Sas874runner
Handloader
- Oct 10, 2012
- 476
- 2
So as I begin a new load work up for the 270 win ablr. I sat and looked at the bullet next to a 140 ab. They are two completely different animals. I decide to take some measurements. Found the bearing surface of the 150 ablr to be .106" less than the 140 ab. Then the wheels start turning... the bearing surface of a bullet is what creates most of the pressure? If someone has a comparator and could give me a bearing surface measurement of a 130 ab for comparison I would appreciate it. Now. My previous load with magnum didn't show pressure until I hit 69 grs. At which point I started to see a slight flattening on the primer and stopped there. Mostly because of pressure but also because accuracy was not there either. Ended up at 64.5 gr. After sizing, brass only needed trimming of .002-.003". This time around I will be trying mag pro. And of course working up safely from the minimum 150 gr bullet charge. But looking at what the last load development showed I am curious as to what you guys think as well. Is bearing surface the main contributor to pressure? Also. nosler states that 1:9 twist is optimal for stabilization off the 150 ablr. Can speed compensate for twist rate? Am I reading to far into this?
