505 Gibbs

The following data was developed by our friend Nick Caico

  This is my personal rifle I had built for me by one of the small South African companies I represent  through my website "BigBores.Com". It has a 22" Truvelo Barrel (R.S.A.) on a new CZ-550 action with no brake. It has a mercury recoil tube but a standard English style pad.

My focus was to have a most powerful heavy game rifle that remained shootable in the field.

To this end, I selected a faster than usual powder, in RL-15, in hope of achieving the desired 2300+ fps with a minimum of powder burned, thereby minimizing felt recoil. I think I have accomplished this as the rifle is not much more difficult to handle than is my .458 Lott shooting 450 Grain bullets at 2450+ fps. Having no baseline data I started at 98 Grains of powder with 5 grains of Dacron filler.

The "Pressure" readings are taken at the expansion ring (or pressure ring) just forward of the extraction groove. As with belted cases, I find that .0035" expansion ( above the unfired case dimensions of 0.6350) indicates a maximum loading. As the 120 Grain loads here measure at .6375", they indicate + .0025" above the unfired case allowing further powder if desired.

  All bullets were moly coated, and the Federal 215 primers were used in all the loads. Groups size of some of the loads are shown in the EXPANSION column.