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Rifle Magazine
December - January 2004
Volume 39, Number 6
ISSN: 0017-7393
Number 232
On the cover...
The Stainless Ruger No 1 .204 Ruger is topped off with a Leupold Vari-X III 3.5-10x variable scope. Rifle photo by Stan Trzoniec.
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Over the past couple of  years, I have received several questions and complaints regarding reliability issues with .357 Magnum revolvers, due in part to guns and ammunition, so will share some of my experiences and observations, as well as solutions to certain problems.

The .357 Magnum cartridge has been chambered in a variety of guns, mostly of good quality, but there have been a few lemons, not worthy of mention. For the purposes of this discussion, let’s focus on revolvers from Smith & Wesson, Colt and Ruger, which represent the vast majority of guns in use.

The single most common reliability issue with .357 Magnum revolvers is found in the primer and firing pin/recoil shield relationship. Due to pressure, the primer flows one way or another into the firing pin hole upon firing. This may only be slight, but it is enough that it can make cocking the revolver for the next shot very difficult, since the deformed primer drags on the recoil shield, or in extreme instances, the cylinder locks up firmly. We can only imagine the huge problem this could pose for a gun used in a defensive sit­uation.

Until recently, Smith & Wesson Models 27, 28, 19, 66, 586 and 686 were equipped with hammer-mounted firing pins. Often when these guns become “high mileage,” the recoil shield’s firing pin hole increases in diameter and gives primers an opportunity to flow into small, unsupported areas around the firing pin.

If a gun happens to have excess cylinder end shake or headspace, the above problem is magnified. And if the gun has been fitted with a reduced-power mainspring (or has had an action job wherein the hammer mainspring is lightened), again primer flow into the firing pin hole is invited, and the primer can actually push the firing pin and hammer back out the hole. The above problems have been observed with new, unaltered, out-of-the-box revolvers so is not limited to worn or high-mileage guns.

Firing pins that are frame mounted, such as recently manufactured Smith & Wessons, Ruger single- and double-action revolvers and most Colt double actions, generally have less primer flow issues, but they are not entirely excused from problems. In these instances, the firing pin generally locks (or binds) in its forward position and is held forward by the spent primer, again tying up the gun. (Keep in mind that frame-mounted firing pins are spring loaded and should automatically rebound when the hammer is cocked or rebounds.) This problem may be traced to a firing pin of incorrect length, or incorrect headspace, but it is usually traced to loads that are high pressure or a primer that flows excessively. In most instances, guns suffering from the above issues will fire and function reliably using lower pressure .38 Special ammunition.

Solutions

Handguns that have worn firing pin holes, incorrect headspace or firing pin length should obviously be corrected, but if primer/firing pin problems still exist, it can usually be controlled through care­ful selection of components and loads without sacrificing performance. In other words, some shooters reduce loads or pressure to avoid these problems, but I prefer full-house loads in .357 Magnum sixguns but also demand reli­ability. Before discussing specific solutions that have worked in a variety of guns, it should be pointed out that current SAAMI average working pressures for the .357 Magnum by ammunition companies are held to 35,000 psi (which was previously 46,000 CUP) and is wise in my opinion. All loads discussed herein are within that limit.

Generally speaking, Small Pistol Magnum primers are designed to withstand greater pressures and will flatten and flow less than a non-magnum version. The problem, however, is that some powders are designed to ignite with a non-magnum primer and will develop excess pressures prematurely when used in conjunction with a hot magnum primer. An example would include Alliant 2400. According to the Speer Laboratory, 12.5 grains of 2400 behind a 158-grain JSP bullet and capped with a CCI 550 Small Pistol Magnum primer produced 1,089 fps and just under 35,000 psi from a Smith & Wesson Model 19 with a 6-inch barrel. By switching to a 500 Small Pistol non-magnum primer (and using the same bullet), the powder charge was increased to 14.8 grains for 1,265 fps and produced the same chamber pressure. So, if we select a magnum primer with its harder cup to prevent primer flow but use it with a powder designed for non-magnum priming, the increase in chamber pressure will probably make the primer flow anyway, not to mention the extra wear on the gun due to increased pressure. There are many other excellent powders commonly used in the .357 Magnum that perform better when ignited with a non-magnum primer.

On the other side of the coin, there are certain powders that need a magnum primer to obtain reliable ignition and prevent erratic ignition spikes or squib loads in cold weather. One example is Winchester’s 296 Ball powder, which has become popular among magnum revolver shooters, as it gives high velocities while maintaining pressure levels that are within prescribed limits. It is generally best to use the type of primer (magnum or non-magnum) the powder manufacturer recommends, which will help prevent excess chamber pressures.

Most Small Pistol primers (both standard and magnum) have a cup thickness of between .015 to .020 inch, but their thickness has little to do with how easily they are ignited or how they flow around the firing pin, as each is annealed and hardened to different specifications. Certain standard primers, such as the Federal 100 and CCI 500, generally give good results with loads that generate up to 35,000 psi, and because of their great sensitivity, I prefer to use them when possible. (In this way I can have a sixgun with a slicked-up action and lightened mainspring that still gives reliable ignition.)

If a handgun is still showing firing pin/recoil shield problems, it may be necessary to select a powder (such as Winchester 296, Hodgdon H-110 or Lil’Gun) that is suitable to be used with a Small Pistol Magnum primer. In these instances the Winchester Small Pistol Magnum, CCI 550 or Remington 5 1/2 will give good results and will generally cure most cylinder rotation issues.


In those unusual instances, when a revolver is being particularly stubborn with cylinder freeze-up or dragging, even after trying the above suggestions, we may have to select a Small Rifle primer to cure primer flow issues such as Remington 6 1/2, Winchester Small Rifle and Federal 200. Before taking this step, however, understand that most revolvers will require a full-power (or factory original) mainspring to reliably ignite the tougher rifle cups (designed to withstand substantially greater pressures without deforming). And be absolutely certain to select powders that won’t jump pressures substantially due to the faster ignition of the rifle primer. Again, examples include Winchester 296, Hodgdon H-110 and Lil’Gun, and it is strongly suggested to not exceed recommended powder charges in spite of primers indicating that pressures are low.

Regardless of the primer selected, it is imperative to seat them .003 to .005 inch below flush. This assures that a “high” primer won’t drag on the recoil shield while the cylinder is rotating and prevents the possibility of setting off primers of remaining cartridges during recoil.

In the past few years, certain foreign cases have been observed that had excessively large flash holes and allowed greater pressure to the primer, causing deformation and considerable flowing. Select cases carefully and avoid using mixed brass.

While the focus has been on priming, reducing pressure will also reduce primer flow and flattening. While most commercial .357 jacketed bullets have a single crimp groove, some cast bullets feature double crimp grooves, allowing them to be seated farther out of the case, thus increasing overall cartridge length. This increases powder capacity, while reducing chamber pressures, assuming we are using the same powder charge.

I have an old (1955 vintage) Smith & Wesson Combat Magnum (pre-Model 19) that gives sticky cylinder rotation when loaded with a 165-grain cast bullet (Ly­man mould 358156) seated into its upper crimp groove behind 14.5 grains of Alliant 2400 and capped with a Federal 100 primer. By simply seating the same bullet into its lower crimp groove and leaving the powder charge and priming the same, pressures are reduced enough that no cylinder rotation problems have been detected. With the above bullet seated deeply, with an overall cartridge length of 1.580 inches, muzzle velocity runs 1,398 fps, whereas loads with the bullet seated out to an overall length of 1.670 inches, velocity dropped slightly to 1,379 fps. That’s a slight decrease in velocity but enough of a decrease in pressure to make the old Combat Magnum work smoothly.

We live in a world of tremendous information, but make certain that sources for handloading data are known (as there has been much published data on the Internet from unknown sources that is dangerous). Stay within recommended pressure limits of credible sources. The above tips for assembling reliable .357 Magnum handloads may seem minor, but they have helped my sixguns tick as reliably as Swiss watches.

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