The best I ever did with 4064 was 43.5 grains out of my 20" tactical. Groups hovered around 1/4 to 3/8 inches or so edge to edge. This was about the same as FGMM which was newer stuff that happened to find it's way to my patrol car after a day at the range. So much for my next polygraph exam huh, LOL. I wasn't into precision shooting prior to two years ago so I really can't offer an opinion on the older FGMM. Mostly Ruger hunting rifles where close was good enough with 3031.
However, I tried your 45 grain Varget load and damn near cut the same hole twice in two three shot strings from a bench at 100 yards. Seriously they were off just enough to not be prefectly round holes. On my worst day with this load it's never opened up more than maybe a dime. I've only tried it past 100 yards once before the weather got cold and was able to center punch a golf ball at 200 yards from a bag across the hood of my truck. Minute of bad guy for sure. I'm pretty convinced this is my rifles pet load. A buddy of mine shot a few Varget loads out of his brand new SPS Tactical, probably thirty or so rounds down the tube, and got 1/2 inch groups or so at 100 yards with no problem. I'm sure that will get better as more rounds are fired. This same load does real well with a 165 Nosler BT as well.
I used Winchester cases to length, Varget, CCI 200 LR primers and 2.8 OAL, same as with 4064. I really need to invest in a chrony to see what velocities I get from all my handloads but just haven't done it yet.
Now, with that said, if you were so inclined to mess around with some .223,,,,,, just kidding.