can anyone shed some light about scope mounts not setting flush on these rifles.

Your description of the problem is a little scanty but I think you mean where the scope mount hangs over a bit where the barrel taper begins. This happens with Weaver mounts. If you get the T/C Duorings, there is no overhang. In my opinion though, the Weaver bases are preferable.

Yep. What Grumulkin said.

Burris has two different bases. One for pistol and one for rifle. The rifle hanges over the front but has a set screw on front to the supprt the base.

If you're not using the hang-over part, just cut it off. It's alluminum and cuts easily with a hacksaw.