I've been polishing (INSIDE and out) some old double-stack, extra-hi-capacity, all metal (except the follower), pistol mags, that would not feed reliably due to friction caused by a poor/cheap and slightly rusted finish inside the mag. This is how I am doing it. Feel free to make adjustments for specific mags and supplies at hand.
Supplies:
Scouring pads. The soapy kind (Brillo, etc.) I only used these on the inside of the mag for about a dozen passes.
Non-oil based cleaner/de-greaser. I used spray bottle "Windex" on the first one and spray bottle "Charlie's Soap - Kitchen & Bath Natural Cleaner" on the second one. I liked the "Charlie's..." better. You could probably just use your sink with warm water and dish soap if that's all you have. Anything non-oil based should work. Don't use anything from the garage (WD-40, etc.)
Hair dryer OR fan OR a sunny day for fast drying (to prevent rust.)
Large wire cutter. Used to cut the dowel and zip ties.
Wooden dowel. I used a 5/16" x 48" dowel... the cheaper more flexible one, not oak, but it doesn't really matter. I cut it into 3 sections. Approx. 18", 18", and 12". (I needed the longer lengths because of the length of the extra-hi-capacity mags). I used all three sections in the process.
Steel wool. I used "0" and "00" grades. You could probably start with grade "1" or even "2"...just be sure to finish with "00".
Very small zip-ties. I used 4" (10cm). I used 4 to get me through 2 mags. Will use more when I have to attach fresh steel wool to the dowels.
Gun oil & cleaning patches OR cloth of choice. I used "Frog Lube."
OPTIONAL: Breathing respirator or paper mask. Latex of nitrile gloves. The steel wool "dust" irritated the back of my throat and sinuses later that night after I polished the first mag...so I'm wearing a respirator for the steel-wool part of this process now.
The Process:
Pre-cleaning. I started by disassembling the mag and took all pieces to the kitchen sink. I then wet/rinsed the mag shell and thoroughly wet a Brillo pad. I inserted the Brillo pad into the base of the mag and then used the short (12") piece of dowel to plunge the Brillo back and forth through the mag about a dozen times. I had to alternate pushing from the bottom, and then the top of the mag to accomplish this. Removed the Brillo and thoroughly rinse the mag. Then I sprayed the outside of the mag and the remaining parts (spring, base plate assembly) with non-oil based cleaner/de-greaser. Let soak in for a few minutes. I spent a little extra time here on the mag spring by wiping each coil with a cleaner soaked rag or paper towel. Then I thoroughly rinsed all parts again. Then I placed the all pieces on a paper plate / paper towel and dried in the Sun or with a hair drier.
Then, while waiting for the parts to dry, I completely unrolled a "0" steel wool pad (the best I could) and then wrapped/rolled it snugly (straight, like toilet paper, not diagonal) onto (about 3" from the end) of one of the longer (18") pieces of the dowel. Then I affixed the steel-wool to the dowel with two small zip-ties spaced evenly apart (spaced a third of the length from each end of the steel-wool). The zip-ties must be as tight as possible. Cut off (flush) the excess pieces of the zip-ties with the wire cutter. I repeated this process with "00" steel-wool onto the other 18" dowel.
Then I carefully inserted the "0" steel wool end of the plunger (used my finger to guide the steel wool smoothly into the mag base) and began rapidly plunging in and out *insert dirty joke here*. I was sure to get in the corners and all around the feed ramp by applying pressure and angle on the dowel in all the appropriate directions and areas. I also, turned the dowel 90 or 180 degrees every so often (usually had to remove, rotate, and re-insert). After approx. 100 in and out plunges, I switched to the "00" steel wool wrapped dowel and repeated the process. I spent about 10-15 minutes per mag on this part of the process. The first time I did it with only 1 zip-tie holding the steel wool (in the middle) and the steel wool came loose. I cut off the zip-tie (with wire cutter) and replaced it with 2 zip-ties spaced evenly apart (spaced a third of the length from each end of the steel-wool). The zip-ties must be as tight as possible.
After I polished the inside, I set the dowels aside and started on the outside with steel-wool in hand. I began with "0" then finished with "00", careful to completely polish all of the surface. Note: Using the steel-wool will fade the "blueing" or black oxide finish just a tad. It will darken up a little once the oil is re-applied.
Then I brought the mag to the kitchen sink and rinsed off all the loose particles. Then I rapidly dried the mag (depending on the weather or time of day/night) by either using a hair dryer OR by placing in the Sun while on a clean surface (paper plate or paper towel)...careful not to contaminate the metal with sweat or body-oil or anything else before the oiling process.
Once it was completely dry, and still warm in the Sun or by hair dryer, I thoroughly wiped the mag inside and out with pre-warmed "Frog Lube" using a gun cleaning patch or other cloth. I also wiped the base plate assembly and mag spring (thoroughly, every coil) at this time (making sure they were warm too.)
I then placed the whole disassembled mag on the clean surface and let it completely warm in the Sun or by hair dryer.
Then I wiped off any excessive "Frog Lube", inside and out, and then reassembled the mag.
FINISHED.
