I did a cursory test as a teaching opportunity 8 or 9 years ago with a new rifle shooting student/mentee using 55 grain Vmax bullets. This bullet is widely available in factory ammunition from multiple manufacturers; factory loads from HSM, Hornady, Underwood, and Remington (labeled as “Accutips”) which all use the 55grn Hornady V-mac were fired against the coarsely developed handload we picked from the book. Despite all 5 loads using the exact same bullet, none of the 5 had the same POI, and the test proved considerable variance for group size. Given any of the factory loadings, he assuredly would have believed his newly built custom AR was a lemon - delivering 1.5-2” groups at 100yrds, while the haphazardly developed (no seating depth test, just 10 thou jump and a 80% max book charge weight) printed 5 rounds inside 0.7” three times in a row.
Such is the reason so many of us cede so many hours of our lives to reload even our low volume hunting ammunition, rather than choosing the convenience of factory ammo.