I read an excellent 3 part series on handloading from the Journal of Mountain Hunting, my favorite part was no. 3 where Darin goes into great detail on the complex topic of load testing and development.
He shows us several ways to develop a good working load using various techniques.
My favorite part is below.
The 12-Step Program
Let’s review some of the key points that will help you evaluate load precision and decide which will produce the best results come hunting season.
- Test seating depth first and use the best seating depth for ladder testing.
- Test ladders at relatively short range – 100 yards is adequate in most cases.
- Run a pressure ladder to evaluate the range of viable charges and avoid loading multiple rounds that would have to be disassembled later if pressure signs show up before load book maximums. My rifle showed pressure signs 2 grains below Berger’s listed maximum.
- Test loads in 1% powder increments or finer to evaluate 5-7 charge weights in three to five-shot groups.
- Consider using a tool like the $12 On Target Software to analyze your groups.
- Consider average distance to center (ATC) to evaluate precision of each load.
- Look at group size (extreme spread), because the worst case should always be considered and understood. This will help you understand your rifle’s capabilities and make informed decisions on ethical shot distances.
- Consecutive ladder steps that produce group centers close together often (though not always) indicate pressure insensitive charge weights that can produce optimum results.
- If possible, utilize a reliable chronograph and record velocities for each shot. Look for low velocity spreads to improve long-range accuracy.
- Always verify the best loads from ladder testing with additional 5 or 10-shot groups to more thoroughly test those charges.
- In the final evaluations, a primer change can sometimes reduce velocity spreads and tighten up groups even more. However, if you’re already loaded near max pressure, it’s always a good idea to back the charge weight off by a grain or more because primers can dramatically affect pressure, and in some cases, cause a dangerous pressure spike.
- Once you’ve determined the best load for your rifle, always go out and shoot your rifle in field conditions at longer distances to confirm your bullet drops and ensure that you and your rifle are well prepared to make ethical shots at the ranges you plan on shooting.
This technique and set of processes is one way to go about load development, we suggest doing the load testing first and then fine tuning with seating depth, but everyone can choose their favorite way to get to the end result.
It's well worth read, go here for the full article: