[Jeff Higgins]

Well, I learned something new today. I have quite honestly never seen .45 ACP brass with small primer pockets. I wonder what the reasoning behind this might be. The only reason I have ever heard to justify their use on cases that would otherwise accept large primers is an attempt to greatly increase pressures. The small primer pocket allows for more material to remain in the case head, which will hopefully allow it to contain increased pressures better.

The .45 ACP is about the last candidate on Earth for this kind of "hot-rodding". The most common pistol in this caliber, the old 1911, leaves a good deal of the case unsupported at the bottom of the chamber, just in front of the case head/web area. Any significant increase in pressures over SAAMI specs will blow this portion of the case out, sending hot gasses down the magazine well and sometimes even blowing the magazine out the bottom. Exciting stuff. Too exciting for me.

Jim, flattened primers are a poor indicator of pressures, particularly in a low pressure pistol round. It may be a valid approach in some higher pressure rifle rounds (and even there it is very questionable), but primers just will not even begin to flatten in "standard" (non-magnum) pistol or revolver rounds until pressures are well past maximum acceptable levels. Pistol primers do have softer cups than rifle primers, but they still will not flatten until it's too late.

"Standard" pistol rounds opperate in the roughly 12,000-18,000 CUP range. "Magnum" revolver rounds can hover around 40,000 CUP, with the .454 Casull topping out well over 50,000 CUP. It will flatten pistol primers even in safe loads, hence its requirement for small rifle primers. It will even flatten some of those in perfectly safe loads. High pressure, bottle necked rifle rounds run well over 50,000 CUP as well. Some combinations flatten certain brands of primers long before they reach safe maximum pressures. Some will exceed 70,000 CUP before flattening a primer. Yikes...

Anyway, back to your primers, Art. Even with the small primer pockets, I would stick with the standard primers. Unique will never need a magnum primer. If you have access to a chronograph, it would be interesting to shoot both loads - standard and magnum primers - and compare velocities. In my experience, the magnums will provide both higher velocity and a good deal more shot-to-shot variation when used with a fast burning pistol powder such as Unique. They really only come into their own with much larger quantities of much slower powders, like H110, W-W 296, and Alliant 2400. More velocity = more pressure (when other components remain fixed), so be careful there. More variation = an indication of something out of balance. In this case, for lack of a better description, "over-igniting" the powder charge. I think you will find the standard primers more consistant with Unique, and therefor more accurate.