Methods for filling large pitting

[kombi1976]

I have an octagonal bbl from a 32 WCF Peiper rook rifle and I'm in the process of cleaning it up before having it re-threaded and re-reamed for fitting to a BSA Martini Cadet action.
I had it bead blasted to find out what the true state of the bbl was under all the dirt and a few horrors have appeared.
These weren't entirely unexpected.....some where in the past moisture must've got under the original fore end and the result is some pretty ugly pitting that won't be smoothed by filing; it's simply too deep.
My question is this: is they a process to fill these so I can blue the bbl?
Alternatively, could I have it nickel plated if the process will not allow bluing?

[John Traveler]

Replacing severely rusted away gun steel is usually done with precision TIG (tungsten inert gas) or MIG (metal inert gas) welding.  It is commonly done on museum quality restoration of historically significant guns.

Unfortunately, the heat from welding often warps barrels, and produces irregular hard/soft spots.  Then too, the filled-in areas usually do not blue exactly as the base material, producing a mismatch.  The cost of doing this welding may be prohibitive as well.  Expert hand filing and polishing follows the welding.  It is usually only a last resort on non-stuructural parts of receivers, trigger guards, levers, etc.

Electroplating with first copper and then nickle will bypass the bluing problems, but still does not solve the possible warpage and cost.  It is possible to selectively plate with copper to fill in the pits, polish down level, and add the final nickle plate.  It will require the services of a first-class plating shop and skilled operator.

These processes are not usually done on common shooting guns because of the cost factors involved.

[kombi1976]

Ahhhh......
So instead I should drawfile every thing I can smooth, minimise the yucky stuff that's there and then hide it under the foreend when I have another one made, right?

[John Traveler]

That's correct.  Refinishing a badly rust pitted gun usually goes as far as drawfiling flat surfaces to remove most of the shallow pitting, and polishing.

I once examined a Marlin .22 lever action that was lost on a trail, exposed to the elements, and found by the owner TWO YEARS later on another hunting trip.  Badly rusted and pitted, but the bore was almost perfect from firing greased .22 LR ammo.  The gunsmith handfiled and polished it up, leaving the deeper pits.  He described having to hammer on the receiver to loosen the caked-on rust.  The refinished gun almost looked like new with the refinished wood and reblue, except for the deep pits, of course.  Fully functional now.

Good luck on your project!

HTH
John

[Mikey]

kombi:  A couple of tricks I heard about may help you here.  A gunsmith I know had a similar situation with a badly pitted rifle barrel.  The pitting and rusting were all external but some fo the pits were pretty deep under the fore-end stock.  He chose not to heat the barrel or drawfile it because that would still leave the deeper pits and re-bluing wouldn't prevent more moisture from collecting in those pits even after being refinished.

He chose, instead, to use either JB Weld - which is a cold weld type adherant or a bedding compound mixed to match the color of the bluing.  Since most of the serious pitting was not readily observable as it was under the fore end stock he used the JB weld there and the bedding compound on the more exposed partion of the barrel.  He removed the rust first, filled the pits and smoothed the materials to the original barrel contours and then used a wheel rim paint to finish the rifle into a very nice matt black finish.  The owner had initially thought he would re-blue the rifle but was very pleased with the matt finish.  HTH.  Mikey.

[benchracer]

I just finished a mauser build on an FN action that had some fairly deep pitting in non-critical areas.  My chosen finish was Duracoat.  The company that makes Duracoat also offers a product called Durafil.  I sandblasted the receiver to clean out the pits, applied several coats of Durafil to fill in the pits, sanded the action back to bare metal, and applied Duracoat in my chosen color.  I was pretty pleased with the results.  I don't think that Durafil is compatible with bluing, but it should work with any spray on coating.  The real question is whether or not you like the looks of spray on finishes.  YMMV. If a spray on finish is out of the question, I think the idea of using color matched bedding compound has merit.  I used Acraglas to affix a scout mount to my rifle and dyed the acraglas to match the color of the mount.  One has to look pretty carerully to spot the acraglas.  Hope this is helpful to you and good luck on your restoration.

[gunnut69]

The real key is to completely eliminate the little kernel of rust at the bottom of the pit. If you don't the rust will hold moisture and continue rusting, even under any filler. I have welded up several and greatly prefer MIG welding for the purpose. Especially on modern guns. The main drawback is the type of metal used as filler. A MIG introduces the least amount of heat possible into the part being filled. I have also used powder coating to fill the pits in a ruger auto loading pistol that had been in contact with toilet bowl cleaner! We masked off the serial number and applied a heavy coat. After processing the piece looked great!!

[Les Brooks]

One way to fill pits is to use dental burrs and grind the hole out to allow for an undercut all around at the bottom of the hole.  Use a soft iron wire and peen in place.  Try to keep the hole 90 degrees to the surface where the metal fits  into the hole.  This is a trick engravers use when there is a little slip.  I used the picture frame wire found in most hardware stores.  This may not be best in your case if you have several pitts to fill.

[wncchester]

I don't attempt to fill the pits I can't file/sand/buff out, I "hide" them with a mat finish. 

Even small imperfects show up badly on a mirror polish but with a bead blasted mat surface they frequently won't be noticeable.

Even deep rust can be "electroplated" out with a battery charger and a bath of common household lye. 

[koginam]

What ever you decide to do you must kill the rust first I would use some muratic acid on the barrel to kill the rust just prior to refinishing, it only takes a minuet to do the job.  it will also remove any old bluing but the metal must be refinished right away or coated with oil.  Good Luck

[wncchester]

[quote koginam  - "I would use some muratic acid on the barrel to kill the rust" ]

kog is correct,  muratic acid WILL dissolve rust - ferrous oxide - pretty fast. 

Down side is the fumes!  Acid fumes will damage your eyes, nose passages, lungs, etc. unless you work in a WELL VENTILATED area.  I only use it outdoors, usually on a breezy day.  And any stay fumes will condense on other metal objects and cause them to rust badly unless washed with a solution of baking soda, ditto giving your de-rusted metal a soda wash even before you steel wool/wire brush the black residue off or oil it.  Wear rubber gloves and goggles, immediately flush any skin contact with soda water.  (Any well carbonated soft drink will do but the dried sugar will be sticky!)

Follow these same safety rules with the previously suggested Lye/electrolysis system but use vinegar as a neutralizer.  Lye vapors are  much less harmful but still, be careful with any strong chemical.
 
Acid has liabilities, but it do work!   (And don't put aluminum parts in an acid OR lye bath!)

[gunnut69]

Actually the electrolysis process works just as well with baking soda instead of the lye. It's a lot safer too. The chemicals actually just facilitate the electrical flow in thru the water. I make it a habit to aviod dangerous chemicals when possible..