For cast bullets.
In an ideal world you would like to have the "throat" .001 to .002 thousands larger than barrel grove diameter, preferably .001!!
But Ruger spcifications are anything but a "perfect" world these days! You really don't know what you are getting untill you can slug the barrel and throats, measure and see if the gun can be reasonably (price) corrected to shoot "cast".
Other specifications (ideal situation) would be cylinder gap of .002 to .003 thousands, all chambers "line" bored relative to the barrel and highs and lows in barrel runout.
That said, the Ruger's are the buy of the centry in my estimation!!
If you want all of the above things done, contact "Bowen firearms" and check out the cost! That Ruger will look like a steal to you after you see what that kind of attention to detail and specifcations will cost.
changling