While home one Sunday during supper I heard shotgun shots nearby. Shortly after the last shot there was a knock on my door. To my surprise I saw my neighbor with a shotgun leaning at his side. He said the gun needs my gunsmithing services. The action was open so at a glance I was able to see the chamber unloaded. I immediately point this out thanking him for his safety courtesy.
He explained the gun was his friend’s and they just finished shooting skeets (which is why the barrel was still warm). The owner had dropped it in a mud puddle sometime ago and he wanted it de-rusted and cleaned so my neighbor told him he knows a gunsmith who just happens to be his neighbor.
He said the safety was stuck in the “off-safe/fire” position. When I glanced inside the open action I could see it was bone dry and showing wear from being shot a lot and/or with no lubrication. I asked him if the owner was going to contact me and if he was in a rush, my neighbor said yes. I will admit I have not seen many guns in my life but what I did know from a quick glance is this gun is a Mossberg 500.
Later that evening I looked the gun over. The data stamp on the receiver reads as such:
I looked in the Numrich parts catalogue but they do not list a Mossberg 400G. I searched the internet and found someone saying these guns were manufactured in the 1970’s at Lakefield Arms, Ontario, Canada and given a name different than Mossberg 500 due to regulations of the time (manufacturing, etc.), hence the name 400G. Apparently the company was struggling and in 1995 Lakefield Arms sold out to New York Savage Arms.
Although this is a Canadian manufactured gun the barrel is made in the USA.
The 400G firing pin is non-spring loaded (newer models are spring loaded). The bolt assembly and bolt carrier differ between the 400G and the newer 500 models because of that.
The primary cartridge stop design and function are pretty much the same in both the newer and older models. The 400G secondary cartridge stop differs in design and function than newer style 500’s. the difference being how it is activated. In the new style 500’s the secondary stop is activated by the bolt carrier as the action is cycled rearwards. In the 400G as the elevator (cartridge carrier) bottoms out (fully lowers) it hits a shelf on the secondary stop and activates it.
Action slide tube assembly: removal
When the barrel was removed I could not remove the action slide tube assembly like I could on newer style Mossberg 500’s so I reviewed the Mossberg 500 DVD in AGI’s Professional Gunsmithing Course. The magazine tube must first be removed before the action slide tube assembly can be removed.
A couple of days before unscrewing the mag tube I placed a few drops of penetrant (Ballistol) in the area where it threads into the receiver then stood the gun upright to allow the penetrant to seep on down the threads. This was a smart move because the mag tube was fairly difficult to remove and rust was in the threads.
Now that the mag tube was removed I was able to remove the action slide tube assembly from the receiver and remove the forend from the action slide tube. I could then see the band on the mag tube that had to be removed first to be able to remove the action slide tube assembly.
Internal areas of rust
The internals of the action was a bit gritty from sand (the fire control being no exception). Rust was abundant on the magazine tube spring and the bore had it’s share as well. Small amounts of rust were found on the bolt, bottom of the bolt carrier, primary and secondary extractor springs and fire control springs. The majority of the rust being on the exterior of the barrel and exterior of the magazine tube. The receiver must be an alloy of some sort because there was no rust whatsoever.
I did know the customer wanted the gun cleaned and de-rusted so that is what I began to do. I used my all time favorite gun oil (Ballistol) and saturated everything metal (inside and out). I set the parts aside and let the oil do it’s magic (soak) for at least two days.
As for the safety being stuck in the off-safe/fire position, this rendered it an area of critical concern. I figured it was stuck because of rust and/or grit so I put a few drops of Ballistol around the lever and let it seep about. In five minutes the safety was free and working.
This doesn’t mean I was done with it–I carefully removed the safety screw and disassembled the components. It was dirty with sand and a bit of rust so I cleaned everything then lightly oiled the metal parts. Using laquer thinner I degreased the safety screw, the safety screw hole threads in the safety post, air dried the parts, applied medium strength LockTite threadlocker on the safety screw threads, re-assembled the safety mechanism and confirmed it functioned as it should.
Exterior: Rust removal
After several days of Ballistol soaking on the exterior of the barrel and magazine tube I wiped them dry with a clean shop cloth. This removed a lot of rust that the Ballistol had lifted and the gun was looking better already.
I applied another coat of Ballistol to the entire exterior surfaces of the barrel and mag tube and let it soak for a day. Leaving the oil on the gun I soaked a brass bristle brush (DO NOT use steel bristle brushes) with Ballistol and scrubbed all areas of rust.
More rust was removed and the metal was looking better, but high and low spots of rust remained so I moved on to using 0000 steel wool. The process is as follows: apply Ballistol to the gun metal, let soak a day, LIGHTLY scrub (with 0000 steel wool soaked with Ballistol), wipe dry with a clean cloth, inspect. Repeat the process until rust is gone then apply a light coat of oil to the metal and you’re done.
The barrel takedown screw was also heavily rusted so I used the same process explained above using a brass bristle brush soaked with Ballistol to get into crevices.
When all the rust was removed pitting was evident in several areas of the barrel and mag tube, but that’s the way it goes when rust is dealt with.
Cleaning the stock
With the rust removed the gun was looking so much better so I decided to experiment with cleaning the stock in hopes to give the gun a better overall appearance. The finish of the wood was wearing off, was dirty and any help it could get was a welcome.
First thing I tried was rubbing the wood with Ballistol, let it soak several hours then wiped it down. This did not do much at all. Next attempt I used a shop cloth soaked with 99% isopropyl alcohol and gave it a good wiping. To clean between the grip serrations on the forarm I used a nylon brush soaked with alcohol and scrubbed. I repeated the process one more time getting it about as clean as it could get using this method.
Since the finish was so far gone (I did not have permission for a stock refinish job) and now de-oiled from the alcohol, I decided to apply a carnauba paste furniture wax product I originally aquired for use as a release agent for epoxies. The idea here being the wax helps protect the wood from absorbing dirt and moisture. Using a small piece of foam I applied some wax to it and rubbed it on the stock. I used foam because it doesn’t absorb and waste the wax like using an absorbent cloth would. You can see in the photo that the overall improvement was minor but effective.
Long story short, when the customer arrived I showed him the gun. His face lit up with an ear to ear smile. He was pleasantly surprised how much better it looked. The gun has sentimental value and has been passed down two generations. To be honest I do not think he thought the metal would ever be able to look so “rust free” (that’s the kind of smile I seen on his face).
He is going to return the gun after hunting season for a cleaning. On top of that he brought me another gun that has feeding problems and needs a detailed strip and clean. Gotta love happy customers!