Closed cylinders in WH40k weapons

Been making a bunch of WH40K Eli Patoroch Bolters and Lasguns. The weapons have small rolled cylinders that have a small disc glued to one or both ends. I know how to roll the cylinders but I suck at gluing them to the correct diameter and am even worse at gluing the disc on top of the cylinder end(s). Any help out there?

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Frustrated in Alabama