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Drillbit

Fire Lapping

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Who here has fire lapped a revolver barrel.  What did you use, or who's product did you use.

I have a 38 spl with a very noticeable tight spot at the barrel/frame junction.

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If I recall correctly tight spots at the barrel frame area are normally caused by a over torqued barrel, It seems to me that fire Lapping would not remove enough material to make much difference and if it did it would also enlarge the rest of the barrel about the same and that is probably not a great result.

 

I may be wrong or miss understanding the issue you are describing.

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The tight spot is caused by a barrel that is overtorqued, has too much "crush fit", or whatever you want to call it. The 2 ways to fix that are (1) remove the barrel and turn the shoulder back on the lathe so it's not so tight in the frame. Or (2) Fire lap the barrel.

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Right. I had forgotten about that one. I'm not a fan of Taylor throating, It is one of the options, though.

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I’ve done it on several revolvers using the LBT compound and excellent instructions from Veral Smith.

It was kinda fun, though messy, shooting the lap loads. The bullets are so slow you can see them in flight.

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I did the same as FWSixgunner.  Definitely worth the time and effort.  Veral will help you if you need it gut it's real simple.  I gained a few FPS but don't remember how many and my groups got a little tighter, always a bonus.

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18 hours ago, FWSixgunner said:

I’ve done it on several revolvers using the LBT compound and excellent instructions from Veral Smith.

It was kinda fun, though messy, shooting the lap loads. The bullets are so slow you can see them in flight.

I looked at the LBT web site, what a mess. I could not find a price any where on his kit.

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15 hours ago, AzShooter said:

I did the same as FWSixgunner.  Definitely worth the time and effort.  Veral will help you if you need it gut it's real simple.  I gained a few FPS but don't remember how many and my groups got a little tighter, always a bonus.

Tighter groups is what I'm after.     A slug from the barrel is at .356.

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If it slugs .356 you want to use .357 or .358 bullets.  Mine worked best with .358.  Good luck.

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I'll be the dummy on this one. What's fire lapping?

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On 9/28/2019 at 10:59 AM, AzShooter said:

If it slugs .356 you want to use .357 or .358 bullets.  Mine worked best with .358.  Good luck.

Well;  the slug from the bore measures .356 after it goes through the tight spot at the barrel frame juncture. 

I'm going to try to slug the bore before the restriction. Half way sounds good.

 

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4 hours ago, Drillbit said:

Well;  the slug from the bore measures .356 after it goes through the tight spot at the barrel frame juncture. 

I'm going to try to slug the bore before the restriction. Half way sounds good.

 

How do you propose to do that?

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several short rods. slug it halfway from the front, stop, flip revolver around put in a series of short dowels, tap them back up. Sorta like digging an oil well.

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I looked at the LBT web site, what a mess. I could not find a price any where on his kit.

 

Yeah technology isn’t Verals strong suit. I suggest you call or email. He responds very quickly.

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Well;  the slug from the bore measures .356 after it goes through the tight spot at the barrel frame juncture. 
I'm going to try to slug the bore before the restriction. Half way sounds good.
 


You need to measure the chamber throats, too, either by slugging or with pin gauges. I doubt they could be smaller than .356 but if you’re after accuracy with cast bullets, you need to know. A quick test is to take the bore slug and see if it will fit through the chamber throats. Cast bullets need to be just a hair smaller than throat diameter.

What make is the gun and how many grooves does it have? An odd number (like S&W) can’t be measured with a regular slug & micrometer. The slug won’t have opposing grooves and will measure smaller than actual groove diameter.

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On 9/30/2019 at 2:33 AM, Joe4d said:

several short rods. slug it halfway from the front, stop, flip revolver around put in a series of short dowels, tap them back up. Sorta like digging an oil well.

Great minds think a like.

I did that very thing on another gun, worked good.

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20 hours ago, FWSixgunner said:

 


You need to measure the chamber throats, too, either by slugging or with pin gauges. I doubt they could be smaller than .356 but if you’re after accuracy with cast bullets, you need to know. A quick test is to take the bore slug and see if it will fit through the chamber throats. Cast bullets need to be just a hair smaller than throat diameter.

What make is the gun and how many grooves does it have? An odd number (like S&W) can’t be measured with a regular slug & micrometer. The slug won’t have opposing grooves and will measure smaller than actual groove diameter.
 

 

The cylinder throats are .3575, measured with a telescoping gauge. The slug will drop through the cylinder with out resistance. 

The gun is a k frame smith.  I wrapped a strip of aluminum can around the slug to measured it.    

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Posted (edited)

I fire lapped two Ruger Vaqueros in the late 1990s. I used the NECO kit linked by pskys2.

Both guns leaded the barrels badly starting just beyond frame/barrel areas. The frame choke

areas on each of these .45 Colt guns measured less than .449". The cylinder throats on both

were originally way too tight (around .448") but a gunsmith opened them to a .4525" each

prior to my fire lapping escapade.

 

I followed the NECO directions but it took many bullets (225gr truncated cone bullets without lube;

BHN 18 at .452" -- do not use soft bullets)  with the 220 grit to get the constrictions a tad under

.451". I then switched to the finer grits to finish up the opening of the choked areas and polish the

barrels. I used 2.5 grains of Red Dot but seated the prepared bullets so that their bearing areas,

which had the lapping compounds embedded in them, were totally covered by the cases.

 

Preparing the cases was very messy. The lapping compounds got all over the place and me. I used

a lot of paper towels and Hoppes #9 to clean my hands and the prep area. I removed all of the

dies from my press and scrubbed them with mineral spirits to remove any lapping compound.

 

I typically fired 12 rounds, cleaned the barrels and cylinders with Hoppes #9 and Bore Scrubber

and many cotton patches. To measure my progress I used Hornady .454" lead balls to slug the

barrels and a micrometer to asses the progress. FWIW, the first dozen or two rounds (220 grit)

removed the most material. Thereafter progress slowed.

 

I fired the bullets into sheets of 8.5x11 paper to make sure each bullet exited the gun.

 

It took hours to do the firing of the lapping bullets (and the cleanings and the measurements). I had a

small audience watching at times. I got some "interesting" comments from several of the watchers.

 

The results? The frame chokes were eliminated, barrel leading was almost totally eliminated, the

barrel was extremely polished. Cleaning the barrels became much easier. Accuracy with my

Cowboy load went from over 3" at twenty-five yard, bench rested, to about 2.5" - 2.25". I considered

that pretty darn good with the gross sights on the Vaqueros and my eye sight (in my late 40's then).

 

Edit note: The frame choke areas were originally less than .449" not .459" as I typed in my post. Sorry

for any confusion I caused!

Edited by MifflinKid

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You can also buy Bore Lapping Compounds, there are at least 2 different grits, and do it manually with a patch and cleaning rod.  I did this and it helped quite a bit.

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23 hours ago, pskys2 said:

You can also buy Bore Lapping Compounds, there are at least 2 different grits, and do it manually with a patch and cleaning rod.  I did this and it helped quite a bit.

Can you give me more detail on your process? 

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8 hours ago, Drillbit said:

Can you give me more detail on your process? 

Go to Brownells they sell the compound and it comes with instructions.

I did the following:

1) Thoroughly cleaned the barrel

2) Rubbed the compound onto a cleaning patch and ran it through the bore, multiple times

3) Thoroughly cleaned the barrel

4) Repeat until I felt it was smooth enough

5) Put finer compound on patch and ran through bore multiple times

5) Thoroughly cleaned the barrel

6) Tested groups

 

Don't have to use the finer grit, but I did.

 

I'm not sure if it would remove a constriction, defininetly won't help with a bulge (like you can get if a bullet encounters an object in the barrel, usually another bullet, and doesn't produce enough pressure to blow up a barrel) and can be used to remove really bad copper fouling.  It did smooth out the barrels I used it on.

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14 hours ago, pskys2 said:

Go to Brownells they sell the compound and it comes with instructions.

I did the following:

1) Thoroughly cleaned the barrel

2) Rubbed the compound onto a cleaning patch and ran it through the bore, multiple times

3) Thoroughly cleaned the barrel

4) Repeat until I felt it was smooth enough

5) Put finer compound on patch and ran through bore multiple times

5) Thoroughly cleaned the barrel

6) Tested groups

 

Don't have to use the finer grit, but I did.

 

I'm not sure if it would remove a constriction, defininetly won't help with a bulge (like you can get if a bullet encounters an object in the barrel, usually another bullet, and doesn't produce enough pressure to blow up a barrel) and can be used to remove really bad copper fouling.  It did smooth out the barrels I used it on.

Thanks.

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