I’ll offer the dissenting opinion on Nikon scope mounts, both P series and M. They’re cheap, they’re available, but they’re really not a good product. I build a lot of AR’s, a couple dozen each year still, over 200 ground up, and more than 600 as rebuilt uppers. A lot of customers/colleagues/friends ask about the Nikon mounts since they are so “affordable.” If a guy is going to spend the time lapping and aligning them, great. But it’s a lot of wasted elbow grease just to save a few bucks. I have never experienced a brand of rings with more eccentricity and misalignment. Many sets of P series mounts I have installed have had less than 25% surface contact out of the box.
Warne and Vortex make far better products for not much more money than the Nikons. Warping or denting your scope tube to save $30 is nonsensical.