From Start to Finish, Page 2

With the barrel work complete the only otheadstampher modifications to the Ruger were the feed ramp and to create all the depth possible in the magazine box to allow for three of these big cartridges and still be able to close the bolt over them with an empty chamber. For the magazine capacity, the removal of about thirty thousandths off of the bottom of the follower did the trick. With three cartridges the bolt will just close over the cartridges and allow you to have a fourth round in the chamber. The feed ramp was widened a bit because the Mbogo cartridge has a minimal body taper and is .5750 at the shoulder. Bill Crosby of Burnaby B.C. did all of my gunsmith work and to date has put together three 470 Mbogo’s. He was able to solve the problem of re-chambering an existing 416 Rigby chamber to a 470 Mbogo without running into chattering as the reamer engaged. A longer pilot would be recommended for a re-bored barrel with an existing 416 Rigby chamber. The cartridge was designed for a maximum case capacity while having a thirty five-degree shoulder and enough neck length to allow for a good bullet hold. The large case capacity along with a .400-paralleled throat really helps to keep the over all pressures down.

I settled on Reloader 15 powder for this cartridge as it seemed to be very accurate and I was able to get soft points and solids to impact together with this powder. With a measured amount of Reloader 15* and a 500-grain Swift A-Frame it was very easy to reach the 2500 feet per second mark that I was looking for. Many of the cases used were reloaded ten to twelve times and the primer pockets were still as tight as the new brass. All other pressure signs were mild also, case head expansion, primer conditions and extraction. Using the Load from a Disk program the approximate pressures should be in the 53,000 psi area. The maximum pressure level for a cartridge of this type should be in the 64,000 psi area. For solids I picked the Trophy Bonded Sledgehammers which loaded to 2480 fps grouped together with the Swift A-Frames. With the loading portion complete for the cartridge and the rifle all together my hunting partner Chris and I were ready for Africa.

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