One of the more interesting questions I’ve received lately had to do with handloading shotshells. The reader was aware that recipes using slower-burning powders, such as LongShot, can produce faster velocities without exceeding pressure limits than a fast-burning powder, such as Red Dot. He wanted to know why a rifle powder couldn’t be used to provide even faster velocities from shotguns.
The reason you don’t see rifle propellants slower than LongShot, Lil’Gun, H110, and W296 recommended for shotshell loading is primarily because rifle propellants are designed for very different pressure regimes than are shotshell propellants. They must work differently to succeed in their respective pressure environments. It’s not a simple “one-reason” issue, but the really big hitters in this difference can be explored with this analogy.
On your concrete shop floor are two toolboxes that weigh the same. One’s base is fitted with rollers and the other’s fitted with metal skids. To move either, you must overcome two physical forces: inertia and friction. Inertia is the property of all matter that causes objects at rest to stay at rest; friction is the physical force created when two objects or surfaces resist rubbing against each other.
Both toolboxes have inertia, but the one with rollers will experience trivial frictional forces against the floor. It needs but a short, fast push to get it moving and keep it moving. The one on skids needs a long, slow push to overcome both inertia and friction and commence moving. Once moving, the box on skids also requires more energy to maintain motion against the effects of friction.
In ammunition, a shotshell is the toolbox with rollers, and a rifle cartridge is the one on skids. Inertia is the big issue with shotshells; they must move 5/8 ounce (273 grains) or more ofpayload. However, frictional forces are rather low in shotshells. Once you overcome the payload’s inertia, a plastic wad sliding in a loose-fitting plastic case offers only modest resistance compared to a metal-jacketed rifle bullet exiting a metal case and entering a tight barrel throat. Inertial forces in sporting rifle cartridges are usually less than shotshells but are offset by much higher frictional forces.
The plastic crimp in a shotshell is relatively easy to overcome. A crimped rifle case requires much more force to overcome. In addition, it takes much less force to move plastic down a smooth and somewhat loose barrel than to move a copper object through a tube that is both snug-fitting and rifled.
Inertial and frictional forces are the major reasons that shotshell propellants are engineered for the short, fast push and rifle propellants are designed to create the long, slow push. There are obviously other factors, such as velocity/energy goals, cartridge case and firearm strength, and the physical shape of the charge in the case, but these are small compared to inertial and frictional forces.
If what the reader proposed really worked, I’m pretty sure the shotshell data developers would have let us know by now.
Reduced-Recoil .44 Magnum Loads?
Another reader’s question had to do with making reduced-recoil loads for a .44 Magnum revolver. The reader was contemplating using plated bullets, and he wanted to know if using a .44 Special max load, such as 7.0 grains of Unique, in .44 Magnum cases and working up from there would be advisable. He commented that even minimum .44 Mag. loads seemed to produce a great difference with the same bullet and powder than maximum loads in the .44 Spl., sometimes about 300 fps according to his manuals.
His question about using .44 Spl. loads as starting loads for reduced .44 Mag. loads raises an important but too-often-overlooked issue: Too little pressure can cause almost as many problems as too much pressure.
The least of the evils of too little pressure is inconsistent ignition, resulting in wide swings in pressure and velocity. The worst possible outcome is sticking a bullet in the bore, potentially ruining a fine firearm. Low pressure causing a bullet-in-bore (BIB) condition is much more likely in revolvers and also when using revolver cartridges in rifles/carbines.
There are so many variables involved that for safety under a wide range of conditions the rule “Use Only Published Data” exists. All bullets are not created equally when it comes to sliding down a rifled gun barrel. A heavily lubricated cast lead bullet like the RCBS 250-grain SWC I used in the .44 Mag. loads in the Speer Reloading Manual #14 will generate much less frictional force in the bore than a plated or conventionally jacketed bullet. If he were to try using maximum .44 Spl. loads as start loads for the .44 Mag. with a plated or a jacketed bullet, he could very likely encounter a BIB condition.
Likewise, differences in propellant burning rates enter the picture. If one attempts what the reader proposed with slower-burning propellants like 2400, Accurate No. 9, H110, W296, and others, he would almost surely find himself at the bench trying to remove a stuck bullet from the bore.
In the .44 Mag. loads discussed, I had tried 8.0 and 8.5 grains of Unique before working at Speer but found too much variation in velocity. When I saw the data from a Speer pressure barrel, I could see that my 9.0-grain load was just above the low pressure threshold for consistent performance, which instantly explained the problems I had with the lighter loads.
In .44 Spl. the maximum load of Unique with the same bullet was 6.9 grains—far under the .44 Mag.’s pressure that I consider appropriate for proper performance. Looking at cast-bullet data for .44 Mag. in the Speer Reloading Manual #13 and #14 shows the start load for Unique is 9.0 grains, set not by my informal experience in my pre-Speer days but by hard pressure test data.
To experience .44 Spl. velocities and recoil in the .44 Mag., simply load lubricated cast lead bullets in .44 Spl. cases. I’ve fired thousands of such handloads, and they are accurate and showed no ill effects.