FWIW, Sabi Rifles in Nelspruit South Africa made me a 500 Jeffery on my Weatherby action and it's just brilliant. They also make them on vaarious other actions like Mauser & Rocky Mountain etc and they can make them with staggered or straight feed mags. They tell me that the straight feed is easier to get to cycle reliably.....but that said, even the staggered feed rifles they make I've seen of theirs work well...... I think it's just a matter of having to put more work into a staggered feed.

I'm not a gunsmith, so can't tell you how they do it, but you could contact them on www.sabirifles.co.za if you want to.