Unspellable,

Thanks for your comments. I was looking into every book I have (it does not seem that I have enough books) to find some data on the correlation between powder charge increase versus pressure increase.

As far as I can see from the previous messages I have learned the following (please everyone, correct me if any statement is incorrect):

1) To safely proove any gun, you must fire it remotely by means of a long string attached to the trigger and the gun must be in a sort of "fixture" that holds it in place. Shooter must be protected to avoid injuries;

2) As for the loads to be used we have two methods in discussion here:

a) Increase pressure 30% by means of increasing the powder charge of a maximum working load by 7%.

This looks like a good rule of thumb, but I think that two important considerations must be included: the proportion of charge X pressure increase may be considerably different from one powder to another, and, without any means of measuring the pressure, how can one be sure of the pressure in tests?

b) As an alternate method, increase muzzle energy 10% by means of increasing bullet weight 10% on top of a maximum working load.

Does anyone know if an increase in bullet weight would correlate to a proportional increase in pressure, i.e., if by increasing 10% of bullet weight, pressure will also be 10% higher?

As a side note, I have been thinking that, whenever someone mentions any change in a double rifle or shotgun, we tend to think of proofing or re-proofing. How many bolt action owners have rebarreled their rifles and never given any thought of re-proofing them after the change?

Fred