Not a dirty riddle.

I've been trying for a while now to get a RIA TAC 10mm to eat 220 gr hard cast at 1,200+.

Anyway,  just back from the range and here are the upgrades-

heavier recoil spring

shock buff

23# main spring

flat bottom firing pin stop.

I went trough 4 mags without a glitch....

then the hammer started riding the slide home. Then it didn't. Then it did.

Today was the first time out for the new main spring.

Is that the culprit?

Are your your hammer hooks cut  to 90 degrees? This angle will increase follow thru.  Did you replace sear spring? Sear bounce can cause follow thru. I'd say flat bottom hammer stop is the culprit.

if you have an over travel stop on the trigger, back it out to make sure the trigger releases the sear all the way, which should allow it to catch the 1/2 cock notch in the hammer... if that is ok, check the sear spring and that it has not slipped off the disconnector, then for broken parts.... disconnector,  hammer half cock notch, and sear itself

Anything from not even energy to move the slide back far enough to sears not catching on the hammer hooks.

What’s your recoil spring weight?  With a flat bottom firing pin stop on a 10mm it should be 20# if I recall correctly.

ETA- never mind I just re read and saw the load you’re shooting

Jesus, a 220 at over 1200 fps has to be battering that gun to death.

As for hammer follow, it usually means the hammer hooks are too short or cut wrong or you have insufficient sear spring tension.