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PF Loading Puzzler


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Here's a fun one!

I have two pistols for USPSA: STI Edge, and a newly acquired Glock 35, both 40s. (Please, no 1911 vs. Glock blah blah on this thread.) I run 5.9 grains of power pistol for the Edge. Good load, consistent, good load density, even on a cold day meets power factor, 920 FPS.

I figured this load would be a good starting point for the Glock. The glock has a barrel length that is 0.1 inches longer, and I figured that it would shoot a little faster. Nope. I chronographed this load out of the glock at 725 FPS. This was a good reading because I ran the STI during the same session, and it was consistent with past data. Wow, big difference.

I figured that the difference was due to the recoil systems of the two guns. The spring on the STI is considerably lighter and probably better tuned for efficiency. So, I went to my loading manual and decided on 6.4 and 6.6 grains of Power Pistol with a target velocity of 920 FPS. When I chronograped these rounds from the Glock, they were equivalent with past data for the STI when I was developing the above load, roughly 1020 FPS. Too snappy!

Any clue why this could be? Is there a break-in on a Glock that would affect velocity this severely? I will plod along and develop the load, but I'd like to understand why this happened.

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David, your load of 5.9 gr shot 200 fps slower in your Glock? How many rounds did you fire

in that string?

Then, your load of 6.5 gr was 100 fps faster than they should have been in your Glock?

My guess is that you're measuring too few chrono readings, or too few powder charging

grains, or both.

To measure how many grains of powder I'm throwing, I throw five loads, dump the powder

back into the hopper and throw five five more loads - weigh the total and divide by five;

or FPS from my Chrony, I measure

20 actual cartridges and average them.

My guess is that would solve your problem???


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