Is a powder change needed for my mauser 43

[Patrick Chadwick]

The answer is - in principle - yes. However, there are so many variables that play a role. For instance, if the diameter of the lighter bullet is just a tad (US unit of measurement) or gnat's whisker (British) larger, then it will be a wee bit tighter in the neck and may well achieve a higher velocity. On the other hand, if it is set to the same overall length, then there is a small space under the lighter bullet, causing reduced peak pressure and hence muzzle velocity ... and then, again, etc etc...

In other words, forget theory, you are going to have to try it out. As a first step, I suggest you load the cases with the lighter bullet to exactly the same overall length as for the heavier bullet, establish the difference in the height of the bullet base, and adjust the powder accordingly, to have the same packing density as before. Assuming, of course, that the seating depth was optimized in the first place...

Sorry I cannot be more precise!

Patrick