Hello. The only magazines I'm aware of that were sold as Browning higher-than-normal-capacity were 20 round magazines. Don't know much about them, but I am not aware of any FN-made or authorized 30 round magazines.
I own a 30rd U.S.A. magazines for the BHP that I bought before the 94 crime bill took effect. What a piece of crap! I was taken hook line and sinker on this impulse buy. Used once then still lying in a junk box in the basement. Gave the other one away to a friend who reminds me about all the time concerning quality and reliability. Basically stay away from the listed 30rd mags for this pistol.
I do own a few FN contract and Mec-Gar 20rd magazines. Both of fine quality and MG's are readily available. Have not seen many FN contract 20rd magazines in sometime. If you can find them and determine they are FN, snatch them up!