I bought a T/C Bone Collector (Triumph) to expand my hunting season a bit earlier this year.

I mounted a Leupold VX Freedom 3-9x40 (#174180) on it in a T/C one piece scope mount and hit the range to sight it in.  I shot 100 grains volume of Blackhorn 209 and a couple of different projectiles (300 gr hornady XTP in T/C sabots and 250 & 290 gr barnes Spitfire EZ's).  CCI magnum 209 primers.

I was off the paper low at 25 yards.  Cranked the elevation all the way up and it was still low.  Aiming at the top of the target got me on paper, and I was about 12 inches low at 25 yards.

I moved to 50 yards on the off chance that might make it better, but no dice, still very low at 50 yards.  I upped the charge to 120 grains of blackhorn and gained about 2 inches at 50 yards.  Aiming at the top bulleye in a 4 block target got me a decent group at 50 yards (looked to be an inch or two, didn't measure it), on the bullseye about 12 inches below the one I was aiming at.  And the scope was not loose in the mounts nor on the gun.

Thinking it was the alignment of the scope, I ordered a new Leupold 1 piece dual dovetail scope base from Midway and mounted my VX-Freedom in that.  Hit the range again and close to the same result (although, it was only like 5 inches low at 25 yards with the elevation maxed).

Shit - so it's highly unlikely it's the moun (two different mounts, same result).  That leaves the gun or the scope.  Don't believe it's my load as recoil feels appropriate, although I admittedly didn't chrono anything.  

I called Leupold and they told me to call Thompson.  i don't want to have to send the gun back if I can avoid it.  I tried calling T/C today, but did not get through.  

I am contemplating ripping a scope off a different rifle (if I don't have one laying around still in the box) and checking to see if that fixes it.

I guess I'm posting here for any other suggestions you all might have.

Side note, Leupold has my model scope marked as "No longer for sale" on their website.  Truthfully, I was a bit put off by how dismissive the Leupold customer service guy was.  No offer to send shims or give advice.  I own a LOT of Leupold scopes (and bino's and a range finder) and have only had to call their customer service once before, and it was handled like a boss.  I am going to be both relieved and pissed off if it turns out to be the scope.  That's what I get for buying cheap optic ($200).

Are you sure it's not you?

After all the dust settles, it may come down to one choice..."shimee shimee coco bop
shimee shimee bop. "

Sorry. Morning coffee has turned me into Goofy. ??

Not sure if serious, but yeah, I'm pretty sure I'm capable of not consistently shooting 5-12 inches low at 25 yards.

After shooting the T/C (and getting a 1.5" group at 50 yards, albeit a foot low), I shot some loads I developed for my son's CZ 527 at 100 yards and was getting between 1.13" and 3" groups, on target.

So I don't think it's my trigger pulling.

I think it may come down to this if swapping the scope out doesn't work.  Unfortunately, the Triumph has four screws to mount the scope base, and all of them are to the rear of the base, so the front of the base is floating out there a bit.  It's kind of a shitty design, to tell you the truth, and I believe it will make using a shimmy a little bit difficult, as the length you have to work across to get the lifting effect is pretty short.  In order to get a secure mount between scope base and receiver, wouldn't I need to have three tapered shims to fit underneath the back three screws?

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I would have felt more confident if they had one more mounting hole in the forward position.

Shims? Is this 1984?

You should have no need, or want, to shim a scope in any modern rifle.

If you pick a target, say 150yds away, so it doesn't fill the scope view, and look through the breech plug through the center fire channel, line it up perfect center on something, then look through the scope, are you centered on the same thing?

Honestly it could be scope or gun with older Leopolds, they do pretty commonly have issues. But how does that scope zero on other rifles?

Also your scope mount doesn't look like the current Thompson scope mounts whatsoever. Is it a real Thompson product or just made for the T/C?

Sounds like the mount is the culprit.
Perhaps try one straight from Thompson?

Thompson medium height for 1inch tubes

If you are consistently shooting relatively tight groups it would make sense that the rail is off from the barrel.  
I am sure you know this, but you should be using only one specific load and round to eliminate differences in bullet weight and or charge.
Plus cold bore versus hot bore could also change your point of impact but you should still be in a fairly close group.

Recheck your adjustments to verify you are adjusting the scope properly...Ask me how I know, Doh!

Bill

Boresighting the gun was a bit difficult as I didn't have a good solid rest that could accommodate the rifle solidly with the action broke open.  

I have not mounted the Leupold freedom scope on another rifle yet to test it.  

This picture is after I replaced the T/C one piece mount/rings with the Leupold one piece base with turn-in rings.  I took it to show the base mounting screw pattern (all 4 screws near the breech).

That's the mount I had on there originally.  It was shooting 12" low with the elevation of the scope jacked all the way up.  

After I switched to the Leupold base/rings, it was only 5" low.

So I ended up mounting a Vortex Viper 3-9x40 BDC in place of the Leupold Freedom scope.

I have successfully got it on target at 100 yards!  Whoo Hoo!

This scope has 92 MOA elevation adjustment, vs. the Leupold, which only had 60.

I still have 2" of adjustment at 100 yards left on the scope - 8 clicks at 1/4 MOA/click.  

This saves me from having to send the gun back before hunting season.

With my 110 grain Blackhorn load under 290 gr Barnes T-EZ, it's shooting 2" groups, centered on the bullseye.  

Now I can work on my shooting.  I don't plan on shooting at a deer beyond 150 yards, and hopefully, I'll keep the shots under 100 yards.  

...

Two different scope mounts and two different scopes.  

Each time, the bases and scopes were installed using my Wheeler torque wrench to the correct ft-lbs.  

I think the culprit has to be the mounting interface on this gun.  What I'm surprised about is how no one else has run into this.

Guess I'll have to reach out to Thompson at some point.

Well, sounds and looks like you've done your part/tried everything the end user could try.
Guess either barrel contour is off (slightly smaller OD by the mount screws than forward of them) or they managed to let a barrel slip thru Q/C where the bore isn't concentric with the the OD of the barrel (tilted down).
If two different mounts are producing the same results, and you're nearly maxed out on one scope, and maxed out and still way off with another, it's gotta be the barrel.

Hopefully T/C does better for you than Traditions did for me (which was NOTHING) when I had a similar bad barrel experience. Had a Pursuit where the mounting holes were aligned 98 MOA left of the centerline, and they wouldn't admit the problem or swap out the barrel. Kept sending it back to me "boresighted", which translated to forcefully (with a large mallet from the looks of it) bending the mounting rings on the weaver bases... It would fire 1 shot on paper, then be all over the place as the rings were incapable of staying in their "beaten" position.  Spent more time with the gun in UPS' hands than my own.  Eventually gave up, traded it for case of beer to a buddy who thought he could fix it.... he ended up using the barrel as a grounding rod for his generator.

My plan is to hunt this years Muzzle loader season, and see how I feel after that.  I may not want to send it back to T/C as I generally don't like messing with something that works.

For now, at least, it looks like this will work.

It's definitely the gun.  Shooting it at the range to final zero before muzzleloader season, and between shots I happened to look down the length of the barrel from the side - it's clear that the last 7 or 8" of the barrel are bent downward!

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It's hard to capture it with my iphone, but easy to see in person.  I had several guys at the range look (without telling them) and they all saw the barrel is bent.  Additionally, carefully looking through the barrel, it's obvious that you can see the top of the barrel at the muzzle end, but cannot see the bottom of the barrel at the muzzle end because of the bend.

I tried calling Thompson, was placed on hold until 5 PM  EST when they promptly disconnected the call (because they close at 5 PM EST), so I sent them an email, pictures and background.  I'll update this thread with their response.

That is a pretty obvious bend in the barrel, did you buy this gun new or used?

In to see what TC has to say. My Dad’s TC is bent like that.  Got it in the bargain cave at Cabela’s.

I bought it new in May of this year from Muzzle-loaders.com.  It was new in the box, no handling marks that I noticed.

I didn't get to shoot it until a few months later.  

What's strange is that the bend is straight down.  No left/right deflection that I can see.  This makes me think it's got to be from the factory.  The box was/is in fine condition, no damage that would indicate the bend happened after shipment from the factory.   So maybe it happened while they were putting the front sight on?

I'm kicking myself for not taking the barrel off the stock and bore-sighting it properly in a rest the first time I set up the scope - I could have saved myself a lot of frustrating range trips, wasted ammo, and buying an extra scope mount if I had detected this up front.  At least I can use the extra scope I bought on a different rifle.

Wow. I’ve never seen that before. Please update us after you hear from t/c

I got the gun back last week.  There was no communication from T/C during this return process.  Apparently, they replaced the barrel (or at least they said they did).  It looks straight so I'm hoping it's good to go.

I actually called them yesterday because I noticed the barrel had the same serial # as the one I sent in, and the Repair Order Completion paperwork says  
"Comments:
Accuracy Issues
Bad or No Rifling    The last several inches of the"  (this comment ended just as quoted here)

"Performed Service:  Evaluate/Repair" with "Replace Barrel" directly underneath Evaluate/Repair

I called T/C to confirm they actually replaced the barrel (vs. trying to true it up somehow) and asked about the serial number being the same.  They have obviously test fired it (bore is dirty, and I cleaned the old one thoroughly before sending it back), and there's some wear on the finish by one of the ram holding lugs.  So I'm not 100% sure it's a new barrel.  I had to take the rear sight off to mount my scope, so the one I sent in had no rear sight, and the barrel I got back also had no rear sight.  

The guy I was talking to didn't seem particularly helpful (he just said he could only see what I saw on the return paperwork).  He didn't ask for the work order number or anything to identify my particular situation, but put me on a brief 5 second hold and came back and said, yeah, they replaced the barrel and stamped it with the same serial number it had before.  I didn't leave that phone call too reassured.

Anyway, hopefully this thing shoots well enough to get me into the field next year.  

lucky it didn't cause a bore obstruction.