Hoppe's is a great solvent, but it has zero rust preventive qualities; it wasn't made to have any. A swab or patch dunked in 30wt. non-detergent motor oil and run thru the bore afterwards will likely prevent what you are experiencing & a tight fitting paper towel 'patch'/wad run thru before use again will remove enough residual oil film for it not to be a worry.
FN Browning's are noted for their ability to almost rust their chambers before your eyes in our humid environs. A motor oil patch after use will prevent it from taking place & its better if you have a chamber brush of some sort to use first. Speaking here to field use and not being able to do a thorough cleaning until later. Petroleum jelly can also be used in that regard to good effect.
If we are honest about it, no plastic body shot shell is as effective from an obturating perspective at it's crimp as a paper hull and once a paper hull 'pin holes' at the brass it too is blowing some hot spent powder gas onto the chamber's wall. Spent powder gas will quickly burn off any slight film protectant, whether the primers are non corrosive or not. Bill's use of WD-40 in that manner may be just what you need. I've not tried it in that manner. I do know it builds up a rather tenacious film and can cause a revolver to lock up if left unattended for an extended period of time, as I've experienced that.
Its been my contention that shooting new Federal paper hulls of the older variety that were made w/the wound paper base wads imparted some of their paraffin to the chamber walls and you didn't get the instant rust syndrome near as quickly, but as Russ was prone to say, I could be wrong.
addendum: there is now a Rem Oil w/a VCI rust preventive in its formulae. I've only seen that in the small 6oz. pump-squirt bottles.
Last edited by tw; 07/26/19 08:51 AM. Reason: adendum
