Rim Rock 25 ACP Boolits - Request and Info

[ButchC]

Howdy all, I picked up some Rim Rock ~60gr boolits (57.8 gr, 0.508 long) for the 25 auto a while back and thanks to a few members boosting my brass supply, I've set about to see how close I can get to Buffalo Bore's HEAVY 25 ACP loads (same boolit, in the neighborhood of 850 fps). Now I started out working in Gordon's Reloading Tool and have a Bullseye load to test at 1.1 gr, keeping in SAAMI spec (0.890 OAL, 25k psi), this is predicted to run around 760 fps (21k psi, 2.4" Jetfire).

While Bullseye Rim Rock offer an external ballistics improvement over factory ~750 fps, 50gr FMJ, I'm naturally inclined to think there has to be another way available to us without R&D equipment.

Looking through some old Alliant data, I see Green Dot as an option with a boost in velocity. Naturally, Gordon's does not have a Green Dot profile. Would someone with QuickLoad be kind enough to take a look at appropriate charge weights for GD with the above parameters and clue me in on where the line in the sand appears to be with pressure and charge weight? If I can't hit the 850 fps mark, no problem, if I can safely go over, great! Either way is piece of mind as those of you like me will recognize this sort of question will occupy one's brain for days. Thanks!

[ButchC]

OK, some data back: the GRT data is highly suspect, 1.1gr of BE in the above configuration will not provide the 760 fps predicted, a lot closer to 1050 fps. Obviously, this is ridiculously overpressure, the anvil imprinted and odd blown primer will back up the statement. GD at 0.9 gr, while closer to 1000 fps is not the way to be either. Upon seeing these numbers, I confirmed the chrono wasn't nuts with some PPU factory in the 760 fps ballpark.

Some further information from this saga: case capacity seems to vary a small but significant amount between manufacturers so plugging a reference value in to a model like GRT is likely to cause problems. Notably, I used a measured volume as opposed to whatever spec I could locate through the web.

[ButchC]

Today's update, 0.6 gr of Green Dot (2nd case from the left) will produce 817 fps, 0.5 gr Bullseye (3rd from the left) will deliver 780 fps. The first case comes from the 1.1 gr of Bullseye, and the last trio are factory PPU.

The sharper imprint from the firing pin/definition of the anvil in the reloads, baring any other information, leads me to believe pressures are still elevated with the reduction in charge weights for this test batch. Granted that may be dependent on WSP cup hardness vs whatever PPU are using.

For someone else looking for a starting point for the 60gr boolit in 25 auto, I'd recommend starting charge weights below half a grain for a suitable powder (then again, I dont know what constitutes "too low" with such a small volume) . Accurately and consistently measuring such small weights may present a challenge however.


Software models may not have a good pressure estimate, but perhaps someone will jump in with a value in time. Pressure testing may well be the only other appropriate means of developing something safe and functional for this weight with a known value unless the powder companies just happen to be sitting on the data, admittedly I have not inquired for the purpose.

This project emphasizes how tight tolerances need to be when working outside the normal parameters and published data for a small volume cartridge. I'd be wary of all of this data of I were you. Obviously, use thereof is 100% at your own risk as a change in primer or case manufacturer could make things real interesting real quick here, nevermind age and construction of your firearm.

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[barnetmill]

60 grain bullet and case volume variability. you need some way to classify the cases by volume. Weighing the cases might indicate differences in volume and allow them to be sorted.