Hi,
In general most open bolt SMG's for military use can run hot loads w/o immediate damage. Spring force and bolt mass remaining the same, I tend to develop loads that make the gun run smooth, reliable, and accurate. On days that I don't heed my own advice, I've developed loads w/158gr bullets running at 1025fps from a 10" barrel Uzi. In the end, I slowed the load down to about 980 fps as unlike the military, I can not afford to replace/repair my guns more often than required.
Read older reloading manuals and watch your OAL carefully and "hot" loads are easily developed. (Never load a "hot" load short as pressures go up in a hurry with the 9x19.) It appears the latest crop of manuals have a bit more margin built in for folks not following the book.
Enjoy,
K2