1st question... it's my understanding, that micro groove rifling doesn't work as well on cast bullets, which I like to shoot, have any of you had good luck with cast bullets in the micro groove barrels ???
There is a lot of misinformation about micro-groove rifling, but before we talk about it, consider the Marlin .22 rifle, many of which had microgroove rifling. They all shoot cast bullets well.
When you make the jump from jacketed ammo to casting your own, there are a number of factors you have to consider. Bullet fit is paramount, but other considerations are also important. Lube, alloy, bullet design, twist rate, all play a part in how well a particular bullet travels down a particular barrel. The blanket statement that a microgroove barrel can't shoot cast bullets is simply false, as is most blanket statements.
It didn't help that Marlin changed rifling methods a couple of times, depending on caliber. I have a .45-70 microgroove barrel that shoots cast bullets extremely well. It was one of the last New Haven microgroove barrels, and shortly after it was made, Marlin went to Ballard rifling in that caliber.
I also have a .30 caliber microgroove barrel that shoots cast bullets okay. I suspect the twist rate is wrong for the bullets I've tried, but it's easier to simply load jacketed. It's a rifle I don't use much and I haven't invested the time and energy to find the cast bullet that it likes. Probably something in the 150 grain range, but that's a project for another day.