Gun Notes: High Pressure Loads
by John Linebaugh
Time-proven technology along with metallurgical and propellant advancements have given the modern shooter the greatest boost in performance ever witnessed in history. Every serious sixgunner knows the .357 was the first "high pressure" loading in the great country. It stood as KING for 20 years until it was replaced with the .44 Magnum. Both of these rounds were loaded to approximately 40,000 CUP levels.
Dick Casull started the very first experimentation with real super guns in the late 1950's and after 20-plus years of work and experimentation finally realized his dreams come true when Freedom Arms began producing his fine .454 Casull revolver. Others followed the "high performance" game and we now have the greatest assortment of sixguns and 5-guns to be found in the world available to us.
Many shooters stayed with their standard .44 and .41 Magnum revolvers but over the years have "crept up" on heavier loads, many through their own experimentation or the urging of other's printed results. The trend now is for heavier bullets and higher velocity. This is all fine and well if the overall picture and results are kept in perspective. But one one must remember: Nothing comes for free, and, Walk! Don't run! in the search for increased performance. Perhaps this sounds a bit dogmatic coming from the maker of some of the biggest-bore revolvers in the world. But in 10 years of sixgun building and experimentation we have seen a few results most shooters will never see.
Hardly a day goes by here in the shop that we don't receive a phone call that the subject doesn't finally turn to heavy bullets in .41 and. 44 Magnum revolvers. Many seriously ask "Why can't I just 'heat up' my .44 and keep using it?"
The answer is, you definitely can. But keep in mind the gun and caliber limitations. Just adding more powder isn't the answer. Just getting more pressure isn't the answer. And often times even if you do gain more velocity through your efforts, it still may not be the answer to increased performance. About 8 years ago I had just finished a .45 Colt on an old Abilene frame. Barrel length was 7 1/2 inches and the 6-shot cylinder was oversize in diameter and full frame length. Our load was 30 grains of Hercules 2400 and 225 gr. Speer JHP. Our goal was 2000 fps, just like Dick Casull called for in the .454. Velocity was in the range of 1700 fps so more powder was needed. We ended up shooting 36 grains of 2400 and our top velocity was 1960 fps. We never did reach the magic 2000 fps goal, but did knock several nickel-sized corks out of a 5/16' steel plate.
From what I know today after studying pages of pressure-tested load data and comparing powder performance and pressure curves, I believe we were shooting loads well into the high 50,000 CUP level that night. This kind of pressure in this barrel length should have given us 2000 fps +. But it didn't. The gun was tight and built right. It did its part. It was a few years later before I fully understood what was taking place. In this application the lightweight slug wasn't offering enough resistance to make the powder work to its full potential. It has been our findings that it is much easier to get more velocity with heavier slugs than with light ones.
More pressure is generated of course, but the powder works better and more consistent results are the norm. But the serious condition exists when we add more powder and the pressures go up, but we don't get more velocity in return. Impossible you say? Modern powders are great propellants but have their limitations. Each powder is designed to operate within a certain pressure level. If you apply said powder below its "happy" pressure level it will give disappointing results. Hangfires and even misfires can result. Load the same powder in an application that is not harmonious with its personality and it will develop pressure well off the scale compared to the velocity you get in return.
This application or condition can be created by caliber, by too heavy a bullet, or (a REAL culprit), too heavy a bullet that is seated too deeply into the case. All three of these conditions add up to one major overlooked condition and that is "capacity". CASE CAPACITY. All powders need enough "room" to work properly for their application. By using a lot of slow-burning powder under extremely heavy bullets, results can vary from excellent to questionable.
The trend among handgun shooters today is heavier and heavier slugs. All cartridges have limitations and balance points. I've said it before that the 300 to 320 gr. is absolutely the maximum weights I will use in the .44 caliber. The 350 gr. weights are the maximum in the .45 Colt. With weights beyond this in guns of a "NORMAL" cylinder length (which limits the overall loaded cartridge length) length begins to crowd the case capacity and seriously affect the volume the powder has to work in.
Some may argue that their charge of 296 will act the same no matter how it is compressed. And it is true that this powder and its brother H-110 work best under mild compression. But when we push our powder charge well into the bottom of the case and cork it with a slug too long and heavy for that caliber we are changing several things.
We change the "dwell time" - the time the bullet sits in the chamber (after the powder is lit) before it starts to move. The more time taken here the sharper the pressure curve becomes. The reduced capacity limits the working area of the powder which means it has to try and do its normal amount of work in a less than normal space.
We also change the burning rate. With retarded bullet movement due to excess bullet weight the burning rate of the powder increases (it burns faster) generating more gases and vicious circle is created.
And we change (or "shift") the problem area to the gun. The quick pressure curve that now lasts longer than normal due to increased dwell time, and the faster burning rate which generates more gas and more pressure than normal, hits the gun in the cylinder right at the base of the bullet. I have seen many cracked and blown cylinders to prove the blowup starts in the bolt notch. The greatest part of the pressure is put on a small part of the cylinder, usually near the bolt notch. With a normal type load of proper bullet weight - not seated too deeply in the case - the pressure curve should flow through the cylinder well into the barrel throat and frame.
For a moment, think of your cylinder and barrel frame area as a stack of washers with chambers and bores through them. If pressure was exerted through the whole stack, say for nearly 2", wouldn't that be stronger and safer than trying to apply the same amount of pressure on only the first few washers?
Thousands of rounds of testing here have proven to us that gun life is better with safe heavy loads using slow powders than it is with light loads using fast powders. Case life agrees. The fast powders "hit" the gun very quickly and the slow powders "take up the slack" so to speak, slower and with less hammering effect.
I have measured one of my early .500's on a Ruger frame recently that I know for certain has had over 1000 Proof-Class loads and a few hundred maximum loads. I cannot measure or detect any movement or wear in the gun. All loads used H-110 or WW-296 powders.
When we talk of "Proof Loads" here our pressures are in the mid to high 40,000 CUP level. Still well within the bounds of H-110 or WW-296 to operate properly and in a normal manner. Some .44 Magnum loads I see recommended, the pressures, due to bullet weight and case capacity, are clear off the scale for this caliber. I have seen pressure data from special pressure guns that proved to me the loads were not operating properly. By overloading any gun we prove nothing and gain little. Over slow powders too much and soon your gun shows the same signs it will show with fast powders. However, instead of working with mild pressures we are generating excessive pressures.
The visible signs may not be the only damage done to the gun either. Metal fatigue goes unnoticed until something serious happens. The blast and sharp recoil patterns I find with overloads are the worst part of the shooting game, to me. The first few head of big game I shot with a handgun were with full power loads. A few I have taken were with about 1/2 power loads. They were taken just as quickly and humanely as before. Once we completely penetrate a target we cannot do any more. Heavier slugs and more speed help a great deal to accomplish this goal, but everything has its limitations.
In this time when hunters are looked over very seriously and often times unfairly, we need to put our best image forward. Safe hunters, safe gunhandlers, and safe HANDLOADERS are needed to teach our young shooters of tomorrow.