Potent Powders

Guns Magazine, April, 2000 by Charles E. Petty

Powder selection for 38 Special hand-loads may well be the most difficult part of the load creation process. In one sense almost any fast-burning powders will work in the .38 Special, but the low charge weights leave an awful lot of empty space under the bullet.

The .38 Special originated in the days of black powder and it took a fair bit to get it up to speed. It's hard to believe, but the .38 Special was once considered to be quite powerful. The danger, however, is that all that leftover space makes it very easy for a double-charged case to get by unnoticed.

Chances are, you've heard of something once called, "the Bullseye Surprise." The "surprise" came when a gun ostensibly shooting a charge of 2.7 grs. of Bullseye with a 148 gr. wadcutter would experience a catastrophic failure. Reloaders initially claimed that the powder had detonated, causing the disaster.

We still see such claims today and I've seen articles discussing the problem in other magazines. There's only one thing wrong with this scenario. Metallurgical examinations of guns that supposedly detonated do not show that type of high-pressure failure.

It is easy for a trained metallurgist with only minimal equipment to tell the difference in the fracture patterns of detonation compared to simple high pressure loads. The other flaw in the detonation theory is that despite repeated efforts it cannot be duplicated in the laboratory -- and believe me, they've tried.

The definitive work on this subject was done by William C. Davis Jr. and published in the December 1978 issue of the NRA's The American Rifleman. In the article, Davis details the tests done by the NRA, H.P. White Laboratories and Hercules (now Alliant) Powder Co. all of which attempted to duplicate the catastrophic failures. The test load was 2.7 grs. Bullseye (which remains a standard) with a wadcutter bullet.

Even when the equivalent of a blasting cap replaced the primer, detonation could not be achieved. Then they tried double charging cases to 5.4 grs. Even then -- although pressures were considerably higher -- catastrophic failure levels were not reached.

It wasn't until they combined a double charge with seating the bullet 3/16" below normal that pressures capable of destroying guns were reached.

Although it happens very quickly, gunpowder burns. Detonation is a much faster phenomenon, which does not occur until the powder burning rate approaches 15,000 to 25,000 fps.

Davis' work reports that, under normal conditions, Bullseye burns at a rate of 3.6 inches per second at 10,000 psi. Burning rate is influenced by pressure and increases as the pressure rises, but the maximum burning rate for Bullseye is 30 inches per second at a pressure of 100,000 psi. This doesn't even come close to detonation velocities.

I've asked engineers and powder experts at just about every manufacturer if they had ever seen a documented case of detonation in a small arm. Their answer has always been no.

Since burning velocity increases with pressure, it is possible, in theory, that if enough powder was confined to allow it to burn and accelerate long enough, pressure might reach the point of detonation. This would take a quantity of hundreds, if not thousands, of pounds of powder to accomplish; however, it isn't going to occur with a few grains.

These reports are not limited to Bullseye either. I've seen other reports naming several common handgun powders. The claim of detonation doesn't hold up for them either. Remember, Bullseye is one of the fastest burning powders we have. If it can't reach detonation velocity, how could one that is even slower?

Of course the detonation theory is very popular because it places the blame somewhere other than on the shoulders of the reloader. When one of these wrecks occurs, the offending cartridge is destroyed so we can't prove that it had a double charge. The metallurgical evidence, however, is almost always conclusive, but few shooters have the training to look at the remains and see that the catastrophic failure was caused by excessive pressure.

As with any other activity corresponding to the laws of physics, attempts to push the handloading envelope can have disastrous consequences. Obviously people don't deliberately double-charge cases but it doesn't always take that much effort to cause problems. Lots of people reason that a grain of powder is a tiny amount so one little grain couldn't possibly do much harm.

In terms of quantities, one grain is 0.002 ozs. or 64 milligrams and that surely is a little bit. However, we're talking about a very energetic material composed, usually, of nitrocellulose and nitroglycerine. It doesn't take much to go from "just right" to "too much."