I put one on an Encore barrel I had made custom in .45 Auto for testing pressure. It is on top. It actually works well, giving me readings of just over 19,000 psi on military ball ammo rated at about that. It's back edge is just barely a quarter inch forward of the breech end of the barrel; maybe 0.3". I'll have to dig it out and look.
I don't think being over the exact middle of the case is necessary. I would take a case that has been fired and resized a few times and use a caliper to identify where the pressure ring is forming and would be sure the back edge is at least that far forward to be sure the chamber steel under it is exposed to maximum pressure.
I don't think being over the exact middle of the case is necessary. I would take a case that has been fired and resized a few times and use a caliper to identify where the pressure ring is forming and would be sure the back edge is at least that far forward to be sure the chamber steel under it is exposed to maximum pressure.
