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Deburring & Cleaning the Flash Channel of TC's Patent Breech

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OldNo7

36 Cal.
Joined
Feb 13, 2005
Messages
171
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Location
Southern Maine
This is my 4th or 5th Thompson Center sidelock since the early 80s and I've followed the same procedures for cleaning and pre-shooting prep for this one as on all the others. I'd never had one that gave me such issues with misfires before, but the beautifully-stocked TC Cougar .50 I'd acquired recently (bought used) can't make it past 7 or 10 shots before the caps won't ignite the powder charge...

Even after pulling out the nipple, using a nipple pick and putting in a small charge of fresh powder -- she still won't go off. On one of my images, you can see some wrench marks on the barrel -- and I suspect the prior owner had the very same issues I'm having, and had tried to remove the breech plug. My guess now is that he wasn't successful -- and sold it off instead!

Anyway, Kudos' go to Idaholewis for this image of his cut-down TC breech which he'd posted back in 2019, as it clearly shows the patent breech and the flash channel.
TC Breech 00.jpg


I suspect there's a burr on the corner of the flash channel in mine, so I set about to clear and clean that -- and here's how I did it. I ran a piece of heavy 30# test mono down the nipple hole, up the flash channel and out the end of the barrel. Then I tied a 9" length of string (from a cellar overhead light pull cord) in the middle with one overhand knot in the mono and started pulling it into the flash channel.
TC Breech 01.jpg


Towards the end of the string I tied another knot to secure it, and I had applied some lapping compound to the string -- and then I pulled it back and forth through the flash channel maybe 200 times, stopping several times to applied more compound. By the end, it was noticeably smoother when pulling through.
TC Breech 02.jpg


After that, to clear out the compound, I tied on one of the smallest pipe cleaners I had available (you can typically see a variety of sizes or "fluff" in cleaners from the same package) and started that pulling that up into the channel flooded with Naptha (lighter fluid, it dries quickly, with no residue). It took some additional "liquid lubricant" (swearing!) and a little effort to get it started, but before I'd done the lapping compound step -- I couldn't get a pipe cleaner to go in at all...
TC Breech 03.jpg


The pipe cleaner was re-wet with the lighter fluid several times and pulled out from the muzzle several times, wiping if off each time.
TC Breech 04.jpg


If you've used those pipe cleaners before, you'll know they can drop some fibers and I didn't want them being stuck in there. I'd previously tied a large loop on the breech end of my pull-through mono line, so I just pulled the knot through the channel and you could seem some fibers come out with it at the muzzle end.
TC Breech 05.jpg


I didn't do it yet, but I'll also apply some high-pressure air to the nipple end to ensure there are no fibers left in the channel.

One other change I'll make to my shooting routine is that after each shot, I'll use a short length of tubing put onto the nipple and blow air UP the barrel to ensure the flash channel is clear (as yes, I know that the NMLRA and many ranges discourage shooters from blowing air "down the barrel" -- with your head positioned right over the bore).

I haven't gotten it back out to the range yet, but I will try to get back out very soon and she how it goes.

Old No7
 
This is my 4th or 5th Thompson Center sidelock since the early 80s and I've followed the same procedures for cleaning and pre-shooting prep for this one as on all the others. I'd never had one that gave me such issues with misfires before, but the beautifully-stocked TC Cougar .50 I'd acquired recently (bought used) can't make it past 7 or 10 shots before the caps won't ignite the powder charge...

Even after pulling out the nipple, using a nipple pick and putting in a small charge of fresh powder -- she still won't go off. On one of my images, you can see some wrench marks on the barrel -- and I suspect the prior owner had the very same issues I'm having, and had tried to remove the breech plug. My guess now is that he wasn't successful -- and sold it off instead!

Anyway, Kudos' go to Idaholewis for this image of his cut-down TC breech which he'd posted back in 2019, as it clearly shows the patent breech and the flash channel.
View attachment 283489

I suspect there's a burr on the corner of the flash channel in mine, so I set about to clear and clean that -- and here's how I did it. I ran a piece of heavy 30# test mono down the nipple hole, up the flash channel and out the end of the barrel. Then I tied a 9" length of string (from a cellar overhead light pull cord) in the middle with one overhand knot in the mono and started pulling it into the flash channel.
View attachment 283491

Towards the end of the string I tied another knot to secure it, and I had applied some lapping compound to the string -- and then I pulled it back and forth through the flash channel maybe 200 times, stopping several times to applied more compound. By the end, it was noticeably smoother when pulling through.
View attachment 283492

After that, to clear out the compound, I tied on one of the smallest pipe cleaners I had available (you can typically see a variety of sizes or "fluff" in cleaners from the same package) and started that pulling that up into the channel flooded with Naptha (lighter fluid, it dries quickly, with no residue). It took some additional "liquid lubricant" (swearing!) and a little effort to get it started, but before I'd done the lapping compound step -- I couldn't get a pipe cleaner to go in at all...
View attachment 283494

The pipe cleaner was re-wet with the lighter fluid several times and pulled out from the muzzle several times, wiping if off each time.
View attachment 283495

If you've used those pipe cleaners before, you'll know they can drop some fibers and I didn't want them being stuck in there. I'd previously tied a large loop on the breech end of my pull-through mono line, so I just pulled the knot through the channel and you could seem some fibers come out with it at the muzzle end.
View attachment 283496

I didn't do it yet, but I'll also apply some high-pressure air to the nipple end to ensure there are no fibers left in the channel.

One other change I'll make to my shooting routine is that after each shot, I'll use a short length of tubing put onto the nipple and blow air UP the barrel to ensure the flash channel is clear (as yes, I know that the NMLRA and many ranges discourage shooters from blowing air "down the barrel" -- with your head positioned right over the bore).

I haven't gotten it back out to the range yet, but I will try to get back out very soon and she how it goes.

Old No7
Thank you so much for the detailed description and pictures particularly of the sectioned breech plug.
I had another idea that might work also. What if the breech plug is pulled and sand blasted through from the barrel side with 70 grit Garnet sand and followed by glass beads to smooth it up?
I think that would clear out any casting slag or rough metal in the flash channel impeding cap flash.
 
What if the breech plug is pulled and...

Good luck doing that -- that's how the ugly vice marks got onto my barrel. :eek:

I've read numerous reports that the dang things weren't meant to be taken off... Although I do recall TC selling breech plug wrenches back in the day. (I don't think they worked well, but never tried one...)

Old No7
 
Last edited:
Good luck doing that -- that's how the ugly vice marks got onto my barrel. :eek:

I've read numerous reports that the dang things weren't meant to be taken off... Although I do recall TC selling breech plus wrenches back in the day.

Old No7
A properly fitting plug wrench and some torch heat after a good week of penetrating oil soaking will take them off. Most folks are afraid to apply heat generally because they think it weakens the barrel or breech plug.
Neither are hardened and barrels are normalized (annealed) at 900-1200 degrees F during some of the rifling processes.
You can't get enough heat out of the normal propane hand torch to do any damage metallurgical-ly speaking to a breech plug or barrel. I've never even ruined a blue or brown job from it.
 
Thanks for looking.

* * *UPDATE * * *

I got 100% ignition!!
-- and some nice groups at 50 yards today (despite the cold, high wind and snow squall) for 12 shots. Fired 6, then swabbed the barrel several times, and used the brush shown below to scrub the patent breech, then wiped it out with a moist patch put onto that brush. Then I fired another 6, again without scrubbing the bore between shots (50 grains of Schuetzen FFF, 0.015" Ox Yoke lubed patch, 0.490" balls). All 12 shots fired -- yay!

I did bump the left side of the breech area after pouring in the powder charge, as I've always done, but maybe with a few extra thumps I'll admit.

The image shows some BP bore brushes I'd forgotten I had -- I'd put them away when I was shooting a .58 Zouave for awhile, as it had a flat breech face and I used a flat scraper, and didn't need these. Glad I found these in my BP stash (new brush on the left -- "used and shaped to fit" the TC breech on the right) and I'll use them now all the time on this Cougar.

I am "cautiously optimistic" I can now enjoy shooting this TC without any issues, but I'll get her out to the range again soon to try it again.

Tight groups!

Old No7
 

Attachments

  • Breech Brush.jpg
    Breech Brush.jpg
    41.8 KB · Views: 0
This is my 4th or 5th Thompson Center sidelock since the early 80s and I've followed the same procedures for cleaning and pre-shooting prep for this one as on all the others. I'd never had one that gave me such issues with misfires before, but the beautifully-stocked TC Cougar .50 I'd acquired recently (bought used) can't make it past 7 or 10 shots before the caps won't ignite the powder charge...

Even after pulling out the nipple, using a nipple pick and putting in a small charge of fresh powder -- she still won't go off. On one of my images, you can see some wrench marks on the barrel -- and I suspect the prior owner had the very same issues I'm having, and had tried to remove the breech plug. My guess now is that he wasn't successful -- and sold it off instead!

Anyway, Kudos' go to Idaholewis for this image of his cut-down TC breech which he'd posted back in 2019, as it clearly shows the patent breech and the flash channel.
View attachment 283489

I suspect there's a burr on the corner of the flash channel in mine, so I set about to clear and clean that -- and here's how I did it. I ran a piece of heavy 30# test mono down the nipple hole, up the flash channel and out the end of the barrel. Then I tied a 9" length of string (from a cellar overhead light pull cord) in the middle with one overhand knot in the mono and started pulling it into the flash channel.
View attachment 283491

Towards the end of the string I tied another knot to secure it, and I had applied some lapping compound to the string -- and then I pulled it back and forth through the flash channel maybe 200 times, stopping several times to applied more compound. By the end, it was noticeably smoother when pulling through.
View attachment 283492

After that, to clear out the compound, I tied on one of the smallest pipe cleaners I had available (you can typically see a variety of sizes or "fluff" in cleaners from the same package) and started that pulling that up into the channel flooded with Naptha (lighter fluid, it dries quickly, with no residue). It took some additional "liquid lubricant" (swearing!) and a little effort to get it started, but before I'd done the lapping compound step -- I couldn't get a pipe cleaner to go in at all...
View attachment 283494

The pipe cleaner was re-wet with the lighter fluid several times and pulled out from the muzzle several times, wiping if off each time.
View attachment 283495

If you've used those pipe cleaners before, you'll know they can drop some fibers and I didn't want them being stuck in there. I'd previously tied a large loop on the breech end of my pull-through mono line, so I just pulled the knot through the channel and you could seem some fibers come out with it at the muzzle end.
View attachment 283496

I didn't do it yet, but I'll also apply some high-pressure air to the nipple end to ensure there are no fibers left in the channel.

One other change I'll make to my shooting routine is that after each shot, I'll use a short length of tubing put onto the nipple and blow air UP the barrel to ensure the flash channel is clear (as yes, I know that the NMLRA and many ranges discourage shooters from blowing air "down the barrel" -- with your head positioned right over the bore).

I haven't gotten it back out to the range yet, but I will try to get back out very soon and she how it goes.

Old No7
I’ve tried a many cleaning procedures, but have to try what you suggest so I can’t comment. But if you happen to have a steam cleaner….

I picked up one last spring at the urging of @chorizo for cleaning breech channels (among other things) and find it hard to beat. With the nipple removed clean the bore as normal, then blast the steam into the breech (through the threaded hole with the nipple still removed) and you will be surprised at the crud that comes out.
 
Log Cabin Shop sells a brass T C cleaning attachment that supposedly fits into, and will scrape the ignition chamber on TC rifles.
I don't have a TC, so I can't say how it works. You might give it a look see.

Dave
 
Any concerns about the lapping affecting the nipple threads?

Good eye, and good question! No, none. I left the tag end of string uncoated, so was careful to only pull back & forth after the string laden with lapping compound was past the threads.

Log Cabin Shop sells a brass T C cleaning attachment that supposedly fits into, and will scrape the ignition chamber on TC rifles.
I don't have a TC, so I can't say how it works. You might give it a look see.
Dave

Thanks Dave, I do have a TC scraper shaped like the chamber too, but I find that brush I posted above does really well too. I just have to use it religiously.

Old No7
 

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