Question? I am a long distance F Class TR shooter, both 223 and 308. In load development for the 223, I ran across something that I do not fully understand, yet .....
Tikka T3x Sporter with a 31" Bartlein heavy palma 1 in 7 twist barrel, 0.169" freebore. I am loading Berger 85.5gr long range hybrid target bullets (sorted for weight) with Lapua Match brass (new), FGGM primers and Varget powder measured very accurately to +/- .02 grains. Use expanding mandrels for neck sizing, thus neck tension. Loaded 40 rounds exactly the same, after full length resizing and mandrels, I noticed 10 of the rounds required a bit more pressure to seat the bullets (thus slightly more neck tension) than the other 30 rounds.
Went to the range to shoot 4 ten round groups at 200 yards. Accuracy was what I expected, all four groups less than 3/4". But, the velocities were interesting. The one series was the slightly higher neck tension at 2730 fps average and all of the three lower neck tension groups were at 2710 fps average. The ES average for all 10 shot groups was under 8 fps as well as the SD average being less than 4.0. LabRadar was used for velocity.
Why the difference, as far as loading the only difference was the neck tension. Thoughts? Is this normal?
Tikka T3x Sporter with a 31" Bartlein heavy palma 1 in 7 twist barrel, 0.169" freebore. I am loading Berger 85.5gr long range hybrid target bullets (sorted for weight) with Lapua Match brass (new), FGGM primers and Varget powder measured very accurately to +/- .02 grains. Use expanding mandrels for neck sizing, thus neck tension. Loaded 40 rounds exactly the same, after full length resizing and mandrels, I noticed 10 of the rounds required a bit more pressure to seat the bullets (thus slightly more neck tension) than the other 30 rounds.
Went to the range to shoot 4 ten round groups at 200 yards. Accuracy was what I expected, all four groups less than 3/4". But, the velocities were interesting. The one series was the slightly higher neck tension at 2730 fps average and all of the three lower neck tension groups were at 2710 fps average. The ES average for all 10 shot groups was under 8 fps as well as the SD average being less than 4.0. LabRadar was used for velocity.
Why the difference, as far as loading the only difference was the neck tension. Thoughts? Is this normal?
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