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Flattened Primer Question for 300 RUM

 
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  #1  
Old 01-21-2013, 04:53 PM
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Location: Arkansas
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Flattened Primer Question for 300 RUM

Hunting season has ended and shooting season has begun where I am at! I have a 300 RUM Sendero, stock 26 inch barrel that is capable of sub moa out to 1000 yards if I do my part. My load is 92 grains of Retumbo, 215 Bergers, Rem brass, Fed 215 match primers, 3.690 col (can fit one in magazine), and it chronos at 3100 fps. Velocity seems to be in line with what most folks are posting. (I know, everything on the internet is true) The only pressure signs I'm getting are flattened primers. No sticky bolt lift all. My question is this....Should I back off until primers quit flattening or keep this load? What would you do? It's scary accurate and I'm somewhat hesitant to change. I have 48 pieces of 2x fired brass tumbling right now. Going to give the gun a good a cleaning, shoot my final two rounds as foulers and either duplicate the load posted above or change it up a little as time allows.
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  #2  
Old 01-21-2013, 05:28 PM
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Re: Flattened Primer Question for 300 RUM

How are the primers seating after the case has been reloaded 3-4 times? if still decently snug your good on that front. How are you resizing your brass. FL size and only bump the shoulder back 2 thousandths max. Are you wiping your cases good and clean after reloading? make sure all traces of lube are gone. I wipe mine with a cloth soaked with a little rubbing alcohol. You want that case body to make a good grip on the chamber walls at the instant of ignition. This reduces potentially excessive bolt thrust. A few simple thoughts... others may have better suggestions.
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Old 01-21-2013, 07:04 PM
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Re: Flattened Primer Question for 300 RUM

Your flattened primers are most likely due to you setting the case shoulders too far back when you FL size.
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  #4  
Old 01-21-2013, 07:06 PM
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Re: Flattened Primer Question for 300 RUM

Sounds too hot, probably not by much, but a 215 running 3100 fps is on the warm side.
db
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  #5  
Old 01-21-2013, 07:18 PM
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Re: Flattened Primer Question for 300 RUM

My load with same rifle and 210 Bergers is VERY similar to yours with about 3130 fps. I also have slightly flattened primers with no sticky bolt. Good thing about Retumbo is, it is slow and very stable. I FL size just enough to to chamber the round snugly and easily. My brass lasts 4-6 firings on average before the pockets go. I've put several hundred rounds through of various loads using Retumbo and getting slightly flattened primers,

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Old 01-21-2013, 09:57 PM
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Re: Flattened Primer Question for 300 RUM

Thanks for the replies. I'm going to load a couple with new brass and see how the primers look. If they look good, i'll know it's my FL sizing. If not, I'll back off a grain for two.
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  #7  
Old 01-21-2013, 10:11 PM
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Re: Flattened Primer Question for 300 RUM

I have a wsm that flattens the primer regardless of the load and I only neck size never bumping the shoulder. I have other rifles shooting hotter loads with the same reloading practices that never flatten primers even with over pressure loads that kill the primer pocket grip in one shot. Different brand primers have different thresholds. In the rum brass primer pockets are probably the best indicator and as posted above loading one 3-5 times will tell the story if you primer pocket holds up. My .02
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