Sorry, I’m no good with a spear.
An M4 or .357 magnum? I’m your guy. Or a bow. Or 3 feet of 1095 steel.
Wonder if the later would be effective? Mine cuts 1 1/2 inch diameter rose bush branches like they’re made of Nerf...
an M4, or a 357 magnum vs a mammoth? Sounds like you got a pair, but that might be too risky, if you’re shooting something that big, I’d probably stick with the .470 Nitro Express, make sure it gets done right. Only reason I would want to spear the thing is for bragging rights, there is no other practical reason.
I’m thinking 3 feet of 1095 steel would be effective, from what I have heard, mammoths are ferocious and aggressive, unlike most of their elephant cousins, I think it would take a stout heart to fight one in close combat heh. Talk about earning your meal.