I have a G31 and I want to pick up a 40 cal barrel for it. It's my understanding that a factory barrel will work and there's no need for a conversion barrel, the mags will work too, is that right? My main question is where would be the best place to pick up the barrel at the best price? Also I was wondering if anyone has bought ammo from luckygunner.com and if they're a good outfit to deal with. Looking for the best online ammo prices with a reputable dealer.