Butte to Helena

[Alps]

Question about the general route out of Butte heading north. The easy way is I-15. The hard way is Browns Gulch Rd., Hail Columbia Gulch Rd., over to Lowland Rd., Kit Carson Rd., Boulder River Rd. Has anyone taken that route before? Obviously it's unpaved, but it appears to all be reasonably open Forest Service routes. Should I be concerned with washouts in late May? Is the road well graded or should I not attempt in a passenger car?
Etc.

[corco]

Hahaha, rural county roads in Montana well graded

I haven't been on most of these specific roads. I will say that Jefferson County isn't exactly known for their road department. My guess would be traversable in a passenger car, but do so slowly and at your own risk.

[Alps]

Well you haven't taken it so I guess you can't answer the next question... is it worth taking? I can't tell if this was ever a former state or US highway, though it seems doubtful.

[corco]

Browns Gulch is a state highway in places, none of the rest are former highways.

Can't answer if it's worth taking.

[usends]

I'm looking at Benchmark's atlas of Montana; they are typically field-checked pretty well.  It shows Browns Gulch is paved a couple miles north of the interstate, approx. to Bull Run.  The rest of your proposed route back to I-15 is classified as "unpaved", but not "high clearance".  I'm guessing most of this route would be maintained by the Forest Service, not the county.  I see there are several F.S. campgrounds along the route, which I interpret as another good sign that a passenger car would be able to handle it.

I'm thinking the route itself would be fine, I'm just not sure about the late May timeframe.  If they have a lot of snowfall the previous winter, that might complicate things.