Nothing beats a small, high quality vise. The moving jaw must stay parallel with the front jaw when tightened, moving jaw must not lift when vise is tightened. Otherwise, the work will squirt out the top of the vise while milling or drilling. But if you have a big drill press table, get a big vise, as the jaws open wider, and are deeper. This larger size not only gives you more capacity, but holds the work more securely, ensuring YOUR safety as well as that of the workpiece.
You need to get the work up near the top of the jaws so you can see what you're doing. But how do you hold a tumbler from tipping as you apply drill pressure? Support pieces, called parallels, are used under your parts.
Sets of parallels and various packing pieces for the vise are essential. I have a set that runs from 1/2" tall to 1 3/4" tall, all of them are 1/8 thick.
Lathe tool bits make good parallels, coming in squares from 1/8" sq to 3/4" sq and larger.
You can paw through your scrap bin and find shorts of steel or aluminum that are parallel sided.
Shaped or tapered packing pieces are useful for holding a barrel surface level so you can install a vent liner without the barrel moving on you. (of course you must support the other end of the barrel.)
Eventually you'll want a tipping vise so you can tweak those lock bolts thru at just the angle you want.
