I am brand new too 10mm and I just got my g29 I added + 2 pierce extensions to both my mags. So now my glock 29 is 12 + 1 instead of 10 shots. I did this because, when I got my g29 1 mag hand no pierce ext. and 1 mag. had + 0 pierce ext. but my pinky still felt like it wanted more handle, so I got the + 2 extensions put on my mags. I have NOT shot my new g29 yet. 1. I was reading about some guy who said he had 13 shot mag and he was asking about springs in the mag. others were asking him if he was cramming the 13th round into the mag. and he said NO. he wanted to know if his mag. spring was shot or weak? will I have to get a different spring for my g29? or g29 sf? (please glimpse @ my next ? concerning g29 sf) 2. I was entertaining the thought of trading my g29 for a g29 SF. will my 29 mags work in the 29 sf ? or are the mags. for the 29 sf a different size? Thanx in advance.