Yes the 40s&w's are 15round mags.Maybe you have 10 round mags but doubtfull,yours would be large frame mags. When new they are hard to load. Do take apart and clean and oil lightly with break free or some other synthetic oil and use a finger nail fill and knife to clean up any plasitc, radius and smooth all edges. Then load your mags to ten rounds and let it set over night and try again tomorrow. I about broke my thumb loading mine at first and still took a couple weeks to get that last round in. Do the mags you have work in your gun? If you do put 10 rounds in and the rounds cover the last hole on the side of the clip and when you clean it there is no block in it they should hold 15 rounds. Another good place for witness info is( brian enos eaa forums )and for accesories and help is (henningshootsguns) Aftermarket mags seem to be all 10 round mags ,seem they don't know the full size frame guns are made but eaa has been good for me and henning is a good place of mags, sites all kinds of upgrades. I think eaa also has a 25 round mag you can order.