Kuduae, you are correct on pressure exerted on the bolt lugs and few realize this important factor.

I was in the midst of designing a 50 BMG action in 1995 and "discovered" the proper manner in which to calculate bolt lug shear strength and the forces generated by various cartridges on the bolt lugs. I obtained the cartridge case rear area by sectioning cases and precisely measuring for calculations.

I "built" an Excell Spreadsheet to calculate the shear strengths of various actions, and the resulting force generated by many of the big bore cartridges at various chamber pressures.

If anyone is interested I will post the data calculated, it is extremely interesting to a big bore rifle builder.

I also have used the Oehler M35 Velocity and Chamber Pressure system. This instrument has given me valuable insight in what is real and what is false concerning cartridges and pressures.