Another question, just how fast do you shoot, how many shots before you stop? Are you going to let the barrel cool completely between groups? How many consecutive shots before you clean the barrel?
The following is a system that I have evolved over twenty five years. This is a person opinion and suits my requirements; it may not be suitable for you, the reader. However it has produced reliable accurate ammunition to my standards, consistently.
Load a minimum of three/five cases for each powder load, usually five different charge weights is sufficient, working from the lowest load. Increase powder charges by 1/2 grain, or if a smaller case, 1/3 grain increments for each load. Firing commences with the extracted/calculated minimum powder charge shooting over the chronograph. As the powder charges increase the group size should tighten up as you approach a specific load, usually below the maximum.
Having reached this peak the group will tend to increase in size. This optimum should be shot several times to confirm that the original was not mere chance. Each shot is fired at a comfortable pace without excessive haste. All shots that are “pulled” should be noted. Records should be kept of group size and average velocity.
After each three/five shot group the rifle is removed into the shade and the barrel is allowed to cool to ambient temperature.
The barrel is cleaned whilst warm at the end of each nine shots (three shot groups), or each ten shots for five shot groups. I believe that it is important to use the same cleaning procedure after each group or groups. Once the wind starts, even the faintest breeze, stop shooting. I will admit that I am not experienced enough to read the wind, very few shooter’s are. Accumulated data needs to be recorded as shooting is likely to be spread over several days.
In addition to short term needs such data can be useful at a later date and can prevent repetition. Be aware that there will be some variation in velocity with changing temperatures. If you have shot, say five groups, there will be sufficient initial data to indicate if you should proceed with this powder. If the groups are not getting smaller and if the increased powder charges are producing rapidly decreasing velocity gains I would suggest that it is time to consider another powder. You will have to re-shoot the whole process. I am assuming that you will continue to use the same projectile and primer. Large variations in velocity may be caused by low loading density.
It is obvious that most factory cartridges are flexible about the type of powder used whilst some wildcat designs are a little more stringent in their powder requirements. There are good reasons for this state of affairs.
When developed many of these designs lacked the two vital items that made them, equal to, or better than factory cartridges of similar size and capacity. They were heavy projectiles in relation to calibre and slow burning powders to propel them.
Remember each rifle is a law unto itself. Should the chronograph show velocities well below averaged book values, a further one or two increases in powder charges may be justified. You just need to proceed with caution and look for realistic values. Added velocity is useless if groups continue to grow in size.
Actual velocities compared with averaged book values will indicate when you are approaching maximum loads for that rifle, plus of course all of the usual pressure signs. If you are comfortable with your initial results they need to be confirmed by at least a further two groups of the best load, again in windless conditions.
I do not claim that my particular process is better than any other. It is merely a starting point to develop a system that you are comfortable with. Three important points.
If you are going to do a lot of load testing a chronograph is, I suggest, vitally important, without one you are just guessing. Mine is a plain vanilla model that only gives velocity, nothing more. It is sufficient for the task required.
Secondly, a good ballistic computer program is, I suggest, also a requirement. And finally, if meaningful results are to be obtained keep accurate records.
I came across the following in an old issue of Handloader magazine that seems to sum up the whole process of testing rifles and ammunition. No 6. Page 57. “Too often assumptions are accepted as fact simply because no other reason is apparent. This I feel is a mistake. To speculate is one thing, to make a statement of fact is quite another”.
Shoot safely. Matthew Cameron is a retired Australian Airline Pilot who flew domestically within Australia and Internationally out of South East Asia. Interested in long range varminting and pig shooting for many years, he reloads for a variety of calibres and has written articles on reloading and associated subjects since the early 1990’s, published in Australia, South Africa and New Zealand. In the last few years he has enjoyed bench rest shooting and gliding when not reloading or writing.Join the discussion of this article with the author HERE at the Article Discussion Forum.