New and even used firearms can often benefit from polishing key parts to improve smoother operation and reliability.
Modern firearms are seldom as smooth as they could be due to the constraints of what the factory can do and still keep prices down. The owner can do quite a bit to improve a gun with a surprisingly small amount of work, but all too often people do it wrong or do too much and actually ruin a gun. So, here's a short general course on what to do and what not to do to improve a firearm from a gunsmiths perspective. These methods work on most guns so this won't be specific to any one firearm.
First and most important is that when we speak of "polishing" we actually mean "to smooth”. Too many people hear "polish" and think "like a mirror”. Polish any gun part to a brilliant mirror shine is not only unnecessary, it's how many gun parts get ruined. In order to bring a part to a bright mirror, shine requires removing metal and that often removes too much or makes critical surfaces uneven. What’s desired is that a key part is smooth enough not to drag or catch on other parts. When a gun part is machined or stamped the process leaves some area with ridges or imperfections that can cause rough operation. The intent is to remove JUST enough to prevent this. It isn't even necessary to remove ALL the roughness, just enough to level roughness to the point it won't cause drag.
So, why do many custom guns have mirror shiny parts like feed ramps?
This is because a customer pays the gunsmith for a "polished" feed ramp and if he doesn't see a mirror shine he thinks the gunsmith either forgot or cheated him by charging for something not done. Because of that, a gunsmith will put in a mirror polish even though a simply smooth, honed surface works perfectly. The difference between a professional polish job and a job done by an owner is that the pro gunsmith knows how to do it without ruining the part, or starts out with a new part that's slightly oversized just for this purpose. In smoothing operation of a firearm, less is more. Meaning the less you work on a part the less chance of ruining an expensive part.
A consideration is often WHICH part to work on. A key rule of gunsmithing is: Work on the part that's easiest/cheapest to replace if something goes wrong. As an example, when fitting a trigger to a 1911 pistol, the part worked on is the trigger, not the frame. Triggers are cheap and easy to get. Frames are neither. Often smoothing one part will work as well as working on both, or the major amount of work can be done to the less critical part.
TOOLS AND SUPPLIES
Polishing requires some sort of abrasives capable of abrading metal. Among the usable materials are:
Fine wet or dry sand cloth. This can be bought in finer grits at automotive supply houses where it's sold for use in painting cars.
Crocus cloth. This is a very fine abrasive that gives a very smooth surface. It can be bought in sheets or in rolls from industrial supply houses like McMaster-Carr.
Rubber bonded abrasives used in power tools like a flex shaft or the Dremel tool.
A good brand is Cratex. The most useful are 1/2 inch diameter Bullet shapes and 1-inch x 1/4 inch diameter wheels. If you can't find the 1/4 inch thick wheels you can "stack" several wheels on the same arbor.
The best grits for use in polishing gun parts are Medium and Fine. Coarse is usually too coarse and is best used for heavy shaping of metal.
Good sources of rubber abrasive shapes are Brownell's and jewelry supply houses. Do an online search and you'll find a number of jewelers and watchmakers sites that sell rubber abrasives and the various types of mandrel shafts that will work in small power tools like the Dremel.
Medium to fine stones work very well and often are better for this purpose.
The most natural and many synthetic stones wear quickly and develop a dished-out shape that makes it hard to maintain critical shapes. My favorite stones are ceramic rod shapes in square and triangular. Ceramic stones don't wear much if at all no matter how much they're used. They need no oil and can be cleaned with a solvent like lacquer thinner or in a sink with soap and water and a small brush.
Good ceramic stones are sold by Brownell's and while they coat more, they last a very long time and maintain their flat surfaces. For polishing gun parts a smooth stone works best and isn't too aggressive.
Flat sticks, files or plate glass for backing abrasive cloth.
When using abrasive cloth you need somewhat to keep it flat. One method is to use a flat stick or file and wrap the abrasive cloth around it. This is then used like a file to smooth surfaces. If you need to work on a larger part, you can put the abrasives on a piece of 1/4 inch plate glass. The abrasive cloth can be held on by using hobby or art store rubber glue, by wetting the glass so the cloth will stick, or by simply holding it in place.
To polish a flat surface on the glass it seems to work best if you push the part away from you instead or pulling it toward you, and it doesn't work well by rubbing the part back and forth. Just push it away from you, lift it off and reposition it for the next stroke. It helps to keep the surface flat if you rotate the part every stroke or two so you keep the surface uniform.
Often people ask about packing a gun with an abrasive like valve grinding compound or even toothpaste.
NEVER DO THIS.
Using an abrasive paste of any kind is not controllable. You need to work on specific surfaces and leave all other areas as-is. Abrasive pastes attack all surfaces and will round off parts that need to be kept sharp, like sears and hammer notches. Using an abrasive paste in a gun can destroy the gun or abrade away metal that would take many years of normal use to do. People will tell you that it worked fine for them, and it may seem like it until you look at critical surfaces under magnification and see the damage.
Work area, light, and magnification.
You can do an acceptable job on a kitchen table, but you still need as much light as you can get, and you need magnification because you can't control what you can't see. An ordinary desk light will do, and for magnification, a magnifying visor works perfectly. Most hobby shops and online sources like Harbor Freight sell magnification visors.
While it's not usually needed a small jewelers vise can be handy. Pad the jaws with a copper sheet or synthetic pads to prevent scarring parts.
It's almost never necessary or a good idea to use files to smooth gun parts. Often the parts are hardened and you can't file them, but in any case, a file, even a fine cut file removes too much metal too fast. In the rare case a file is useful, a set of small fine cut Swiss needle files can be used.
METAL MANUFACTURING AND CAUTIONS
Before starting any polishing, you need to understand how gun parts are made durable enough to stand up to use.
There are two main methods manufacturers use, surface or case hardening and through-hardening.
Case hardening is a process where a very thin "crust" of the surface is given a glass hard finish. There are two types of case hardening, standard case hardening, and color case hardening. Color case hardening is today mostly a decorative treatment that gives the surface a hard mottled, splotchy look of usually blues and greens. This is usually used on receivers, hammers, levers, etc.
Standard case hardening can't be seen and is used to make key parts like sears and hammers hard enough to withstand wear, but soft enough internally not to break from the shock of use.
To detect a case-hardened part, simply run a smooth cut file over a hidden area. If its case hardened the file will just skid over the metal without cutting.
A color case hardened rifle receiver. Standard case hardening can't be seen.
Through hardening is when the metal is the same hardness all the way through. This is often used for modern pistol hammers and sears and action parts.
You need to be very cautious when polishing parts unless you know exactly whether they're case hardened or through hardened. If you begin to stone or polish a case-hardened part it's very easy to break through the very thin hard crust and expose the softer inner metal. This ruins the part. The exposed soft metal will not withstand use and quickly wears, often causing unsafe triggers or guns that won't stay cocked if bumped. An example of guns that use case hardened action parts are the later Colt double action revolvers like the Mark III, Mark V, King Cobra, Anaconda. etc. In these guns, the only work that can be safely done is to install a spring kit to improve the trigger pull.
An example of through hardened parts is most of the Ruger pistols and revolvers. These parts are the same hardness all the way through.
Another thing to be aware of is the process used to make parts. These are forged, stamped, cast, and today, Metal Injection Molding or MIM. Forged parts are made by heating a lump of metal in a forge and while it's red hot, beating it into a mold with a power hammer forge. What comes out looks like a part made of clay. After forging, the part is machined to final shape than either case hardened or through hardened.
A forged Colt 1911 pistol frame before machining.
Stamped parts are made by using a metal press and dies. A sheet of metal is laid on the die and the stamping machine presses the metal out like a cookie cutter. This stamping method leaves a rough parting line on the steel where the press pushed it into the die to cut it out.
Cast steel parts are made by either pouring molten metal into a mold or by the lost wax process.
Steel is cast by pouring molten steel into a metal mold. When cooled, the mold is opened, a semi-finished part is removed, then machined to final shape and hardened. Depending on the molding process and the amount of final machining, cast parts may have few areas rough enough to benefit from polishing.
An example of a cast steel part is a Colt 1911 grip safety.
The lost wax process was perfected for guns by Ruger. In this process, a wax replica of the part is coated with a ceramic "investment" material, then heated in a furnace until the wax melts and flows out. Molten metal is forced into the ceramic investment and once cool the investment is broken away, leaving a nearly finished part. All that's needed is limited final machining of key areas and hardening. Lost wax's big advantage is that multiple parts can be joined to a casting "tree" and many parts can be poured at the same time. When the investment ceramic is broken away the individual parts can be cut off the tree. Since the parts and the tree are molded, any parts that aren't perfect and the tree itself can be simply re-melted and cast again. This is a major advantage over forged and machined metal where if at any point something goes wrong, the entire part is scrap and you've lost all the machine time in making it.
Metal Injection Molding is today's most controversial method of making parts using powdered metal.
Colt Firearms first introduced the use of powdered metal manufacturing for guns in the Colt Mark III series of double action revolvers in 1969, and in their automatic pistols for making sears and disconnectors. This was known as "Sintered steel". Today's version of this is Metal Injection Molding.
In this process, powdered metal is mixed with a polymer and injected into a mold. The mold is heated and the polymer burns away as the steel melts. The molten steel fuses into a solid mass and shrinks a known amount.
When the mold is opened a virtually finished part is removed, needing only hardening. Most gun makers today are making more and more parts of guns from MIM. A good way to identify MIM parts is the slightly porous appearance and tiny round marks that are left by the pins that push the part out of the mold.
Forged and machined parts and stamped parts often benefit from polishing to smooth out the ridges and machine marks left by the machine tooling that cuts the parts to shape. Cast parts and molded parts seldom need any polishing because since they aren't cut by machines, there are no machine marks or roughness on key surfaces. Since these parts are already usually very smooth, they usually don't benefit from polishing.
The first step is to examine the gun to spot the areas of friction that might benefit light smoothing.
Simply sit down with the unloaded gun and look at the parts as you operate the action. Look for parts that operate with other parts that are rough or burred or seem to feel rough or sticky as the action is operated.
Not every part needs or should be worked on. As an example, polishing the slide and frame rails of an automatic or the bolt of a rifle or shotgun are areas usually not touched in a fluff and buff job. Many areas are only addressed by a gunsmith doing a much deeper level of work.
After deciding what needs to be worked on, disassemble the gun only as far as needed to access those parts. Don't remove parts or attempt full disassembly unless you know what you're doing and have the needed tools to do it.
With most guns, there's no good way to determine if they're surface hardened or case hardened. All you can do is use your judgment and common sense. Again, less is more. The less you do the less risk of ruining a case-hardened part.
Once you can access the parts examine them closely to identify the working surfaces that might benefit from polishing, and figure out how you're going to polish them without changing their shape. The trick here is to maintain the original shape. Flat surfaces must remain flat, and curved surfaces need to keep the original contour.
When working on a flat surface, it's often beneficial to lightly bevel or "break" the sharp edges around the flat area. This prevents a sharp edge not necessary to operate from digging into other parts.
When polishing surfaces, it's absolutely necessary to keep the abrasive cloth flat by wrapping around a stick or file, on the plate glass, or by using stones.
If you use power polishing with rubber abrasives in a flex shaft or Dremel tool, you must be extremely careful not to allow the tool to "run away" or slip off the area and run across another area, especially a finished area.
One slip and an abrasive tip running across another area can leave scratches that are surprisingly deep and can take a significant amount of work and metal removal to remove. For this reason, always work with plenty of light, magnification, and by bracing your arms and hands in a comfortable position.
Whatever methods you use, again, do the bare minimum possible to just make the part smooth enough not to drag or catch, and take care not to change the contours or angles of the surfaces. Once the parts are polished, clean them off with a fast-drying solvent. Lacquer thinner, Acetone, 90% alcohol, and denatured alcohol work well, but keep it out of other areas. Once the part is dry, apply a lubricant to prevent rust and to lubricate the parts. On some parts, a good grease is very beneficial.
Doing a trigger job is not part of a fluff and buff job.
Due to the complex nature of trigger work and the strong possibility of a botched job, trigger work is not considered to be something to be done as part of a light polish to improve the smoothness of a firearms operation. Trigger work is highly technical and requires the learned skills and tools to do the job correctly.
A common post on the forums is by someone posting that his automatic pistol hammer is dropping to half-cock. This is often caused by amateur attempts to "improve" the trigger pull and getting it wrong. Doing a safe and effective trigger job requires special guide jigs and stones, along with the specialized knowledge of how to use the tools and exactly how a trigger job is actually done.
Hint: It isn't done by hand with a stone
The old timers did trigger work this way because they didn't have the special jigs we have today.
For that reason, a lot of parts were ruined, a lot of guns were unsafe, and their trigger work was never uniform. They may have been very good, but even the best could seldom repeat the same trigger feel on two different guns.
It's best to leave trigger work to a known expert gunsmith who has the tools and knows what and how to do it. A pro can give a gun a precise weight of pull and repeat it on another gun on demand. This is because the special stoning jigs and fixtures take the human element out of it.
Because brands and types of firearms are so different, it's beyond this short article to discuss exactly what parts to work on. Just look at the parts and inspect for any roughness that can impede smooth operation, keeping in mind that not all parts need to be polished even if slightly rough.
Go slow and polish the bare minimum and you'll be surprised at how much smoother operating a gun is that's had a proper fluff and buff.