Magnum Primers for Standard Pistol Loads
Date: Feb 15 2015
The ongoing shortage of reloading components has been forcing some handloaders to think about things they might never have even considered previously. The last pistol primers available in these parts were small pistol magnums.
Conventional wisdom has long told us to use standard primers for standard loads and magnum primers for magnum loads, and there’s plenty of that reloading data available. However, in Handloader No. 207, Brian Pearce did an excellent job of showing that magnum loads in his .357, even using H-110, actually perform better with standard primers. He also showed that although velocity spreads using standard primers are slightly smaller, the actual velocity difference between standard and magnum primers is insignificant.
But what happens to our favorite nonmagnum loads if we’re forced to use magnum primers? What if things are further complicated by being forced to use some other powder than our favorite because it’s simply all there is to be had? How do various powders react to magnum primers at lower pressures? Do the greatly differing granule sizes and shapes make a difference in how different powders of similar burning speed react to the increased flaming of a magnum primer? I decided to find out now, before the situation becomes any worse during the current shortage – or the next one. Although these are valid questions for rifle loads as well, the subject is restricted to .38 Special loads.
There are many powders that work in the .38. To keep the project manageable, only 10 commonly used powders were chosen. In searching through reloading publications for starting and maximum loads, I became aware of something I had never even considered using in the .38: recommendations for H-4227 and Alliant 2400. These two are normally used for +P and .357 Magnum loads. Slower-burning powders like these are known for needing higher pressure levels to achieve complete ignition. What would happen with these two powders at the lower pressure levels of standard .38 loads with both types of primers? The list of powders to test increased to 12.
All loads were fired in a Ruger GP100 with a 4-inch barrel over a Shooting Chrony Alpha (shootingchrony. com). I also used a Charco Off Duty with a 2-inch barrel to test a few loads of personal interest to see if anything bizarre happened with the shorter barrel. The results are shown in the accompanying table. As a precaution against corrupted data and do-overs, well-used Winchester cases were used for the standard primers, and Federal and Remington cases were used for the magnum primers. The bullets used were Lee’s TL358-158-SWC design (leeprecision.com), cast from one batch of wheelweight metal in a six- cavity mould and tumble-lubed with Lee’s Liquid Alox. Rounds were loaded to an overall length of 1.443 inches.
It was interesting to see that the loads least affected by the switch to magnum primers in the GP100 were the normal loads full of the fastest powders: Bullseye, Red Dot, HI-SKOR 700-X, Trail Boss and Accurate No. 2, and also with slower W-231. In other words, as pressures increased, the velocity increase percentage from the primers decreased. Most unexpected were the powders and charges that actually recorded a slight velocity decrease with magnum primers.
With this data in hand, I decided to also see what happens with the 9x19mm, using the Helwan version of the Beretta 51 made on the old Beretta machinery left behind in Egypt. Starting load pressures with this cartridge are far beyond +P pressures for the .38 Special. A middle-of-the-road powder was chosen, Winchester 231, that showed a little velocity increase with magnum primers at .38 Special pressures; Rainier 115-grain LeadSafe Total Copper Jacket “TCJ” bullets (rainierballistics.com) were used for these. As can be seen in the table, the velocity increase percentage actually decreased to nothing as the pressure from a larger powder charge increased. For the sake of comparison, three different 115-grain FMJ factory loads were also tested.
From all this, my conclusion is that substituting magnum pistol primers for standard primers is a nonissue. Perhaps Winchester has been trying to tell us the same thing for years, if we would only pay attention. Long ago it quit making two types of large pistol primers and now makes only one large pistol primer to be used with either standard or magnum loads. If you want to be cautious, simply do what astute handloaders do anyway whenever they get a new lot number of powder or primers: Go back to the recommended starting load and work back up until you find happiness.