Barrel Lapping?

[Scota4570]

I received a barrel that has tight and loose spots. The muzzle is flared and the middle is tight.  This is obvious when slugging the barrel.   The bore scope shows that it did have some wire edges in the rifling that might be making it feel tighter in the middle.  The muzzle really is flared.  I suspect the barrel maker is not slugging his barrels based on it having swarf in the plug threads and on my first cleaning patch.  The feel of the naked lead ball when slugging it makes the tight and loose spots obvious.   

It is from a well respected barrel maker.  He is extremely busy and he did get my barrel done very fast.  I do not want to send it back.  I don't want to argue with him.   I do not want to be ungrateful.  I don't want to get get on his bad side. 

I have lapped many barrels.   I decided to lap this one.  It is going very slow.  After four hours I have a smoother barrel with a flared muzzle and a less tight middle section. I have cast three laps and used #220 Clover silicone carbide grit.  Maybe a thousand strokes so far.  The middle section requires beating the rod and barrel on the ground and a slide hammer for extraction.  Near the breech and muzzle have no friction. 

When I take it up again should I use a different abrasive?  Maybe #120 to size it then the finer grits later?  Clover Silicon carbide??  Is the modern stuff junk?  I am making little progress.  It is not the disintegrating type of lapping compound.  Are there abrasives that cut faster on leaded steel with a lead lap?  I could not imagine a real barrel maker lapping a barrel like this. 

The flared muzzle concerns me.  Choke is good,  blunderbuss bore is bad.  I can not measure it, it just gives no resistance to the lap, like the bottom third.  I fear no matter how much I lap it may never shoot well.

Opinions on any of this?   

Thanks

[JPK]

I have never found lapping to remove a significant amount of metal. It will smooth a bit of machine marks and burrs but a truly tight spot will take more effort then I could justify the hours doing. It surely won’t remove pitting. It can improve a barrel as to fouling and cleaning though.

[A.Merrill]

  I heard valve polishing compound will really smooth it up fast.    Al

[rich pierce]

I’m with JPK. Lapping is more polishing than metal removal.

Lead is, as you know, so much softer than steel. The lap is being lapped as the steel is being lapped. That’s why laps wear out. When you go to a coarse abrasive your laps won’t last long at all. You might need 20 laps and when you’re done your rifling will be rounded and not grip the patch. Sorry for the bad news/view.

If I were to try this I’d cast the lap then file it and trim it till it only engages the tight spot. Tedious but you don’t want to lap the loose bits.

You’re a heck of a considerate fellow. If I didn’t want to bother the maker I’d rather buy another barrel if I didn’t know how to fresh rifling with cutters set in laps. That’s really your best solution.


After all your work, with thousands of strokes under enormous pressure and with loaded abrasive, your views of ramrod wear at the muzzle may change also.

[Mike Brooks]

I'd send it to Hoyt and have it reamed and rifled.

[oldtravler61]

  Valve polishing compound does work. But it is a slow process.
  Bobby Hoyt is your best solution..
   Oldtravler

[Bsharp]

"he bore scope shows that it did have some wire edges in the rifling that might be making it feel tighter in the middle. "

Remove these, then try again.

[jgraham1]

I have had Bobby Hoyt fix a few barrels for me.  Fast, efficient and excellent work at a decent price.  Like the others said, use Bobby.

Jerry

[Scota4570]

I switched to 120 grit.  After 6 more hours of work it is almost all one size.  It is surprising how slow 120 cuts and how machine marks on the lands could survive, but they are still there.  The finish is very smooth.  Time to take a rest. 

[jgraham1]

Glad it worked out.  Barrels with issues are not always amenable to fixing as you did.  Shoot it and hopefully you can tell if it is okay.  Good luck.

Jerry

[Bob Roller]

There is a good chance the driving side of the lands will be polished off and then your barrel will shoot with the best smooth bores made anywhere.Being involved with Bill Large from 1953 until he passed in 1985 taught me something.Anther fine machinist here was Clyde Gibson who told me lapping was trying to cover a mistake of some kind.I told Bill I was going to lap one of his barrels and save the owner the trouble of wearing it out by shooting it . He grinned ans said  "Go for it.". I never did and don't recall ever seeing ANY polishing compounds in his shop.
Bob Roller

[Bob Roller]

I received a barrel that has tight and loose spots. The muzzle is flared and the middle is tight.  This is obvious when slugging the barrel.   The bore scope shows that it did have some wire edges in the rifling that might be making it feel tighter in the middle.  The muzzle really is flared.  I suspect the barrel maker is not slugging his barrels based on it having swarf in the plug threads and on my first cleaning patch.  The feel of the naked lead ball when slugging it makes the tight and loose spots obvious.   

It is from a well respected barrel maker.  He is extremely busy and he did get my barrel done very fast.  I do not want to send it back.  I don't want to argue with him.   I do not want to be ungrateful.  I don't want to get get on his bad side. 

I have lapped many barrels.   I decided to lap this one.  It is going very slow.  After four hours I have a smoother barrel with a flared muzzle and a less tight middle section. I have cast three laps and used #220 Clover silicone carbide grit.  Maybe a thousand strokes so far.  The middle section requires beating the rod and barrel on the ground and a slide hammer for extraction.  Near the breech and muzzle have no friction. 

When I take it up again should I use a different abrasive?  Maybe #120 to size it then the finer grits later?  Clover Silicon carbide??  Is the modern stuff junk?  I am making little progress.  It is not the disintegrating type of lapping compound.  Are there abrasives that cut faster on leaded steel with a lead lap?  I could not imagine a real barrel maker lapping a barrel like this. 

The flared muzzle concerns me.  Choke is good,  blunderbuss bore is bad.  I can not measure it, it just gives no resistance to the lap, like the bottom third.  I fear no matter how much I lap it may never shoot well.

Opinions on any of this?   

Thanks

It'a a dud and waste no more time on it and send it back to the maker.Tight in the middle and loose at bothends was called an Arkansas choke at one point in time and poor workmanship at any point in time.Ranks with a matching lock that has collapsed the mainspring and can't stay cocked either.
Bob Roller

[shortbarrel]

if you lap a barrel, it is the same as a worn out barrel. have the machines to make barrels and have made many. never lap a barrel that has lands and grooves in it

[Dphariss]

if you lap a barrel, it is the same as a worn out barrel. have the machines to make barrels and have made many. never lap a barrel that has lands and grooves in it

Most if not all single point cut rifle barrels outside MLing are lapped. AS well as people in the past like Warner, Brockway, Pope and others lapped barrels to finish them.
The OPs barrel can probably only be corrected by freshing or having it redone by someone who knows how to make barrels. I have gotten such things from people most here would consider “competent”.  It needs to be sent back to whoever rifled the thing. Its useless as is. Lapping will not work. BT tried that.

[Bob Roller]

I doubt if Pope,Warner and Brockway ever had a bad "Arkansas choke"to contend with as described here.
My Whitworth had an Alex Henry barrel that had a noticeable choke and about 8 inches down it frees up and
the bullet,Lyman 451112 moved a bit easier down to the powder. When it went off it had a keen "crack". Does ANYONE make such a barrel today with the unique rifling of the Henry and with the obvious "choke"? This shot really well with patched round balls and I loaded it like that with a .445 ball and 45 grains of 3fg DuPont so small boys could fire it without recoil and a man in a wheel chair enjoyed it as well.Is there any reason such a barrel can't be made today.It could be made with any twist from splines to near screw threads.Bill took a very close look at the Henry barrel and did make an 8 groove simile and it was a proven winner.
Bob Roller

[G_T]

Anecdotal here, but I had a barrel that wouldn't shoot and was very hard to load. It shreaded patches. When I ran a lead ball down it I found it rather tight for roughly a foot at the muzzle end. It had tooling marks all over the lands in that section, but was much better towards the breech. Grooves were super deep.

I machined a series of long brass laps each at most 0.0003" larger than the previous one, with spaced grooves along the length. They also had a very slight taper at the muzzle end. I think I used 400 grit lapping compound. It took quite a while and was very messy work, but I smoothed it out. I did much of it with a slow speed on a drill, with a brass centering guide at the breech, and some extra lube. I spent as little time as possible with the lap protruding from the muzzle, running long strokes in the barrel. I quit using a lap as soon as it freed up. I left the barrel still having a slight choke towards the muzzle but no more tooling marks on the lands and no hard step a ways back from the muzzle. Lapping was more straight than rotary at the end of the job.

Of course this work did nothing for smoothing the grooves, unlike cast lead lapping.

It no longer shreaded patches, and loaded much easier. Still didn't shoot all that well though! Sometime I'll pull it out and make an attempt at bending the barrel, since it wants to shoot pretty high at 50 yards.

If it wasn't already in a stock I wouldn't have bothered with it.

Gerald

[rich pierce]

Lapping is a lot more tedious than using cutters to re-cut the lands and grooves slightly. I’m not sure they did a lot of lapping in the flintlock era. I reserve it for tiny problems and finishing a freshed barrel. Extensive lapping can result in rounded off lands. Slight but real.

[Scota4570]

To create a choke at the muzzle I see no simple option other than lapping. 

A choked bore could be made with a tapered spiral reamer.  If you made a choked bore, then rifled it, the grooves at the muzzle would be faired.  The rifling head cutter box needs to push against the bore to make a chip.  IT would require a very long cutter box to have it cut other wise.  Then you may have an issue with the cutter box being undersized for most of the bore if it were to pass the choke.  I do not know it 0.001" or 0.002" clearance would matter. 

To make the cutter follow the choked bore would required some mechanism to raise it as it moves? 



I have made a choke that is only a the muzzle by lead lapping with coarse grit and not working the muzzle.  The coarse grit finish, say #100 is smoother than as cut ML barrels I have played with. 

I'd like to know how Pope and others did it originally.  It must be simple?

The choked bores are wonderful to load and shoot very well in my experience.  I am not sure why slightly rounding the corners of the lands matters.  Don't round bottom barrels have lands with angled sides? Same thing, sort of ...  Many barrels have been made with rounded lands  on purpose.  Some even polygonal too.

[rich pierce]

Let’s see some targets! Interested in seeing how this barrel shoots.