Fire Lapping ?

[jvs]

What are the basic advantages and disadvantages of fire-lapping?  I've heard a few.

[gunnut69]

Fire lapping is a method of squeezing a bit more use from a damaged bore.  It uses abrasives on a bullet fired down the bore to remove the rough edges from rifleing and pits that may be catching bullet fouling.  It wonm't remove the pit just soften the edges a bit.  It cuts the most at the rear of the barrel as the abrasives begin breaking down almost immediately.  It is basically accellerated wear.. It advances the throat of a rifle to a degree and is really only marginally useful.  If the rifle has a rough barrel and you wish to salvage it, a regular lapping process should be done.  The fire lapping is a bunch easier and that allows them to sell more to shooters.  It takes more time and effort to use a normal bore lap but there is no real advantage except firelapping is a lot easier..  of course it's a lot less effective too..

[Rustyinfla]

It can also be used on a brand new barrel to smooth things out a bit. Getting rid of tool marks and such. If the barrel is leading when shooting cast bullets it can help that too.
   You might also have tight spots in a bore such as where a revolver barrel passes thru the frame or where a front sight is attached.

  There has been quite a bit written about it on the leverguns.com forum. do a search there and see what it turns up.

               Rusty <><

[jvs]

I have sat in on some of the talk about fire lapping in the levergun forum and that is why I get confused about the prosess.  My conclusion about what I read about it so far is that it accelerates wear in a barrel with the hope of removing rifling defects, sloppy maintenance or bad metalurgy.  It caught my attention at first because it seemd so easy and the testimonials were slanted to the pro side.

But the more I read about it, the more I'm convinced that smoothing out a bore is a smithy's job.  I can't even imagine buying a firearm with a barrel in such shape that I'd have to shoot carborundum through the barrel.

But I do see advantages with cast bullets concerns.

My next question would be:  is there a way to tell if a used gun was fire lapped?  Or would that be a another chance you take ?

[John Traveler1]

An experienced eye using a borescope could see the results of firelapping in a used gun.  Air gauging would also reveal tight or loose spots.  This requires the laboratory equipment and the ability to use it, of course.

For the amatuer without the equipment, a good look at the throat and leade of the chamber should show if the barrel has had firelapping done to it.

[Kivaari]

I think John is correct in that to use this tool (fire lapping) the correct way a good borescope should be handy. This way you could see results right away. To carte blanche firelap something with a standard recommended regimen may do more than needed, for example. NECO's system starts with laboratory grade abrasive of #220...that's pretty coarse, moves to #400, then #800, and then #1200.

I recently "fire lapped" a Finnish M28/30 as the bore was pretty frosted and the main motivation was to enable it to clean better w/ reduced copper fouling. I used David Tubb's system and prefer that to the NECO system I have. Tubb's abrasive seems much less aggressive and more appropriate for a "regimen" of recommended grits and sequence.

[gunnut69]

A gunsmith wishing to polish a bore casts a lap in the bore and embeds it with the abrasive.  It is then pushed and pulled the length of the bore with attention being paid to even handedness.  In this manner a bore can be polished without excessive wearing of the throat.  Of course this requires a gunsmith or the cost of hiring one.  The chief advantage of firelapping is it is cheap.  If a bore is already pitted then firelapping may be acceptable.  In most other cases I would see it as doing more harm than good..

[johk01]

I have used Beartooth's lapping compound & soft lapping bullets to lap out the barrel constriction in 2 Blackhawk 45s, clean up a really rough Cabela's Millennium revolver bore, & lap out the constriction under the dovetail cuts of 2 Marlin 45-70s. But, if it's not broke, don't fix it. Firelapping is a form of controlled wear that, if done properly & judiciously, can remove bore imperfections. At least, that's my experience.