Refinishing An Aluminum Receiver
January 04, 2011
With the barrel removed from the receiver of the Marlin Model 60, the full extent of the "hammer attack" can be seen. The aluminum receiver can be easily refinished using aftermarket spray-on finishes.
When I was a much younger gunsmith, aluminum and aluminum alloys were seldom used in the better quality, higher grade firearms. There was widespread prejudice among most gun people against the use of any metal other than standard chrome-moly steel. Generally, aluminum was used only in the cheaper firearms. Often incorrectly identified as pot metal, aluminum was often used only for noncritical parts such as trigger guards or buttplates.
Well, a lot has changed since then. The public has come to appreciate the many virtues of aluminum. Not only can parts like receivers be made significantly lighter with aluminum, you never have to worry about rust, the nemesis of all chrome-moly steel guns. Then there is the cost factor. Aluminum can be cast and machined for a lot less than steel, and this means lower cost for the manufacturer and less expensive guns for the public.
While this is all good, aluminum does have problems. It's softer than steel and can be damaged more easily. In the past, aluminum has been anodized, which is an electroplated surface finish or coating. This was not a process that could normally be done by the neighborhood gunsmith. In fact, for many years there was no generally accepted and available way of refinishing aluminum parts.
I remember the first aluminum gun I was asked to refinish. It was a Marlin Model 99 .22 semiautomatic rifle, and it belonged to a farmer who raised a lot of produce for sale to grocery stores in my area. He kept the rifle in his pickup and used it frequently to dispatch rabbits and the other critters that literally ate into his profits. The rifle had seen a lot of use and was in really sad shape. However, it functioned flawlessly, and he liked it.
He wanted it blued. I explained that I could blue the steel barrel, but I couldn't blue the receiver because it was aluminum. In fact, blueing salts would dissolve the receiver! He thought for a bit and then said he would settle for anything that would make it look better.
I was in a quandary. Then I had an idea. I went to the local auto parts store and bought a can of flat black engine block spray paint. I figured if the paint was tough enough to withstand the heat and stress of being on an automobile motor, it would hold up on a little .22 rifle.
I blued all the steel parts, refinished the stock, and then coated the receiver with the engine block paint. It looked great, and the owner was delighted. The rifle returned to its position in his pickup and was used for many more years. The last time I saw it, the finish on the receiver was still lookin' good. It seemed to have held up better than the original finish.
Recently a friend asked me to take a look at a Marlin Model 60, which is almost identical to the older Model 99. Unlike that earlier rifle, though, this one had not seen much use. When viewed from the left side it looked unused. The problem, however, was readily apparent when it was viewed from the right side.
Some time back, the rifle had jammed with the bolt stuck in the forward position, and someone had decided the way to get the bolt open was to beat on it with a hammer! Not only was that a bad idea, but they weren't all that accurate with their aim. There were countless dings and divots all around the ejection port and right side of the receiver. In fact, the ejection port was so chewed up it looked more like a rat hole.
Prepping The Receiver
Marlin, like many other arms makers, has gotten away from electroplating or anodizing aluminum parts. As best I could tell, this new receiver had been painted rather than plated. That was good in that it made removal of the original finish a bit easier.
After removing the original finish with bead-blasting, Reid smoothed out the dents and dings with a cloth-backed abrasive backed by a flat file. The receiver was bead blasted again to blend the polished area with the rest of the receiver.
The first step was to strip the rifle and pull the barrel from the receiver. Like many modestly priced .22s, the barrel was secured to the receiver with a transverse pin. Just knock out the pin, secure the barrel in a padded vise, and carefully drive the receiver off the barrel shank with a plastic hammer.
With the barrel removed I then used my bead-blasting outfit to quickly remove the paint from the outside of the receiver. Once the paint was blasted away, I used a variety of cloth-backed abrasives wrapped around a flat file to smooth up the right side of the receiver. I also used a small half-round needle file to contour the edge of the ejection port. It was just a matter of patience and time until virtually all evidence of the "hammer attack" was removed.
I then carefully bead-blasted the surface to remove any sanding marks from the abrasive. This also helped to prepare the surface for the next step. The receiver was then cleaned with Tipton Insta-Clean, my favorite aerosol spray solvent that is available from MidwayUSA, to remove all traces of abrasive and any oil or fingerprints.
It's important to keep in mind that fresh aluminum begins to oxidize immediately upon exposure to air, so you will want to apply your finish as quickly as possible after preparing and cleaning the metal surface. If you don't, a layer of oxide will develop and your paint will not adhere properly. Work very quickly!
Applying A Durable Finish
While engine block paint could be used, there are many other better products now on the market. I chose the Wheeler Engineering Cerama-Coat, which is sold by MidwayUSA for about $14. This is a durable, flat black aerosol paint that contains ceramic particles. This provides an additional element of durability unlike anything else available on the market.
I used the Cerama-Coat on aluminum, but it can be used on virtually any metal surface. It's a great coating for regular steel guns used for duck hunting that are regularly exposed to water. In fact, Cerama-Coat will provide more protective finish than standard blueing.
I made a point of keeping as much of the spray out of the inside of the receiver as possible. (I don't think any of the "spray-on, bake-on" finishes should be used on any internal moving parts.) I sprayed two light coats of Cer
ama-Coat on the receiver, allowing it to dry for 30 minutes between coats. I was especially careful to avoid any runs, which are normally caused by getting a bit heavy handed with the spray. I held the receiver about 8 inches from the spray can and made short, light "shots," constantly moving the spray can and never allowing it to stop on the receiver.
After air-drying for 30 minutes after the last coat, the receiver was placed in a preheated toaster oven to "cook" for one hour at 350 degrees. (You could use your wife's kitchen stove, but I wouldn't advise that. For some reason women seem to have a totally irrational opposition to allowing their husbands to refinish guns in their ovens. That being the case, I long ago decided it was best for my health and marriage to just go ahead and pick up an inexpensive toaster oven for use in the shop.)
Be sure to get an accurate oven thermometer. You need to know the exact temperature, and most inexpensive toaster ovens don't have accurate or precise temperature controls. More than likely you'll find the numbers on the temperature control on the oven will not correspond to your thermometer. Go with the thermometer.
Cerama-Coat was applied to the cleaned, bead-blasted receiver, and the receiver was "cooked" in a toaster oven. The refinished aluminum receiver looks as good as new.
Once the receiver had cooked for an hour, I removed it from the oven and allowed it to cool down. It took a while because the receiver was very hot! I let mine set over night. I then inspected it for any missed runs or surface imperfections.
It looked fine, so I reassembled the rifle. My friend was just as pleased with the results as that old farmer was years ago. The rifle showed virtually no evidence of the hammer attack.
This type of finishing project is well within the capabilities of most hobbyists and gun owners. And there are lots of old and worn aluminum guns and parts out there that could certainly use some TLC.
Until next time, good luck and good gunsmithing!