Alright, here's the thing.  When I used the old 10rd magazines with JHP bullets, i didnt have a single problem.  

Now, that I switched to the 15rd magazines, I sometimes have problems with JHP.  When using the WWB FMJ ammo in a full magazine, I can load it into the pistol just fine.  

Once in a while, I'll say, maybe 10% of less, when I'm using JHP, and try to load a new magazine, while the slide is locked back, the front of the bullet, will jam in front of the ramp of the barrel.  When you're using FMJ, this problem doesnt happen since there isnt a cone where it can catch on.

How do I fix this problem??  I know, it doesnt happen all the time, but it does.  It appears, the ramp on the barrel needs to be lower/longer by about 2mm and it wont have this problem.

First thing I would try is another mag, and if it works OK then find out why the old mag is binding.  Take it apart and clean and lightly oil and see if that helps.  If not, then you might try stretching the spring slightly.  If the spring is getting weak it could be not giving enough upward force on the cartridges to make them feed properly all the time.  If stretching the spring works, replace with a Wolff +10% power spring.  If stretching the spring slightly does not work, and a new mag does swork, take careful measurements of the feed lips distance apart.  You may have feed lips that got bent in and not letting the cartridge nose come up high enough, but I really doubt that is the problem.
In short, try these in order.

Another mag and see if the problem is still there.
Clean and lightly oil the inside of the magazine.
Very slightly stretch the spring in the offending magazine (this is what I would bet on being the problem).
If the feed lip distance between lips is different between a known good mag and the mag that hangs, try spreading the feed lips very slightly with something that will not scar or mark the lips, such as smooth jawed pliars.  This is the last thing I would try as I don't have a lot of faith in this being the problem and you do this at your own risk because you could end up messing up a magazine.  I would not do this if you do not have any experience in feed lip adjustment.