You'll want a fast-acting fuse on the mains input.
Done, kind sir
You probably also want to conformal coat the high-voltage parts to make sure you don't accidentally place your hand on them while charged.
I see no bleed that discharges the capacitors when you're done with them -- self-discharge will do that over time, but a quicker and more assured way might be nice.
There is no way that 4 AA batteries will generate 8A of current AFAIK. Maybe with fresh Lithium cells?
Going to chuck the resistor in as billhowl said, no idea why the 8A is there, expecting much less than that haha.
Are you making Coil Gun?
From 240V AC, you will not be getting 400V, it only about 330 to 340V DC.
Connect a 1 Mage Ohms across the cap for bleeding.
best used a mains transformer with a ratio of 1:1 for safety, and reduces noise signal as well.
Certainly is a wee coilgun, i know the mains wouldn't hit 400v, not too fussed about getting it spot on at the moment, moreso just getting it to work, then i can play around with transformers and whatnot after. Cheers for the idea of using a 1:1 on the mains though, probably wouldnt've thought of that one.