Well, both are flanged. The .375 Flanged 2 1/2 NE could I guess be called an extra long blown out .303 case. The 375 Flanged Magnum NE is similiar to, but not the same as the .375 H&H.

I was going to build a .375 Flanged Magnum on a 100 year old+ Westley Richards Martini Henry MK III style action. I could not get comfortable with that, because I do not know what the composition of the steel is in the action. The action was probably made any where from the late 1880's up to the early 1900's. I definitely would not build a .375 Flanged Magnum on any former Military gun. The type of steel is just an unknown factor. I don't think the gun will burst, but I do believe it will stretch.

My 375 Flanged 2 1/5 and I have killed a lot of paper, but the gun and an animal and I have not been present on the same field yet.

The fellow I bought the gun from was using it to shoot High power rifle matches at ranges of 200, 300 and 500 yards.