I don't know, but it seems that my S&W's magwell is a little smaller than on other 1911s I have. Some magazines are a tight fit in it's magwell but not in other guns. The Wilsons aren't one of them, though.
I havent had this problem, I have 6 WC mags all off them work great.
One thing I will mention, is if you over tighten the grip screws it might grab the side of the magazine creating a tight situation. The boss the screw feeds into on the Smith frame came loose on mine one time. It had been striped at the factory, I orderd new ones (free) from Smith.
I just bought new WC grip screws the other day and they went in with out a hitch.
I currently use Houge rubber wraparound's
Both my stainless sw1911 and my scandium came with Wilson mags from the factory. My friend bought one not too long ago and it looked like Smith is using Novaks mags. I have never had a problem with my Wilson mags.
That is sort of a hoot as back in about 2005 or so I bought a S&W Commander size pistol with the Scandium/Aluminum frame. As part of the deal you got two extra free mags. Did not sway my decision to buy the pistol but I sent the coupon in with a copy of the sales receipt. Now the pistol came with two ACT mags made in Italy. They worked O.K. Anyway when the free mags came they were Wilson 8 rounders. They work fine. Need picture of the pistol where I did switch the grips out for some from Carbon Creations.