Need help determining correct OAL

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  • cst
    Warrior
    • Jan 2014
    • 239

    Need help determining correct OAL

    Ive been reloading 123scenars for a couple years now....and I have always loaded em according to ojive measurement......but when u really measure the overall length there is a huge variance due to inconsistent bullet length. The meplat tip is different on every round....how do u determine what the correct length is?
  • Bwild97
    Warrior
    • Jan 2015
    • 217

    #2
    Stick to using the ogive oal, this is the measurement that is relative to your chamber allowed oal.

    You can purchase a meplat uniformer, if you have coal issues with your mags.

    Comment

    • cst
      Warrior
      • Jan 2014
      • 239

      #3
      Anyone know the ojive measurement of the AA 123scenars loads? Bill has them listed at COAL 2.265"(with hornady comparator )

      Comment

      • rwh
        Warrior
        • Jun 2014
        • 188

        #4
        I use the ogive measurement and determine the correct length by testing different lengths to see which shoots best in the rifle. I haven't found that it makes much difference in a SAAMI grendel chamber so I just use an OAL that's just short enough so that every round will feed through the magazine.

        Comment

        • Bwild97
          Warrior
          • Jan 2015
          • 217

          #5
          Originally posted by rwh View Post
          I use the ogive measurement and determine the correct length by testing different lengths to see which shoots best in the rifle. I haven't found that it makes much difference in a SAAMI grendel chamber so I just use an OAL that's just short enough so that every round will feed through the magazine.
          Agreed!!

          Comment

          • PrecisionFirearms
            Warrior
            • Apr 2011
            • 767

            #6
            2.265 is fine for the 123 Scenars. I wouldn't really worry about the OAL otherwise. In the Grendel it is really forgiving. I have a lot of reports of Sub .3 MOA using our ammo and we load to 2.265 COAL using the Base to tip measurement.

            Mark Hostetter
            "Precision - The Pinnacle of Perfection."

            Comment

            • cst
              Warrior
              • Jan 2014
              • 239

              #7
              Originally posted by PrecisionFirearms View Post
              2.265 is fine for the 123 Scenars. I wouldn't really worry about the OAL otherwise. In the Grendel it is really forgiving. I have a lot of reports of Sub .3 MOA using our ammo and we load to 2.265 COAL using the Base to tip measurement.

              Mark Hostetter
              Mark.....what is your muzzle velocity on your loads? Barrel length..?

              Comment

              • PrecisionFirearms
                Warrior
                • Apr 2011
                • 767

                #8
                24 inch Muzzle velocity average is 2550 FPS in a semi auto.
                "Precision - The Pinnacle of Perfection."

                Comment

                • Thomas
                  Unwashed
                  • Sep 2015
                  • 3

                  #9
                  Just built a rifle using a Shilen 20 inch barrel. I didn't know going in that there are several different chambers for 6.5 Grendel. Shilen does NOT use SAAMI spec on their chamber. I asked about it, and they sent me a drawing of their reamer. They use a shorter leade than the SAAMI spec. I loaded some 120 AMAX to mag length of 2.250,
                  and all went well for about 30 rounds, then I had a misfire. Tried to cycle the bolt, and it was stuck. When I finally got it open, the bullet stayed stuck in the throat. Needless to say, that stopped everything for that day. Got the bullet out and then used the hornady oal gauge to find out where I went wrong. The 120 AMAX uses an altogether different ogive than the 123 AMAX and MUST be seated short! 2.180 will do it. This was a stupid mistake on my part and could have resulted in a blown up rifle! Never assume that magazine length is fine for COAL when using a new bullet! I consider myself lucky that I don't have a face full of scrap AR15 receiver. From now on, every bullet change gets checked. No more guessing.

                  Comment

                  • biodsl
                    Chieftain
                    • Aug 2011
                    • 1714

                    #10
                    Originally posted by Thomas View Post
                    From now on, every bullet change gets checked. No more guessing.
                    Thank you for your honesty, Thomas. This is good advice for new reloaders such as myself.
                    Paul Peloquin

                    Did government credibility die of Covid or with Covid?

                    Comment

                    • lwminton
                      Warrior
                      • Nov 2014
                      • 143

                      #11
                      Originally posted by Thomas View Post
                      Just built a rifle using a Shilen 20 inch barrel. I didn't know going in that there are several different chambers for 6.5 Grendel. Shilen does NOT use SAAMI spec on their chamber. I asked about it, and they sent me a drawing of their reamer. They use a shorter leade than the SAAMI spec. I loaded some 120 AMAX to mag length of 2.250,
                      and all went well for about 30 rounds, then I had a misfire. Tried to cycle the bolt, and it was stuck. When I finally got it open, the bullet stayed stuck in the throat. Needless to say, that stopped everything for that day. Got the bullet out and then used the hornady oal gauge to find out where I went wrong. The 120 AMAX uses an altogether different ogive than the 123 AMAX and MUST be seated short! 2.180 will do it. This was a stupid mistake on my part and could have resulted in a blown up rifle! Never assume that magazine length is fine for COAL when using a new bullet! I consider myself lucky that I don't have a face full of scrap AR15 receiver. From now on, every bullet change gets checked. No more guessing.
                      I decided a few days ago to try Lapua 103 gr bullets in my 6mm Grendel. I had been shooting Berger 100 gr BT at mag length. After reading this post, I decided to check the Lapuas even though I never thought there could be an issue. It turned out the OAL touching was 2.265. Not a lot of extra room there!
                      It only takes a few minutes with the StoneyPoint and how often do we try new bullets? This is good advice.

                      Comment

                      • LR1955
                        Super Moderator
                        • Mar 2011
                        • 3355

                        #12
                        Originally posted by Thomas View Post
                        Just built a rifle using a Shilen 20 inch barrel. I didn't know going in that there are several different chambers for 6.5 Grendel. Shilen does NOT use SAAMI spec on their chamber. I asked about it, and they sent me a drawing of their reamer. They use a shorter leade than the SAAMI spec. I loaded some 120 AMAX to mag length of 2.250,
                        and all went well for about 30 rounds, then I had a misfire. Tried to cycle the bolt, and it was stuck. When I finally got it open, the bullet stayed stuck in the throat. Needless to say, that stopped everything for that day. Got the bullet out and then used the hornady oal gauge to find out where I went wrong. The 120 AMAX uses an altogether different ogive than the 123 AMAX and MUST be seated short! 2.180 will do it. This was a stupid mistake on my part and could have resulted in a blown up rifle! Never assume that magazine length is fine for COAL when using a new bullet! I consider myself lucky that I don't have a face full of scrap AR15 receiver. From now on, every bullet change gets checked. No more guessing.
                        Thomas:

                        We learned that with the 120 AMAX when it first came out. However, we learned it by using dummy cartridges to find a length and not when shooting. Some guys had to seat that specific bullet so far into the case for it to chamber safely that the neck went past the shank of the bullet. Not a good design for the Grendel so few use it.

                        I never trust the OAL from any printed source. I always use a dummy cartridge to find the right seating depth. Most of the time with the Grendel it ends up what the printed material stated but not always.

                        LR55

                        Comment

                        • Thomas
                          Unwashed
                          • Sep 2015
                          • 3

                          #13
                          Well, they say experience is the best teacher. I did a lot of reading to find powders, etc., and never came across anything about 120 amax bullets, good, bad, or indifferent. Just figured if 123's worked, chances were that 120's would also, since the store didn't have any 123's. My only other choice was 140 grain Sierras,and they looked WAY too long. The hell of it is, the loads all shot really well. Every one sub MOA.
                          I wonder what they would do with a jump to the lands? Factory Hornady 123 amax match shot 1 1/4 inch at 300 yards, so I'm really pleased with this Shilen barrel.
                          Does anyone know the reason Lapua uses such small flash holes in their Grendel brass? Something to do with PPC case design, is it? Curious what the advantage might be.

                          Comment

                          • A.D.D. AR
                            Warrior
                            • Oct 2014
                            • 125

                            #14
                            Thomas-
                            the hornady bullet comparator tool is your friend with the countless 6.5mm bullet choices we enjoy today!
                            before the 123 amax came out, I used the 120 amax in the grendel and had great results (SAAMI chamber, 2.185'' oal) I used BLC2 powder.
                            But the 123 amax has a better BC & better ogive profile to work in the grendel chamber, so most people don't use 120 amax in the grendel any more.
                            I believe Lapua was trying the small flash hole idea to send out a longer flame "jet" into the case for more consistent burn- I don't know if it actaully works or not
                            here is an article on it:
                            Conventional .308 Winchester brass has a large primer pocket with a large, 0.080-diameter flash hole. In 2010, Lapua began producing special edition .308 Win Palma brass that has a small primer pocket and a small flash hole, sized 1.5mm (.059) in diameter. Tests by U.S.

                            -hope this helps

                            Comment

                            • Thomas
                              Unwashed
                              • Sep 2015
                              • 3

                              #15
                              Thanks A.D.D. I now own a Hornady Comparator, should be a huge help. None of this was an issue with my .223/5.56 rifles, they all have enough leade that if you load to mag length there are no problems. I didn't expect any different with this rifle. Know better now. The longer flame jet makes sense, I guess. Must be common to the PPC family of cases?

                              Comment

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