HF has a 10" length ratchet cutter that I have chopped 350 MCM wire with. 140% the size of 4/0. Using ONE of my weak hands. Single handed - you read it right. 1000MCM wire will fit but that's way beyond my crippled hand ability. About six times the copper of 4/0.
I use a carbon probe to spot weld super thick copper around the tang. A circle of 12-zaps keeps the tang and pad from leaking and lead-free solder seals everything tight for later use of SN60. My entire battery bank uses extra-long tang 2-bolt lugs made of 1" copper pipe 1/4" thickness. Only the batteries have a single 1/2" bolt which is 316 grade stainless with the rest of the hardware. Bussbars are copper 3/4" X 5" with 1/2 threaded stainless studs.
Hard Knocks: the HF cutter works OK for awhile then dulls.
CRESCENT makes a pair of 8" dykes with compound cutters like used on bolt cutters. My choice for larger dykes. Unbelievable cutting strength. Blue & gray plastic grips. I've nipped my way through 2/0 cable with these. Takes patience but the wire is left in good shape.