ive had the same problems with my mk3. doesnt matter the ammo type and it seems to do it on all 3 of the mags it came with.
taken it apart given it a good cleaning, etc still same problem
Please don't modify the gun until you make certain the magazines are not at fault. If the gun is clean, lightly oiled and assembled properly, that pistol is one of the most reliable pistols ever made! I suggest that you buy a couple of NEW Ruger (only) factory magazines and try them. Your mags may be factory made but one unlucky drop on a hard surface could screw up any magazine.
The new extractor is always good advice and can't hurt but make only ONE change at a time so you can find out what the cause really was. The magazines and or ammo are always #1 on the suspect list for a malfunctioning semi automatic. Ruger MK2's aren't ammo fussy so that leaves the mags.
I modify machinery and guns to make them work better most of the time. I dont let anyone do work that I can do. I fixed my mkII works flawlessly. No worries.
ok. The mark II has a stamped receiver. The pistol has mag stabilizers, ruger had some problems with the stabilizers being too deep. What happens is if the magazine doesnt have the right amount of side to side play it creates bolt friction. Mine didnt have much play at all.
So break the pistol down separate the barrel from the trigger(lower half). Remove the grips. Insert a magazine and move it side to side. It should have 1/64" amount of play. If it doesnt, remove the mag, look down you will see indentations about the size of a dime on each side. Take a flat jeweler's file and run it CAREFULLY with several passes. Test it. Repeat till its got 1/64" of play. REMEMBER YOU CAN ALWAYS REMOVE METAL BUT YOU CANT ADD IT BACK!!Then blow the metal shavings out, oil, and reassemble.