Which one?
I have a a magnus waitting for the radiant crystal revert to upgrade. I have a 4* alchemer. Which would be best?
Also, 2 pro tips (LOL AS IF)
1) Magnus bullets can bypass wheel shields same way that polaris and AP and blitz can.
2) Idk why, but the vial barriers can damage trojans if they are facing you. Just pop one on, and watch the ball go thru trojans. Weird, huh?
This question has been asked countless times. You might try a web search such as callahan iron slug site:forums.spiralknights.com. Briefly, Callahan is a fun but underpowered piercing gun. Iron Slug has one of the worst reputations in the game.
You might want to wait for the impending gunner update, which will offer several new guns.
In general, don't upgrade an item to 5 stars just because you have the 4-star version. If you don't actually want the 5-star version, then just let the 4-star version sit in your inventory un-upgraded.
Are you also asking about your alchemer? I don't understand the question, but 5-star alchemers are great.