Some years back the Rifleman ran an article on chamber rusting with the, then New, plastic hulls. Their conclusion was the paper hulls which had previously been in use did indeed leave a wax deposit on the chamber walls which protected them.

Plastic hulls left no protection & the chambers were left in a bare & unprotected condition. I believe this very well agrees with TW's comments.

One question on the motor oil. Is there a specific reason it should be non-detergent? Another question, what are the rust protecting qualities of Synthetic motor oils vs the regular mineral oil types.
I use Mobil-1 for lubrication purposes on some items I use regularly with very good results, but am unaware of any synthetic motor oil which is non-detergent.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra