Same small shank barrels.
I got tired of waiting for Savage to supply parts for the impulse line, so I already designed, made and tested a barrel nut that has flat sides on it that fits into the stock.
The impulse barrel nuts are short and beveled.
You'd have to hog out the stock a pretty good amount if your going to use any of the aftermarket barrel nuts.
I also had an issue with the recoil lug fitting over the threads on the new carbon fiber barrel, but a few short passes with some emery cloth on the barrel threads took care of that.
The CF barrel threads were real pointy compared to the six other barrel threads from different manufacturers I had on hand.
All of the other barrels had no issues with the recoil lug fitting on them.
In another week, all of the parts should be made and tested, so I'll be putting the rifle back together to do some long awaited field testing while predator hunting in NY state.