We drilled a 0.060 inch hole in each test case, matching the transducer fitting in the test barrel. The cases were then neck sized and loaded with test loads. In general, 5 rounds were tested for each load.
A word here: Loads that do not fill the case completely are quite variable in both pressure and velocity. If the powder charge is located at the back of the case, pressure and velocity will be higher, if located toward the front pressure and velocity will be lower. Total effect depends upon the empty space available. This is believed to be caused by adiabatic heating of the charge when the empty volume is pressurized at the front. When the void is at the rear, the primer plume probably overpowers compression-heating effects. Test technicians at Norma test labs are very familiar with this phenomenon and take precautions to assure the charge is always located at the back of the case for worst case conditions when developing loads for their loading manuals. McPherson and I recommend a charge that completely fills the case or is slightly compressed for best repeatability.
The bullet bases for both cartridges were located exactly at the internal neck-shoulder junction for all tests. This is done to assure the focus of the elliptical shoulder in the SMc cartridge is away from the bullet base, preventing heat loss to the bullet. At the same time, this minimizes length of powder column in both cartridges, which in some situations could be located in the neck, reducing efficiency. Most of the cases lasted for 4 to 5 tests before erosion around the pressure test hole became severe.
Bullets tested were 70 gr. Sierra match, 105 gr. Lapua Scenar, 105 gr. Berger VLD moly coated, and 115 gr. Berger VLD. Powders tested were Norma 204, MRP, MRP2, Reloader 19 and VihtaVuori N-550. Powder burn rates were matched roughly to bullet weights. Norma uses NECO moly coating process on all their production target loads as they have noted a significant improvement in barrel life in their tests.