I ended up with a 7mm-300 based wildcat finish reamer that I decided to build a rifle off of. I already built the rifle and have necked down brass for fireforming now I’m looking into custom dies. I don’t have a resize reamer to go with the chamber reamer, so I’m just going to send fired brass to Widden for a full length die. My question is about the seater die. I would like to make a sleeve to go inside my 300 win mag Redding competition seater die. I’ve never made a die before and I’m curious if there are things i should watch out for. The part looks very simple and the process could not be much different than cutting a rifle chamber. I had planned on buying a L.E. Wilson chamber die blank but I don’t have any other dies of that variety nor do I own an arbor press. Have any of you guys machined a Custom comp seater insert? What should I watch out for?