ihmsa70,
The current NRA Cowboy Silhouette Rifle record for the 60 shot course is 57x60. The fellow that set it used a .30-30 Marlin 336A (24" barrel / partial magazine) that he bought for less than $200 on the internet. He was using jacketed bullet loads though.
Like NoBade, I have had no accuracy problems with micro grooved rifling using cast bullets. As he indicated, just fit the bullet to the barrel which is also the case with 4 and 6 grooved barrels. In the case of my Marlin Micro-groove it does just fine with .309" diameter cast.
Unfortunately, I don't know own a 336 Cowboy .30-30. I do know 2 fellows that shoot at my club that do and they are fine shooting rifles with cast as Dr. A has proven.
The three Winchester '94's I own shoot cast very well also.
One suggestion I would make, is that for best accuracy on the average try finding a lever action rifle that doesn't have barrel bands. Rifles with barrel bands can be made to shoot better, though, by creating a little clearance between the band's and the barrel, allowing the barrel to float somewhat.
Here's a 336A
http://www.auctionarms.com/search/displayitem.cfm?itemnum=6455088I have one of these WInchester Centennial Rifles and it is a shooter with cast.
http://www.gunsamerica.com/guns/976554125.htmGood luck,
w30wcf
