Search keeps yielding 30 cal. instead of 30mm. Does anyone do these in either plastic or resin?

Accurate Armour does for modern English gun
https://accurate-armour.com/aa-products/135th-accessories/a026

HTH

Ryan, thanks for posting. I did find that set, but I forgot to mention it's for Apache ammo, which comes in different cans. The rounds are unfortunately shaped differently as well.(not enough shouldering on the casing) I'd like to also make the 11 round clip that go in each can. 23mm Soviet ammo has a good shape but is obviously too small. The search goes on...

That changes things. The only helo ammo cans I have heard about are the ones used for the door gunners but never any main gun. Maybe a Cobra drum but no S4 type cans that your wanting, no love for them. Best of luck on your search.