To gain space at the rear you must allow the bolt to travel further back.
The bolt stop must be modified and it's better to choose an ejector blade with oval pivot hole.
Making a special magazine box that fits the receiver machined -the original opening is extended at the rear- with a restrained modification of the feeding ramp, allows sufficient room for the cartridge.
Notice also that to prevent any jam when unloading an unfired cartridge, the loading "window" on the left side as to be opened and that's a good choice to replace the original short extractor by a longer magnum one.

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