Maximum loads and pressure: going over the top in handloading

There are many good reasons why you should not exceed the maximum loads specified in reputable loading manuals, but the reality is that you have no way of knowing the actual pressure developed by a particular load under your specific circumstances. Every barrel is a law unto itself!

In fact, you may not even see pressure signs before you reach a specified maximum load. 

When pressure signs appear, you are already in the danger zone. It is a warning to back off the load. As one gun writer put it, if you make a mistake and load half a grain over or so, it is unlikely that you will blow your rifle to bits, but there is a difference between a mistake and a deliberate action. 

I have read some who claim that it is necessary to know what your maximum load is. Perhaps it is an individual choice, but I would rather stop at the point where maximum accuracy is achieved. In my experience of more than 35 years of reloading, with only a couple of exceptions, the most accurate load is achieved with a couple of grains under the recommended maximum and, in one case, one grain under the starting load.

OVER-THE-TOP PERFORMANCE?

You have to be immediately suspicious if a loaded round produces velocities over what the manual(s) suggest. The extra speed can only be a result of increased pressure; while the value may be unknown, it has to be there. 

If your bullet’s velocity is excessively slow compared with the manual’s figures, rather than increasing the powder charge, a change to another powder would be a more appropriate choice. Perhaps you should start with a powder that is midrange for a particular projectile weight.

Further, there are so many variables relating to generating pressure within a cartridge case that there have to be allowances to cover all situations. Aside from many other considerations, the structure of barrel steel differs (even from the same manufacturer) and again causes variations in pressure. What appears to be a simple science is in fact a very complicated process with infinite variations.

In the long run, the powder manufacturers do the hard work for us by testing the potential combinations. They then predict, via multiple testing regimes, which powders are most suitable for a particular case when matched with specific weights and/or classes of projectiles. 

Of course, there are safety factors built into the process, but that is not a licence to exceed the maximums in order to seek better velocity.

PROCEED WITH CAUTION!

How do you then develop a load for a wildcat case without any reputable loading data? The key issue here is research. Probably the powders used overseas will not be available here; try to find powders with similar burn rates. Modern computer programs can assist by suggesting powders for a particular combination.

When working up a load, I think it is best to stop when the accuracy peaks. Usually, groups will reduce in size with an increasing powder charge and reach a minimum; thereafter, they will start to open up again. 

There are good reasons to respect the load development rules; properly followed, they will prevent disaster.