If the cartridges are going to be in a wet and/or wet enviorment and you feel it is needed you can use some nail polish around the primeers once they are seated for sealent. Cast bullets that have been lubed don't needed one because the bullet lube serves the purpose of a sealent. For jacketed bullets you can get some asphalt and then it dwon and use a Q-tip to put just a dab into the case mouth. Would be a good idea if you are going to use the asphalt to work the loads up from starting loads as the asphalt's pull could change the pressure of the round. The asphalt is a lot of trouble, but if you want the rounds water proofed with a jacketed bullet, your best bet.
Good luck,
Ron
