funny topic here. I am running an experiment going into the 4th year and counting. I made a small cannon for July 1st Canada Day. Lots of fun and great noise and air burst loads that can be heard for some distance.
Now , this is the ongoing experiment :
I decided NOT to clean the cannon AT ALL after using it the first time , to see how bad it would get. Instead , I sprayed the bore with LOTS of WD40 until it run out of the touch hole. It is made out of mild steel and the bore is 5/8" , the wall stock is over 1/2 thick and the loads never exceeded 120 grains of FFFG, never the less I set it in a safe place and light the fuse with enough time to get myself out of danger, should it burst .
I have fired it countless times in the last 4 years , and I'm yet to clean it once.
So far , not a trace of ANY rust and all I have to do is just get the black mud ( burnt powder + WD40) out of the bore before I put it to use.
Based on the results so far, I decided to try it on one of my guns for two days after a shooting session. Lots of black gunk came out of the barrel after cleaning . Only a heavy duty cleaning got rid of the black lines on the cleaning patches , but no effect whatsoever on the gun at all.
Since then , I don't use anything other than just tap /stream/ lake / river ( you get the point ) water to clean all my guns , followed by really soaked patches with WD40.
Yes, you still get that bit of black on the patches , but , no rust and same accuracy as when new. Gun does not care at all , nor do I...