Believe it or not
Regarding the 870, and storage, lube, etc. Back in 1985 up to about 1992, when we moved to the Hill Country, I used to Goose hunt a bunch in muddy, plowed-under corn fields, near Port Lavaca, Texas. It was a pretty good march out to where we put out the rag spread, and anyone whose ever done much goose hunting in muddy plowed fields, knows how much mud you get in your shell bag, on your hands, in your shotgun, etc. from setting out decoys and rags, and then laying down in the mud to wait for birds to decoy in.
(There really is a purpose in me telling you this)
By the time you got home, you always had plenty of mud around, on, and in, your gun. We used the 870, since an auto-loader 1100, etc., would only perform for about the first five minutes, and then start jamming, because they won't work with mud in the action, while a pump will. You were doing good not to plug the barrel with mud, because you are laying down in turn rows while it's raining, sleeting, etc. (An Autoloader, will not work in that environment past the first bird)
The only way to possibly get the mud out, was to use the garden hose. (I am not kidding) So when you got out of the field, and near the closest water hose, you would blast water from the hose down into the action, down the barrel, etc. and off the stock, and then dry it with a towel, and then proceed to spray an entire can of WD 40 in the action, down the plug tube, down into the barrel, and just basically coat the entire gun with WD 40 til it was completely saturated, and dripping wet with WD 40.
(The only "proper" thing I did, was to use Hoppes # 9 in the barrel, with brush and patches when I got home, to clean the bore religiously)
But I then made sure to spray the barrel, action, etc. again, with WD 40 before putting it in the gun cabinet to await the next trip. So imagine what four or five straight years of mud bath, garden hose treatment could do to a shotgun. But anyway, I haven't used the gun very much at all, for the last ten years, and mainly just spray it down with WD-40 about once a year and wipe it down.
Well, just about a month ago, I decided to break it down and refinish the stock, and see what kind of rust damage was awaiting me. I figured the metal inside the gun would look like a deck cleat on a shrimp boat, and I would need to reblue parts inside the trigger housing.
I was astounded to see that there was not one spot in that gun, of any rust, whatsoever. Zero.
All my life, people have told me that WD-40 is not good to use on a gun.
I will tell you that it was sure good that I used it on that paticular Remington model 870.
You can't abuse a gun more than that, without trying. All I had to do was clean out all the gunk in the receiver, trigger housing, etc., stain and finish the stock, and put it back together. I did not use a bit of bluing, or a piece of steel wool, etc., as there was ZERO rust. Now I know, many folks will probably say, that the gunk was there due to using WD-40, and the spent gases of gun powder, etc., but it worked like a champ for 20 years, and never once jammed.
So I would suggest, to go ahead and just spray the heck out of it, inside and out, with WD-40, and then put it away. It may not be the professional way, but mine is now about 20 years old, and after I refinished the stock, it looks like the day I bought it, inside and out.
I found out this weekend that WD-40, is named WD, for "water displacement", and the 40 stands for the 40th formula developed to remove moisture from electronic radio wiring on aircraft.
Don't know why people say not to use it on guns. Maybe they mean the really expensive, collector type guns. But I strongly support using WD-40.