dude there is plenty of 7.62x39 Veprs, supr Veprs too. and the supersuper Vepr in 308 whoah baby.
Anyway I think Saiga has its own magazine and Vepr has its own magazine.
Im pretty sure that with Vepr you are using Vepr mags, and Saiga you're using saiga mags. I know from reading plenty about it , Saiga you can modify to use AK mags ,I am not sure if at all you can do that to a Vepr.
One of my quandry was ,around Christmas classicarms.us had a sale (Still mostly on) of Saiga 7.62's for lik $330 bucks, and they actually had converted into AK looking Saiga's for only $499. now they had all sorts of magaxzines on sale but NJ you can't use hi Caps. So if I got hte converted $499 Saiga I would have to find me some AK Magts in 10 rounds (Dont even bother looking for 15 rounds thy just aint findable) ... I read that once you conver the Saiga to use Hi Caps, you can't any more use the regular saiga mags. They were sellinng new factory Saiga mags for $9.99. (10 rounders). So what I figured was, all in all, it woould be smartest for me to buy the $330 Saiga 7.62 "sporter rifle" and maybe 10 (or 15-20 if i had the money which i really didn't) of the Saiga 10 round magazines,... and I've have a great great last-forever 7.62 rifle and plenty magaazines that wwre new and good deals. Then I could decide what to do with the Saiga (I'm leaning to say the Midwest Industries quad rail, an Aimpoint Micro/Eotech XPS/ Primary Arms microdot reflex sight, an Angled Fore Grip by magpul for the bottom, XTM panels across the sides, and just have a killer scout rifle in 7.62...