[Charlie98]

IMR3031 would be a better choice for cast in the .30-30... it's what I use. Generally speaking, you don't want to drive a cast bullet past 1800fps or so unless 1) it has a gas check, and/or 2) you've slugged your bore and the bullets you are using are sized for that bore. Just using 'jacketed' data does not automatically lead your barrel, I use a starting 'jacketed' load for loading cast in my .348WCF, including IMR4064, but I have bullets properly sized for the bore. It's true, overdriving cast bullets can exhibit barrel leading... but that is a typically a product of too much velocity, coupled with a poor bullet choice.

That being said, I show the same 27.0grn IMR4064 starting load for a 170grn jacketed bullet (Speer manual,) I don't see any reason not to give it a try, or reduce that to 25grn and give it a go. I wouldn't load more than 5 rounds or so, as a tester. Your rifle will tell you in pretty short order if it likes it or not.

My experiences with a shorter barrel and IMR4064 (in my 20" .348) have not been favorable, the velocity was down compared to IMR3031, all else being equal, but the only way to tell is to try it in your rifle... a little longer barrel with the smaller bullet diameter might work very well.