The #34's are the same as a CCI 250 except with lower sensitivity due to a larger angle of spread in the anvil feet that gives it the lower military spec sensitivity. The number 200's will be more sensitive and will make a bit less gas (the 250 and 34 are magnum primers). So, will it work? Sure. Is it maximally safe from slamfires like the #34? No. But the AR mechanism, despite its floating firing pin, is generally considered to be less slamfire prone than the Garand and M14 actions the primer sensitivity specs were developed around originally.
I can't tell you what to do nor can I take responsibility for any mishap you might have doing it and neither can The Firing Line board, so I'm not going to advise you to use the #200. However, I will tell you that in my experience using the arguably even more sensitive Federal 210M in a Garand and M1A, I never had a problem. I believe that was due to having checked that firing pin protrusion was within specification and to being meticulous about seating the primer deeply enough. The majority of slamfires come from improperly seated primers.
Primers need to be seated until their anvil feet touch the floor of the primer pocket and then compressed an additional 0.002-0.004" deeper. They should end up about 0.004" below flush with the face of the case head. If you do that, the odds of a slamfire go down. But, that said, we have one board member named Slamfire who has had two Garands blow apart on him due to out-of-battery firing with those same Federal primers I used. So, never say never.
Over a number of years shooting service rifle matches, I can think of all the times I heard slamfires occur on the command to load. I've estimated from that experience that it was about one in 15,000 rounds. I can't guarantee the accuracy of that number, but it seems to be in the ballpark. So if you decide to go ahead with the #200's and you have a lot fewer than that, I just wouldn't buy them for that AR again when they run out. I'm not clear how much advantage the less sensitive primers will give you. I was present for a slamfire with a round of Lake City ball ammunition one time, so I know the less sensitive primer with proper seating isn't an immunity guarantee. It is just likely to improve the odds of avoiding a slamfire or an OOB (Out Of Battery) firing.
