Absolute max at 60 degrees ,will it lock up my rifle up at 80 degrees ? ( 74grs of Magpro 140 gr Berger VLD )
If I were to guess? I'd say no to lockup but you could definitely wreck your brass.
In my recent .270WSM workup I chose to use another powder so I didn't specifically test your combination for temp but in my opinion the 140's max'd at 3250 and I chose to drop to around 3100fps for an all-round hunting load because if one were hunting in 80-90 degree weather and the rifle were exposed to direct sunlight the POWDER temp could easily be hotter.....And those rounds have the bullet hanging 'wayyy down into the powder chamber. (see pic below of the 130 Barnes VS the 150 NBtip) Incidentally these two bullets just define the .270WSM IMO. Get the 130 at 3200 and the 150 at 3000 and the two rounds will essentially match trajectories clear out to 600yds where energy finally falls under a ton. You can practice w/the NBt's and hunt with the Barnes and it's all automatic.
For testing the temp thing...
What I do is stick 3rds in front of a heater for several hours and shoot them with a Napa spot thermometer. I dunno how these things work but you just point and click to get a reading.
I also stick three rounds into the freezer overnite and shoot them over the chrono. The results are less than scientific but still enlightening.
Regarding the 80 degrees with a 60degree load...... I've lost too many cases at matches, in the dogpatch or after driving 2-3hrs to get to a 1000yd vantage........... or hunting another state. I just shoot for 50-75fps under my personal maximums....... and my personal maximum is that point where the load will not expand primer pockets.
I shoot at home and when I find a maximum load I then drop about 40fps "just because" and another 50fps for temp variation. Then I try to tune...... it really sucks when the tune wants to be UP...... And I'm not afraid to go DOWN.... and if it gets too far down??? then I change powder
Here's a weird thing...... FOR ME it commonly happens that I'll shoot for hours playing around at maximum velocity. Maybe I'll do it again the next day...... and then I'll load up some rounds "in case I see a coyote" or whatever. A few days/weeks/months later I'll fire one and WHAM!!! Shave a halfmoon right off the casehead or even leak a primer.
I have no idea why.
I leave my working guns fouled at the end of the day, I don't have any weird oiling/greasing/prep'ing regimens....... but I always drop about 40fps off max "just because."
I think that for anything but the PPC tuning depends a lot on luck and perseverance. I don't know any tricks although good equipment sure makes it easier to use the "ladder" or sine wave methods.
Your Mileage May Vary
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