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any load change to switch from 124 gr JHP to 124 gr FMJ


cecil
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for obvious reasons i had to switch from 124gr JHP bullets to 124gr FMJ bullets to load for 9mm minor..

my question will i have to adjust my powder load from what i am presently using ? which is 5.0 gr WST to 1.15 COL - 1011FPS

thanks,

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Great question, I am in the same boat as you but I use Win 231. If you get some feed back I feel sure we can get a good load. I am thinking 4.5 grn. 231 the adjust oal to the difference between JHP and the new FMJ

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Not an expert here, but besides the 'best' load being potentially different, you need to consider not necessarily the OAL, but the case volume and bullet setback with each projectile.

If your FMJ projectile is longer than your JHP is/was, using the same OAL will result in less case volume and further setback into the case, increasing pressures. If it's the same length, you should be fine, although possibly not the ideal load.

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A little off topic:

1.15 COL - 1011FPS

You're currently running a 125.3 power factor (at declared bullet weight)? That's playing it pretty close.. a slightly different chrono, one low charge, or a bullet weight not up to spec.. you shoot for no score

You might weigh a few bullets.. see if they're really 124 or a little over

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This won't directly answer your question, but it is what I have experienced and might be an indicator of what you may see -

I load 124/115gr FMJs and JHPs primarily for .38 super and at major velocities I've consistently found the JHP version to be slightly faster than the FMJ version by about two power factor points. So, for instance I'll get 168pf from FMJs and 170pf from JHPs using the same charge weight and powder. This difference seems to be consistent among the powders I use (N350, AA7, SR4756). Also, I've experienced this with the FMJ and JHP bullets seated at the same OAL (1.250) and at my typical OALs (1.235-1.240 for JHPs, 1.250 for FMJs). I've dabbled with the CMJs and they seem to be the same as the FMJs as far as velocity/vs powder charge goes.

Good Luck and post your findings!

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