Thanks for all the replies. Took the gun and the FTF loads to the range today. Got the gun out, got set up, and cycled through a few rounds still no firing. Frustrating.
Started looking the rifle over. Guess what? Bolt handle was kind of loose. Then I realized the bolt main rear bolt (the one that has a hex cutout for removing it and disassembling the bolt) was backing out! It was a good 2-3 turns loose. Holy crap! I felt like an idiot. No wonder it was progressively getting so bad so quickly.
I don't think I torqued that down after I disassembled and changed the bolt head face to 223. Probably hand snogged it and got distracted at the time.
Tightened it down and all of the FtF rounds fired except one. Sheesh.
One more thing to add to the checklist before shooting...
Scope base
Rings
Actions screws
Bolt

Easy fix though Ha Ha.