Those measurement explain why it hasn't been an accurate shooter.
With lead bullets which fill the cylinder throats it will shoot very well but be sure the chambers are large enough to chamber a bullet that fat. If they will not let a loaded round in with a .439 bullet diameter, you will have to get a mold that is as large as can be chambered, then use relitively soft allowys which will slug up and seal off gas blowby. If the first drive band can be as large or slightly larger than barrel groove diameter, it will shoot quite well, but will shoot best if we can get a .439 bullet chambered.
Please email me with any technical questions regarding measuring or whatever, as such a problem is the first I've encountered in my 33 years of mold making, so not many readers will need to know how to do the fix.
But, there are plenty of other problems which shooters run into and might need help with. If any reader has such, email. I get about anything shooting from 22 caliber up to 8 Bore.
LBTisAccuracy@localnet.com