Conventional wisdom is you can't get this round to feed. I have gotten all sorts of rounds to feed in these actions so I am wondering if this is doable, before I go ahead and rent the reamer and chamber the barrel. What's so hard about this round in a staggered magazine? It's just a short 243.

I know its not a Mauser but I have a Howa 1500 chambered in 6BRX that I put together as a hunting rifle for my daughter. It feeds fine most of the time, for what ever reason it has some trouble with the lighter varmint bullets.

Hi Russ, Can we assume the action is currently in 243 Win.? Which model 98?

The only feeding problem I see could be caused by the shoulder width. It is only slightly wider on the 6mm BR. But, the shoulder position is further rearward than that of the 308 or the 243 for that matter.
You might get lucky with a half inch spacer in the back of the magazine possibly followed by a slightly wider 6.5 Creedmoor follower.
Any further tweaking (if needed) should be done by a qualified gunsmith with feeding experience.

I tweaked one myself. But, it was my own gun which was a 8mm Mauser to 6.5 Creedmoor conversion. The spacer helped a whole lot. Then a Rem 700 243 follower was used. 2 out of 4 rounds feed now. I plunged into the right rail work and was successful. One or two thousandths metal removal at a time got me there. Took hours. A qualified pro, much less time I'm sure.

So, it's doable.

I tend to use a 1/2 inch ball end mill and it takes a minute per side, to remove the inner rail that is for 8mm/7.65 feeding. That is for 400 Whelens. Maybe two minutes.
For smaller rounds, with no taper, just make the rails not as tapered.
Best to block off the box to match the round.
Remember that all new rifles don't use cartridge specific feed rails; they control feeding with sheet metal boxes with the lips bent to suit.
Clean up any part you can't reach, with carbide burrs. Then smooth.

It's just an action, and it's a 93 (so 7x57). I know the pressure is over what is normally considered safe but with that super straight case I figure the back thrust is going to be lower and in any case I reload so I control the pressure.

I have done 250 Sav in a 98 and yes, the rear of the mag is blocked off and a shorter follower used, commercially available. That works like a charm with no further mods.

I have done long belted mags in a 98 and that does require a lot of surgery and trial and error mods to the rails and the feed ramp. I made custom mag boxes for both the 98 and the P14.

I just got my PHD in sheet metal magazine feeding/design by getting a 41 mag to feed in a Sav 340. Took days to figure that out.

Really looking for someone who has done this BR in a mauser crf action and got it to work. Every forum posting I have read says it can't be done.

People are not always right. Maybe, they intend to mean that THEY can't do it unless there is something in a 93 action that I'm missing. I think you have the persistence & knowledge necessary to make it feed.

I've got a 22 BR, on an old Sako L 579 action that was original a 243, feeds like butter with no work. Because of the shortness I have to be a bit careful with loading the magazine.