Of course!
Essentially, keep everything like a standard rifle, but either open the bolt face to magnum or use one already opened, such as a David Lloyd bolt.
Remove material from the back of the action in the majority, and a small amount from the front. You will need to alter the feed ramp substantially to a larger curvature and width, a dremel or similar is useful for this as it can come in from the mag weld side.
The feed lips within the action need to carefully and slowly be rounded to a larger case, so essentially making a larger internal curvature again. They will need to be shortened substantially in the front, up towards the feed lip area, and again, with a round ball head polisher or grinder, very gradually made to fit the case dimensions. You can also turn the receiver on its head, upside down, and looking down into the mag weld, keep running a ball head grinder up and down the underside of the feed rails until you get a nice fit. Then you need to turn your attention to the feed angle, which is a similar procedure, and a bit of metal needs to be removed very very gradually until they slide fri. The new shaped feed rails, right onto the feed lip and into the chamber. This part is really ‘feel’ work.
I also chamfered the outer edge of the extractor claw to allow the bolt to slip over a round that jumps into front of the bolt accidentally.
You will need to remove some metal from the rear bridge front and upper sides, take it back enough to align with where you stopped lengthening the action internally, and follow this upwards, gradually curving it into the top rear bridge for a continuous look. In the front, just a small notching is potentially needed.
Now, some advocate cutting the rear mag wall and moving it backwards, then lengthening the magazine walls and making a release catch.
In my case, I adopted a more vintage London style, and cut the entire mag box off the bottom metal, and then used the internal walls of the stock as the mag box, ensuring the stock in letting made a perfect fit with the receiver. The stock was relieved of wood to match the lengthening of the rear bridge. In fact, the stock was relived by an additional 2mm approx, and a piece of flat steel was screwed into the stock, to act as the new rear mag box wall, the cases glide better with a steel rear mag box wall, but I didn’t want to build this into the floorplate/bottom metal.
The floorplate was welded shut to avoid risk of round dumping under recoil.
The follower angle was amended to allow for the wider cases of course.
Not opening the feed rails too much is absolutely key to avoiding the issue described above, with cases jumping out of the magazine from the top, and I suggest when rounding the inside of the feed rails, to eat metal into the under sides of the action, to essentially widen it inside under the feed rails. If you have a mill, it’s an easy job, and the slightly ‘wider’ internals mean there’s more feed rails to stop cases popping out
