Making your own fire lapping paste

[Cosmic_Charlie]

Just got a jar of 320 grit silicon carbide and wondered if there is a preferred grease to mix it with? Was thinking a high temp grease. Have any of you made your own?

[SwissShooter]

IMHO with inexpensive kits available making your own is not worth the effort.

[country gent]

Look in an older Machinists Handbook, you will find the methods of grading grit, the carriers to use and the procedures used. The fire lapping process Uses 2 steel plates to "impregnate" the compound into the bullet surface by rolling it between them with the grit. The carrier isnt the only thing but also the concentration of the grit to carrier is important.

[Winger Ed.]

Rather than trying to reinvent the wheel:
I'd give credit to the folks that have researched and put together a kit that has a good reputation:
For me--- I'd just give 'em their money, and follow their instructions.

Very seldom have I been chopping and hacking around in the garage and beat the system on something like that
where I had very little to gain, and a whole lot to lose.

Also, 320 grit sounds pretty coarse and harsh.

[M-Tecs]

No grease required. Just follow the instructions here. https://www.ktgunsmith.com/firelapping.htm

[Cosmic_Charlie]

Thanks fellas. I have the steel plates. Ended up using canola oil. Made a light slurry that worked well impregnating the bullets. 240 gr. pure lead tumble lube style bullets and a 5-1/2" barrel. 2.5 grains of bullseye gets them out.

[flounderman]

I had a 25-06 barrel that I had used some corrosive primers in, without knowing they were corrosive. I attempted to salvage it with some cast 25-20 bullets and some valve grinding compound, using loads that barely pushed the bullets out of the barrel. Totally ruined the barrel. If you don't really know what you are doing, don,t. You won't like the results.

[country gent]

Valve grinding compound is a mix of grits that is meant to cut fast and break down in use to finer grits in fire lapping the grit dosnt get a chance to break down as each bullet is fresh compound. a valve is coated and used until the finish and surface mating is achieved giving it time to break down and cut finer.

[Cosmic_Charlie]

I had a 25-06 barrel that I had used some corrosive primers in, without knowing they were corrosive. I attempted to salvage it with some cast 25-20 bullets and some valve grinding compound, using loads that barely pushed the bullets out of the barrel. Totally ruined the barrel. If you don't really know what you are doing, don,t. You won't like the results.

I'm just looking to relieve a slightly tight forcing cone. 320 grit is really quite fine, more like powder than grit. Ross Seyfried outlines this procedure in his review of the same Ruger Bisley Blackhawk. He used 320 grit Clover paste. He fired upwards of 100 shots out of the stainless gun and got impressive results. Don't think I'd try this on a rifle as I seem to get really good accuracy out of the box with most of them. Got the load down to 2.1 gr. of Bullseye and the bullets are still making it out.

[EDG]

I once worked with a former employee of a barrel maker that lapped each barrel with a lead lap for uniformity. They used 220 grit diamond paste but the lead lap does not produce as much pressure on the abrasive as does a bullet fired in your gun.
I guess for a pistol forcing cone I would use a cast lap and start with a 400 grit and go very slow.

[Cosmic_Charlie]

I once worked with a former employee of a barrel maker that lapped each barrel with a lead lap for uniformity. They used 220 grit diamond paste but the lead lap does not produce as much pressure on the abrasive as does a bullet fired in your gun.
I guess for a pistol forcing cone I would use a cast lap and start with a 400 grit and go very slow.

Yes, a button rifle mandrel is not going to leave a mirror finish. I usually do the one shot clean, two shots clean, until I get up to 10 shots. Using JB bore paste you can feel the barrel getting smoother as you go. I'm certain the 320 grit is going to smooth out the bore appreciably.

[Bent Ramrod]

Clover 320 paste is what I use. Each shot is one lapping “stroke,” so you’ll be a long time wearing out your barrel. The point of fire lapping is to get the edges of rust pits, tool marks, burrs, tight spots or whatever is causing the problem out of the bore, not putting the highest polish possible on the metal.

I insert the impregnated boolits into the leade with tweezers and push them home with a wooden dowel. I use the same case over and over, repriming and recharging with a light load at the range. Wipe case and chamber every shot, clean the bore with a brass brush, solvent and patches every five shots, do extra cleaning and fire five of your most accurate load at intervals in the lapping process to see how (or if) things are improving. I usually do 20 to 40 fire lap shots, depending on barrel condition, and check with my accuracy load. Figuring out where to stop is kind of a judgement call. I’ve sometimes done a hundred or more fire lap shots, over the course of several sessions, before I’ve figured that I’ve reached the optimum.

The fire lap case will be impregnated with the grit and ruined for any other use, so don’t let it get mixed up with your other shells.

You shouldn’t expect fire lapping to turn a standard factory barrel, slightly pitted or whatever, into a premium target barrel. At best, it will shoot tighter groups of the sort that can be expected from something of its brand, era and price; at worst, it will clean up easier and not be as prone to leading. I’ve never made a barrel worse by fire lapping, and most have been improved significantly in accuracy. I don’t fire lap barrels that are already gilt-edge accurate, nor do I use jacketed bullets or the other weird innovations that have come in the wake of Merrill Martin’s original instructions in Precision Shooting in the ‘80s. That guy knew what he was doing. The later ones, not so much.

[725]

I've used "Flitz" to very good effect. Two steel plates (1" x 4" x 1/8th? / 1/4"?). Roll the copper bullet and a dab of Flitz between the two ~ with some pressure, wipe the brass clean, chamber & fire. Have corrected several wayward barrels like that. Brand new barrels & some real old sewer pipe types. Other than not removing deep pits, it has left good rifling and mirror like lands. Just remember to quit before your final determination, clean, inspect, and make any further evaluations. Works great.

[Cosmic_Charlie]

Thanks!

[country gent]

From a old machinists hand book. to grade separate lapping compound grits if you want to do it yourself.....

Save the wheel ash from pedestal grinders. Grinders with silicon carbide wheels for carbide are great. Save this

In a deep sided bowl fill about 1/2 full of the oil you want to use. pour / sprinkle grit onto it carefully and gently. Let sit undisturbed for 15 mins pour of oil into another bowl this is usually to coarse for use and can be discarded.

let the second bowl set for 15 mins and pour off into first cleaned bowl this is a coarse grit. Continue this till nothing settles out. The settled out grit is finer and finer grits as you go. Wipe bowls out into pill bottles as you go and label the bottle.

You can vary the sit time if desired longer allows more grits to settle.

[Cosmic_Charlie]

So I ran 54 lapping rounds through my stainless .44 special. Bore wiped clean without needing to brush. Gave the gun a good rinsing and cleaning. Shot into a bucket full of rubber mulch so I saved the lead. Will try to get out this weekend and shoot it off the rest to see how it looks. I used unsized pure lead bullets in fired unsized cases with about 2.2 grains of Bullseye. I did bell the cases slightly to help get the bullets started. Pushed them in by hand, no crimp.

[Cosmic_Charlie]

Just an update. Fired an off hand group with my Ruger last evening and had six shots under 2" at 12 yards. Now the rest....
I fired 48 lapping rounds and it was a few too many. Got leading with my normal loads sized to .431. So I loaded up some unsized boolits that came in at at about .4325. These were loaded over 4 grains of Titegroup. The accuracy was great but I still got a bit of leading just ahead of the forcing cone. Problem is the cylinder throats are too tight for that unsized boolit. They are perhaps .4315.

So off the cylinder goes to member DougGuy to have the throats opened to close to .433. Am also going to send my M&P 2 9mm barrel to have it given some leade and a crown. I am confident that the Ruger will be a real shooter after this work but I do wish I would have checked the progress after 25 lapping rounds or so. Like always I learned a bunch along the way so my mistake had some upside.

[Cosmic_Charlie]

Well I still have that thread crush restriction in the forcing cone. Ordered a rental 11 deg. cutter which I will use very judiciously. Be nice to get this revolver shooting like it should. Hard to believe Ruger sends them out like that.

[725]

I used the Brownell's 11 degree cutter and it worked well. Easy job. Probably cheaper than sending it out.