Keyholing with Barnes TSX 120 grain copper solid

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  • Gunfighter25

    Keyholing with Barnes TSX 120 grain copper solid

    Have a problem with this load keyholing at 100 yards. Load is 120 gr Barnes TSX, 22.0 to 23.0 grains BLC-2 in a Lapua case and CCi 450 primers, OAL is 2.250". At 23.0 grains, I had flattened primers, ejector marks and headstamp compression.

    Barrel is an 18-inch, 3 land, polygonical, mid-length gas on an AR-15 upper. Headspacing was checked with go/no-go gauges - within spec.

    Keyhole strikes are almost the entire bullet profile.

    The kicker is this rifle will shoot 1/2 MOA with Nosler 120gr Partitions and Sierra 120 gr Pro Hunters.

    I couldn't think of anything else to consider except velocity but if the bullet was yawing that much I didn't want to risk my chronograph. Any ideas?

    Thanks,

    Gunfighter
  • BjornF16
    Chieftain
    • Jun 2011
    • 1825

    #2
    22-23 grains of BL-C(2) seems like a light load for 120 grain bullet, especially to be getting flattened primers. Are you sure you haven't loaded the bullet too long such that it is into the lands when chambered? (You can load one then extract it to see if the bullet stays in lands or has land marks on it).
    LIFE member: NRA, TSRA, SAF, GOA
    Defend the Constitution and our 2A Rights!

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    • topcaat1
      Bloodstained
      • Nov 2011
      • 52

      #3
      My understanding is that a light load can mimic high pressure signs like those mentioned. Not enough pressure for the case to expand and grip the chamber, so the case slams back onto the bolt face.

      Comment


      • #4
        BjornF16 makes a good point. Velocity is one of the key components in developing the spin rate needed for gyroscopic stability. The other is rifling twist rate. The all-copper bullet tends to be a bit longer than classic bullets and would need faster velocity or twist, or both.

        Do you know what your twist rate is?

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        • bwaites
          Moderator
          • Mar 2011
          • 4445

          #5
          My load of BLC-2 was much closer to 31 grains, and I had no problems. I suspect that you are not expanding the case, allowing it to properly obdurate against the chamber sides, so you are getting the flattened primers because of low pressure, not high.

          The wild card here is that I was using a rifle with standard rifling, and polygonal rifling has not been very well explored in an AR, at least not in the Grendel.

          Bill

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          • #6
            Another question is, "will a solid copper projectile deform enough to engage polygonal rifling, or will is drive up pressures because it isn't deforming all all. I'd try a lighter solid copper bullet if possible.

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            • #7
              I've found the 100 gr TTSX much easier to load than the 120 for the Grendel. I'll probably use my 120's in the Creedmoor. The 120's will definitely need a fast twist and a faster velocity to end the tail spiral that it will have when it leaves the barrel. Depending on the clearance from the brake, if one is used, it could cause further upset of the bullet with a larger tail spiral in the bullet as it passes through the brake. I've been a dedicated Barnes shooter in recent years, and I'll find people who don't think they are accurate, but when they shoot the loads adjusted for the velocity needed for their twist rate, they find them to be tack drivers. If you're getting keyholes, you're a long way off from the correct load in that particular rifle, and the comments above would be correct.

              Comment


              • #8
                Originally posted by Gunfighter25 View Post
                Have a problem with this load keyholing at 100 yards. Load is 120 gr Barnes TSX, 22.0 to 23.0 grains BLC-2 in a Lapua case and CCi 450 primers, OAL is 2.250". At 23.0 grains, I had flattened primers, ejector marks and headstamp compression.

                Barrel is an 18-inch, 3 land, polygonical, mid-length gas on an AR-15 upper. Headspacing was checked with go/no-go gauges - within spec.

                Keyhole strikes are almost the entire bullet profile.

                The kicker is this rifle will shoot 1/2 MOA with Nosler 120gr Partitions and Sierra 120 gr Pro Hunters.

                I couldn't think of anything else to consider except velocity but if the bullet was yawing that much I didn't want to risk my chronograph. Any ideas?

                Thanks,

                Gunfighter
                This is also what jumped out at me. That's a light load for a .223 Remington with the heaviest bullets you can get for the mouse gun. Crank that load up, but keep in mind that the long solids will eat a lot of case capacity, which also drives up pressure. What loads are you running with the 120gr Partitions and 120gr Pro-Hunters?

                Also, physics seems to indicate that a polygonal barrel would deal with pressure better, since you have less surface area contact with the projectile, and less aggressive contact with regard to the projectile deformation. Also wondering what your twist rate is.

                Comment

                • Gunfighter25

                  #9
                  Thanks for the replies.

                  Yes, the powder charge is very low. What stopped me was the high pressure signs. Stopped all load development for this bullet and tried the Hornady 123 gr Amax, Nosler 120 gr Partition and the Sierra 120 gr. Pro Hunter - all with about 30.0 to 31.0 grains of BLC-2 with success. Just never went back to the Barnes until now.

                  Barrel rifling is 1-8" Black Hole Weaponry barrel. Thought the three-land polygonical would give me better ballistics and allow higher pressures for longer ranges due to less friction.

                  Will restart by loading from 28.9 to 31.0 grains of BLC-2 and see what happens. On the OAL - 2.250" will fit in the standard magazine. The Barnes TSX has three grooves. Will leaving one or two of the grooves out of the case neck cause any issues?

                  Thanks

                  Gunfighter

                  Comment

                  • Ned Christiansen

                    #10
                    As to 3 grooves having less contact with the bullet than 6 grooves, that would really depend on the exact rifling profile, but BHW has undoubtedly done the homework on this and I wonder if this is actually not barrel-related but something else....? Twist-wise, 1 in 8 has worked for me with this bullet and the Barnes 110-grain turned brass one using
                    loads by Carson Specialty Development.

                    Comment


                    • #11
                      Hodgdon lists a Overall Length of 2.200". Which is how I've been loading the 120gr TSX for my rifle. I've got a 1 in 7.5" twist and am getting excellent results with that bullet over H335.



                      It might not hurt to make up a dummy round and chamber it to see if the bullet it hitting the lans. If it is, the COL could be a contributing factor to your high pressure signs. It has been my experience, and that of others I've talked to, that Barnes Bullets like a little more jump anyway.

                      I am not familiar with the powder you're using so I cannot comment on the charge or case capacity, but in my rounds the bullets are showing half of the top ring, the other tow are covered.

                      Good Luck,
                      Brian

                      Comment

                      • BjornF16
                        Chieftain
                        • Jun 2011
                        • 1825

                        #12
                        FWIW, I've measured factory AA OAL as 2.235" for the Barnes TSX. IIRC, Barnes bullets like .030-.050" jump for best results.

                        I would start with 27 gr of BL-C(2) with an OAL of 2.235 and check your results (there would be one band just out of the case for this length).

                        I use a Hornady OAL gauge with a modified case to measure distance to lands for each of my hand loads. Each particular barrel will have different results with the jump distance (for each bullet type). Once you find an intermediate load that cycles correctly, play with different jump distances to see if there is any changes in grouping size; use the jump distance that gives the best results. Then fine tune your powder charge.
                        LIFE member: NRA, TSRA, SAF, GOA
                        Defend the Constitution and our 2A Rights!

                        Comment

                        • Gunfighter25

                          #13
                          I've got a Hornady OAL mod round for 5.56 and .308. Got a modified 6.5 Grendel case inbound to check the distance to the lands. Sounds like once I've got the max OAL to the lands, I need to back off to 0.040" and play with it from there.

                          Thanks for all the input

                          Gunfighter

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                          • #14
                            Let us know how it works out. I'm seriously looking at a BHW barrel for the next build.

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                            • #15
                              .050 is where Barnes recommends to start, and I've usually found that to work great, and increases the velocity a bit with the jumpt to the lands.

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