Use standard velocity ammo like the Winchester 115gn white box low cost ammo you can find in Walmart.
Don't use something that is rated as "NATO". It's higher power and higher velocity.
The Remmington ammo is apparently about 50fps hotter than the Winchester.
One thing to verify is that the recoil spring is the right one for the model Luger you're shooting, and that it's in good condition (consider a
new Wolff replacement for the Luger you'll be shooting regularly).
You can get a range of recoil spring strengths in a kit as well...
Marc
__________________
Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.