Originally Posted by scooter123

It's quite possible for a powder to have the internal ballistics change without any change in the burn rate.

For example if the manufacturing process or formula is changed there can be a corresponding change in the Density. When that happens if you don't change the volume of the powder measure you are using you can see a large change in the produced velocity. It' something that drives me a bit nuts in the Shotgun World. Every time loads are discussed it's "you should use bushing X for that load and bushing Y for this load". Ask them how many grains you get with Bushing X and you get a blank stare. What is really scary about this is that current bushing tables can be 10 or 20 years out of date and I've talked to some folks who are using bushing tables published back in the 1950's because it's what their father used. Folks you need to get a scale so you know the weight of that powder charge because relying on bushing tables is potentially dangerous.