Originally Posted by Steve Redgwell

When someone experiments and deviates from published load data, they are going into unknown territory. Doing this takes some skill, and in almost all cases is unnecessary. Relying on chrono readings alone isn't smart. And other tools, like test labs or pressure test equipment, aren't in the hands of many reloaders.


Blind adherence to published load data can get you into trouble also, don't think that you can chuck all caution to the wind just because you can read a cookbook.

Years ago I compared two loading manuals, Lyman and Nosler, for 7mm rem mag data. The powder I wanted to use had a 7 gr. difference listed max load for the 140 gr. bullet I was using. I started low using a chronograph and quickly figured out that the Lyman data was complete bullchit, I hit the listed max velocity in the Lyman manual 4 grains before their max, which was 3 grains over the max Nosler listed. If I had been following Lyman's data I'd have been seriously overpressure and the least, and probably into the blowing primer territory.

If you have a decent chronograph and you're at all familiar with it then you can pretty quickly tell if it's giving you good data. I can pull out my 6mm BR and shoot one of my 30.8 gr. Varget/105 Amax loads across it and it'll be 2860 +/- 10 fps at 70 degrees. If it isn't then something is wrong, but it hasn't lied so far.

Data from your own rifle is far more reliable than data from a min spec pressure barrel. Sure their velocities are accurate for that barrel, but that doesn't mean much in YOUR barrel. Far too much is made of supposed inaccuracies of chronographs, recent ones are very accurate and I'll trust them before I will some data shot in a pressure barrel 20 years ago with different lots of powder, brass, primers, and bullets.

Loading manuals are a guide, nothing more. Anyone that thinks they're gospel is fooling themselves, even the guys writing them will tell you that. Use a bit of common sense.