What year did Marlin transition from Microgroove rifling to Ballard style in the 444 SS and did Marlin produce the 444 SS with Ballard rifling in a 1 in 38 twist or just 1 in 20?
Not sure when they went from micro-groove to Ballard type but they went to micro-groove rifling around 1954,a 1 in 38 twist is standard for most .44 Magnum &.444 but with some ammo makers making factory loads that use bullets that weigh more then 240grns. in weight buy a Ruger Deerfield simi-auto .44 magnum or their lever action .44 magnums because they have a rifling twist of 1 in 18 that will stabilize the heavier 300grn.plus bullets and don't use the micro-groove rifling,also leading can be a problem in micro-groove barrels if your using soft lead and load them to more then 1200 feet per second so for that reason your better off to stick with jacketed bullets of not more then 240 grains when loading ammo for rifles with micro-groove barrels with the 1-38 twist if your going to be using heavy loads.Hope this info can be of some help to somebody, I have also noticed that the Ruger Deerfield rifle with the faster rifling twist gives a better bullet mushroom as opposed to the old 1-38 twist.If you'd like to learn a little more about this fascinating topic,type rifling characteristics into a search with Google and you will find a lot of interesting information on different types of rifling used by different manufacturers.
New .444's now have a 1 in 20 twist. I hope they do the same in the .44 Mag soon. The 1 in 20 will stabilize 300 grain bullets while the 1 in 38 will not.