best place to hunt giga bullet save???

[shakowski]

im farming crimson S. is there a better place?

[Soukosa]

If you want to solo it, probably none better than Mine Defense S. No gunner unfriendly enemies in the way and you'll know if you got it by the time you reach block 2.

[Hrith]

Most spawns can be skipped, too, it's really fast.