ericthemantis

Reloading Image 1

Numbers represent grains of H4831 behind a Barnes LRX .277" 129gn

Reloading Image 1
ericthemantis, Sep 29, 2018
    • CaptBligh
      My $.02 - I would consider 59 grn as max with your combination of rifle and bullet.

      How did I get there?

      It looks to me like your firing pin hole in your rifle's bolt is just slightly oversized which looks like "cratering" at even mild loads. Radius edge on primers doesn't start to flatten until 59 to 59.5. Primers are notoriously difficult to accurately gauge pressures. The micrometer measure of expansion is probably better, but you need to take care that you're measuring the same spot on the case before and after firing.

      Looks to me you have scrubbing of the case head showing up from 59 grains and getting more pronounced as your charges increase. The case is stationary in the chamber as the bolt head rotates on opening. To me, R-P cases are usually softer and this scrubbing shows up earlier than with some other brands.

      I usually chrono factory loads with same bullet, if I can find them, and use that velocity to ballpark max loads. If I'm starting to see mild primer flattening, no extractor marks and velocities near factory levels with accuracy I need for the use I`m planning I'm happy.

      I haven't done extensive load development with the .270 Win, but in a Husqvarna and a Sako I ended up at W-W case, CCI 200 primer, 130 gr Hornady SST, and 60.0 gr H4831SC (you need short cut to fit in case w/o heavily compressed load in W-W case). Hodgdon max is 60.0 and Hornady is 62.0 at 3100 fps. 60.0 gave 3133 fps from the Husky so that's where I ended up. Your max with the Barnes bullet will likely be lower.
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