Ive mounted hundreds of these in the past. It had to do with manufactures of gun companies not thinking through the process of mounting a scope and designing a gun.
Here is a example of a FN Mauser action that required the hence longer tube in the back and a shorter tube in the front. A Longer Tube in the front would have interfered with the Rear Sight. Yes one could remove the rear sight on certain rifles with a removable rear sight but as you can see on this particular model it had a integral REAR base making it impossible to remove. Many Safari rifles of the time with Magnum bolts had extremely awkward bolt throws and hard to fit scope mounts. Picatinny rails were non existent and Weaver bases were deemed insufficient to hold up to recoil to heavy recoiling rounds in a safari rifle. Weatherby, FN, Sako, Browning and several other manufactures were all Guilty of making rifles that required these odd scopes of the time. They were most popular in the 70', 80s to late 90s.
BOB EMMONS 375 WEATHERBY MAG TOTAL CUSTOM- FN MAUSER ACTION- 1/4 RIB with INTEGRAL SCOPE BASE- QD MOUNTS- 2.5 x 8 LEUPOLD- ACCURATE RIFLE- 98% COND. for sale online.
www.gunsinternational.com
Browning ~ High Power Safari ~ .30-06 Springfield for sale online.
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Caboth/Kaufman .416 Rigby for sale online.
www.gunsinternational.com