Re: 300 Weatherby mag Handload
The problem you will run into using retumbo with the 180 grain and lighter bullets in the 300 wby is you run out of case capacity and will have a very compressed load. A faster powder would be better. Something in the h4831, re22, imr 7828 range. Retumbo will work you will just have a very compressed load with a very full case. Your 80 grain load of retumbo is way to light a load for the 300 wby with 86-88 grains being a good load but you will be crunching powder.
Predictions are difficult, especially when they involve the future