Sierra 123 gr SMK vs. Lapua 123 gr

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  • Sierra 123 gr SMK vs. Lapua 123 gr

    I don't know if JBMs data has changed in the last 6 months but I have just run some imputs on the 123gr SMK and 123gr Scenar and it appears, despite having a lower BC, that the SMK is now the better long range bullet. At 2550 fps the SMK remains supersonic longer than the Scenar. Has anyone else found the same thing?

  • #2
    You could try checking the ballistic coefficient and type listed near the top of the output page.

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    • #3
      Yes that's what I've been doing and the SMK despite the lower BC goes transonic further down range than the Scenar.

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      • bwaites
        Moderator
        • Mar 2011
        • 4445

        #4
        Are you using G7 BC's or G1's?

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        • #5
          Ah yes, it's easy to forget that Sierra uses velocity-dependent G1 BC's. (I just realized I'd forgotten too.)

          The Lapua has three listings in his pull-down menu. Two of them are G7's and the one listed as 123 Scenar (CD) doesn't show a BC.

          So, we may be hard-pressed to extract the drag vs velocity curves from the data to compare.

          FWIW other posters have tried the Scenar out to 1000 meters and, possibly beyond, in formal ranges where spotters were stationed near the target. They reported that the supersonic crack did not appear to be evident.

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          • #6
            Hi Bill,

            You just plug the bullet in and it computes automatically. I was speaking to Bill A the other day about this and he wasn't sure either. JBM's site has changed I think, last year when I ran the same numbers the Lapua came out on top, but now it has changed. If you go to JBM's website you'll see what I mean. If you choose a velocity of 2550 the SMK stays supersonic to about 1100 yds where as the Lapua drops below mach 1 at 1075.

            Regards, good to hear from you again.

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            • bwaites
              Moderator
              • Mar 2011
              • 4445

              #7
              I understand that, but which BC are you using, G7 or G1?

              JBM is using quite a bit of Bryan Litz's data now, and we've always felt the Lapua BC might be overstated, so I'm not completely surprised by the new numbers.

              QC might have played a part in the past numbers too. I've had Sierras that sure didn't make the drops I expected based on their BC's, although in the last 1-2 years that seems to have resolved itself as well.

              When it comes to QC for the bullets I shoot, Berger is tops, Lapua second, then Sierra. As I said, though, Sierra seems to have jumped quite a bit in the last 1-2 years. (That said, the best and most consistent load I've found from my 28" Grendel is the 107 Sierra, so I really don't have an axe to grind there!)

              Welcome back, good to see you, too!

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              • #8
                I have had great results with the 120 Berger's too. Unfortunately they go sub mach 1 at about 925 yds. I've been getting 2520 fps with these out of my 22 inch JP using a healthy dose of TAC. I've been using your pet load of X-Term with the 107s, but even that bullet has dropped when computed thru JBM's website now. I can push the 107s to about 2730 fps with X-Term. This load now barely makes it past 1000 yds at mach 1, going sub sonic at 1025. I've just picked up a box of 123 SMKs so am going to try Win 748 to see how they run. If I can reach 2550 fps I know these are meant to be good to 1100 yds according to JBM. JBM's calculations have definitely changed from last year which is a little disconcerting.
                Last edited by Guest; 06-20-2011, 07:31 PM.

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                • #9
                  sititunga,

                  I would look at Lapua's radar data with Quick Target Unlimited or Viking Ballistics. You don't need to mess with theoretical BC drag models anymore with Lapua bullets now.

                  Either way, I wouldn't be taking any drop data from those programs and expecting 1000yd performance with those weight of projectiles at those anemic velocities. I'm not even happy pushing the 123gr Scenars out of my .260 Rem past 600, and I'm throwing them at 2960 fps. Too much wind drift when the winds get over 10mph. I even know some Norwegian Snipers that hot-loaded their 6.5x47's with the 123gr Scenars at well over 3300 fps, and I'm not sure it helped them at even 900 meters.

                  I think for 1000 yds, you really need a heavier/longer 6.5 projectile going pretty fast if you want to get your money's worth, unless there are no winds.

                  You should be able to get more velocity than the 2500's with a 22" pipe. I get 2520 with the 120 SMK's and TAC out of my 16" Grendel. Maybe you need a slower powder...

                  LRRPF52

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                  • #10
                    Any recommendations on loads and powders to push the velocities up with the 123? The velocities might be low but I have had some very good results in matches out to 1000 yds with the 107s.

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                    • #11
                      Originally posted by LRRPF52 View Post
                      sititunga,

                      I would look at Lapua's radar data with Quick Target Unlimited or Viking Ballistics. You don't need to mess with theoretical BC drag models anymore with Lapua bullets now.

                      Either way, I wouldn't be taking any drop data from those programs and expecting 1000yd performance with those weight of projectiles at those anemic velocities. I'm not even happy pushing the 123gr Scenars out of my .260 Rem past 600, and I'm throwing them at 2960 fps. Too much wind drift when the winds get over 10mph. I even know some Norwegian Snipers that hot-loaded their 6.5x47's with the 123gr Scenars at well over 3300 fps, and I'm not sure it helped them at even 900 meters.

                      I think for 1000 yds, you really need a heavier/longer 6.5 projectile going pretty fast if you want to get your money's worth, unless there are no winds.

                      You should be able to get more velocity than the 2500's with a 22" pipe. I get 2520 with the 120 SMK's and TAC out of my 16" Grendel. Maybe you need a slower powder...

                      LRRPF52
                      What's your TAC load data?

                      Comment


                      • #12
                        Originally posted by JASmith View Post
                        Ah yes, it's easy to forget that Sierra uses velocity-dependent G1 BC's. (I just realized I'd forgotten too.)

                        The Lapua has three listings in his pull-down menu. Two of them are G7's and the one listed as 123 Scenar (CD) doesn't show a BC.

                        So, we may be hard-pressed to extract the drag vs velocity curves from the data to compare.

                        FWIW other posters have tried the Scenar out to 1000 meters and, possibly beyond, in formal ranges where spotters were stationed near the target. They reported that the supersonic crack did not appear to be evident.
                        Interesting maybe the Scenars don't destablize as they drop below the sound barrier. I've had good results with the 108 Scenars out to a 1000 yds.

                        If you watch the tailend of this youtube video (Grendel to 1000 yds) it sounds like you can hear supersonic cracks - hard to tell though.

                        Last edited by Guest; 06-21-2011, 04:09 AM.

                        Comment


                        • #13
                          sititunga,

                          16" AA pipe/bolt combo, mid-length gas system, carbine recoil spring, Spike's ST-T2 buffer, SLIP 2000 EWL
                          Lapua brass, once-fired, polished
                          Remington 7 1/2 Small Rifle Primers
                          120gr Sierra Match King
                          30.0gr TAC

                          2567, 2513, 2513, 2525, 2516......AVG: 2526.8 fps Notes say 4/5 cases had light ejector swipes from that load. I think I was 2.250" COAL on those loads. I just went and measured one of those cases from that batch, and it is in fact 2.250" COAL on the money, so I would say that is on the hotter end for sure. Don't make large increments of powder charge increase with the Grendel when getting close to the hotter end, as the pressure curve is not linear. I saw this with my very first whimpy super-slow starting loads when I first started developing for the cartridge.

                          LRRPF52

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                          • #14
                            Just sent you a message. My 120 Berger load is 29.1 grains and I'm getting the same velocities. Uhm that's quite a steep load. I guess I could expect to add another 100 fps to my velocity given my 22 inch barrel.
                            Last edited by Guest; 06-21-2011, 04:13 AM.

                            Comment


                            • #15
                              Originally posted by sititunga View Post
                              ...I guess I could expect to add another 100 fps to my velocity given my 22 inch barrel.
                              Try the velocity estimator at http://shootersnotes.com/calculator/velocity-estimator/ to refine estimate for the longer barrel.

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