TC lock tuning?

[badwolf]

Trying to get a lighter trigger pull on my .tc big bore single trigger and I think I should tune the lock and lighten the springs. Any help would be appreciated.

[Artificer]

Is your lock one of the original TC locks with the coil springs in it? 

Is your trigger attached directly to a boss that is one piece of the guard?  IOW, is it not an adjustable trigger? 

I have never worked a TC lock with a coil spring set up, so I guess I had better mention that next.  I did take mine apart in the early 70's, but just put it back together after cleaning and lubing it.

However, I have done loads and loads of trigger jobs on original and repro UnCivil War Era percussion guns including the various types of rifle musket locks, Sharps locks, Maynard lock mechanisms and WAY too many original and repro Smith Carbine locks.  Even with the Smith Carbine locks that went as high as a trigger pull of  28 lbs., I strongly advise against taking material off the mainspring.  You need the full strength spring both for fast lock time and to ensure there is enough spring tension so the hammer is not thrown back to Half Cock or more when the rifle goes off.  Besides, that is not really the problem anyway.

The problem/s most likely is/are the amount of sear engagement in your lock, the angle of the sear tip to the tumbler face and to a MUCH lesser extent, the tension of the Sear Spring.   You can take a LITTLE off the sear spring, but if you go too far, you will wind up with a lock that won't hold at full cock 

Messing with the angles of the sear tip and tumbler are really not in the purview of many hobbyists.  Too easy to get it wrong and wind up with too light of a trigger, too heavy, or if you can't properly reharden the parts afterward, the parts will wear too fast or dig in within a couple to a few dozen times you pull the trigger. 

Reducing the sear engagement is a lot easier, but one still needs to know what one is doing.  Perhaps the easiest method is to SOFT solder a brass shim to the tumbler to reduce sear engagement.  If it winds up taking away too much sear engagement, you can file it down or use a thinner shim.  A more difficult method is to spot anneal and drill a tap a hole for small set screw in the tumbler and file it down to where you have enough, but not too much sear engagement.  If you file too much or when it wears too much, you start over with another screw. 

Then maybe some FINE polishing of the sear tip and the tumbler engagement surface with a HARD WHITE Arkansas stone, but NO India stones, PLEASE.

I've heard repair/replacement parts for TC coil spring locks are drying up.  If you decide you want to work on your lock and wind up messing it up, then more traditional style replacement locks are available from L & R lock company. 

Oh, I have NO interest in working on a TC coil spring lock, so I'm not trying to get you to have me work on it.  I also have NO connection with L&R locks nor Track of the Wolf, other than being a customer of the latter for many years.   Just wanted to point that out.

Perhaps someone else on the forum actually has worked these locks and can give you more information.
Gus.

[badwolf]

The lock has a coil spring that seems to power the hammer. I don't see any trigger adjust screw. It seems to be a simple trigger with a return spring. The sear lever on the lock has a return spring that you feel when pulling the trigger. Would taking a coil off that reduce trigger pull without causing problems?

[Bob Roller]

  I reassembled a TC lock for my wife's brother in law and that has been my total experience with one.
 
  Bob Roller

[Artificer]

  I reassembled a TC lock for my wife's brother in law and that has been my total experience with one.
 
  Bob Roller

I was hoping you might have worked one before because you know more about locks than most anyone else.
Gus

[Artificer]

The lock has a coil spring that seems to power the hammer. I don't see any trigger adjust screw. It seems to be a simple trigger with a return spring. The sear lever on the lock has a return spring that you feel when pulling the trigger. Would taking a coil off that reduce trigger pull without causing problems?

Thanks for the further info. 

The problem you can run into by cutting a coil or even a half coil off a spring is you MIGHT get the spring too short to put any resistance against the sear at all when the sear is fully engaged (and the tail is at it's lowest point) in either the half cock or full cock notch.  So the minimum length of the spring is critical.  IOW, after cutting a spring it may still have good compression power, but now it is too short to push the detent down far enough on the rear of the sear to keep the tip held up under spring tension in the sear engagement.  I hope that is a little more clear than mud.  Grin.  The better method is to use a spring that does not have as much compression strength, but is still long enough to keep proper tension on the sear tail.  Usually this is done with a spring that has smaller diameter coil wire or the number of coils per inch are fewer AND the spring is still long enough to put pressure where needed.

I lost my disassembled parts diagram, for my TC Hawken, 30 or more years ago.  The best one I can find is this one:  http://www.rmcsports.com/flint.gif  I can't tell if the bottom end of the sear spring fits inside the plunger, but it looks that way.  What I was concerned about was if there was a short stub on the end of the sear spring plunger that the internal hole in the spring has to fit over. 

Personally, I would try to find a spring that has less compression strength and fits and functions properly RATHER than cutting the spring in the lock.  That way you don't risk cutting your spring too short and not working at all.  It also makes it MORE difficult to find a spring when the original coil spring was cut too short.

The problem with this for most people is they don't have access to a large assortment of small springs.  One MIGHT be able to find a spring that would work in the Big Box Hardware Stores IF you have a precision dial caliper to check the diameter and length.  However, don't hold a lot of hope for that.  A better place to find a spring that might work is at a gun show with a parts dealer who has a lot of different coil springs.

HOWEVER, the bad news is that the MOST reduction in trigger pull that you will get by using a lower strength compression coil spring for the sear may be less than 1/2 pound or even less and not really noticeable. 

Reducing Sear Engagement is the surest way to reduce trigger pull weight by any significant or even noticeable degree.  The methods I mentioned earlier are really in the purview of a gunsmith or machinist and not most home hobbyists.

Not sure where you live since you didn't list it on your registration page, but if you would like to inform us, perhaps we can suggest someone close to you to help you.

Gus 

[LRB]

  If the geometry is correct between the sear nose contact face and the full cock notch face, you will not reduce the actual weight of the trigger pull by reducing the notch contact. Only the travel, or creep, which can be perceived as a weight change, but really is not, although a very helpful and worthwhile modification.  The same principles also apply to set trigger pull weights. To reduce actual pull weights, you have to reduce spring power, not contact. The only job of the sear spring in a side lock is to fully return the sear to it's needed positions in the tumbler. If spring power is required to hold the sear in the full cock position, you have a geometry problem, and a less than safe arrangement. I do agree on leaving the mainspring as is, unless it is truly too strong, which is not very common, but sear springs are commonly much over powered for their intended job. Usually to make up for poor geometry in cheap locks, or to cover liability   legal issues in quality locks.  Brownell's used to have a wide selection of small coil springs.

[Artificer]

Yes, if the geometry of the full cock notch is wrong, I.E. not perpendicular to the center of the tumbler, it will give a lighter or heavier trigger pull depending on which way it is off.  When that line is too far forward, it won't even hold the sear notch.  When too far back, it will make the trigger pull heavier as you are actually "cocking" the hammer more as you pull the trigger.  The wrong angle on the sear tip will do similar things. 

However, when the tumbler and sear are in the correct geometry, then reducing the sear contact or engagement does reduce the trigger pull.

OK, the basic flaw in the reasoning that reducing sear contact will not work for reducing trigger pulls is the fact it does (and has) indeed reduced trigger pull weights in many  thousands of both original and reproduction Civil War period locks and lock mechanisms for many years in NSSA competition guns. It works just as well on original Flintlocks dating back hundreds of years that do not have set triggers to trip the sear.   

This is not fiction because it has been measured with trigger pull weights before and after the reduction was accomplished by using a shim on the tumbler or a screw on the tumbler to reduce sear contact with the full cock notch.  Further, if a shim soft soldered to the tumbler reduces trigger pull weight too much, then filing it down will increase the weight of the trigger pull.  Again, this has been proven countless times with trigger pull weights. 

Every Spring or Fall National Shoot of the NSSA requires every Competitor to have his/her trigger pull weighed with trigger pull weights  on every Rifle Musket, Smoothbore, Carbine and Pistol they shoot in competition.  There are literally thousands of such guns weighed at every National Shoot.  Trigger pull weights take the human error out of the equation and that includes for the folks doing "trigger jobs" on these guns.. 

Now, perhaps the question is, "Why does it reduce the trigger pull weight?"  I am not a mechanical engineer, so I can't explain it like one.  What I think is "going on" is that when the sear tip is way up in the sear notch, the resistance of the tumbler against the sear is greater AND for a longer period of time than when the sear is down closer to falling off the notch.  I "think" there is more mechanical advantage as the sear gets closer to falling off and that's why the trigger pull weight is reduced.  Or, it may just be a matter of the geometry of the parts with lesser sear contact does the trick.  However, there is absolutely no question that reducing trigger pull weight by reducing the sear engagement absolutely works.

Now, one wrong way to reduce trigger pull weight is to file or cut down the sear notch on black powder locks and mechanisms, especially if there is no fly in the tumbler.  You change the geometry of the working parts and after doing it, one risks the sear catching in or breaking off the half cock notch and other problems.  Short answer, reducing trigger pull weight by shortening the full cock notch is almost always or at least normally not a good idea in an otherwise correctly functioning lock.  . 
Gus

[LRB]

  Look at it as with a set trigger. A set trigger weight of pull is not changed by it's sear engagement. Only it's distance of travel. To change it's pull weight, you have to change it's spring power. If there is a difference in principle, explain.

[Artificer]

  Look at it as with a set trigger. A set trigger weight of pull is not changed by it's sear engagement. Only it's distance of travel. To change it's pull weight, you have to change it's spring power. If there is a difference in principle, explain.

A set trigger trips a lever under quick spring tension that whacks the sear tail and quickly drives it upwards and pushes the sear nose from the notch or tumbler face.  Sort of like a punch compared to the pull one feels when not using a set trigger.  (Also, the face of tumbler notch on civilian locks are normally not as large/long as military locks.)  So of course you won't see a difference with less sear engagement in the lock, as you are pulling against the same spring tension force in a set trigger (and not the lock's mainspring)  each time you pull it at the same setting.  With a set trigger, the only time most people will feel a reduction or increase in a set trigger pull is when an adjustment screw is turned one way or the other. 

For a more in depth description on how a set trigger works and pictures, here's a good link:  http://home.insightbb.com/~bspen/triggerterm.html

I honestly don't know if a fly in the tumbler is absolutely required when using a set trigger.  I suppose if the spring in the set trigger is strong enough, the full cock and half cock notches short enough and the lever tall enough (maybe); the punch of the set trigger lever may push the sear nose out of the way long enough for the half cock notch on the tumbler to rotate past the sear nose and not hit it.  However, a properly fitted fly ensures the sear nose will not hit the half cock notch when using a set trigger, because it keeps the sear nose out of the way of the half cock notch.  So many if not most better quality locks we see today have a fly in them.

However, NSSA rules prohibit the use of a fly in a tumbler as most military locks even as late as the UnCivil War did not have them.  A notable exception to this was the Whitworth Rifle that did have a fly in the tumbler.  I would have LOVED to have used Whitworth tumblers in other reproduction Military Enfields used in the UnCivil War.  However, the NSSA decided not to allow the Whitworth Tumbler in other reproduction Military Enfields as the original military models were not made with them.

On locks without a fly, it is the shooter's trigger finger continuing to pull the trigger and raise the tail of the sear - after the sear nose is pulled free of the notch, so the sear nose does not hit the half cock notch as the tumbler rotates around.  This is why it is not normally a good idea to shorten the full cock notch because when the sear nose is released, the shooter may not be pulling the trigger enough or long enough to push the tail of the sear high enough to clear the half cock notch.   As a matter of fact with big military locks,  I always made a point to take a little off the half cock notch so in case a shooter did not properly "follow through" or hold the trigger pressure long enough, the sear nose would not hit the half cock notch as it rotated by the sear nose.   

Gus

[D. Taylor Sapergia]

I have to agree with Gus on this.  The weight of trigger pull according to a digital gauge is reduced by reducing the contact time.  And the same applies to a set trigger too.  The same amount of energy is being applied to the hammer trigger no matter how fine the triggers are set up.  But the time of the contact is so reduced as to reduce the numbers on the gauge, and also the felt weight of the set or simple triggers.  You are correct, that it is the time that makes the difference, but it is measurable for sure.

[LRB]

  Hi Taylor. Back out the adjustment screw on a quality set trigger until you have noticeable travel, then pull with a gauge until it releases taking note of the pull weight required. Then adjust the screw to a minimal travel and gauge it the same. You will find the same weight reading, assuming the surfaces are dead true and polished with no roll off toward the release. I had this proven to me by an engineer some years back, as I too did not believe it. To gain a lighter pull, you must lighten the spring power. It is a matter of force and leverage. If the leverage does not change, then the force must, if any actual weight difference is desired. Perceived advantage would be a factor in the end result, but the actual weight of pull remains the same. In the case of a side lock simple trigger weight measurement, you are adding another lever with the trigger which will give greater advantage depending on the fulcrum position.
  Gus, I know how set triggers work, and adjusting the engagement screw does not change the weight of pull with them. Only the travel. The spring has to be adjusted to change actual weight of pull.

[Artificer]

First of all, I do not use spring powered or digital trigger pull gages as they allow too much human error and are just not as accurate as solid trigger pull weights.  This is why in National and International Competitions for Modern and Muzzleloading guns (where minimum weights for trigger pull are required), require solid trigger weights be used by referee's and juries in arbitrations of trigger pull.  There are a very few modern or muzzleloading  shooters worldwide who can actually feel a difference of one or two ounces in a trigger pull, but the "feel" of how a trigger breaks is far more important than a difference of an ounce or two of trigger weight.  

I do not know which set triggers you refer to when you state the trigger pull does not change when adjusting the screw in or out.  

If one screws the adjustment screw too far in on many modern and muzzleloading set triggers, the engagement surfaces are contacting in such a miniscule area, it only takes a light bump to allow the engaging surfaces to become dislodged and the lever released.  However, when one unscrews the screw from that position, engagement surfaces increase and the lever can no longer be so easily released.  This translates directly from a too light trigger pull to a heavier one that will safely hold the spring tensioned lever.  The trigger pull weight can be checked with trigger weights, if one chooses, and it shows the trigger pull indeed got heavier because there is more engagement surface that has to be overcome OR the way the engagement surfaces contact each other was changed.  

Further, as the screw is adjusted In and out, the relationship of how the pawl on the set trigger and the nose of the trigger bar engage each other physically changes.  Since those two engagement contact area surfaces change in physical location to each other, there is going to be a difference in trigger pull.  The only way for the trigger pull to remain exactly the same would be if the relationship of those two parts was exactly the same position when the adjustment screw is screwed in and out.  

In a high quality and polished set trigger mechanism, those changes in position of the two contact surfaces may be less different and harder to feel when polished than in lesser quality set triggers, but they still have to be in different physical locations and thus change the trigger pull when the adjustment screw is screwed in and out.  

Gus






  

[LRB]

  The screw only controls creep, but that's fine, have it your way. I quit

[Standing Bear]

Badwolf has a hard trigger pull on a TC with single trigger.  All of my rifles have set triggers.  

The gentleman building my single trigger flint target pistol told me that knowing the intended purpose of the pistol, he would locate the pivot pin of the trigger to lighten the trigger pull.  

While all of the discussion of springs and Whitworth tumblers has been interesting, does anyone have instructions for Badwolf to lighten the trigger pull either by adjusting the trigger or other?  Will a TC set trigger fit the mortise of a single trigger Hawken?  How about the trigger guard?
TC

[Artificer]

Badwolf has a hard trigger pull on a TC with single trigger.  All of my rifles have set triggers.  

The gentleman building my single trigger flint target pistol told me that knowing the intended purpose of the pistol, he would locate the pivot pin of the trigger to lighten the trigger pull.  

While all of the discussion of springs and Whitworth tumblers has been interesting, does anyone have instructions for Badwolf to lighten the trigger pull either by adjusting the trigger or other?  Will a TC set trigger fit the mortise of a single trigger Hawken?  How about the trigger guard?
TC

Standing Bear,

This is why I asked Badwolf what kind of trigger he had in his rifle way up the thread.  I looked up TC Big Bore rifles and found they generally had a single, non adjustable trigger like the one shown in drawing number 62 in the link I posted way up the thread and will post here again:  
http://www.rmcsports.com/flint.gif  

So regular TC double set triggers and trigger guard won't work as a drop in fit.

I also searched for a single set trigger for this model rifle and could not find one. I just contacted a TC customer service agent and was informed TC never made a set trigger mechanism for that rifle.  I could not find an aftermarket set trigger mechanism for that rifle on the internet.  So it seems the only way to get a set trigger mechanism  into that rifle would only be as a custom job.

This is also why I went into a discussion on lightening the trigger pull in the posts above.

Sorry I don't have better news than this.
Gus

[D. Taylor Sapergia]

Of course the poster can improve his trigger pull.  He needs a new simple trigger that has a much deeper pinning area.  The original trigger can be still employed, as long as a new piece of steel is silver soldered to the base plate of the trigger, and then the trigger needs a axle pin drilled through the stock's wood up in the area of the sear's pivot screw.  This is illustrated in many of the builder  books most of us have, and perhaps the poster can do some research on his own.
The problem he's having is that the trigger is pinned in the trigger plate and so it has very poor mechanical advantage to trip the sear.  You can likely add to that a very course engagement of the sear's nose in the full cock notch.
I enjoyed the set trigger discussion, and do not consider it a distraction from the poster's question.  Whererelse can you get free education.

[Smoketown]

Badwolf,

In what area/state do you reside? (I usually reside in some state of confusion ...)   

OK, other than being powered by coil springs, T/C locks are not that complicated.
They are just not always nicely finished.

Even though the parts are 'within spec’ sear engagement into the tumbler can vary a LOT!!
”It’s called tolerance stacking”

Now, let’s cover the obvious.

Is it a long gritty pull?

Or, is it a hard pull that ‘breaks cleanly’ when enough pressure is applied to the trigger?

With the lock out of the rifle, does the trigger move freely with-out binding?

Are there any marks in the stock where the sear bar may be rubbing?

Hold the hammer at full cock and move the sear bar up and down. Is there any binding?

Hold the sear up and check the hammer for free movement through its arc.

Put it back together.

Is too tight a side-plate screw bending the lock plate?
Is the side plate screw so long that it’s rubbing the back side of the hammer?

If all of the above checks out we’ll go to step two.

For a ‘gritty’ trigger pull:

If it’s a percussion lock, put a faucet washer or a piece of leather over the nipple.
For a flintlock, a small block of wood in the pan to stop the hammer should do nicely.

Put a dab of grease on the sear nose and in the full cock notch.
Bring the hammer to full cock and progressively apply heavy thumb pressure to the back of the hammer when pulling the trigger.
Do this a few time to ‘burnish’ the engagement surfaces.
Some improvement should be noted.

Now, I'll catch flak for this but, here it goes.

Try a dab of real 'molly paste' on the sear nose and full cock notch, also where the trigger touches the sear-bar and repeat the above.
As stated in a previous post, coil spring stock is available through Brownell’s – As is the molly paste.

For anything worse than that, it looks like it may be time for a smith to do some stoning, polishing, OR, sear engagement work as Artificer - Gus mentioned.


LRB,

As we seem to be picking fly-@#$%/!! out of the pepper ...

In a perfect world with a 'well tuned trigger assembly', changing the engagement screw would do little or nothing.

Yet, increasing the engagement also increases the amount of sliding friction to overcome.

Here where I live, the levers stay the same length and pivot about an axis which changes the angle of contact which can in fact increase the pull weight.


Cheers,
Smoketown

[LRB]

  That is your opinion and not scientific backed fact. You might want to study the physics involved before being so sure of yourself. Where I live, the laws of physics are still in effect.

[badwolf]

I'm in Pa. The trigger pull is heavy but crisp. Weighed 8 lbs then after toiling it went to 6 lbs. The trigger modes freely with the lock out, it's seems like the weight. I feel is the sears lever return spring. Perhaps changing the pivot point as suggested will improve it.

[chubby]

If your sear returns to the same position on half and full cock you could drill and tap your plate for a slotted 6/40 screw with a 60(^)degree point to adjust your sear engagement on the tumbler like some of the original lock plates had. that could change your pull needed   Chubby

[Artificer]

I'm in Pa. The trigger pull is heavy but crisp. Weighed 8 lbs then after toiling it went to 6 lbs. The trigger modes freely with the lock out, it's seems like the weight. I feel is the sears lever return spring. Perhaps changing the pivot point as suggested will improve it.

Perhaps the best thing for you to do is Contact T/C and see if they will do anything about it..

Phone:  (866) 730-1614

.tca_customerservice@tcarms.com

Gus

[LRB]

If your sear returns to the same position on half and full cock you could drill and tap your plate for a slotted 6/40 screw with a 60(^)degree point to adjust your sear engagement on the tumbler like some of the original lock plates had. that could change your pull needed   Chubby

This is one I don't believe I have ever heard of or seen. Please explain how that works. Do you have an example you could show, or a drawing? Anybody??

[WaterFowl]

Trying to get a lighter trigger pull on my .tc big bore single trigger and I think I should tune the lock and lighten the springs. Any help would be appreciated.

Check out the R.E Davis deer slayer set triggers...Item #1007
Have 3-4 on T/C rifles...adjustable........big improvement.

[Artificer]

Trying to get a lighter trigger pull on my .tc big bore single trigger and I think I should tune the lock and lighten the springs. Any help would be appreciated.

Check out the R.E Davis deer slayer set triggers...Item #1007
Have 3-4 on T/C rifles...adjustable........big improvement.

Please refer to my post Number 15 above.  Badwolf's trigger is a single trigger that is pinned to a boss that is part of the trigger guard.  So to use the R.E. Davis set triggers, he would have to inlet for those triggers and replace the trigger guard.  Not trying to be critical of Badwolf, but it sounds like that is outside his range or ability at this point.  That's also why Taylor suggested taking the trigger off that boss, building up the top of the rear of the trigger and pinning the trigger to the stock where it is in a better mechanical position to give a lighter trigger pull.

Gus