forget the 1200fps it really doesn't matter & should be the last thing on your mind.
If you're looking for accuracy then do ladder testing with all the powders you have on hand that are known target load powders.
I have a 629 classic also and use a redot on it. When doing test loads I put a burris 7x scope on it. i have several "target" loads for that 629, quit testing when I found 13 different loads that would do 1 1/2" or less 6-shot groups @ 25yds.
6.0gr to 6.5gr of clays with any 200gr to 250gr bullet
6.5gr to 7.0gr of bullseye with any 200gr to 250gr bullet
Redots can be challanging to say the least. I put a burris fastfireIII on a 10" bbl'd contender to play around on the 100yd line beating & banging on steel between set with a 308w/cast bullets. I stapled up 5 50yd smallbore targets and used the top 3 targets to zero that redot. Man, a couple of clicks go a llllloooooonnnnnnnggggg way. Once I got the hang of how much to move the dot (clicks) and used to the 3MOA dot covering the black/consistent centering, I started on the bottom 2 targets.
Shot the bottom left target 1st, was still having trouble with the dot so I turned the brightness down 1 setting and shot the bottom right target. Ended up giving the redot 1 click down & 1 click right and started banging steel. Don't take much stock in 3-shot groups other then sighting something in. The bottom left target was 3 1/2", the bottom right was 1 1/2".
That final sight in target, 3-shot group @ 100yds using a 260gr bullet & 7.0gr of bullseye in 44mag cases using a 10" bbl'd contender rested sitting at a shooting table/bench.