Howdy
The slide stop engagement lip on the magazine follower is probably the reason that your slide didnt stay open. And also probably a weak mag spring. The magazine you described is NOT an original and would be of marginal quality. I use an original for carry and Shootingstar full size mags for practice. I have heard of other complaints about pinky fingers getting bruised? I can't see how unless firing from a bench and your finger is under the gun? This happened to me ONCE with a 38 super Combatmaster. After that pain I was convinced to use a sandbag rest. I would try your gun with other mags before you start looking into anything else. Make sure they are known good mags first. All my Combatmasters function great with just about any ammo/load I put in them. Of coarse mil spec ball is the best for reliabilty.
Hope this helps!
See some of the other posts hear as there is ALLOT of good info.
BE ADVISED! If your gun is a very early example, it has a cut/welded slide and frame. Probably not a gun that you would want to run thousands of high-test loads in with out checking it periodically for stretch and weld failure.
L8r
Conley Janssen
USMC 87-93