The RCBS uses a rubber "O" ring as a seal in the lube plunger, which works fine but the Lyman uses a leather cup, sandwiched in steel washers, that is unless they changed so my choice would be the RCBS. The lyman also has a point at the bottom of the sizer that can leak lube terribly. I'd go with the RCBS but before you buy a sizer, cast and lube your bullets and shoot them as they drop from the mould. You might find that sizing isn't needed and they shoot fine. I casted for years, before buying a Lee sizing kit and adding gas checks. Lee alox or Johnson's Paste Wax works fine as a lube for a light cast bullet load. The Johnson's isn't as sticky after it dries but still works fine. An amount of wax, the size of a raisin can lube a couple dozzen 38 caliber handgun bullets. I keep and old aluminum pot, to warm the lube on the stove enough to melt it, swirl the bullets in the wax and pour them out on an old baking pan. In two days of drying, they can be loaded and the wax is hard and in place. A little goes a long way. If you can see it, it's too much. This method is for loads around 1,000 fps and under, but velocity can be increased slowly until accuracy drops.
Welcome to casting!!
