Hollow point resist shred doesnt proc. Hollow point will even prevent crippling headshot resist shred if depending on what was bought first.
Testing in practice range, buying hollow point alone, proccing it, then selling it results in 4 more damage on abrams 35 bullet hit to 38.
Buying headshot booster then hollow point causes one headshot to proc additional damage to bring it up to 39-40. Shooting twice causes both to proc leading to 42-43 per shot. This is equal to -21% resist according to the stat shown when taking control of the character being shot.
Buying Hollow Point THEN headshot booster causes no bullet resist shred to occur at all (Shot does 35).
Seems to me hollow point works on its own but doesn't proc correctly when stacked with weakening headshot bought AFTER. If WH is procced, HP doesn't proc, and the WH shred isn't applied. If you don't proc WH and hit a body shot with HP, the HP resist will occur. Shooting an headshot after the body shot will not increase the shred by the 13 (12)% This is certainly a bug. Good find.
I am wondering what you mean when you say HP isn't proccing at all. It definitely is. I hope you can find a way to replicate that.
Tested with BRS as well and it seems like the bug doesn't affect that at all.
This also seems to apply to crippling headshot. Testing with that, buying HP first will make it so that neither resist is applied on headshot (and subsequent body shots will not apply the shred from HP). This will also prevent the Spirit shred and antiheal from proccing. The stats on the left paint a clear picture. Something is going very wrong with CH when it is bought after HP.
@Yoshi I'd call this bug a medium high priority problem with a low cost of debugging (best guess Idk)