Weird pressure issue

[243winxb]

Pressure spike in large rifle cartrides - Magnum Primers Needed.

I cut the chamber myself. It is a long throat Norma chamber. The data is for the Winchester chamber. The data is conservative for the long throat chamber.

Hard bolt lift from a pressure spike from early bullet movement, 58 grs. Sort of like a plugged barrel. https://thefiringline.com/forums/showthread.php?p=4928827#post4928827

We tested loads at both maximum normal pressures and at the starting loads (some labs calculate start loads—we shot them). Standard primers caused no ignition issues at the max load but posted higher extreme variations in pressure and velocity in the lower pressure regimes of the start loads. In extreme cases, the start loads produced short delayed firings—probably in the range of 20 to 40 milliseconds but detectible to an experienced ballistician. Switching that propellant to a Magnum primer smoothed out the performance across the useful range of charge weights and completely eliminated the delays.

Read more: http://www.shootingtimes.com/ammo/ammunition_st_mamotaip_200909/#ixzz50m9kdZvO