03-11-2020, 10:57 AM
Lawrence,
What range were you shooting those groups? If this is 100yds then it looks normal for an average barrel. TBox with bolt is at the top end of pricing however so I would expect it to perform as well as a Lilja, Bartlein or Kreiger. We don't hear much about TBox on the forum. Maybe the 107 doesn't like the fast 1:7.5 twist given the norm is more 1:8.
Your extreme velocity spreads will not be the fault of the bullet and may be something else like neck tension. The second group with two groups of two holes could be not enough neck tension in an auto loader. The cartridge slams into battery and the bullet continues on into the lands. This then causes a pressure spike and higher MPI. Do you know your neck tension (a common standard is .004" for auto loaders).
Regardless of the velocity data a couple of those groups look actually pretty good. Have you had much experience with an AR? It is certainly not an 8kg heavy barrel F-Class gun with 3" wide parallel tracking stock.
What range were you shooting those groups? If this is 100yds then it looks normal for an average barrel. TBox with bolt is at the top end of pricing however so I would expect it to perform as well as a Lilja, Bartlein or Kreiger. We don't hear much about TBox on the forum. Maybe the 107 doesn't like the fast 1:7.5 twist given the norm is more 1:8.
Your extreme velocity spreads will not be the fault of the bullet and may be something else like neck tension. The second group with two groups of two holes could be not enough neck tension in an auto loader. The cartridge slams into battery and the bullet continues on into the lands. This then causes a pressure spike and higher MPI. Do you know your neck tension (a common standard is .004" for auto loaders).
Regardless of the velocity data a couple of those groups look actually pretty good. Have you had much experience with an AR? It is certainly not an 8kg heavy barrel F-Class gun with 3" wide parallel tracking stock.