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Clark · September 18, 2011, 10:15 PM

The tricks I have learned for the 300 Win Mag, or 7mmRemMag, or 338 Win Mag or most belted magnums:

1) The first shot is headspaced off the belt. After resizing the firing pin may push the cartridge forward until it is stopped by the belt or by the shoulder. If you push the shoulder too far back, it will be working off the belt. The problem with that is that the factory rifles are head spaced more that .220" and the belt on the brass is less than .215". The brass is not going to last long getting worked like that. So for long brass life, push the shoulder back .001" or none at all and just neck size. This means the brass might get dedicated to one rifle.

2) The case right in front of the belt will expand, and the sizing will not resize it. The brass will fit back in the rifle that fired it, but to use the brass in more than one rifle, you may need Larry Willis' collet die. This means the brass might get dedicated to one rifle.

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

3) The parent case, the 1925 invention of the 300 H&H magnum is a little stronger than the 1889 7.65x53mm Mauser case head [30-06 type case head], but not much. Hot loads will make the primer pocket loose. The Mauser case head with large Boxer primer will have a threshold of ~ 71kpsi Quickload and the H&H case head ~ 78kpsi. Subtracting off a safety margin for a litany of variables will bring the loads down closer to 65 kpsi. This is expensive brass to be throwing away. A good measure of a load not being too hot, is that a piece of brass was fired 5 times with that load, in hot weather, and the primer seating still takes force. This means not only good note-taking is needed at the range as to what was the load, accuracy, and velocity, but good tracking of the history of each piece of brass. That is too complicated for me and too time consuming to drive to the range. So I walk from the reloading bench to out in the woods and shoot one in the dirt. Repeat, repeat, repeat, repeat. Then the safety margin must be subtracted from that proven load. Vernon Speer 1956 would reduce powder charge by 6%. Loads developed from this process are then the arrows shot into the fence and SAAMI registered max pressures are the target later drawn around the arrows in the fence. Load books are later loosely based on the target painted on the fence. Load book fundamentalists carry pieces of the fence in an ark and conduct rituals with strain gauges. These men, like Indiana Jones, will warn you, "Don't look at the brass!"

107kpsi on a belted magnum case... destruction..don't do this

September 18, 2011, 10:15 PM	#4
Clark Senior Member Join Date: December 4, 1999 Location: WA, the ever blue state Posts: 4,678	The tricks I have learned for the 300 Win Mag, or 7mmRemMag, or 338 Win Mag or most belted magnums: 1) The first shot is headspaced off the belt. After resizing the firing pin may push the cartridge forward until it is stopped by the belt or by the shoulder. If you push the shoulder too far back, it will be working off the belt. The problem with that is that the factory rifles are head spaced more that .220" and the belt on the brass is less than .215". The brass is not going to last long getting worked like that. So for long brass life, push the shoulder back .001" or none at all and just neck size. This means the brass might get dedicated to one rifle. 2) The case right in front of the belt will expand, and the sizing will not resize it. The brass will fit back in the rifle that fired it, but to use the brass in more than one rifle, you may need Larry Willis' collet die. This means the brass might get dedicated to one rifle. CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information. 3) The parent case, the 1925 invention of the 300 H&H magnum is a little stronger than the 1889 7.65x53mm Mauser case head [30-06 type case head], but not much. Hot loads will make the primer pocket loose. The Mauser case head with large Boxer primer will have a threshold of ~ 71kpsi Quickload and the H&H case head ~ 78kpsi. Subtracting off a safety margin for a litany of variables will bring the loads down closer to 65 kpsi. This is expensive brass to be throwing away. A good measure of a load not being too hot, is that a piece of brass was fired 5 times with that load, in hot weather, and the primer seating still takes force. This means not only good note-taking is needed at the range as to what was the load, accuracy, and velocity, but good tracking of the history of each piece of brass. That is too complicated for me and too time consuming to drive to the range. So I walk from the reloading bench to out in the woods and shoot one in the dirt. Repeat, repeat, repeat, repeat. Then the safety margin must be subtracted from that proven load. Vernon Speer 1956 would reduce powder charge by 6%. Loads developed from this process are then the arrows shot into the fence and SAAMI registered max pressures are the target later drawn around the arrows in the fence. Load books are later loosely based on the target painted on the fence. Load book fundamentalists carry pieces of the fence in an ark and conduct rituals with strain gauges. These men, like Indiana Jones, will warn you, "Don't look at the brass!" 107kpsi on a belted magnum case... destruction..don't do this __________________ The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought?