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S&W-Smithing Maintenance, Repair, and Enhancement of Smith & Wesson and Other Firearms.


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Old 07-29-2020, 10:29 PM
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Has anyone lapped a barrel buy coating the bore with compound and firing a round, instead of coating the bullets. Think I will try it this weekend. May just blow it out the end. guess will see.
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Old 07-29-2020, 11:24 PM
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No to using a coated bullet, but I have lapped a few with lapping compound and a cleaning rod. They were all rifle barrels and I made improvements in both accuracy and lowering the copper fouling to all I have lapped over the years.
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Old 07-29-2020, 11:35 PM
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The traditional way is to pour a bit of melted lead into the bore you want to lap.
Of course, you need to plug one end of the bore, and need to allow for removal. I have used a piece of oak dowel that has been tapped into the barrel about 3/4". A piece of 3/8" dowel can make a handy 38 cal plug. I soaked the plug in Remoil to facilitate removal and to keep it from burning.
You can use a cut off piece of a bore brush to pour the lead around. That will help in the lapping process, as you can thread a cleaning rod to it.

When you have your lap cast and removed, you want to use some light oil on it so your lapping compound will adhere. But, first, it helps to try pulling or pushing your lap through with no lapping compound, just oil. This will make the job easier.
You can roll the lap on a hard substance like a flat slab of marble to embed the compound. Go easy with the compound!
Fit the lap in from the forcing cone, thread the cleaning rod on, then pull it towards the muzzle an inch or so, then reverse.
Usually you want to work the breech area, then as the lap begins to wear, extend your contact towards the muzzle.
Ideally, you will have a smoother barrel with a very slight choke towards the muzzle.
If nothing else, you should get a barrel that's easier to clean!

Last edited by 6string; 07-29-2020 at 11:43 PM. Reason: Details added
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Old 07-30-2020, 12:29 AM
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I use coated bullets with finer and finer compounds until I get to where I want to be. It's a labor intensive process and requires a lot of cleaning, but it works well for rough bores that foul in excess.

I personally haven't heard of anyone coating the bore as you suggest so I can't comment on its efficacy. I shot at fairly high levels of competition over the years and I've listened to a lot of theories by some very knowledgeable shooters on making rifles accurate, but no one ever mentioned that method. Lots of high masters did manually lap their bores or at least bought barrels that were hand lapped by the likes of Krieger, etc.
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Old 07-30-2020, 01:26 AM
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Quote:
Originally Posted by drgbike View Post
Has anyone lapped a barrel buy coating the bore with compound and firing a round, instead of coating the bullets. Think I will try it this weekend. May just blow it out the end. guess will see.
My concern would be the bullet pushing a small "ring" of lapping compound ahead of itself as it traveled down the bore.

That "ring" would logically increase in size as the bullet moved down the bore and could reach a point where it would resist movement and the bullet could pass over it and "ring" the barrel.

I would keep the the abrasives on the bullets.

John
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Old 07-30-2020, 03:11 AM
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Rifle or revolver/pistol barrel?

To fix what problem?

In my revolvers which had a constriction at the barrel-frame union I've hand lapped out the constrictions (~.0010"-.0015") using a very tight cotton patch (usually several layers) on a cleaning rod, with a generous amount of abrasive compound on it, & concentrating action in the area of the constriction.

Extra elbow grease is optional.

The constriction is detected using a set of pin gages by confirming smooth passage of the largest gage thru the whole length of the barrel.

Repair is confirmed once the gage passes the constricted point.

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Old 07-30-2020, 10:07 PM
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Yes I am familiar with procedure.As to the to the increasing resistance, it is a really thin coating. Soooo on with it and we will see. I am too lazy for the embedding and reloading.
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Old 07-31-2020, 09:05 AM
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After using several finer grits lapping a barrel by hand . I finish the process using " Mothers Mag and Aluminum Polish " . I run several dry patch's through afterwards , then a light coat of oil . A set of pin gauges are worth the investment as it takes out all the guess work . I got mine off Amazon . Afterward , if you feel you won't need them anymore you can always sell them right here on this forum . I'm sure they will go fast . Regards Paul
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Old 07-31-2020, 10:10 AM
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Fire lapping reportedly works pretty well on rifle barrels so say the benchrest guys. This technique uses coated slugs or bullets. My opinion is if the barrel shoots then leave it alone cause when I was in the business I saw and owned some really rough barrels that shot hard cast lead bullets very well.

My approach for lapping is to use nothing more than J&B compound and take care to protect the crown. When I get a new gun I take a moderately snug dry cotton patch and push it through once. Then with a bore light take a look inside. If you see cotton strands or fuzz then you have a rough barrels with burrs and nicks on the edges of the landes tearing the patch and your bullets. The old school liked to shoot jacketed through the barrels to hopefully smooth things things. I use an oiled patch wrapped around a tight bronze brush then load the patch with some compound and go to it. The J&B compound will not hurt the bore and with a bit of elbow grease the barrel will shoot cleaner and clean easier
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Old 08-01-2020, 08:11 AM
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I have used polishing compound and a patch on severely leaded or jacket fouled barrels and barrels that had rust in the bore. I've not fire lapped a barrel, not found a need to with commercial or military grade barrels.
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Old 08-01-2020, 03:21 PM
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I have fire lapped several revolver barrels on S&W's with great results . I would shoot 4-5 rounds , stop and pull a bore snake through the barrel . Reload and fire 4-5 more on a different target so I could compare the group size . I could see the group size getting smaller and smaller as I progressed . When I had the rounds touching or almost touching at a distance of about 20 yrds I knew it was time to stop . I would finish up hand lapping using finer grit and finished with the polish . I would rest my fore arms on a bench rest for consistency , but not resting the firearm . Regards Paul
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