I’ve heard of that too, but only recently. Main trick I was taught was to use water—preferably hot soapy water—to dissolve and wash the primer salts out of the barrel.
Interestingly, while use of ammonia dope was supposedly banned by the US Army in the 1930s, a 1950s manual from FN of Belgium (describing depot-level maintenance for the FAL rifle) still listed the recipe and how to use it.
Some people have told me it would ruin a gun but I have been using it for over 40 yrs and never had a speck of rust! it is also good with black powder.