Question on casting

[gunshot98]

I have a 45-280-M RCBS mold. don't need it for anything so tried selling it. A man asked me what diameter it dropped at, so i heated up the lod pot and cast some to measure. They came out .448 to .449 so my question is shouldn't it cast over .450?
I have never cast with a mold like this so i don't know if it was me and my inexperience or something else. Any help would be a blessing. Thanks

[Lead Fred]

Yeah somewhere around .454 would be nice

[pete501]

Muzzle loader bullet and not colt or acp.

[gunshot98]

So am i doing something wrong?

[s mac]

Did you only cast a few or did you get the mould to a happy operating temp? They be a little bigger once the mould gets up to temp.

[pete501]

Muzzle loading bullet has to fit unpatched down the bore. The hollow base is meant expand on ignition and imprint on the rifling.