I have a Uberti 1851 Navy .36 and a Pietta 1851 Navy Yank .44 and the cylinders are not the same size... the .44 cal being longer and larger in diameter.
Pietta makes both .36 and .44 Navy Models and the Uberti Navy is only available in .36. Uberti makes an Army model in .44 but not .36. So if you check out Pietta the barrels and cylinders for their .36 and .44 might be the same size...hope this helps