I have recently completed load development for my 1:8 twist .223 with Sierra’s 69 grain Match King BTHP. I wanted to experiment with the tipped version in the same weight. While waiting for my TMKs to arrive, I scoured the internet and various load books for information and data. I found that comparisons between the two were hard to come by. So was specific load data for the 69 grain TMK. In this thread I will attempt to provide the answers to the questions I had and invite others to share their experiences with the TMK.
Q: If you have a load worked up for the standard MK, can you just use the same powder charge and expect similar results?
A: Probably not. Nor is it necessarily safe. They are not the same bullet. The SMK is .892 long. The TMK is .978 long for a difference of .086. The ogive is in a different place. The 69 SMK touches my lands at a COAL of 2.321. The tipped version touches at 2.369 for a difference of .048. The difference in amount of bullet length in the case with both the same distance from lands is .038. So, as you can see, one would expect pressure differences using the same powder charge and distance from lands interchangeably between the two. The normal safety rules of reloading apply. Start low and work up.
Q: Did you do that?
A: Of course not. I noticed in the VV manual that they actually had separate data for the 77 TMK and the BTHP version. The TMK data actually had higher max charges listed with my powder which surprised me since the 69 TMK reduces case capacity and thus, increases pressure. I also know that in my own load development the 75 Hornady BTHP uses .5 grains less of Varget than the 75 grain ELD Match. So, that made two sources that made me think I would end up with a higher powder charge with the TMK.
Q: So, what did you do?
A: I started at my regular 69 SMK charge weight (VV data max) and worked up in .1 grain increments to .5 grains over my starting charge. I seated the TMK at the same distance from the lands as my regular SMK load. I shot 5 rounds of each, looking for pressure signs. Luckily, I never saw any until the last group. The primer flattened just slightly. That group had a MV of 3149 and a SD of 12. The group before it with a .4 grain increase had a SD of 3.2. It was stupid not to start lower but I was fortunate.
Q: So, what was the difference in velocity and accuracy?
A: For me, in this 100 yard session, my regular SMK load was more accurate. I put 7 rounds in a roundish .5” group with a 7.9 SD and an average MV of 3035. The TMK with .4 grains more powder grouped 13/16” but was completely horizontal with a 3.2 SD and a MV of 3082. The TMK with the same charge weight as my SMK load had a MV of 3032 and an SD of 17.2. 5 rounds produced a 3/4” group. Close to the same?
Q: So, what powder and charge weight?
A: VV N135 at a charge weight that started at published max (my regular SMK load that was carefully worked up to) and exceeded their data by .5 grains. Told you - it was stupid. I have a Wylde chamber so I don’t mind exceeding .223 pressures a little. At least I went up in .1 increments.
I’m going to keep that low SD load for occasions where I want to exceed 200-300 yards and want a little better BC and a little more velocity. I think it’s a little warm for constant use. I’m not sure 50 fps is worth it.
* I might try a slower powder next like VV N140 or Varget to see if I can get a little more velocity. The problem with that though is that with these sexy long bullets and the compressed loads that achieve higher fps, your regular seating stem can mark and/or deform the bullet. A custom stem is often required. The obvious solution is to use a faster powder like TAC, N135, or H4895 that won’t be compressed with near max charges.
Anyway, hope this helps somebody.
Q: If you have a load worked up for the standard MK, can you just use the same powder charge and expect similar results?
A: Probably not. Nor is it necessarily safe. They are not the same bullet. The SMK is .892 long. The TMK is .978 long for a difference of .086. The ogive is in a different place. The 69 SMK touches my lands at a COAL of 2.321. The tipped version touches at 2.369 for a difference of .048. The difference in amount of bullet length in the case with both the same distance from lands is .038. So, as you can see, one would expect pressure differences using the same powder charge and distance from lands interchangeably between the two. The normal safety rules of reloading apply. Start low and work up.
Q: Did you do that?
A: Of course not. I noticed in the VV manual that they actually had separate data for the 77 TMK and the BTHP version. The TMK data actually had higher max charges listed with my powder which surprised me since the 69 TMK reduces case capacity and thus, increases pressure. I also know that in my own load development the 75 Hornady BTHP uses .5 grains less of Varget than the 75 grain ELD Match. So, that made two sources that made me think I would end up with a higher powder charge with the TMK.
Q: So, what did you do?
A: I started at my regular 69 SMK charge weight (VV data max) and worked up in .1 grain increments to .5 grains over my starting charge. I seated the TMK at the same distance from the lands as my regular SMK load. I shot 5 rounds of each, looking for pressure signs. Luckily, I never saw any until the last group. The primer flattened just slightly. That group had a MV of 3149 and a SD of 12. The group before it with a .4 grain increase had a SD of 3.2. It was stupid not to start lower but I was fortunate.
Q: So, what was the difference in velocity and accuracy?
A: For me, in this 100 yard session, my regular SMK load was more accurate. I put 7 rounds in a roundish .5” group with a 7.9 SD and an average MV of 3035. The TMK with .4 grains more powder grouped 13/16” but was completely horizontal with a 3.2 SD and a MV of 3082. The TMK with the same charge weight as my SMK load had a MV of 3032 and an SD of 17.2. 5 rounds produced a 3/4” group. Close to the same?
Q: So, what powder and charge weight?
A: VV N135 at a charge weight that started at published max (my regular SMK load that was carefully worked up to) and exceeded their data by .5 grains. Told you - it was stupid. I have a Wylde chamber so I don’t mind exceeding .223 pressures a little. At least I went up in .1 increments.
I’m going to keep that low SD load for occasions where I want to exceed 200-300 yards and want a little better BC and a little more velocity. I think it’s a little warm for constant use. I’m not sure 50 fps is worth it.
* I might try a slower powder next like VV N140 or Varget to see if I can get a little more velocity. The problem with that though is that with these sexy long bullets and the compressed loads that achieve higher fps, your regular seating stem can mark and/or deform the bullet. A custom stem is often required. The obvious solution is to use a faster powder like TAC, N135, or H4895 that won’t be compressed with near max charges.
Anyway, hope this helps somebody.
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