Lugers like to be clean, and oiled.
Also, the original springs (talking mostly main spring here), unless they were tampered with in the past, they are generally the best option. They seem to last forever. Count the coils. If it's a WWI Luger it should have 19 coils, 21 if it's a 1936 to 1942 Mauser. I'm not familiar with Simsons or Krieghoffs (too rich for me
) so I won't address them. And since I have no Erfurts, I won't say anything about them either.
For .30 Luger, I only have one. 1909 Portuguese Army contract. It has 14 coils. And it works great*.
* I have never fired Fiocchi on it. Maybe the problem has already been addressed by Fiocchi, I don't know. But there was at least a batch that had the shoulder in the wrong place and they gave headspace problems. In a Luger an excess of headspace can lead to a broken breechblock(at the rear end), and that can ruin a fellow's day. Seen it happen, and more than once
. Rule of thumb fire five rounds. If you have any pierced primers, don't use that batch in a Luger anymore.
PS. What ammo are you using?