First experiment with fire lapping

[Scott Tschirhart]

I have a Ruger that probably needs bore lapping as it doesn’t behave as it should.

I made 25 rounds of lapping bullets this week.

5 gr of Trailboss in the case, then I picked the lube out of some 270 gr semi wadcutters sized to .453. I filled the crimp groove and lube grooves with 320 grit lapping compound and seated the bullets nose down in the cases. I seated the bullets flush with a bench vice and wiped off the excess compound.

Then I used the crimp die on the Dillon to iron out the flare.

Fermin says to shoot them into a large close target until the bullets start going into the same hole. He says that 18 rounds should do it.

Wish me luck.

[4t5]

I think some prickly pears are gonna get lapped .

[sledman]

Good luck! Which Ruger?

[Pat C]

You cam also just hand lap it , that's how most manufacturers do it after rifling ,at least the cut rifled.

Years ago Remington custom shop had a video. The gunsmith installed a swivel T handle plug on one end , then poured lead into barrel . When it cooled he grabbed the T handle and partially pulled out the rifled ingot . Applied lapping compound and preceded to lap the barrel with lead.

I've done this on old muzzle loader where people shot them and didn't clean right away. Saved some pretty nasty bores.

I didnt pour entire barrel though. I used a two piece block with hole drilled to make my lead cavity just over groove diameter .
You can use bullet puller cleaning rod end with T handle.

I didn't use that coarse of lapping compound though. I was using 1700 grit and finished with JB Bore paste.

[Bill in Oregon]

Think I started with 600-grit Clover the one time I did it. Been many years. Helped!

[JimT]

When I was 16 (1962) I had a Ruger Blackhawk .357 that had a tight spot at the throat, where the barrel screwed into the frame. Dad told me that if I wanted to correct it I needed to pour a lead plug and lap the throat. I blocked the breech end of the barrel, screwed a 30 caliber brush on the end of a cleaning rod, and poured hot lead into the bore .. enough to make a lead plug about 1 1/4" long. When cooled I pushed it out the breech end of the barrel, put fine valve-grinding compound on it and proceeded to lap the barrel. I did 3 short strokes in the throat area and 1 full-length ... for several hours. When I finished the tight spot was gone and the gun not only did not lead in the throat area any more, it was amazingly accurate. I still have some targets I shot at 50 yards ... 5 shot groups around 1 1/2".

From what I've read fire-lapping will accomplish the same thing with less elbow power. I have never done any fire-lapping but I know from friends that it does do the job.

[Walt]

Here's another method that's worked well for me. John Linebaugh told me to use round nosed lead bullets so that the grinding compound is forced onto the lands and grooves. I put the grinding compound, usually 180 or 240 grit directly into the beginning of the rifling on a short Q-tip held with a pair of needle nosed pliers or hemostats so that the chamber throats aren't affected. I use 2 grains of Bullseye and just shoot into a bucket of sand so my neighbors don't become concerned. Eight or ten shots seems to do the trick. I put enough grinding compound into the barrel so theres a significant buildup. It appears that the maximum effect of the fire lapping is in the first inch or two of the barrel.

I have a Ruger .45 Colt that had a ring in the barrel under the frame created by the factory over-tightening the barrel which is apparently not uncommon. It didn't shoot well because my bullets were sized down by the ring and came out the remainder of the barrel undersized. I probably shot about 20 rounds through the grinding compound and it cured the problem. I have used this method on all my large bore revolvers as well as on my 1911s. It has all but eliminated leading.

[Scott Tschirhart]

First six

[Scott Tschirhart]

Second six.

[Scott Tschirhart]

Third cylinder.

The last three went into virtually the same hole.

[Scott Tschirhart]

I didn’t change targets for the last bunch. Just shot the hole bigger.

[Pat C]

What did same target pre lapp look like?
Curious what the chamber throats measure and groove diameter measure?

[junkbug]

Thanks for the guidance. Do you segregate your brass by grit; ie once you use a particular grit in one case, that is all you use it for again?

[Scott Tschirhart]

7.2 gr 231 255 gr Hornady Cowboy

[Scott Tschirhart]

270 gr SWC over 8 gr Unique

[Scott Tschirhart]

Thanks for the guidance. Do you segregate your brass by grit; ie once you use a particular grit in one case, that is all you use it for again?

I’m planning on keeping these cases separate for only this purpose.

[Scott Tschirhart]

Three shots with a 250 gr cast RNFP over 6.2 gr TiteGroup

[Scott Tschirhart]

What did same target pre lapp look like?
Curious what the chamber throats measure and groove diameter measure?

They were consistently bigger but keep in mind that Im shooting offhand and there’s a lot of human error.

Patches are definitely going through the bore smoother and I’m finally getting a lube star on the muzzle.

[Scott Tschirhart]

6.2 gr TiteGroup Hornady 255 Cowboy bullet

[Walt]

Nice shooting, Scott! It looks like you have your Ruger just where you want it.

I think fire lapping puts a very tiny taper in the overall length of the barrel which must certainly contribute to improved accuracy.

[marlinman93]

I've fire lapped a couple firearms over the years, but I simply used fine valve lapping compound on the tips of bullets, and fired them. I fired 5 rounds, then cleaned the bore, and fired 5 more to check the groups. I continued 5 at a time, and usually never got over 20 rounds before stopping. If the groups wont get better by 20 shots then they probably wont ever get better by lapping.

[Scott Tschirhart]

I think the experiment was a success. It’s much easier to clean and the groups are tighter.

I want to step this gun up to around 900 fps with a big SWC. So I’m going to step up to 8 grains of 231 (Linebaugh recommended this load) and see what it does.

Unfortunately 8 grains of Unique is still my favorite.

TiteGroup really heats the gun up even with lighter loads.

[GunnyMack]

Scott, you did the right thing! Don't ya love it when stuff works!

[Scott Tschirhart]

It was almost precisely what Fermin said would happen.

[Ysabel Kid]

Seems like a cool and productive way to spend a Saturday!

[samsi]

Thanks for the positive report, I have a couple candidates for fire lapping but have been hesitant to give it a go.

[Grizz]

My redhawk has tight chambers that swage the bullets before they get into the throat, or during the transition. I am wondering if the lapping bullets have any sizing effects on the cylinder? It's step one to making my pistol my pistol . . . kwim?

[Scott Tschirhart]

My redhawk has tight chambers that swage the bullets before they get into the throat, or during the transition. I am wondering if the lapping bullets have any sizing effects on the cylinder? It's step one to making my pistol my pistol . . . kwim?

It’s probably simpler just to ream those chamber throats.

[Walt]

Grizz, I was unable to find a reamer for my .41 mags although I bought reamers for .357, .44 and .45 so I used the following method. Find a steel rod that's slightly smaller than your throat size and cut a longitudinal slot into it with a hacksaw. The fewer turns of emery cloth you can get on the rod, the better because alignment will be better but it has to be a tight fit. Chuck it into a drill and turn for 30 seconds and check to see if your bullet of choice will push through the throat. In all likelihood it will take several minutes but stop and check often. I use a leather glove to keep the cylinder from turning and also the cylinder will get rather warm. Stop as soon as your emery cloth goes through, put some finer sandpaper on the mandrel to polish the throats and you're done. I put a piece of masking tape around the cylinder marked with numbers so that I'm sure of which chamber throats I've done. I've been pleased with the results of doing it by hand although the reamers work very well. BTW it takes a long time to make a measurable increase in throat diameter so don't worry, it's not something you can screw up in a matter of seconds.

[Scott Tschirhart]

I was able to reach my velocity goals with 8 gr of 231 and 270 grain bullets. Very pleased with the results.

[Grizz]

Grizz, I was unable to find a reamer for my .41 mags although I bought reamers for .357, .44 and .45 so I used the following method. Find a steel rod that's slightly smaller than your throat size and cut a longitudinal slot into it with a hacksaw. The fewer turns of emery cloth you can get on the rod, the better because alignment will be better but it has to be a tight fit. Chuck it into a drill and turn for 30 seconds and check to see if your bullet of choice will push through the throat. In all likelihood it will take several minutes but stop and check often. I use a leather glove to keep the cylinder from turning and also the cylinder will get rather warm. Stop as soon as your emery cloth goes through, put some finer sandpaper on the mandrel to polish the throats and you're done. I put a piece of masking tape around the cylinder marked with numbers so that I'm sure of which chamber throats I've done. I've been pleased with the results of doing it by hand although the reamers work very well. BTW it takes a long time to make a measurable increase in throat diameter so don't worry, it's not something you can screw up in a matter of seconds.

Thanks Walt, I can do this. I think. Do you eyeball the alignment? It would be easy to set up a jig. or perhaps use the drill press. That should be close to square . . .

I can see my bullets exiting stage left . . . I have reamed the old fashioned brake cylinders with good results. Sounds similar.

thanks again

[Walt]

Grizz, I think holding the cylinder in your hand allows better feel of the alignment. If the rod and emery cloth are tight in the throat the alignment will feel correct. Lacking a lathe or a mill, I think the hand held method is still better than a drill press. Replace the sections of emery cloth frequently or you'll be doing it all day.

[Grizz]

Grizz, I think holding the cylinder in your hand allows better feel of the alignment. If the rod and emery cloth are tight in the throat the alignment will feel correct. Lacking a lathe or a mill, I think the hand held method is still better than a drill press. Replace the sections of emery cloth frequently or you'll be doing it all day.

Thanks again. It's going on the active to do list. Somewhere on the list. LOL

[Pat C]

I had an old Super Blackhawk that was made in 1976, beautiful revolver but you couldn't hit a bull in the butt at 20 feet. Looking back I didn't know back then how common mixed dimension throat/bore combos are . My guess throats were tighter in mine causing poor accuracy. I traded in back late 90's . Kinda wish now I still had it to investigate.

[Scott Tschirhart]

They all seem to shoot very well with jacketed bullets. This gun wasn’t bad but it is much better now.

[Paladin]

I have never Fire-lapped a handgun but I have a few .308 rifles we used as tactical weapons and still have one Brownells lapping kit left for .30 Cal. It made a big difference even though the lack of accuracy was from the operator's lack of maintenance.

[Keith D]

Got a Smith model 15 recently that seemed to have tight cylinder chamber throats. .358 lead bullets will not pass through easily at all. So before wanting to ream the throats, I wanted to check the bore size. Pushed a lubricated .375 round ball through with a pencil, after plastic hammer tap start, and found resistance at the barrel throat. Barrel thread choke for sure. Was moving the slug easily until the end when it stopped right at the frame. Looks like fire lapping is needed first then address the chamber throats. I fire-lapped a Ruger Blackhawk years ago, but just may have to try this method this time around.

[Walt]

Good thought process, Keith. Although it's hard to imagine a .357 with barrel thread choke (it's way more prevalent with larger calibers) It's certainly possible. If it were mine I would first be absolutely certain that the barrel is free of any fouling in that area. Brownells sells a throating kit that can be had with a 5° forcing cone reamer and brass lap that would clear out the barrel constriction so that you can shoot cast bullets (especially) more accurately.

Fire lapping would work well also but would probably require quite a few firings with medium grit grinding compound.

[Keith D]

Thank you for the ideas, Walt. I thought the same as you....357 diameter barrels don't have thread choke (at least not often). However, if it can go wrong then it will happen to me. The gun was hardly shot, the barrel is shiny clean, and I slugged it twice. Slug stops at the beginning of the frame. I'll check it over a few more times, but I won't mind fire-lapping it a bit. Not sure if it happens, but it would be nice if the fire lapping opened the cylinder throats a little, too. They are tight.

[Grizz]

Thank you for the ideas, Walt. I thought the same as you....357 diameter barrels don't have thread choke (at least not often). However, if it can go wrong then it will happen to me. The gun was hardly shot, the barrel is shiny clean, and I slugged it twice. Slug stops at the beginning of the frame. I'll check it over a few more times, but I won't mind fire-lapping it a bit. Not sure if it happens, but it would be nice if the fire lapping opened the cylinder throats a little, too. They are tight.

i don't know if this applies or not, but i have found internal tight spots with a tight wad of paper towel. it pretty well shows mid barrel problems, but maybe not thread chokes, idk. plus you can't measure it ! I do this with guns at the lgs for a quick check . . .

very interesting stuff you are dealing with. i have a gnarly redhawk that i need to shape up, thanks for the info