            Absolutely, a comparison of weapon and ammo weights should be part of any presentation.

            Comment

            • stanc
              Banned
              • Apr 2011
              • 3430

              #36
              Originally posted by JASmith View Post
              I am beginning to despair of finding the words to communicate a basic truth:

              Absent a federal contract we are guaranteed to have tests that won't be credible...
              Well, I know the feeling. I can't get you to understand that I'm talking about informal tests only to tell us where we stand at present, while you keep equating it with formal tests done for officialdom at some point in the future.

              They are not the same thing, and the one is no less "credible" than the other. The formal testing you advocate has its place, but it isn't necessary in the early stages.
              This truth should not keep us from seeking tests but it should absolutely keep us from doing tests that we can reasonably expect to produce disappointing results.
              Since we're talking 120gr @ 2500-2550 fps, or 110gr @ 2600-2650 fps, versus 150gr @ 2750 fps, I'd say we can reasonably expect "disappointing results" regardless of what 6.5 bullet is tested...
              Last edited by stanc; 09-02-2011, 06:15 AM.

              Comment

              • stanc
                Banned
                • Apr 2011
                • 3430

                #37
                Here's another reason why I think there should be comparison testing with the Norma 120gr FMJ.

                The logical evolution of this project is the conversion of a belt-fed RPD to 6.5 Grendel. That will likely require financial support, either a lot of money from a few backers, or a smaller amount from many individuals.

                Now, I can't speak for others (like Bill W, who's expressed an interest), but I know that before I'd commit my hardly earned cash to such a project, I would want to see evidence that it had some chance for successfully achieving the goal. That's why my OP stipulated two prerequisites: (a) Buy an RPD belt and see how well 6.5 Grendel rounds fit in it; (b) Do comparison testing of 6.5 FMJ vs 7.62 FMJ.

                The rationale for (a) should be obvious. If the cartridges don't fit in the belt properly, there's no point in buying an RPD.

                My reasoning for (b) is that it'd show relative performance with bullets of the same type. If terminal effects of 6.5 Grendel with lead-core projectiles isn't close enough to that of 7.62x54R with lead-core bullets, it'd be illogical to expect relative capability to be any better with steel-core bullets in each caliber, so again there'd be no point to buying an RPD.

                However, if 6.5 Grendel rounds appear to fit okay in the 7.62x39 links, and if terminal effects/barrier testing showed at least the promise of near-7.62x54R performance, then it would be worth proceeding.

                Rick has gambled $30+ of his own money to check (a). We can wait to see how that turns out, before taking the next step.

                Comment


                • #38
                  Originally posted by stanc View Post
                  ...If terminal effects of 6.5 Grendel with lead-core projectiles isn't close enough to that of 7.62x54R with lead-core bullets, it'd be illogical to expect relative capability to be any better with steel-core bullets in each caliber, so again there'd be no point to buying an RPD...
                  Surprise! We don't need or want to equal or better the 7.62X51 bullet for bullet.

                  Performance of the 7.62X51 M80 round is the standard we are using. Even the pipsqueak M855A1 is claimed to be able to defeat some armors at least as well as the M80. And yes, those claims are supported by government or government-sponsored tests.

                  If steel-cored 6.5 bullets from the Grendel can equal or better both the M80 and M855A1 performance, then we have a case.

                  We are very sure that the lead-core FMJ won't get through the plates as well as the M80, or we would likely have already seen pictures of the event.

                  Let's look for testing that will build a case. Do it privately so that that case can be properly articulated with the right people. The testing will still not be viewed as credible because it won't be official, but it gets our foot in the door.

                  Comment

                  • stanc
                    Banned
                    • Apr 2011
                    • 3430

                    #39
                    Originally posted by JASmith View Post
                    Surprise! We don't need or want to equal or better the 7.62X51 bullet for bullet.
                    I said nothing about doing better than 7.62x51. However, equal is desirable, and "close enough" is essential.

                    But, I do think you are mistaken about the "bullet for bullet" part. If each bullet type (Ball, Tracer, AP, Sniper, etc) doesn't give performance comparable to those of 7.62x54R/7.62x51, then the V4 militaries are unlikely to go for the idea.
                    If steel-cored 6.5 bullets from the Grendel can equal or better both the M80 and M855A1 performance, then we have a case.
                    Unless you have credible information that the V4 plan to use M855A1, its performance would seem to be irrelevant.

                    The pertinent round to compare against is Russian 7.62x54R.
                    We are very sure that the lead-core FMJ won't get through the plates as well as the M80, or we would likely have already seen pictures of the event.
                    Illogical conclusion. For one thing, nobody can photograph an event that hasn't happened. For another, until somebody actually shoots steel plates, cinder blocks, etc, with 6.5 FMJ, we can't know how it fares in that regard.
                    Let's look for testing that will build a case. Do it privately so that that case can be properly articulated with the right people. The testing will still not be viewed as credible because it won't be official, but it gets our foot in the door.
                    The "foot in the door" part is something I've argued all along. Glad to see you're finally coming around.

                    But at present, building a case to present to "the right people" is both unnecessary and premature. That can and should wait until optimized 6.5 bullets have been designed and fully developed.

                    What we need right now is to build a data base so that we can make decisions based on factual information, not beliefs or wishful thinking.
                    Last edited by stanc; 09-02-2011, 11:58 PM.

                    Comment

                    • stanc
                      Banned
                      • Apr 2011
                      • 3430

                      #40
                      Originally posted by LRRPF52 View Post
                      A steel penetrator design based off the 7N6 or 7N10 would facilitate the same velocities as a standard FMJ. Just look at the 5.45x39 velocities for those at 2900 fps out of a 16.3" barrel, with projectile weights at 56gr. M4 with M855 62gr out of 14.5" barrel is 2900+ (not the British down-loaded weak ammo for the L85, but full-power M855). A 120gr 6.5 running quick with the narrow steel rod would smoke some steel.
                      Okay, you confused me with the "narrow steel rod" comment. The 7N6 or 7N10 design is what I had in mind.

                      (53gr 7N6 below. 56gr 7N10 reportedly has a longer steel core.)


                      If I calculated correctly, scaling up would make a 6.5mm "7N10" bullet weighing 97 grains, with ~1.24" length. A little tweaking could probably increase weight to 100 grains, without increasing length. Such a lightweight bullet could be pushed @ ~2750 fps from a 20" barrel, thereby matching 7.62 muzzle velocity. But, would BC be high enough to match 7.62 trajectory?

                      Lengthen the bullet to the 110gr "sweet spot" for 6.5 Grendel, and it'll extend much deeper into the powder space, causing a double whammy against MV. Would the increased BC of the longer, heavier bullet be enough to offset the reduced velocity?

                      Comment


                      • #41
                        Originally posted by stanc View Post
                        ...But at present, building a case to present to "the right people" is both unnecessary and premature. What we need right now is to build a data base so that we can make decisions based on factual information, not beliefs or wishful thinking.
                        So we want to 'voodoo' the Grendel into being good enough by hoping the tests will magically be good enough?

                        You clearly don't believe the facts as presented. Find another ballistician who can help you and the rest of us.

                        Comment

                        • stanc
                          Banned
                          • Apr 2011
                          • 3430

                          #42
                          Originally posted by JASmith View Post
                          So we want to 'voodoo' the Grendel into being good enough by hoping the tests will magically be good enough?
                          Now, there's a moronic statement. I said nothing about hoping. I said I'd like to see actual test data, rather than just speculation.
                          You clearly don't believe the facts as presented.
                          What facts? You haven't presented any facts. All you've done is make silly statements, like the "voodoo" one above, and "that the lead-core FMJ won't get through the plates as well as the M80, or we would have already seen pictures," and "we have to build a case to present to the right people" (even though there's nothing on which to build a case), and "inappropriate testing is likely to be harmful to keeping the momentum going" (even though there's no momentum to keep going).
                          Find another ballistician who can help you and the rest of us.
                          That's fine by me. All the present one wants to do is write requirements documents.

                          Comment

                          • RangerRick

                            #43
                            Originally posted by stanc View Post
                            I disagree. As I read it, the proposal by LRRPF52 is for a Grendel LMG "to provide the same downrange benefits as 7.62 GMPG's such as the PKM and MAG58." Since he also notes the potential for a one-caliber system using 6.5 Grendel, that means it would have to be good enough to not only replace 7.62x54R in the V4 armies, it would have to be good enough to not be outranged by the PKMs used by the Russian army (the threat for which the V4 nations created a military alliance).

                            I don't know if it's necessary to match terminal performance, although the closer we can get to equal performance, the better. More importantly, I think it's vital to match effective range, for the reason noted above.

                            Absolutely, a comparison of weapon and ammo weights should be part of any presentation.
                            OK, I see what you are getting at. We just have to demonstrate that we have an equivalent effective range, not equal terminal effects.

                            How do we define effective range? 50% hit probability was the U.S. Army definition assuming you had the ability to disable the target at that range.

                            I think we'll have at least as good hit probability, but how do define disabling ability?

                            Comment

                            • stanc
                              Banned
                              • Apr 2011
                              • 3430

                              #44
                              Originally posted by RangerRick View Post
                              OK, I see what you are getting at. We just have to demonstrate that we have an equivalent effective range, not equal terminal effects.

                              How do we define effective range? 50% hit probability was the U.S. Army definition assuming you had the ability to disable the target at that range.
                              Perhaps "effective range" was not the best term to use. What I'm thinking is that the trajectory should be at least as flat as for 7.62x54R.

                              The challenge will be to design a FMJ bullet with BC good enough to achieve that trajectory, when launched at a MV for which the cartridge is capable.
                              I think we'll have at least as good hit probability, but how do define disabling ability?
                              Good question. I don't know if there is a generally accepted definition.

                              Maybe it'd be best to just show gel tests comparing wound channels of 6.5 Grendel and 7.62x54R?

                              The old gel test of the Norma 120gr FMJ does look very similar to Fackler's wound profile of 7.62x54R. It's conceiveable that a FMJ bullet optimized for 6.5 Grendel could do significantly better than 7.62 at closer ranges. At long distances (over 400 meters), Gary Roberts says there's no real difference between different calibers.

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                              • RangerRick

                                #45
                                Originally posted by stanc
                                Sounds good.

                                Cool. By chance did they give you a delivery date?
                                Belt should be here (North Carolina) by Wednesday. I'll get your 10 round segment in the mail ASAP.

                                Rick

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