I'm a benchrest shooter and gunsmith, and I use quite a bit of cleaning solvent. When I used to buy it, I would buy it by the pint bottles. While not terribly expensive, it was still a cost. I asked fellow shooters what they used and most did as I did, buy it. Then I asked a very successful shooter what he used and he said "my own brew"! Just what I wanted to hear. He was nice enough to share his brew mixture, and that is all I've used since.
There are a couple main things you're trying to do, or combat, with cleaning solvents: carbon fouling and copper fouling. Carbon is the byproduct of the burned powder. Copper fouling is bullet jacket material that has plated itself in the bore. If you used lead bullets, you would have to contend with that, but I don't, so this is targeted for using copper jacketed bullets. Carbon is probably the toughest to get rid of, it is extremely hard and stubborn. It can build up and degrade accuracy. The best way to keep it in check is to not let it build up in the first place, by cleaning when the barrel is new and not shoot a hundred rounds before cleaning. But sometimes you have to deal with what you have, now. Copper fouling does the same thing, it builds up in the barrel and just keeps getting worse.
If you get a used gun and it is fouled pretty bad, you may want to use something other than this cleaner at first. Abrasive cleaners (JB's, Iosso) do a good job of getting through this stuff. It takes some elbow grease to work it back and forth and you need to keep changing patches, but it will get through it. Once the rough stuff is gone, then using this mixture cleaner will get the rest. [JWR Adds: The general consensus is to avoid abrasive bore cleaners, unless it is absolutely necessary. In my opinion, on a very pressing emergency would dictate that. Otherwise, nothing more abrasive than a brass bore brush should ever be used.]
[JWR Adds This Warning: All of the usual precautions for handling caustic and flammable fluids must be taken, such as wearing goggles and rubber gloves.]
So how to make it? There is an initial expense to this, but it goes a long way and my formula makes quite a bit. First, go to a GM car dealer, and buy a few cans of "GM Top Engine Cleaner", ask if they have it in the metal can. It is my understanding the newer Top Engine Cleaner comes in a plastic bottle, and may not be as effective. I'm not sure since I have the metal can cleaner. I would think it would still work okay. It comes in a 15 ounce can and it the basis for the cleaner. It has the chemicals in it for fighting carbon deposits. [JWR Adds: Very similar products are sold under various brand names as Upper Cylinder Lubrication & Injector Cleaner.] You can scale how much solvent that you want to formulate in a batch by the number of cans of Top Engine Cleaner that you buy. The second ingredient will be the hardest to get, and that is strong ammonia. Ideally, find a blueprint shop, large printing shop, and ask if they have 28% ammonia. It comes in a gallon jug. Trust me, don't sniff it, it will clean your sinus' like you've never known. The next ingredient is Marvel Mystery Oil that you can get in most auto parts stores. Lastly is regular Hydrogen Peroxide which you probably already have.
Get a colored glass container, brown, blue, something that is tinted. All of these solvents comes in colored glass to keep out sunlight. Some of the whiskey/bourbon/scotch bottles are brown and work fine [if prominently labeled "Poison" and with a description of the contents.]. Shake and pour in a 15 ounce can of top engine cleaner. Measure 25 ML of ammonia, 5 ML of peroxide and 5 ML of Marvel Mystery Oil and dump it all in. It won't explode, don't worry. Shake it all up and you have a top notch bore cleaner. The Top Engine Cleaner goes after carbon deposits, the ammonia and peroxide attack the copper fouling, and the MM oil acts like a penetrating oil that helps get under the deposits and keeps the bore conditioned.
The ammonia reaction to copper fouling will turn a white cleaning patch blue, or rather the patch will pick up the blue tint from dissolving the copper. It a good tell-tale indicator of how well the barrel is cleaned. You don't have to get every last bit out, but if there are heavy deposits, it will be a deeper blue, when getting fairly clean, it will be a much lighter blue.
I use this on all of my rifles, and for pistol barrels. Most of my rifles are bolt actions, and cleaning is easy, but use a bore guide to keep the cleaning rod from damaging the barrel. If you have an lever gun or semi auto, you may have to clean from the muzzle. Beware that you can severely damage the end (what is called the crown) by letting the cleaning rod drag over the edges of the barrel end. I would recommend getting a "coated" cleaning rod to help with this, but still, go slow and watch the rod position to keep it centered in the barrel.
There are a couple substitutions I've heard that you can use Mercury Quicksilver Gear Lube. It is a product made by the Mercury Outboard Motor company. It must have the same properties as the Top Engine Cleaner". The ammonia is the toughest to get, and may even have some restrictions now, given the state we're in. You need the strong stuff. The 28% I referenced is what I have. Most blue print shops now use large copy machines instead of the old "blue prints" where the ammonia was used. You may be able to find some strong ammonia at commercial janitorial suppliers. You can substitute Kroil Penetrating Oil for the Marvel Mystery Oil. Kroil is a penetrating oil, not exactly easy to find but it is available. - W.S.