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.

   

 

POWDER

VELOCITY

FILLER

BULLET

EXPANSION

 

 

 

 

 

98 RL 15

2030

5 GRAINS DACRON

570 BARNES X

0.6360

100

2020

 

 

0.6360

102

2060

 

 

0.6365

104

2080

 

 

0.6365

106

2100

 

 

0.6365 2

108

2144

 

 

0.6365

110

2115

 

 

0.6370 2

114

2230

4 GRAINS OF DACRON

 

0.6370

116

2262

 

 

0.6370 2

118

2285

 

 

0.6370

120

2320

 

 

0.6375 1.5

98

1985

 5 GRAINS OF DACRON

600 BARNES SUPER SOLID

0.6365

100

2030

 

 

0.6370

102

2060

 

 

0.6370

104

2060

 

 

0.6370

106

2074

 

 

0.6370

108

2100

 

 

0.6370

110

2157

 

 

0.6370 1.75

112

2190

4 GRAINS OF DACRON

 

0.6370

114

2216

 

 

0.6375

116

2247

 

 

0.6375

118

2280

 

 

0.6375

120

2325

 

 

0.6375 1.0