500Grains

Thanks for the tip on the Lilja website, I checked their article on bolt thrust as you suggested and they use internal case diameter and pressure to calculate the backward thrust generated by a cartridge onto an action.

I had thought of this but as my database only lists external head diameters I have used them in lieu and stuck to relative statements.

But, the good news is, this means we can say that the 45/70 405gn at 1850fps and the 45/90 405gn at 2050fps generate the same back thrust (same pressure same case head).

AR2201
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