PDWs...and other small arms.

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  • #16
    Yes, the .45 ACP/50m effective range reference was from an SMG. Those big, fat 230gr FMJ's have hardly any penetration power as the distance increases as well. One cartridge that I really love that fits the PDW role extremely well is the 7.62x25. I've been wanting to build a 1911 in that cartridge for a while, but sourcing a mag for the 1911 frame that will fit the Tokarev cartridge's COAL is futile. There is a company offering a 1911 barrel chambered in 7.62x25, but it is non-ramped.

    A highly-gifted gunsmith I know in North Carolina built an AR15 chambered in this cartridge. He used a blank lower forging, and broached the magwell to take Soviet PPS mags. He cut the rest of the lower to spec, and cut mag catch holes in the PPS mags so they would lock into the lower a la AR15 fashion. He made a barrel bushing for a PPSh pipe so it would slip into the upper, and you just hand-screwed a carbon fiber handguard onto it. A 9mm SMG bolt and SMG heavy buffer completed the rig. He baked-on some proprietary DuPont metal surface finish meant for chemical pipes, and it turned out really sweet. It would blow right through 1/4" steel plates within 25m.

    I have done side-by-side comparisons of 9mm, .45 ACP, and 7.62x25 on a Finnish Army steel drum from WWII that was in need of being used as a burn barrel. The 9mm and .45 bounced off it repeatedly. The Cz52 chambered in 7.62x25 shot through one end and out the other, even when I shot deflecting aspect shots.

    I also have friends who have shot amazing groups with a Tokarev or Cz52 pistol at 200m with iron sights. You used to be able to get a 1220rd case of it for $129, but I can't seem to find that anymore...word must have gotten out.

    LRRPF52

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    • #17
      My PDW is a 1947 Soviet TT-33, like others I have found that the 7.62x25 will shoot through things I never though it would. And it is accurate enough that I can hit a man sized target at 100yds. Yes the surplus ammo is getting harder to find, and most that is around right now is Polish sub-gun ammo so it really isn't ok to shoot in a TT-33, but would be fine out of a CZ52.

      Greg

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      • #18
        One would think that a major challenge for pistol cartridge PDW's with diameters less than about 10 mm is getting sufficient lethality.

        Is there any testing that illuminates this issue?

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        • Tony Williams

          #19
          Originally posted by JASmith View Post
          One would think that a major challenge for pistol cartridge PDW's with diameters less than about 10 mm is getting sufficient lethality.

          Is there any testing that illuminates this issue?
          The gel tests I have seen show little difference between 9mm and .45 ball. Make of that what you will...

          The real difference is between an FMJ ball and a well-designed hollowpoint: a good 9mm HP blasts a huge wound track compared with a .45 ball.

          I agree about the 7.62x25, it would make a good PDW cartridge (although the hot SMG loadings are rather hot for a pistol - too much flash and blast). I suspect that some interesting things could be done with it given modern bullet designs, but it's been ignored for a long time.

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          • #20
            Thanks!

            I wonder if it's possible to establish a minimum performance standard?

            The M-1 Carbine used a pistol-class cartridge but seemed to be essentially ineffectual compared to the 30-06.

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            • #21
              Here is a gel test on the 7.62x25 vs vest over the gel block.

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              • Tony Williams

                #22
                The M1 Carbine, like the 7.62x25, uses a pistol-type round-nosed FMJ bullet which tends not to yaw too well and punches a rather small wound track. There have been experiments with pointed bullets which ought to perform better (in range as well as terminal effects) but I've not seen any test results.

                Even so, the M1 Carbine performed well enough for many US soldiers to prefer carrying it in WW2.

                Of course, with a modern JHP loading the Carbine round is dramatically more effective, and makes an excellent home defence weapon (or so I am told!).

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                • #23
                  Originally posted by GregP42 View Post
                  Here is a gel test on the 7.62x25 vs vest over the gel block.

                  http://www.brassfetcher.com/index_files/Page1242.htm
                  Very good picture!

                  I will admit to surprise, but that wound channel looks pretty narrow -- similar to Tony's description of the M-1 Carbine ball round.

                  I know that the blunt shape of .38 Special wadcutters and semi-wadcutters make a difference on rabbits. I wonder if a truncated cone might still get through the vest but have more effectiveness in the gel.

                  Alternatively, go with a longer, pointed bullet.

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                  • stanc
                    Banned
                    • Apr 2011
                    • 3430

                    #24
                    Somebody mention my all time favorite gun?
                    Attached Files

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                    • #25
                      Ref #26 --

                      That carbine bullet seems to have tumbled!

                      Next question: "How much room do we have for lengthening either the 7.62X25, 7X25, or 6.5X25 to at least the same as the 110 gr M-1 Carbine FMJ bullet?"

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                      • Tony Williams

                        #26
                        Originally posted by JASmith View Post
                        That carbine bullet seems to have tumbled!
                        Yes, but not very quickly....I think that the contrast with the JSP makes my point very well.

                        Next question: "How much room do we have for lengthening either the 7.62X25, 7X25, or 6.5X25 to at least the same as the 110 gr M-1 Carbine FMJ bullet?"
                        That means that either the overall cartridge length will increase significantly, or the bullet will extend a lot further into the case, further reducing performance.

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                        • #27
                          Originally posted by Tony Williams View Post
                          ...overall cartridge length will increase significantly, or the bullet will extend a lot further into the case, further reducing performance.
                          The principal driver for cartridge length is to more readily back-fit into existing 9mm firearms. Remove that constraint and things change.

                          Could this mean we have an opportunity to do for the PDW what you're working to do with the rifle?

                          Base a new design on plastic cartridges to favor ease of carry but don't get too greedy with ballistic performance? This could mean a stretched version of the 6.5X25, one based on the .401 Win, the 7.62X39, or one based on the .45ACP/7.62?

                          A big part of the weight penalty of the .45 was that 230 grain bullet. Bottlenecking to say, 6.5, and using 50-100 grain all brass, steel&brass, etc. bullets in plastic cases could allow reasonable velocities with an interesting combination of barrier defeat and lethality while remaining compliant with the Hague/Geneva interpretations.

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                          • Tony Williams

                            #28
                            The 7.62x25 is significantly longer overall than the 9x19 (unlike the 6.5x25 CBJ) so wouldn't fit into 9x19 actions anyway. I suspect that is one reason why it hasn't seen any recent development work: you need a long action to use it and a long barrel to exploit the velocity potential.

                            I think that the plastic-cased telescoped LSAT principle brings fewer advantages to the PDW table than it does to rifles and (especially) MGs. The reason is partly that very little PDW ammo tends to be carried or fired (and it's relatively small and light anyway - .45 excepted!), so weight is less of an issue. The other is that the LSAT rounds are fatter than equivalent conventional ones, which would make stacking lots of them in a pistol-grip magazine rather problematic. And of course, the cylindrical shape doesn't aid feeding in conventional actions.

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                            • Variable
                              Chieftain
                              • Mar 2011
                              • 2403

                              #29
                              Originally posted by stanc View Post
                              Since Variable has been shooting a similar short-barrel carbine in 6.5 Grendel for some time, it would seem like a suitable option for a military PDW.
                              Yep, and it still is my personal PDW. I have a Colt Commando, M11, a suppressed SBR PS90, we have MP5's at work, have shot P90's, etc., etc., etc., but my 10.5" is my go to rig period. Sound pressure, and blast: You betcha. Mine keeps the can on always.

                              If someone redesigned the P90 envelope to incorporate the 6.5 Grendel cartridge, I'd sit up and get pretty excited about that one....

                              Overpenetration in a crowd? GI- use a frangible projectile. LE- use the Sierra 85gr. HP. Problem likely solved, if not use a different projectile. I wonder how well a P90 style magazine would adapt to the Grendel cartridge? A relatively compact bullpup in 6.5 Grendel with a 10.5" or so barrel, a horizontal top mounted mag, etc. would be pretty sweet. The mag (and hence the weapon would be wider), but I'd be willing to make that sacrifice! The controllability would be considerably less in auto, but with a Grendel cartridge you wouldn't need bursts. One well placed hit would be far more decisive. I have SS190 ammo (and some SS191) that is supposed to penetrate k-pots at 200 meters from the P90/PS90, but you wouldn't even need AP to do that with the Grendel cartridge. If 6.5 Grendel AP ever does become available, I bet it'll still do peachy out of a 10.5" tube at PDW distances.... I'd be glad to test that one!

                              What the heck happened to Colt's "SCW"? I still would like to have one of those too. I wonder how hard it'd be to Grendelize it? I just wish they'd have folded the stock to the right instead of the left if possible...
                              Life member NRA, SAF, GOA, WVSRPA (and VFW). Also member WVCDL. Join NOW!!!!!
                              We either hang together on this, or we'll certainly HANG separately.....

                              Comment

                              • stanc
                                Banned
                                • Apr 2011
                                • 3430

                                #30
                                Originally posted by Variable View Post
                                I wonder how well a P90 style magazine would adapt to the Grendel cartridge?
                                My first thought was that it probably wouldn't work. IIRC, the 5.7 FN cartridge case has no taper, making it emminently suitable for a long, straight magazine. In contrast, the 6.5 Grendel case has noticeable taper, which would seem to require a curved magazine for capacities greater than 17 rounds.

                                However, there was the Hill 9mm SMG, which -- decades before the P90 -- had a long, straight, top-mounted (and transparent) magazine. Since the 9x19 case has significantly more taper than 6.5 Grendel, now I'm not so sure it wouldn't work.

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