Uncle- please do not take this the wrong way, but will be blunt- you may be out of your depth on this one.
If you have not previously designed a rifle in a lesser power range, what you are doing is equal to deciding to run your first race ever as a full marathon.
There are different .50 cal cartridges- I am assuming you mean .50 BMG- and there are some notes attached for you HERE: .50BMG - Specifications, History, Facts and Myth
You should spend some study time learning what the terminology is, and how it is applied, and the forces involved. Otherwise you are likely to violate ethical standards of engineering, wound innocent bystanders, and require members of the Society of the Steel Ring to come to Australia and smack you in the noggin.
If you do not know what the Society is, talk to one of your Engineering Profs.