[Michael Zeleny]

Originally Posted by SIGP2101

That is the problem, then they start playing with springs, modifying them, exchanging them, replacing them. Then they sell it to the next person and fiddling continues.

Only way to modify P08 to digest modern ammo would be to some how magically increase overall mass of the breach or move forward the point where rear toggle link links with 'S' link . Moving this point forward by even a fraction of a mm would tremendously decrease cycling rate of toggle train.
Increasing or decreasing spring preload will lead only to premature wear and tear of various parts.

You don't need to increase the mass of the toggle train, provided that a heavy and/or long barrel is in place. An increase in the mass of the canon assembly generally suffices to delay the unlocking of the breech to the point of ensuring reliability.