Accuracy question.

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  • Accuracy question.

    My 123gr Amax load will put five in the same hole at 100 yards, at 200 yards I am shooting 2" groups with the same load, at 300 they are spreading out to 3.5-4" groups. I am shooting off a sled to try and get me out of the equation.

    My question, is there a reason other than shooter error that would cause my groups to grow so much when they are all going into the same hole at 100?

    Any thoughts or advice would be welcome.

    Thank you.

  • #2
    What' the twist rate for your barrel?

    The bullet could be marginally stabilized and has time to start yawing out past 100 yards.

    Comment

    • LR1955
      Super Moderator
      • Mar 2011
      • 3355

      #3
      Originally posted by Nimrod View Post
      My 123gr Amax load will put five in the same hole at 100 yards, at 200 yards I am shooting 2" groups with the same load, at 300 they are spreading out to 3.5-4" groups. I am shooting off a sled to try and get me out of the equation.

      My question, is there a reason other than shooter error that would cause my groups to grow so much when they are all going into the same hole at 100?

      Any thoughts or advice would be welcome.

      Thank you.
      NR:

      Your loads from a gas gun are holding 3/4 minute or less and you wonder what is wrong?

      Accuracy is not linear and if your Grendel gas blaster is holding 3/4 minute or less at 300, you have a shooter that is highly respectable.

      If you want to compete in bench rest, get a bolt rifle, use one of the 6mm bench rest cartridges, and then you ought to expect better at 300. For now, your loads are performing exceptionally well given an AR-15 or any other semi-automatic rifle.

      LR1955

      Comment


      • #4
        Originally posted by LR1955 View Post
        NR:

        Your loads from a gas gun are holding 3/4 minute or less and you wonder what is wrong?

        Accuracy is not linear and if your Grendel gas blaster is holding 3/4 minute or less at 300, you have a shooter that is highly respectable.

        If you want to compete in bench rest, get a bolt rifle, use one of the 6mm bench rest cartridges, and then you ought to expect better at 300. For now, your loads are performing exceptionally well given an AR-15 or any other semi-automatic rifle.

        LR1955
        Okay, I didn't think a 3.5" group at 300 was good, I figured that if they were in one hole at 100 that should be tighter. What do you mean accuracy is not linear? How is it measured, how do you figure a 3.5-4" group at 300 to be 3/4 minute of angle?

        I am not new to shooting and have been behind a trigger since I was five but it has all been hunting and plinking. Thanks for taking the time to respond.

        Comment

        • LR1955
          Super Moderator
          • Mar 2011
          • 3355

          #5
          Originally posted by Nimrod View Post
          Okay, I didn't think a 3.5" group at 300 was good, I figured that if they were in one hole at 100 that should be tighter. What do you mean accuracy is not linear? How is it measured, how do you figure a 3.5-4" group at 300 to be 3/4 minute of angle?

          I am not new to shooting and have been behind a trigger since I was five but it has all been hunting and plinking. Thanks for taking the time to respond.
          NR:

          It sounds to me that your rifle and load are fine. Twist of rifling is fine.

          Bullets precess or nutate as they head down range. Ideally, you find a load that alleviates one or the other of these factors enough to give you the performance you require. That said, unless you can eliminate every other variable -- almost impossible with a semi-automatic rifle -- you are left with finding a load that you can depend on to meet your purposes.

          Here is another thing to consider. If you had shot say ten strings of five shots at 300, measured the groups compared them using simple statistics -- and you found the mean to be four inches @ 300 then you would look again at your loads, equipment, and yourself in terms of your ability to hold under a minute consistently, for string after string.

          So, if you haven't shot that specific load enough at that distance to find what it is really doing, give it a try and perhaps it really does hold extremely well.

          LR1955

          Comment


          • #6
            I am shooting a Les Bare with 20" barrel and a 1 in 8 twist.

            I keep reading on here where guys are shooting a .5 at 200 & 300 yards so I thought there was something wrong with either my load or me.

            Comment


            • #7
              Nim
              What you are seeing is most likely the results of wind and range conditions. If you are not using flags (and I would guess you are not) you don't have a clue what is happening downrange. The further you shoot the more difficult it is to keep groups small. My full blown target guns shoot tiny at 100, but only an accomplished shooter can shoot strings of 1 moa at 600. (as an example) Put some inexpensive surveyors tape on sticks and have your eyes opened. Good shooting!!
              Lanny

              Comment


              • #8
                It was slightly breezy and beginning to rain. You know it was such a light wind I never gave it a second thought and just shot straight through it, so some shots could have been taken in a lull and some in the breeze, can't believe I didn't think about it on my own.

                Thanks for the advice.

                Comment

                • LRS_Ranger

                  #9
                  If someone claims .5 inches at multiple hundreds of yards, be a bit skeptical. However, it seems to me that getting under 3 inches at 300 yards shouldn't be too hard given good equipment and loads. Be careful that your parallex is adjusted properly, and you aren't getting any shadow in the scope when taking aim. Also, you didn't specify whether you are seeing your dispersion grow horizontally, vertically, or both. Horizontal is most likely wind, where vertical is probably velocity. How did you work up your load? Try running a 10 round string over the chrono and verify that you don't have a large extreme spread. Have you tried a different bullet/powder etc? Let us know how it works out!

                  -LRS

                  Comment


                  • #10
                    Originally posted by LRS_Ranger View Post
                    If someone claims .5 inches at multiple hundreds of yards, be a bit skeptical. However, it seems to me that getting under 3 inches at 300 yards shouldn't be too hard given good equipment and loads. Be careful that your parallex is adjusted properly, and you aren't getting any shadow in the scope when taking aim. Also, you didn't specify whether you are seeing your dispersion grow horizontally, vertically, or both. Horizontal is most likely wind, where vertical is probably velocity. How did you work up your load? Try running a 10 round string over the chrono and verify that you don't have a large extreme spread. Have you tried a different bullet/powder etc? Let us know how it works out!

                    -LRS
                    The dispersion was a little of both. I am getting a standard deviation of 11 dos with the load, I thought I had it made with the way it shoots at 100. I am going to take the advice given by all and run this load some more at 300 and pay more attention to the range conditions. I am also going to buy some 123 gr Scenars and give them a try.
                    Last edited by Guest; 07-06-2011, 05:35 AM.

                    Comment

                    • LR1955
                      Super Moderator
                      • Mar 2011
                      • 3355

                      #11
                      Originally posted by Nimrod View Post
                      I am shooting a Les Bare with 20" barrel and a 1 in 8 twist.

                      I keep reading on here where guys are shooting a .5 at 200 & 300 yards so I thought there was something wrong with either my load or me.
                      NR:

                      I have shot 1/2 minute groups at 200. Probably at 300 too, and sure have shot 1/2 minute groups at 600 with the Grendel from AR-15's.

                      For every 1/2 minute group I have fired from 200, 300, 500, and 600 using a Grendel, there are five groups that were over 1/2 minute. Even using the same load under the same conditions. Not surprisingly, this ratio swings the other way when using 6mm cartridges and even more when using quality bolt action rifles over gas guns. Even then, holding 1/2 minute more than half the time is a difficult proposition due to environmental conditions, human error, mechanical issues et. al.

                      So, my personal philosophy when using most match rifles is that if a load consistently holds 3/4 minute or less, stop load development and spend the time and material on practice.

                      Just like I am about to do right now in fact!

                      LR1955

                      Comment

                      • LR1955
                        Super Moderator
                        • Mar 2011
                        • 3355

                        #12
                        Originally posted by Nimrod View Post
                        The dispersion was a little of both. I am getting a standard deviation of 11 dos with the load, I thought I had it made with the way it shoots at 100. I am going to take the advice given by all and run this load some more at 300 and pay more attention to the range conditions. I am also going to buy some 123 gr Scenars and give them a try.
                        NR:

                        The SD of velocity may or may not have anything to do with it. Most likely not unless you are getting well over 50 fps SD and are shooting pretty far out.

                        100 yard grouping is deceptive at best so if you can, test loads at 200 with 300 probably being ideal. I would not take 100 yard groups to have much meaning. Basically a waste of time and money.

                        Also, you may find that the short and flat base bullets will out shoot your longer boat tail bullets to 300 in terms of groups providing you are able to dope winds relatively well.

                        LR1955

                        Comment


                        • #13
                          Originally posted by LR1955 View Post
                          NR:

                          I have shot 1/2 minute groups at 200. Probably at 300 too, and sure have shot 1/2 minute groups at 600 with the Grendel from AR-15's.

                          For every 1/2 minute group I have fired from 200, 300, 500, and 600 using a Grendel, there are five groups that were over 1/2 minute. Even using the same load under the same conditions. Not surprisingly, this ratio swings the other way when using 6mm cartridges and even more when using quality bolt action rifles over gas guns. Even then, holding 1/2 minute more than half the time is a difficult proposition due to environmental conditions, human error, mechanical issues et. al.

                          So, my personal philosophy when using most match rifles is that if a load consistently holds 3/4 minute or less, stop load development and spend the time and material on practice.

                          Just like I am about to do right now in fact!

                          LR1955
                          From what I gathered earlier a 1/2 minute of angle group is not a 1/2" group, correct? If so how is that figured?

                          Comment

                          • LRS_Ranger

                            #14
                            A Minute of Angle is an angular measurement, which is 1.04 inches at 100 yards, if my memory is correct. Since it's an angular measurement, the size of one moa is going to get bigger the further you get from the shooter. .5 inches at 100 is about half a minute. .5 inches at 300 yards is about 1/6, or .16 MOA.

                            LR1955 is spot on though about if you get a load to shoot 1 MOA or less at 300 yards, stick with it and shoot shoot shoot! My Grendel with 123 scenars is around .7 inches at 100 yards, and it was still hitting a 12 inch plate at 950 yards this last weekend. Don't get hung up on trying to get your gun to shoot like a beam of light.. you will frustrate the hell out of yourself! If your gun shoots 1 MOA you will drop far more points because of yourself than your equipment, and that goes for most shooters, including myself.

                            Comment

                            • mtn_shooter

                              #15
                              As others have said, once you get past 200yd wind and other conditions really mess with your point of impact and some skillful fine tuning is required. I don't claim to be an experienced "fine tuner", I just know that I had a 2-3 MOA variation in horizontal impacts due to wind alone at 550yd. I was shooting at a 4 MOA wide steel target and was missing a few shots that I called incorrectly, but this rifle holds 3/4MOA groups @100yd. Learning how to judge where to aim at extended range just to hold 2 MOA or better is really exciting for me, personally.

                              Comment

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