As promised, here's a detailed tutorial on how I did the Ammo Drum on the bolter of my Imperial Fists.
First, here's what you'll need:
*a plastic bolter (woa!),
*a bit of plasticard
*a bit of plasticard stick, mine is 0.035" (0.88mm)
*a bit of plasticard tubing, here 0.25" (6.3mm)
Forst step: cut off the regular ammo.
Then, take your tubing bit, and cut out about one quarter of it. Glue the biggest part on a small square of plasticard, and then glue the smallest part inside
the biggest one.
Now, take your plasticard stick, and cut it into parts slightly longer than the width of your tubing bit (hope that's clear), and glue these parts in the gap made by your cut-off.
Now, cut your square base to a round one, to have the thinnest edge possible, and file the hole thing, until you have about 2 or 3mm left, including base.Glue a second square bit of plasticard to close the lot, and cut it you the right shape.
Now, take a final bit of square plasticard, and glue it with a tiny drop on the top of your drum, then, cut it into rounded shape, smaller than your drum. Then fil the edge to make it straight, right before the rounds, to have the sticks facing the outside of the Bolter.
Glue the lot to your bolter, and Tadaa!
Hope it's clear enough and you like it!