After messing with crushed stock wood and fasteners getting loose through humidity caused wood expansion/contraction I opted to make my own screw cups and pillars the clamped my wood stock solidly between the stock screw mounting brackets and screw heads. I do realize that there are screw cups that can be bought, however I wanted to cut my own in steel instead of softer brass.
The screw cups are steel and blackened by heating to red hot and quenching in used motor oil a few times..........
Next I decided to steel post the large HW95 trigger bolt. This was prompted by the base of my trigger guard actually getting "bowed" after a few years of tightening when only supported by wood......
I also replaced my hardware with socket head cap screws to stop "flat blade screw driver slippage", plus the hex bits used for tightening really work well when torquing with the torque driver used for torquing scope mount screws......
Amywhoo.....after adding the steel screw cups and post there is no more wood crushing and stock loosening due to stock wood movement!
"Do you counterbore the cups with a 2 flute endmill?"
Probably a 4 flute center cutting end mill held in the tail stock of my lathe to get a flat bottomed c-bore.
"Do the cups come out hardened?"
I really don't know but I guess it depends on the steel used. If it was some O1 tool steel rod it would be really hard from heating red hot and quenching several times in used motor oil to give them a black finish. I never checked hardness since they were turned from some scrap I had without pedigree. The commercially available screw cups bought decades ago were made of brass so I didn't consider the hardness of the steel to be important. Also, I do know that my factory HW stocks don't have very consistent c-bore depths which is why I made my steel posts a bit long to be filed flush with the inside of the stock.
LOL.............on both my Beeman R9 and HW95 stocks the steel screw cups are a bit different so the rim will be flush with the outside of the stocks so I'm supposing that the "one size fits all" screw cups might not bottom out on the stock mounting bracket.
If bought commercially I do consider the "posted version" to be better than the "flat bottomed cups" because the "flat bottomed cups" still have compressed wood under the cups. Matter of fact, I don't see where the "flat bottomed cups" to be much of an improvement over the factory supplied flat washer and lock washer setup except better looking............
