Here are some .458's - the ones I recovered from the railway rail bed tie along with one 480gr. unfired. To the far right is a 200gr. .375 recovered from a lengthwise shot into a large Aspen log. It went approximately 18".
The copper tubing, was cut from a length of normal 3/8" copper pipe. I have an old mould I bored 3/8" (boring out the grease grooves) but leaving the ogive. Placing a cut-off piece of pipe into the mould, then casting the bullet gives you a jacketed bullet with a pure lead jacket. The flashing form the cuttoff, leaves enough of a flashing to lock this jacket into/onto the poured core. I lost interest in this after firing just a few - they worked just fine.

I forgot to mention, after cleaning the cuttoff cases for pouring the cores, I lightly wiped the inside with soldering flux to obtain somewhat of a bonded core - it seems to have worked! The really balled up .458, was the pure lead cored bullet. It's jacket was made from a 're-sized .250 Savage case - lots of pressure needed to reduce it to .458, but it worked. I used RCBS lube sizing dies for this in a bench vice - hard on the die and potential to break it. A better scenario would be to simply use sized .303, .35 Remington or .30/40 Krag brass. The .35 Rem does not need the rim turned off - but used .35 rem brass is hard to find - thus - .303's get the nod at .457".