loose (or is it tight) spots in Thompson barrels?

[PeterCartwright]

I put a T/C Renegade .50 cap lock together while I was in grad school.  That was 30 years ago.  I've used this rifle to put a lot of venison in the freezer (though not for a few years).  I ultimately decided on this working load:  90 gr. Goex FF/370 gr. Maxiball lubed with "Bore Butter".  When seating the bullet, you can feel loose spots in the barrel, at least that's the way I interpreted the places where the Maxi would "fall" and then stop until the ramrod fully seated the load.  I've also noticed that this particular gun doesn't do well with a clean barrel.  Again, I've assumed the fouled barrel sorta filled in the loose places.


I missed the last deer I shot at (with an unfouled bore).  Miraculously, I was able to get another chance at this uneducated doe, and the fouled bore printed according to the sight picture.  Could I have flinched?  (Who ME???).....Well, sure I could have, but I don't think I did.  Anyway, the end result plays havoc with my confidence in the rifle.  If I take the time to foul the bore, it reliably prints where it looks.  Guess I can do that.  (Like the patient who tells his doc, "It hurts when I do this."  And the doc replies, "Don't do that!")


Has there been chatter about irregular Thompson barrels?  Just curious.


Guess I should also confess, I've allowed my lack of confidence in the Renegade to excuse the purchase of a .54 T/C Hawken in nice, "pre-owned" shape.  I'll be curious to see how the bore in the new (to me) rifle compares with my Renegade.


PC

[Semisane]

Bummer!  That would be a real problem for me Peter, because I want to hunt on a clean dry bore and sight my guns in for that first shot.

Lots of guns are a little tighter at the muzzle than in the rest of the barrel.  But if I understand your problem there are tight and loose spots throughout the bore. 

If lead conicals and Bore Butter have been your standard load for some time, a build up of BB may well be your problem.  It's ofter very hard to detect visually.  I would recommend a thorough cleaning like this.  Give it a good soap and water swabbing.  Then block the nipple with a patch and lower the hammer on it.  Stand the gun on its butt and fill the bore with boiling water.  Let it sit a few minutes and pour the water out.  Then repeat both steps.  Finish up with a lightly oiled patch to protect the stripped bore.  Your problem may be solved.  If not, the next step would be a good workover with JB bore paste on a very tight patch (with a spinjag if you have one, or a range rod with a swivel handle to allow the patch to rotate with the rifling).   Plan on at least 50 full up & down strokes with the JB, adding past after every ten strokes or so and replacing the patch as it wears.

[PeterCartwright]

I don't think it's a lube fouling issue.  I'm pretty meticulous about barrel care, and I also use hot water (though not always boiling) as a part of every cleaning session.  And this isn't a new issue.  It's been present from the start.  I haven't tried the polishing routine with JBs.  For that matter, I have some of Veral Smith's bore lapping compound I could try (fire lapping).  Actually, that's not a bad idea.  Guess my only concern is that Thompson's have pretty shallow rifling as it is (.005 if memory serves).  Maybe I'll start conservatively and try the Bore Paste first.  It's a product I use regularly in my other guns.


Thanks for the reply.


PC

[greenrivers]

I had noted accuracy problems in an earlier post and was referring to sights and aging eyes. A responding comment mentioned bore butter and pyrodex causing bore buildup as a possible cause. Though the rifle had been completely cleaned and lubed after each shooting, I decided to check it with a tight patch and did find restriction midway of the barrel. Using a great many tight fitting patches with solvent and then alternating with a brush the restriction was removed. I then used a very fine abrasive paste to lightly smooth the bore. This did restore accuracy to the barrel. The combined experience and knowledge on this board is outstanding.

[flintlock]

I'd give it a good cleaning and hit it with JBs as well...
 
You're not going to polish off the rifling by hand, unless you give it 1,589,445 strokes...
 
I have a Knight Disc that I tried 777 in and couldn't get the crud ring out...100 strokes of JBs and she was slicker than when she was new...
 
Of course, I hate to point out the obvious but the real problem is that you're not using round balls...

[coyotejoe]

It's not at all unusual to find variation in bore diameter with any make of barrel. It's generally not noticeable with a patched ball because of the elasticity of the cloth patch but with a tight lead slug I've often found "loose and tight spots" as you describe. The difference may be only half a thousandth of an inch but noticeable. The real solution is to lap out the bore with fine abrasive on a lead slug cast in the bore and fitted to a rod with a ball bearing handle. It's not rocket science but it does require some basic know-how and some careful work. It's a process of enlarging the bore to the same diameter as the "loose spots" so that it end up uniform from end to end. I've done a few barrels and in every case the improvement was well worth while.
 Most people seem to think "fire lapping" is easier and safer. I'm not so sure it is but here is a link to "fire-lapping a muzzleloader" which may appeal to you.
http://www.beartoothbullets.com/tech_notes/archive_tech_notes.htm/48

[PeterCartwright]

Of course, I hate to point out the obvious but the real problem is that you're not using round balls...

  Great suggestions.  A good scrubbing with JB's is probably the best place to start, though I'm still pretty sure the issue isn't related to fouling.  The link to the Beartooth article gives food for thought.  I'll have to see if the tight and loose spots correspond to the barrel's dovetails.  My guess is, I'll ultimately need to lap this barrel, whether by hand or "fire-lapping".  (I've done the latter with a stainless Super Blackhawk and it worked fine).


As for round balls, well, I just came home with a nearly unused (the bore really does look factory new) T/C Hawken in .54.  THIS will be my roundball gun, provide the 1:48 does O.K. with them.  As an aside, I've discovered there's just enough more drop on the comb of the Hawken stock to fit me much better than the straighter Renegade stock.  About a half inch longer LOP as well.  And just so I'm not thrown out of the club, I built a pre-Revolutionary Lancaster pattern flinter 20 years ago with a Green River .50 RB barrel.


Thanks all!


PC

[flintlock]

Let me know if you need some .530 balls...I too built a Lancater back in the 80s, although I claim it to be a "Carolina Rifle"...
 

 
 

[PeterCartwright]

Follow up:  I got out to the range this week.  I took four Maxi-balls impregnated with lapping compound I ordered from Veral Smith a decade or more ago. (Actually, I took five, but discovered one was a .45 that slipped into the mix.  Makes me pretty observant, huh!)  I don't know what grit the abrasive is, but it feels pretty aggressive.  My intent was to "fire lap" the gun with the Maxis.  Actually, the abrasive Maxis work twice--once going down in the bore and then while shot.  After the treatment (and a thorough cleaning) I could still feel some differences in the bore while seating a regularly lubed Maxi, but there was significant improvement which could be felt as well.


I got out to a friend's house this afternoon who invited me to the shooting space behind their house.  Once more, I could feel much more consistent resistance against the Maxi as I pushed it down the bore.  I was without benefit of a bench rest, so I had to shoot seated on the ground, resting the gun on my knees.  I shot from only 50 yards.  The first two shots spread less than 1/4" center to center.  (Like I can do that every time!).  Still, the third shot expanded the group to only 1 1/4" center to center.  More importantly, the FIRST shot was in a group with the other two.  I should also note I cleaned the bore pretty thoroughly between shots. 


One three shot group is hardly proof of cure, but I'm pretty encouraged.  Next week I'm hoping I can get back to the range (with bench rest).  If this performance proves repeatable, I will have new confidence in my old Renegade.


PC

[keith44]

That's great news!!!  You can add some graphite to your lube for a short time to help with the final polishing of the tight spots, if you want further smoothing

[greenrivers]

I to have used the fire lapping method to remove tight spots in barrels but only in breach loading guns where bullet is contacting both lands and grooves. The method is obviously sound and works well for those guns as bullets are sized to the full dimension of the barrel. If done in a front loader, is enough barrel material removed to demand resizing of the conical? R/B will fill a bore do to the patch thickness. But a conical simply being pushed down the bore could now be too loose a fit? I do not believe that black powder or it's substitutes cause a flat base bullet like the maxi's to obdurate enough to fill the bore, or am i wrong? I have never recovered fired bullets and measured them. Thoughts?

[keith44]

I am confident that real black 2F will obturate any dead soft pure lead conical. It's when you start alloying the lead that things get pretty iffy.  As for loose fir in the bore the fire lapping removes so little material it is irrelevant. 

[greenrivers]

The improved accuracy does tend to prove your point and to some degree I have to agree, but it would be a good test and one worth trying. Cupped or hollow based bullets that were used tend to make one wonder.

[PeterCartwright]

If you've ever had a chance to examine a Maxi that has been fired, you'd be fully convinced on the obturation thing.  The rifling is graven convincingly on the driving bands of the bullet.  As noted, Maxis must be cast of straight lead.  And paper targets I've shot with my Renegade have beautiful "wad cutter" type holes.  In my experience, Maxis cut the same kind of cookie cutter holes through deer.  (The hides I've turned in for tanning return with neat, round 1/2" holes on each side.)  While I've never had an opportunity to do so, I'm fully convinced that the same load (90 gr. FF Goex/370 gr. Maxi) would penetrate equally well on broadside elk presentations at reasonable distances.


PC