Good way to buckle a case especially if it is a compressed load. The best option in my opinion is to take a reamer to the short chamber and try to get as good of a match as possible. It can be done by hand and if not a major difference then you are basically just polishing the chamber. Another option is to take a fired round from the 788 put some valve grinding compound on it chuck it in a drill and polish the Model 7's chamber. But I would first check the head space on the 788 as they are rumored to have bolt setback problems more easily due to the rear lug lock up. Best option set the barrels back and rechamber both with the same reamer this would give you the best chance of having interchangeable ammo if the throats and chambers match. Not sure if it's available but using nickle cases for one and plain for the other could prevent headaches of just two different head stamps.

My 2 cents and worth every penny.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli