About 25 years ago, I read an article on these and recall they made brass for it by shortening .30 Carbine cases.... Hmmmm....
(gets up, goes to file cabinet... rummage, rummage, rummage, "Ah, here it is, Guns and ammo, August 1974"... 28 years ago next month! Mom always said I was a storehouse of useless information!! [:D])
"The Roth-Steyr had a trigger pull of 11 to 12 pounds... Parts marked with K are made by Waffenfabrik Steyr, and those by Fegyvargyar Budapest are marked with R. A pistol made with parts stamped with both codes was probably made up from spare parts. Most parts were rust blued, while the slide was left in the white and polished. The trigger had a grey hardened appearance. (He notes that some pistols may have been phosphated (parkerized) for issue by the Germans in WWII.) Under the cocking piece there will be a coded stamping for the government acceptance; "w-n" signifies Vienna, followed by the 2-headed Austro-Hungarian Eagle and year of acceptance. On the right grip is a 3/4-inch disc which gives the regimental history of this pistol including its number in that military organizations. Most R-S's examined have had these ID discs blank, meaning they were not permanently issued to an organization. Barrel bushing has the last two digits of the serial number. The barrel, while having no SN, has on its rear locking lug, the letter "o" -- this stands for "oben", literally, this side up when reassembling. The slide has the last two digits on its main spring lug. The left grip assembly has the entire serial number on the inside of this fitted part. The magazine assy. (internal, not the clip charger) has the last 3 digits of the SN at its bottom. The R-S has a very simple takedown system which requires no tools for a full field stripping. "
Unfortunately, he doesn't give details of how to field strip it. They do state ammo can be made from cut-down M1 Carbine ammo but don't give the info on whether inside neck reaming or any other special steps are needed.
I remembered this article because I always lusted after one of them, for some strange reason...
Hope this helps,
John