DH, Xausa is correct.

Getting the feed rails opened up will not help an OAL problem. That can be addressed by taking material away from the feed ramp, etc, but that is not a minor job and you'd probably spend less time working up new loads than getting a gunny to fix it.

Sounds like you might have a single loader there. Many 98 actions {24/47's, some Czechs, etc} are better candidates for the .358 Win or even better yet, the 9x57, 9.3x57 or 9.5x57 than the .35 Whelen. Sounds to me like a fellow got the gun going and left off the mag work.

Your problem is very much like that faced by owners of commercial 96-action Husqvarna 9.3x62's that will not take many factory-length cartridges and must be used with shorter-than-normal length handloads or factory rounds with bullets seated deeper.

I am dealing with a similar oal problem caused by a different reason; leade. My magazine on a couple Ruger 6.5x55's will handle long rounds, but the leade will not. I have had to seat bullets deeper than that allowed by older Rugers and Swede milsurps. So far merely seating deeper has caused no pressure problems for me and may not for you, but then again, I cannot say as seating depth can alter pressures so be careful.