Pitted Chamber fix

[am44mag]

I recently bought a 50-70 Trapdoor and like it, but there is one issue that is bugging me. One area of the chamber has some pitting in it, and it's preventing the brass from fully ejecting. It will extract about 1/4", at which point you can usually pull the case out. Occasionally, you might have to use a pocket knife to get under the rim and give it a little help. The pits are deep enough that you couldn't just polish them out, but I don't feel the pitting is unsafe, especially in a low pressure gun like this (I ONLY shoot holy black in it), but it's definitely annoying. The professional way to fix this probably be to have the chamber sleeved, but that's expensive and I wouldn't feel right about having a historic gun like that modified to that extent.

After some research, I think I found a solution, but I wanted to run it by you guys first. Could I just fill the pits with JB weld?

Here's the process I was thinking of doing.

1) Kill and remove any corrosion left in the pits by plugging the barrel and filling the chamber with Evaporust and letting it soak overnight.

2) Clean and decrease the heck out of the chamber with brake cleaner

3) Apply a layer of JB Weld to the pitted area.

4) Insert a fired case that has been either waxed, or sprayed with mold release into the chamber and let sit overnight.

5) Give the chamber a light polishing.

Am I wrong to think that this would work?

[Ozark mike]

Jb weld might work fer a while but will give over time maybe braze then reream but then you'd have to re temper. Maybe Find a replacement bbl?

[country gent]

I don't think the JB will hold up to the pressure compression or solvents. Brazing down in that small hole is going to a job. And barrel would need pulled to keep from heating receiver and softening it. Actual to a good machinist sleeving it wouldn't be a big job. Bore .100-.150 bigger, turn a sleeve .001 over the finished hole size and press in with a light wipe of loctite then ream.

[elmacgyver0]

Before doing anything too drastic I would put some fine valve grinding compound on a case and spin it in the chamber.
Since it sounds like cases are not sticking too bad it might be enough to make case extraction tolerable.

[Bent Ramrod]

I have a .40-90 SS barrel for a Winchester that had very even small pits in both chamber and barrel. I clamped the muzzle in my lathe chuck, lined it up with the steady rest, took the tailstock off, and rotated the barrel in back gear, while playing a torch on the chamber end.

When it was good and hot, I brushed some solder into the chamber, spreading it with an old bore brush until it looked like the pits were mostly full. I scraped the chamber with a piece of brass as it spun and cooled to get any excess out.

I only fired a few shots out of it before swapping the barrel out for a relined .32-40, but it seemed to extract much easier, (the extractor pulled the shell out, with no need of hammering a brass rod down the muzzle) and there weren’t the bumps, rub marks and scratches on the shells any more.

Kind of an unprofessional, “Hail Mary” approach to the problem, but it seemed to work. The pits were not deep enough to seriously impair the shooting, but the extraction was another matter. There was still plenty of steel to hold the pressure, and I figured the solder wouldn’t move, just press out flat in the pits. If there had been too much solder in there, a fired case coated with lapping compound would have taken it out in short order.

[Ozark mike]

I figgured soft solder would migrate under extreme pressure but these bp guns aren't that extreme either

[Texas by God]

I would try your JB Weld idea; it can't hurt and might help. No solvents needed for black powder- just hot soapy water. I built up a damaged ejector in a M51 Ithaca 20 gauge auto with JB Weld and it has worked perfectly since. That's kind of a severe test I think. Just filling pits in a chamber to smooth it out is child's play in comparison.

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[am44mag]

I'll see if I can't get some pics in the next couple of days so you guys have a better idea of what I'm working with.

I can definitely try polishing. Really if I could get it to a point where it extracts well enough that I don't have to occasionally pry cases loose, I'd be happy.

[ascast]

I can tell you the JB wont last long. I did very same in a 30-30. Got about 40 shots. My 2 cents: you did not ruin it, you bought a price of junk, rusted, neglected scrape metal. If the bore is good (real good) have the chamber sleeved, fixed what ever and crowned or counter bored if needed. Then brag about fixing the old thing .

[john.k]

I would say solder would be satisfactory at the pressure of 50/70.....its all very well talking about yield strength,but in a filled pit,where is the solder going to go?......Provided the solder has no escape route ,its the same result as compressing water ....water has zero yield strength ,but is incompressable.

[Jeff Michel]

Sleeve it, if you polish it, ream it or change the original dimensions, your going to only exacerbate extraction problem. This fixation with JB weld is amazing to me.

[uscra112]

If you try the solder method, let us know how it works out. I'm facing much the same situation with a Stevens 44 which has a rare wildcat chamber. To sleeve it will require shelling out for a custom reamer that I'll never use again.

[Jedman]

I agree with TbG on this. It’s not rocket science, get it good and clean with brake cleaner or acetone and a toothbrush or small metal brush put a small dab on the pit and whittle a stick or what ever it takes to scrape it smooth. If needed later you might make curved wood stick with a piece of Emory cloth glued on to polish It smooth. I have several 50-70’s and the good thing is the chamber is big and short so doing this type of repair is a little easier.

Jedman

[uscra112]

Interesting thought about chroming the chamber. Flash chroming, like they do with AR barrels, won't fill in pits. It might even make the problem worse, because of the way plating builds up preferentially on edges. (e.g. the perimeter of the pits.)

In a previous life (rebuilding big machine tools), we used hard chrome quite often to build up a worn bearing journal, after which we'd grind it back to the nominal dimension. THAT would work, but getting the grinding done in a chamber would be interesting. It would take a very careful setup to keep the chamber concentric, and a CNC machine if the chamber is anything but a straight taper. You'd have to keep the plating out of the throat and rifling, obviously, but that's easy. It sure would be a permanent fix, though!

[uscra112]

Would cleaning with an acid not be best? That would pull any rust out of the pits and present a cleaner surface for the epoxy to bond to than any solvent.

Just thinkin' out loud here..... I suppose Evaporust would do the same thing, or close to it.

[Shawlerbrook]

Lot of interesting suggestions. I will be following the results.

[am44mag]

I could not get a pic of the pitting in the chamber. My camera wouldn't fit low enough into the action to see it, and it's mainly at the front of the chamber. I tried to get a pic of the brass, but I couldn't get a great pic of that either. This one will have to do. This is the worst spot. You can kind of see the bump on the brass.

https://uploads.tapatalk-cdn.com/20200623/d9710841d92e7320802de7ea7ea48c38.jpg

https://uploads.tapatalk-cdn.com/20200623/fc05c493ccdb67440772bee0127566c5.jpg

I think I'll try polishing the chamber and see if that does anything. It might do just enough to aid with extraction.

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[Ozark mike]

Brass with pimples like that will definitely make extraction difficult id sleeve it but you can try jb weld you would lose nothin

[Silvercreek Farmer]

Can you trim your brass back to where it doesn't engage the pit? Hmm, at that point could you strategically lead the pit with an unlubed boolit??

[OldBearHair]

Operated a 16 foot Swather for cutting alfalfa hay. It developed wear in the gear box with an arm that moved back and forth to cause the sycle blades to cut the hay. It was fastened to the shaft with splines. The arm had too much "play" from wearing the splines thin. Made a lot of noise is how we knew what was wrong. Ordered new parts, but, the hay needed to be cut "now". Cleaned the splines probably with Laquer Thinner, coated the splines with JB Weld, slid the arm in to place carefully and left it alone during the night. Then began to cut hay, finishing up in good time. The parts came in just as the next cutting was ready, so we cut it again. Then broke it down to replace the new parts. It didn't have play in it yet. The JB Weld had come loose and looked like little flat grey sticks. Lasted long enough for two cuttings of hay from 30 acres. My next two favorites are Duct Tape and WD40

[john.k]

Yes ,I would try electroless nickle plating .....but the chemicals are expensive ,and the solutions dont last like electroplating solutions .....so unless you have a lot of nickle to do ,not economical ........Mention of hardchrome ....indeed a solution to the problem ,but the chrome deposit is intensely hard ,and sizing the chamber would be a very tedious job of internal grinding with a tiny wheel.....Diamond or CBN ,I d say.......Consequently ,sleeve the chamber with a bit of any HT steel you have .....an old gun may even have a soft iron barrel ,so any steel would be suitable ......Id have the lot done in one hour,ready to try out........There is no need of a reamer for these large cases ,just a small boring bar is good.

[am44mag]

Do you guys know of a good gunsmith that would sleeve the chamber for a fair price? There are no professional gunsmiths around here, so I will most likely have to ship the gun.

About how much would that kind of work cost?

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[LIMPINGJ]

John Taylor
https://johntaylormachine.com/contact/

[John Boy]

Buy a Volks Wagon cylinder honing tool with 1-1/2" to 3-1/8" brushes ... https://www.amazon.com/Lisle-10000-Brake-Cylinder-Hone/dp/B000P0VT3C/ref=pd_lpo_263_t_0/142-7580873-6671843?_encoding=UTF8&pd_rd_i=B0002SQUG8&pd_rd_r=fe4961e3-b8a2-4ce2-8528-69f570e913d0&pd_rd_w=tcdUy&pd_rd_wg=wmRJd&pf_rd_p=7b36d496-f366-4631-94d3-61b87b52511b&pf_rd_r=HBKMEJPXCG8V1HASK4ZR&refRID=HBKMEJPXCG8V1HASK4ZR&th=1
I use the 2 brush tool to hone cylinders

[Ajohns]

Size a case, and put mold release on it. Or if nothing else, wax. Put a little dab of JB in the spot if you can get to it, and carefully put your case in the chamber. Let cure and extract the case. The JB should fill nice, and if mixed properly it should stand up to your pressures. I have done this before, but it was on a 32 rimfire chamber. Still stands to this day.