My shield 9 was a problem child out of the box (Nov 2013 production), and went back twice before they got it to where it would reliably handle 115gr. 124gr was 100% good.

First trip back they tried to "repair" too many things, second trip they "replaced". After all that, it will shoot anything I put through it (a major improvement, as 124gr was hard to find). It still has a random FTB / 100 rounds (115 gr; 124 & 147 work without issue), but they have just sent me a new recoil spring assembly, which is slightly different from the old (looks a bit cleaner in assembly).

I have been very impressed with CS and their willingness to get the weapon right.

I think I did ok with the choice, and have to remember that I can break anything, sometimes just by sitting in the same room.