This one is hard for me to understand, had very good performance using a horandy 40 grain vmax and have worked a load the barrel likes. Picked up some 39 grain sierra just to try and assumed they would be similar. Nope...all over the target. They are loaded with identical powder charge, cases, primer and oal. Did notice they are shorter bullets than the vmax.

This has been a monkey on my back leaning to load. Had this happen with the .243 but not to this extream. It was more forgiving than this .20 caliber. What are the physics of this? Alchemy? Hate wasting time and doe.