View Full Version : Lapping a barrel
May 10, 2010, 08:57 AM
I'm not sure whether or not this post belongs here or on Gunsmithing but since it involves an old pistol, it's here.
I just acquired a British Bulldog pistol chambered for .38 CF - uses a heeled bullet of .375 over a BP charge.
The gun is, given its age, in quite good shape. Timing is good, works in DA and SA.
The barrel - that is where the work will go. It is clear (not clean), rifling is discernible. It is quite rusted/pitted. I'm thinking that I may have to go the lead lap and valve grinding route in order to smooth it out at least a bit.
Before I do that.....any suggestions about removing rust from the barrel interior?
May 10, 2010, 09:09 AM
You can use reverse electrolysis to remove the corrosion. Make sure you find the correct sized rubber stopper to keep the electrolyte fluid in the barrel.
May 10, 2010, 09:33 AM
Definitely a gunsmithing type of thread.
May 10, 2010, 03:33 PM
Happy the moderators moved it. Didn't want to double post.
May 10, 2010, 06:48 PM
See how well it shoots before you do anything.
May 10, 2010, 07:17 PM
These days, modern chemistry can handle rust awfully well. Stay clear of acids, as they activate the surface to promote new rust. A product called Evaporust is quite good. Clean the bore with Gun Scrubber or with brake cleaner spray so it is totally degreased. Put some paste wax on the muzzle and the end of the barrel to protect the bluing. Plug the bore with a Neoprene stopper. Put the gun muzzle-down in a dish and fill the bore from the breech end with the the chemical using a syringe-type turkey baster or one of the syringes sold for mixing oil with fuel for 2-cycle engines, or similar. DON'T get it on the bluing if you still have any? Stand there feeling foolish that you forgot to bring your Ipod or radio. About 15 minutes later the rust is all converted to black powder. Unplug the muzzle and let the liquid run out. Pour water down the bore to flush it out. Brush and clean and oil the bore.
May 11, 2010, 06:22 AM
Unclenick: Thanks for that info. It sounds like good stuff. I have ordered a quart.
Bluing? Not on this gun.
May 11, 2010, 07:01 PM
You may want to protect it anyway. I find the Evaporust will discolor and eventually slightly etch a plain metal surface. Of course, I saw this experimenting with nails and left them in it overnight. You don't need that much exposure. Nonetheless, I wouldn't get it where you don't need it.
When you finish with the rust, you might consider firelapping the revolver, at least lightly? That will tends to dull sharp edges on pits that would otherwise scrape lead off bullets and accumulate it.
May 11, 2010, 09:52 PM
Unclenick: I will take your advice. Also, the fire lapping sounds like a good idea.
How does one go about preparing the bullets?
May 14, 2010, 06:27 AM
Unclenick: Thanks for the lead to Evaporust. It works as you described. The rust is gone. The barrel is heavily pitted, though, and I'll still have to make a lap and work on it a bit..
May 25, 2010, 09:50 PM
Firelapping is usually done with bullets that are about BHN 10-12. That's a cast bullet of 16:1 lead:tin or wheel weights with about 2% tin added. You can go softer, but you really need to pipsqueak the charges if you do, so the the lead doesn't bump up.
The abrasive is usually rolled into the bullets. You use an abrasive-loaded grease, like Clover brand compound. You smear it out on a flat surface (an old piece of plate glass works well) and roll the bullet against it, lube and all, using another flat surface against the top side of the rolling bullet. A short length of steel flat bar, for example.
If this is the only gun you intend to do this to, I would just buy some 320 grit Clover compound and use that. I would avoid the Wheeler kit Midway sells as its coarsest abrasive is a bit too coarse (220 grit), IMHO, and the instructions illustrate an improperly lapped bore and proclaim it to be right. They just don't know what they are doing. The more expensive NECO graded kit uses a coarse abrasive (240 grit) that is only one grade finer that Wheeler's, but NECO uses a laboratory grade abrasive that has a narrower particle size distribution, so its biggest particle is about half the diameter of Wheeler's biggest particles.
I've always use small charges of Bullseye, but I'm intending to give Trail Boss a try on my next go-around. Maybe fill half the space under the bullet. You may need even less?
May 26, 2010, 06:53 AM
Nick: Thanks for the note. I would not have thought to have a plate on top for to apply pressure. I have to wait a bit for the right bullets - have ordered them from GAD Custom.
In the interim, I have gone and made a traditional bore lap. I've been through two so far, more are needed.
May 26, 2010, 01:05 PM
If you have only bullets either too soft or too hard, you can still polish with them firing what would be normal loads for your old gun. The bullets will not remove constrictions well because it will tend to run narrow and wide areas alike, but iot will bear against the bore surface either because of being upset by pressure (the soft ones) or because of springiness of the alloy (the harder ones). Either should tend to dull the edges of the pits.
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