Fire lap has been around a long time, but until a few years ago it was exclusively used by gunsmiths and barrel makers. Now there are kits that you can buy and do it yourself. And there are some companies that will sell you the bullets already processed for loading and fire lapping. One thing you should do before firelapping a bore is to clean the bore as thoroughly as possible before you start your fire lap. You get better results firelapping a clean bore than a fouled dirty bore. You do not use a full load of powder just enough to get the bullet out of the barrel. (see below for charge) You can use lead bullets (recommended) or jacketed bullets,(I have had good luck with them but I up the powder charge to 14 grs. of Red Dot.)
Basically it is shooting a bullet down the bore with an abrasive compound coating it. Now that sounds bad but the abrasion is very fine and you are just taking away micro amounts of metal and that metal is mostly the burrs and machine marks that will eventually be smoothed out by normal shooting in a few years. I use some Red Dot shotgun powder, usually about 12 gr. and some dacron to keep the powder back against the primer. I have a range in my basement and I just open it up and fire my shots go back to my shop and clean and then continue till I have gone through the whole sequence. What you get is a smooth shiny bore with no tight spots and very few places that copper or lead fouling can attach itself to, therefore you can shoot more without accuracy affecting fouling and your barrel cleans up faster and stays clean longer.
Not commonly known by the layman is that after the barrel is rifled and mounted to the receiver, stresses are introduced in the barrel from outside sources. One of those is when the holes for the rear and/or front sights are drilled. Under those holes will be a tight spot in the bore. This can actually be felt when you are cleaning the barrel. also the reaming marks left by the finish reamer are at 90 deg angles to the bore which makes a real nice set of riffles to catch and hold copper and lead.
So to fire lap,you load a cartridge with a bullet that has been impregnated with a abrasive compound, usually starting off with a coarse compound and then graduating to a fine, then a very fine compound. Following each treatment you clean the bore. I usually use about 10 to 12 bullets of each coarseness and clean between each change to a smaller grit. when you get done you will have a very shiney bore and it will maintain it's accuracy for longer times between cleaning. The old time gunsmiths used a variation of this but they used the abrasive bore paste on a cleaning patch and patiently stroked the bore 100 times with each graduation. It was called lapping the bore. Labor intensive and likely you couldn't afford it now a days.
There are several companies that sell the fire lapping kits. The one I use is the Wheeler Engineering bore lapping kit. It has three grits starting from 220, 320,and 600 grit. There address is 5875 W. Van Horn Tavern Rd. Columbia MO. 65203. I believe I bought mine through Midway that is also in Missouri. I found that the firelap will really make a difference with old Mauser rifles that were used with corrosive primers and have rust pits in them. Even new rifles will show a difference except they may not need as many firelap shots through them. The company recommends that you clean the bore after each 5 shot string to see how much difference the bore feels as you run a dry patch through it. And I do that too. Good luck and good shooting
I've read the casting pages here. In particular an idea of dropping the bullets from the mold, into water.
I've tried this, and water alone is a bad idea.
all this manages to do is slpash water upwards, often getting on the mold ... bad state of affairs.
However, if one adds a little dish soap to the bucket of water, and uses a wisk, or a brush of some form to maintain a good head of foam on top of the water, this seems to supress the splash rather nicely.
Also, it seems that the end product tends to be harder than air cooled slugs, while allowing much higher casting temps and eliminating bullet frosting.
again, this shows another advantage in reguards to mold fill out issues.
The only disadvantage I have run into with this method is that the bullets seems to be a slightly larger diamiter.
You can also float a piece of sheet foam rubber about 1/4" thick by 6" dia. on the top of the water and when the bullet drops it will take the sponge down a little but then the bullet will fall off the sponge and the sponge will float to the surface again. No splash and no cleaning off the soap, which keeps the lube from sticking.