How to Remove a Burr in the Chamber

There's an old thread where the OP had a similar problem with removing a burr from a chamber.

http://www.practicalmachinist.com/vb/gunsmithing/burr-chamber-194103/

I have a similar problem with an old rifle I recently acquired and was wondering if there are more ideas on how to rid myself of this problem.

I recently acquired an 1873 Springfield Trapdoor (.45-70) and fired my first rounds (handloads) through her this past week. The groupings were a lot better than I anticipated. However, upon close inspection of the spent cases, I noticed a series of dents (3 in particular) and scratches that uniformly appeared on all of the cases at the 6 o'clock position.



I cleaned out the bore and took a cleaning brush and vigorously scrubbed the chamber back and forth several times in an effort to dislodge debris or rust scale that may be the culprit but my efforts were to no avail as the dents continued to appear on the spent cases.

I then chambered a couple of loaded rounds and removed them to determine if the damage only occurred when the rounds are fired. When I extracted the loaded round, the cases showed galling but no dents as with the spent cases.



I managed to take a few photos of the chamber and was able to capture what appears to be three pronounced ridges in the chamber that matched the dents on the spent cases. The chamber looked heavily pitted but otherwise unremarkable except for the three ridges that could easily be seen.







I took a sharp pick and gently scraped the largest ridge (closest to the lens) to see if I could dislodge whatever was there but was unsuccessful. To my naked eye, the ridges appear to be formed by galling of the metal rather than rust or debris but I really can't tell without having the chamber inspected with a bore scope.

This morning, I squirted a Kroil-based homemade formula of ATF/acetone on the burrs in hopes of loosening whatever the burrs may be if not the chamber wall itself. I'll take a stab at trying to dislodge the burrs later tonight if I have the chance. If it turns out to be part of the chamber wall, I'll have to find a way of removing the burr without damaging the chamber.

Does anyone have any suggestions on how I should approach this problem?

My first thought is a stuck case was involved to begin with. The tool used to remove the stuck case gouged the chamber. I think I am seeing gouges next to the raised spots that are denting your brass. If so your link had one person suggesting a burnishing tool to "iron" out the dents. I might try that with a hardened tool to match the diameters near the dents. Use plenty of high pressure lube pull it out using internal threads in the tool you made. Burnishing will not get it all out, maybe reaming and polishing afterward will get it so it does not damage your brass. If you use a reamer after burnishing make a thin brass shim to keep the reamer shoulder from altering your head space.
Whether these ideas help or you use a better/different suggestion that follows, you will probably still have a blemish after you finish, your goal will be to polish the result so you get easy extraction and not gouge the brass so it can be reloaded safely.

A chamber reamer will take out the high spots very easily. You just have to be careful not to cut the chamber deeper.

Not a gunsmith by any stretch but why not just run a brake cylinder hone through the chamber?

Pressing a hardened steel ball of the correct diameter (with lubricant)? It can be pressed out with a cleaning rod from the muzzle side.

Wouldn't a cylinder hone also take off material from the chamber as well, thereby increasing the I.D at the points of contact?

"Pressing a hardened steel ball of the correct diameter (with lubricant)? It can be pressed out with a cleaning rod from the muzzle side."


I may be overthinking this but I think it all depends on how the ridges were formed and if the material consists of displaced steel that has left an adjacent cavity in the surface or just extra material. If the ridges consists of displaced material caused by an object being pushed from the breach end, the hardened steel ball must be pushed in the opposite direction (from the muzzle end) to push the material back into the adjacent cavity. That may be impossible to do because the chamber is larger tan the bore of the barrel.

Looks like threads breaking through to me. Many, if not all, 1873s were converted from 50-70 earlier models. The barrels were lined per some sites I looked at. This may be one of those or someone may have put a chamber insert in. There were also many that were demilitarized for training and drill rifles. I would remove the barrel and make sure that none of these possibilities are the problem

Mr. Farknocker said:

Wouldn't a cylinder hone also take off material from the chamber as well, thereby increasing the I.D at the points of contact?

Click to expand...

The hone is spun with a drill, so there really aren’t any localized points of contact. They don’t press very hard and should take more off the high spots than the wall itself due to contact area.

Hazzert said:

The hone is spun with a drill, so there really aren’t any localized points of contact. They don’t press very hard and should take more off the high spots than the wall itself due to contact area.

Click to expand...

A brake cylinder hone isn't even good for brakes. It will remove material anywhere it touches and you have no control over it. I seriously doubt that you could find one that would enter a hole under 1/2 inch anyway.
Another possibility is that a cretin tried to remove a stuck case with a drill.

Another possibility is that a cretin tried to remove a stuck case with a drill.

Which would have been a real challenge in a trapdoor without removing the barrel.

GGaskill said:

Another possibility is that a cretin tried to remove a stuck case with a drill.

Which would have been a real challenge in a trapdoor without removing the barrel.

Click to expand...

It would account for the marks all on the bottom of the chamber. I did say cretin, didn't I?

I have repaired lots of damaged chambers,generally by sleeving.....however the liner complicates things....it will be soft soldered in.....I would first try a chamber reamer,if none,then i would try lapping using a split case.....the trapdoor action complicates things somewhat...Any remaining holes/cuts will fill up with bullet lube and stay that way.......If you dont crimp cases,there is little pressure expanding the neck,and you can get away with considerable roughness in that part of the chamber,without damaging cases.

How difficult would it be to remove the barrel from the action so that a chamber can be reamed to remove the burrs? Would the average gunsmithing be up for the job or will it require someone with special tools and experience with trapdoors?

How difficult would it be to remove the barrel from the action so that a chamber can be reamed to remove the burrs?

On an old blackpowder rifle like that one never knows. There is probably at least some corrosion in the threads. I would prefer having someone with some trapdoor experience do the work.

I would fabricate a tool to burnish the burrs away. No disassembly required.

If the gun does have a soldered sleeve,repair would be simple....removing the barrel ,as mentioned is problematic, some old guns are so soft that damage is nearly inevitable,especially if rust is involved....Now if there is a sleeve ,and it can be removed ,then a new chamber piece can be included in the resoldering,without removing the barrel......Anyway,sleeve or no,once the barrel is out,resleeving just the chamber is very easy.

john.k said:

If the gun does have a soldered sleeve,repair would be simple....removing the barrel ,as mentioned is problematic, some old guns are so soft that damage is nearly inevitable,especially if rust is involved....Now if there is a sleeve ,and it can be removed ,then a new chamber piece can be included in the resoldering,without removing the barrel......Anyway,sleeve or no,once the barrel is out,resleeving just the chamber is very easy.

Click to expand...

The question is whether I chance removing the barrel or attempt to treat in place?

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