I think that is a good question, I have always been uncertain too. The basic deal is evident: back thrust is case head area x pressure, which is expressed as pounds per square inch! So a Hornet generates about as much back thrust as a 32-40 schuetzen load, both of which are nearing the Low Wall limit. My problem is yours, I don't know whether to use the whole case head area (bigger for rimmed) or just the area of the base of the powder column. I have read it both ways. If it is just the powder column, you would think there would be no real back thrust difference between the case types. I do know that the rimmed versions (7x57R vs. 7x57) are normally loaded down a bit, possibly because of the rifles they are used in. Maybe a real engineer can explain it to us.
Last edited by 1878; 11/19/11 09:26 AM.
