ORIGINAL: bigbulls
You better listen to vangunsmith.
18 - 30 grains of powder in a case the size of a .270.
You could blow something up real quick.
When a cartridge is under loaded or reduced it can result in a blown up firearm because the powder lays on the side wall of the cartridge and creates a large void and instead of the primer igniting the powder fully from the rear as it would with a full charge and where it is suppose to it sends sparks to the front of the case as well and also ingnites the front of the powder charge. When the powder burns from the front and the back at the same time it creates a huge surge in pressure when they meet.
Think of two waves in the ocean moving toward each other. When the two meet they create a single wave that is double the size of the two single waves. Much the same thing happens in underloaded cartridges. When the two pressure waves meet inside a cartridge you get a huge surge in pressure and bad things can happen.
The phenomenom has been duplicated in the laboritory and was reported in Handloader magazine. I'll look it up if you require the cite. What happens, once in a while, when using reduced loads of really slow burners is the primer impulse bumps the bullet into the leade where the rifling stops it. Then the burnig powder builds up pressure which can't go out the barrel due to the obstruction, and blows the brass case, this gas, inside the action, tears the rifle apart. Some rifles handle escaping gas better than others. So it is just a simple case of bore obstruction, like not removing the spider webbing from the barrel before pulling the trigger.