Mixing diferent Lots of the same Powder

[Montana Cowboy]

Howdy All
I also have read the same 3% figure and can't remember where I read it. Been reloading for 30 years and have done the same thing mixing what was left in the old can with the new can of powder. There isn't enough powder in the old can to load one shell so mixing it wit a pound of the new powder isn't going to cause a problem.
Like a lot of folks here I buy 8 lb kegs so load development isn't a big issue with me.
If I remember correctly it was an artical about how powder is made and how the manfacture go's to great care to make sure that there is very little lot to lot variation from one lot of lets say IMR 4350 to the next lot of IMR 4350 powder. As was stated there is some difference and that is why they have the caution to reduce your load or start over at minimum load and work up when opening a new can of the same powder but different lot number. Was a back issue of the American Rifleman or Shooting times magazine where I read the 3% figure. MC