I bought my Mini-30 less than one year ago. I have recently tested several different "inexpensive" brands of ammo, one box of each, and found that Tula alone still causes a very high percentage (30% or better) FTF.
Many blame the steel casings. Many blame sub-standard foreign standards. I thought that the issue was Berdan primers alone, but none of this is true.
I have absolutely NO problem shooting either Silver Bear or Golden Bear in my Mini-30. In fact, the gun LOVES these brands of ammo.
Wolf (WPA) and Brown Bear also fire just fine, but the Ruger magazines don't feed the polymer coated shell casings as smoothly as they feed Silver and Golden Bear.
I also shot some corrosive primer Yugoslavian stuff with brass casing, and it fired just GREAT, without a hitch. Feeds and fires great.
Tula shoots fine in all of my other guns, including rifles and pisols, but don't try shooting it from a Mini-30 unless you have an SKS to fire the rounds that fail.