Mike Wiskey...Why would LR Magnum Primers give you

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less velocity when used in conjunction with faster burning powders (vs using standard Large Rifle Primers)? I'm curious as to what causes this to happen.?.? I like to understand how/why things work they way they do. Thanks for any feedback you can give me.

MIKE WISKEY

FROM MY (LIMITED[;)]) UNDERSTANDING IT HAS TO DO WITH FLAME DURATION. STD.=SHORTER, MAG.=LONGER. THAT AND SOMETHING CALLED 'BRISIEANCE' (SPELLING?[xx(]). LARGER QUANTITIES OF SLOWER BURNING POWDERS NEED A LONGER IGNITION TIME TO 'LIGHT-UP' PROPERLY. MY TESTING WAS OVER AN OEHLER 35P WITH THREE SKI SCREENS. I WAS TESTING LOADS FOR THE .30/06 AND HAD 50 FPS LESS VEL. (AND A LARGER S.D.)WITH MAG PRIMERS WITH A MED. BURNING IMR POWDER.

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quote:Originally posted by MIKE WISKEY
FROM MY (LIMITED[;)]) UNDERSTANDING IT HAS TO DO WITH FLAME DURATION. STD.=SHORTER, MAG.=LONGER. THAT AND SOMETHING CALLED 'BRISIEANCE' (SPELLING?[xx(]). LARGER QUANTITIES OF SLOWER BURNING POWDERS NEED A LONGER IGNITION TIME TO 'LIGHT-UP' PROPERLY. MY TESTING WAS OVER AN OEHLER 35P WITH THREE SKI SCREENS. I WAS TESTING LOADS FOR THE .30/06 AND HAD 50 FPS LESS VEL. (AND A LARGER S.D.)WITH MAG PRIMERS WITH A MED. BURNING IMR POWDER.



Thanks for the info.

Rocky Raab

There is actually no way to predict the result of a change in primers. The load could develop higher pressures and velocities, lower or have no change. It could conceivably even develop higher pressure but lower velocity. The interactions during those brief milliseconds of combustion are not very well known, simply because no direct observation is (yet) possible.

That's why the sage advice for the past century has always been "If you change any component, reduce the charge and test."

Here's a systematic method for doing so safely: http://www.reloadingroom.com/index_files/95S.htm

MIKE WISKEY

well, time for a test. I loaded 8 rds each of hornady 350 gn. f.p. bullets, r/p cases/ 56.0 gns of imr3031 and fed. 210 and 215 primers. I shot then with my 24" siamese mauser over Oehler (35p)screens on 4' spacing and the results are in
fed. 210's had an ave. vel. of 2116 fps, with a s.d. of 19;
fed. 215's had an ave. vel. of 2121 fps, with a s.d. of 12;
........just about dead even.

JustC

"Brisance" is the amount of and lenght of time of, the flash from the primer. This is why you experiment with primers after you are satisfied with your load. Look at the new Palma cases, a 308 with a SR primer pocket/flash hole.