Hi,
Making a .375 H&H Mag lenght rifle on an intermediate action like the Aregentine 1909 is not a problem if you work on the rear of the magazine.
this is a problem with 98 actions but not on 1909s.
The magazine is lenghted to the back and the bolt stop move back.
I had a .375 H&H Mag. that works perfectly and a friend have a .416 Rigby also.
Hope this helps
Martin