Thread: Obtaining more information from your groups - overlaying groups

The sample size required to have the power to detect whether a load is "better" confidently depends on how much better. If you're trying to detect a 10% improvement, you'd need a very large sample size. 300 rounds? A 25-50% improvement should be visible with 10-20 shots. I'd recommend doing your testing at 100m to remove the variable of wind as much as possible, you'll note your 20rd group is slightly wider than tall - maybe wind, maybe recoil, maybe trigger control, maybe random chance.

It is more sensible to identify your requirements first - then simply select a load that meets those and move on.