In the 300WM
Federal cases have 92grains of H2O (capacity) and,
Winchester has 93.8.
This difference in volume, even with the same amount of powder is going to result in different pressures.
Quickload computer simulation
Using the Winchester cases you get a pressure of 52,887lbs.
Using the Federal cases you get a pressure of 55,378 lbs.
This means there will be roughly 40fps difference between the two manufacturers cases but both are still way below the SAAMI peak pressure of 62,366lbs. You get more velocity out of the Federal cases at about 3,100fps mark (depending on your barrel length) but as far as pressure is concerned they are both mild loads.
Something else is wrong. If it was easy to close the bolt it could still be too much headspace. Not enough headspace makes it difficult to close the bolt and that is way more safe than too much headspace. Too much headspace results in the case rupturing, and that will occur with any load; hot or mild.
Federal cases have 92grains of H2O (capacity) and,
Winchester has 93.8.
This difference in volume, even with the same amount of powder is going to result in different pressures.
Quickload computer simulation
Using the Winchester cases you get a pressure of 52,887lbs.
Using the Federal cases you get a pressure of 55,378 lbs.
This means there will be roughly 40fps difference between the two manufacturers cases but both are still way below the SAAMI peak pressure of 62,366lbs. You get more velocity out of the Federal cases at about 3,100fps mark (depending on your barrel length) but as far as pressure is concerned they are both mild loads.
Something else is wrong. If it was easy to close the bolt it could still be too much headspace. Not enough headspace makes it difficult to close the bolt and that is way more safe than too much headspace. Too much headspace results in the case rupturing, and that will occur with any load; hot or mild.
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