The action was originally a savage 110 in 270 win center feed blind mag, and I now put a 243 win barrel on.

With this set up the 243 round pops out the lips before the bullet enters the chamber of the barrel, creating a situation where the rear of the case jumps out of the receiver, leading to misfeeds / jams.

I have read here that the feed lips of the magazine need to be adjusted (and maybe the magazine spring). The question is, ho do I go about this? Do I close or open the feed lips? and take some tension off the magazine spring or leave that spring alone?

Thanks for the input :)