Strawed parts surface roughness
 

This is for a couple long term projects that are totally unrelated to Lugers, but I happen to really enjoy the finishing work done on my 1936 S/42 P08. I have a couple of bolt action rifles that I think I'm going to try refinishing with rust blue, but the harder/spring parts (extractor, etc..) I wanted to straw finish, and the screws I'd like to temper blue.

I have messed around with various grits of sandpaper, and none of it looks quite the same as my Luger. I suppose it doesn't necessarily have to match exactly, but I like the surface roughness on the Luger parts-- not too coarse, not too polished.

If anyone has suggestions, I'd greatly appreciate it.

Try a wire wheel on your grinder motor.
There are fine and coarser wire wheels, one will probably suit you.

I would be very careful and suggest you not attempt to fire blue/re-straw some of those parts - especially springs - if you don't know what you're doing. Those colors come from heating the metal to a very specific temperature. Heating already-hardened steel, springs, etc., will anneal them/ take the temper out.
YMMV

The "springy" parts are Mauser style extractors and extractor collars. The temperature for straw color is what I'm least concerned about as it's almost a minimum for any hardened part to be tempered. In fact, you'll often see springs of various application already come that color if they haven't been polished since heat treat. The blue color is going to be reserved for screws that don't bear any significant loading.

Tempering twice at the same or lower temp may slightly soften the part but in the case of the parts I'm looking at I'm not worried about it. Worst case scenario I bend an extractor and order a replacement.

I'll give the wire wheel a spin! I hadn't thought of that.

Mauser 1898 rifle style extractors, I mean. Nothing related to Lugers other than I'd like a similar overall finish. Rust blue with heat blue and straw accents. Actions are new production; CZ and American Rifle Company.