After looking at the hunterman bullet link in someones post, i went and pushed a great plains bullet down the bore in my .45 and took measurements of .450 and .461.

What do you think would work best? .451? I would like it to load without a short starter but not to loose. Doesnt look like hunterman sells anything with a hollow base so i may have to email BS and see what he has.

The Whitworth bullet from hunterman looked interesting.

Send Mark Lynch a e-mail with those measurements and see what he recommends. Mark is a good guy and will work with you..

Frontier G

If he offers custom Wts. He may offer custom sizes If it were me I would go .5 bigger than bore diam.
talk to him and see if he can do a .45.5 and .461.5 these will be loaded with thumb presure and not be to loose.
If he dose not offer sizeing the .451 may require a short starter I would call him and pick his brain some.

Go with Cayugad's recommendation. IMO a .451" would not be tight enough.That would only be entering the grooves .0005" upon loading and when fired would more than likely get 'stripped' out of the rifling and would be basically like shooting a smooth bore but worse as you would have too much gas passing around the bullet in the grooves causing a significant loss in velocity.