Polishing a Rough Bore

[Herb]

A friend gave me a Green River Rifle Works .50 caliber barrel that he picked up off the floor of the shop.  Doc White gave it to him as a reject, and 44 years later I got it.  It was not threaded for a breech plug, and had radial chatter marks on top of the lands at both ends.  I sawed an inch off the breech end.


I had a gunsmith with a lathe drill and tap it for a 3/4x16 plug, which cleaned up another half inch.    Next I sawed 3 7/8 inches off the muzzle end to get a barrel 31 1/8" long to make a Carson Hawken.

The bore still had some chatter marks on top of the lands, a few shallow ones near the muzzle but worse at the breech.  I cast a lead lap and tried to smooth the bore.  I finally tired of this and thought it was acceptable.  Gunsmith Bill examined the bore with a Hawkeye Borescope and said it was OK and leave it alone.  But it bothered me and I used my bore gauges to determine the bore was .499 with a tight section about five inches behind the muzzle and then roughness for eight inches ahead of the breech.  Here is a set of .54 caliber bore gauges.  I'll show the .50s later.


Casting a lead lap is a lot of work, so I thought of a different way.  I selected the straightest 1/2 inch poplar dowel the hardware store had, which measured .495.  It fit through the bore.

At one end I cut a two-inch recessed area to take a wrap of 220 grit sanding belt. The recess was as round as I could make it and was filed down so the .015 thick belt sized up to about .499.  I superglued the belting on.  It would not go into the bore, so I started it into the cut off breech piece and tapped it through that.  This compressed the high spots of the belting down, or wore it off, and then it entered the bore.  I tapped it through with a plastic mallet, having removed the breech plug. 


A steel brush was used to clean the grit off the lap, which I also sprayed with Lehigh lube.


I kept this up, lubricating the belt and pounding it through the bore until it smoothed out. Eventually I could push and pull the rod by hand. I concentrated on the tight section below the muzzle and the eight inches ahead of the breech.  After a couple of hours I was able to insert  the .4995 gauge full length, but still had the tight spots.  After more polishing, a .500 gauge went smoothly the full length of the bore.

The gauges can tell you about your bore's size and possible tight spots or roughness.  Another GRRW .50 barrel I have is very even and smooth, but takes a .504 gauge.  That bore will require a thicker patch in shooting.

These gauges are made of the simplest of materials and most anyone could make them and measure bores.  I make them of 7.62x54 rimmed steel cases, which you can often find on shooting ranges.  They are made in brass, white steel and copper plated steel, which is prettiest.  Steel is best, brass is OK if you don't force it and wear it down in the bore.  Drill out the primer with a 3/16 drill, making sure it is centered.  A 10x32 screw or cleaning jag will pass though this hole to hold the gauge onto the end of your cleaning rod.  I use a .50 caliber military surplus jointed rod.  I tap the case mouth over a 5/16 drill bit to open it so it will be a slip fit on the rod.  You can insert a nail into the primer pocket to tap the rod out of the case.

Next the case is inserted into a drill chuck as far as it will go, with the rim below.  Turn the motor on and hold a file against the rim to cut it smaller.  Stop and measure with a caliper or micrometer (best), careful to not get it smaller than your nominal bore diameter.  It can be cut from .566 down to .489, suitable for  .50 and .54 bores.  A .30-30 case can be used for .45 or .50 calibers.  A .38 Special or .357  case will be used for .40 caliber.  For .58 caliber, a .45-70 case is .500 on the body and .600 on the rim.  Other gauges below.



To make a .58 caliber gauge, file a  3 1/2 inch long .500 dowel down to slip fit a .45-70 case over it.  Chuck the dowel in your drill press and file the case rim down to about .570. Test in the bore, file down more until it will just go in.  Then fit it and glue it onto the end of a dowel longer than your bore.  Blacken the rim with a magic marker, which will show the high spots as it goes in.  Carefully file them down, using a micrometer to make sure the rim is round.   If polishing is needed, you can use a paper shim under the emory cloth to make it the diameter needed, as high as the rim.

Here is my polished out .500 bore.


Here are my .50 caliber gauges and a muzzle protector to center the steel cleaning rod.

[Pukka Bundook]

Very good old-style barrel work, Herb!

My kind of work.  Nothing fancy but good results.
Thanks for posting.

Richard.

[Jerry V Lape]

I would have sent it to Bobby Hoyt to be rebored to .54 cal. 

[Herb]

I got .54s.  I needed a .50.  I did send a GRRW .54 barrel that had gone through a fire to Hoyt who rebored it to .58.  That is a very nice bore.  Built a 24" flintlock Leman out of it and hunted elk with it.

[Pukka Bundook]

Not quite the same sense of satisfaction though Jerry, ...sending it somewhere else.   :-)
If it shoots well, that's great!...and if it Doesn't, it could still be sent for out-work, but I think it'll shoot just fine.

[rich pierce]

Looks good. I’d have freshed it using a lead lap with cutters- that way you smooth the grooves too. Hope it shoots well!  My GRRW ballet has some choke, which I like.

[Herb]

Thanks, Rich.  I took only a half a tenth off the top of the rough lands. The grooves are smooth.   A lead lap wears down and is a lot of work.  This 220 sanding belt did not wear down, and it did cut down the high spots.  I could polish it finer with 500 grit belting, but see no need to.  I plan to shoot this rifle before winter gets here.

[Bob Roller]

That looks much like a bad reaming job with little or no lube.cutting fluid or
anything else.I wonder what kind of steel it is.1018 sometimes gives results
like this when reamed if it isn't heavily lubed or too much feed while reaming.
Bob Roller

[Daryl]

Good job, Herb! The smaller the bore, the more 'problems' effect the outcome.

In 1986, my .69 GRRW barrel also had reamer marks - not quite as nasty as Herb's bl. and the bore felt true.  It shot well from the get-go and will
now use a thinner patch than would shoot in it, in the 80's. I assume that is due to the smoothing that roughly 5000 (or more)shots will do. Initially
 it would only shoot well with .030" denim patching, but now will actually shoot 10ounce denim I now measure at .021".
You can see the "memory" of the across-the-land reamer marks in this muzzle shot. As with Herb's barrel, the grooves were smooth.

[WadePatton]

Really like how you worked it out Herb.  That's what I call the "cowboy way" a/k/a what works works.

[B.Habermehl]

With a large part of the tool marks running fore and aft it should be a easy loading and easy cleaning barrel. BJH

[Bob Roller]

The real proof of success will be at the range.

Bob Roller

[Herb]

Thanks, all.  I really took half a thousandth off the top of the rough lands.

[577SXS]

From the looks of the burrs on one side of the lands it looks like that barrel was reamed after it was rifled. This is kinda hard to believe someone would do that. Your polishing job looks good, it will be interesting to see how well it shoots. I have gotten several barrels from well known makers that have horrible reamer marks in bore. I have one I call my zipper barrel because it sounds like a zipper when you run the ball down. It shoots ok though. Why the bores aren't polished before they rifle them is crazy.

[Herb]

Good eye!  Left-click that photo and when the little + sign comes up, left click that.  Something was done to the end of the bore, as if they started to run a tap into it.  Later this morning I'll post a photo of the end of that piece of barrel, which shows that. 

[Herb]

Some procedure was started on the breech, possibly starting to drill it for a plug tap.

My lap may be hitting the grooves.

Here is the breech now.

I melted the superglue with a torch and fitted a new piece of 220 grit belt.  It fit so tight I had to hammer it through the bore, but it cuts!  I am now up to .5005 and stopping there.

Here is the muzzle.

[Pukka Bundook]

Look forward to trial results, Herb. 
It looks very good.