Clear fingernail laquer works just fine, and it's a lot cheaper than $9/bottle. Get a small, pointed paintbursh from a hobby supplier, and then put a drop around the primer and let it flow into the groove. If you put your reloads into a case holder tray, you can put something under one side to tilt it slightly to the side and then use the same method for sealing the case mouth; the laquer will flow into the groove.
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Shoot straight & make big holes, regards, Richard at
The Shottist's Center