Deburring & Cleaning Flash Channel of TC Patent Breech -- UPDATED

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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 a poster on another BP website for this image of his cut-down Renegade from 2019, as it clearly shows the design of TC's 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 a poster on another BP website for this image of his cut-down Renegade from 2019, as it clearly shows the design of TC's 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
Good ideas, and nice post. Please let us know how it turns out.

WRT cleaning, seems to me that some specialty tools would be very useful for keeping TC flash channels and powder chambers clean: 1) A wire brush shaped like the powder chamber; 2) A flexible wire brush designed to go down the flash channel; and 3) A long jag that has the end shaped to fit the powder chamber. For the latter, I've been using a special powder chamber scraper that screws into the end of a cleaning rod - first as a scraper, w/o a patch, and then I put a patch on it. Even after the most thorough cleaning, this technique removes a lot of crud. October Country sells them.
 
Last edited:
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 back when I was shooting a .58 Zouave for awhile as it had a flat breech face and I used a flat scraper, and I didn't need these. Glad I found these in my BP stash (new on left -- used and "shaped" to fit the TC breech on the right) and I'll use them all the time now 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
 

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