Not sure you can get a ½oz load into a 2" case. The original load for a 2" .410 case was I believe about 5/16oz, 3/8 at most. The ½oz load of shot will I believe take at least an inch of the case length & deduct for base wad height, crimp length & wadding, don't think you'll have anywhere left for the powder.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra