I have a brand new 600 Jr for .410. Wanting to load #7 1/2 shot, and can't get a consistent drop. My shot has been stored dry since I moved quite a few years ago, and haven't needed to load any for any of my other gauges since before I moved (12 years). Shot seems to have oxidized I guess, has a light gray appearance and quite a bit of dust. Using an Adusta-Drop-Charge-Bar from Ballistic Products. Tapping on the shot drop tube seems to get a stuck charge to release but the drop varies from 320 grains to 370 grains. Then it will drop 170 grains. Any ideas would be great.