I purchased a new Savage Hunter rifle in 6.5 C. I don't shoot that caliber, but I've always wanted to get hands dirty with a barrel swap. So I ordered a .260 Rem barrel (a caliber I shoot, and reload for) from Northland Shooters Supply. Also ordered the necessary wrenches and go/nogo gauges.

The swap appeared to go well. Bolt would close on go gauge, not close on nogo. It was going so well, I installed the ASR brake and timed it so it was at 12 oclock as expected. Took it to the range and had about 50% light primer strikes.

My initial reaction was, I must have F'd that up somehow. So I got it home and spun the barrel in a bit more. Bolt barely closed on the go gauge, and closed on factory fresh Lapua brass.

Next trip to the range, same thing.

So I spun it down a little more, bolt did not close on go gauge but did close on the Lapua brass. Yesterday was 3rd trip to the range, and still getting light primer strikes.

I have an idea how to proceed but I'd like 2nd opinions. Did I miss something obvious?

Do you have any factory ammo to try?  Maybe that brass is slightly undersized for your chamber?  Could also be the firing pin protrusion, did you ever fire the gun as a 6.5cm?

Got light primer strikes with factory ammo as well as handloads (same load works fine in another rifle).

Never did fire the rifle in 6.5C.

I'm going to say your problem is not with the barrel.  Have you disassembled the bolt to make sure there weren't any chips from manufacturing, excessive grease, or other deformities with the firing pin or spring?

I have similar thoughts. OP, have you fired the rifle before you did the barrel swap? It's way more likely there's an issue with the action, probably in the above mentioned areas.

Make sure you don't have any debris in the extractor hook and the bolt face edges are scraped clean.
The firing pin protrusion is adjustable if necessary.
Instead of no-go gauge you can get a bit tighter with one to two layers of scotch tape on the back of the go gauge as a no-go gauge.  Factory ammo is loose and undersized most of the time if that is what you are shooting.
Just the ways I've found works is all.

Agree. I've been watching bolt disassembly vids and plan to tackle that next.

Thanks to everyone for suggestions. I'm happy to see someone posted the firing pin protrusion is adjustable, I was thinking I needed to bubbasmith that.

You might do a bolt lift kit and extractor upgrade while you're in there.

Remove the ejector when setting up your barrel with the Go/ No Go gauges.
You realy don't need a No Go gauge. Just set it up that it closes on a Go gauge and it doesn't close when you add 2 layers of scotch tape to the back of the No Go gauge.

When setting up firing pin protrusion on a Savage 10/110 You want between 0.032" and 0.045" firing pin protrusion.
Factory Savage setting is in the 0.052" - 0.055" range.
You then want around 0.080" clearance between the bolt body and the cocking piece.
If you set up your firing pin spring to have a length of 1.9" on a short action you should have proper clearance.