I dont really mind if you dont do anything about this, but i just wanted to say if you were to use the cost of steel from a foundry (30 metal), the cost of casting piercing rounds would be 70 molten iron, instead of 90
again, i dont mind if you dont do anything, really its a small price to pay for casting directly, I just wanted to note it because you kept to the costs of the other magazines.

Very cool mod regardless, I wanted to do something like this for a while now for my platforms, save an assembler or two

idk how I didn't notice that! I must have had 50 as the value for copper and iron before and then just added 40 for the firearm magazine. I'm currently considering making the recipe easier to do with advanced metallic astroid processing (it gives 4 copper 10 iron). If I were to follow through with that the new recipe would probably look more like 75 molten iron and 30 copper. If I don't end up doing that I will most likely make it 70 iron instead of 90.

Have any thoughts on whether I should make it easier with metallic astroid processing or just make it be the normal recipe?

I feel either could be good, considering that the casting LDS recipe doesn't follow what the cost of 1 LDS normally is (it requires 250 molten copper or the equivalent of 25 plates), but also I enjoy the challenge of having to balance using the normal processing recipe and the advanced processing recipe using circuits (or other methods like splitter stuff and voiding items), so honestly I think it'd be more interesting to go with 50 copper and 70 iron, but that's really up to you.

I decided to go with the 70 iron 50 copper recipe and have updated the mod release!