About 10 years ago i built my first 50BMG rifle, although it was a riot to shoot, i was intriqued by the BMG case. I have seen lots of wildcats over the years on the big 50 case, seems they just didnt take off due to the fact of just too much case capacity. I was allways going to shorten one up and design a shorter version. Seems the whole project just got lost in my note book. I found my old plans several weeks ago and re-started the idea. Since my first thoughts on this i have been designing and building actions so that part is simple now. Next item was what Cal.? Back then, not much for high BC bullets and i didn't want a 50 cal. I was thinking of something in the 40 cal range, I feel the 338 is just too overbore in this large case. Then came along the .408cal bullets, now there are choices and more on the way in high BC projectiles. This sparked my interest in the project again. I had started to make form dies to shorten the BMG cases but found that the military allready has one called the 50 Spotter case. It is 3" long, perfect for what i had in mind, H2o capacity is 200grns on a military case. I procured some to work with and see what can be done with the little sticks of dynamite! After several hours on the Auto-Cad program redrawing the case to a more prefered dimension, i have come up with a great looking new cartrige.
Here are some of the specs:
.800 base dia.
.731 shouler dia
Base to shoulder 2.350", moved foward .300"
Base to neck 2.550
Neck dia. .443 od.
Neck dia. .405 id.
Overall case length 3.00"
Shoulder angle 37 deg.
The case taper was not changed from Military specs. This case will extract very easy even in high pressure loads. 55,000# to 63,000# will be the usefull range for the BMG case. With the 400 or 419grn bullets, estimated speeds are 3300fps, that will give just over 10,000# of muzzle energy.
500yd sight in: +14moa will =1000yd hit. +45moa= 2000yds
These are early estimates.
The new case design resembles a WSM short mag case on steriods!
This will only work in a BMG type action due to the large case head dia. I have designed a short BMG action just for this case, 1.900"diax 10.5" long...single shot or repeater.
Two lug bolt similar to a rem 700 action. My test rifle will have a 1 x13 twist bbl 32" long. I should have test results sometime this summer.
This is the 10,3mm Sniper-Tactical with 419grn bullet.
Here is a comparison with a Pepsi can.