Lock/trigger problem

[WKevinD]

I have just come from the shop and I am very frustrated.

I just inlet an L&R Schuetzen lock and Davis single set triggers. The lock inlet is clean and there are no "hangups" The trigger inlet is also clean and solid. The trigger bar hits the sear bar about dead center with the last third of the trigger bar. It will not disengage the sear from the tumbler.

I have polished the sear and sear spring. The sear spring feels over strong.

When I trip the sear with a pushrod it requires much more effort than what I am used to.

I almost always use Chambers locks and know how the feel. I never build with percussion locks (now I know why) but this if for a Schuetzen target gun and this lock was the only available visual match.

Any suggestions?

Kevin

[Daryl]

Sear tumbler engagement is 90 degrees.

Trigger spring is adjustable for strength.

Cap-lock mains do not need to be overly strong.

That is all I know, which is very little and elementary.

[45-110]

"I never build with percussion locks (now I know why)"  this has nothing to do with your problem. take a breath, step back and have another look........the fix will be apparent and easy to address. everyone that scratch builds runs into this type of problem prior to the tuning of the components stage.
best
kw

[stubshaft]

You can try to adjust the trigger spring and/or lighten the sear spring.  I usually grind down the side of the spring slightly and check frequently.

[Bob Roller]

You can try to adjust the trigger spring and/or lighten the sear spring.  I usually grind down the side of the spring slightly and check frequently.

Be careful with this grinding but new sear springs are not costly.
Check the fit of the sear screw thru hole in the sear.IF it isn't
within .001 the may be a lift/rotate problem before the sear releases.
Post a picture of the inside of that lock. I have used a number of these
plates with another hammer for a German customer.

Bob Roller

[WKevinD]

I just removed the sear spring and the lock fired easily. Looks like an over ambitious sear spring.

"new sear springs are not costly."  Thanks Bob I'll be ordering a new one before I start cutting/grinding!

"Check the fit of the sear screw thru hole in the sear." I did check that fit...snug and square.

I polished and relieved the back of the sear and it moves without binding.

Bob I'll get a picture of the inside of the lock and post it, thanks.

Kevin

[WKevinD]

Inside the lock at half cock.

Kevin

[smylee grouch]

You might want to check and make sure that the sear spring isn't pushing against the part of the sear that the pivot goes through and only bears against the top of the sear. " slightly grind the end of the spring" if it does.

[Bob Roller]

The untapered mainspring has to be putting a heavy back thrust on the sear at
full cock.If possible,use a 3 cornered whet stone and clean the full cock and the
engagement area of the sear.

Bob Roller

[WKevinD]

The untapered mainspring has to be putting a heavy back thrust on the sear at
full cock.If possible,use a 3 cornered whet stone and clean the full cock and the
engagement area of the sear.

Bob Roller

Should I be making that engagement smaller?
Kevin

[Bob Roller]

The untapered mainspring has to be putting a heavy back thrust on the sear at
full cock.If possible,use a 3 cornered whet stone and clean the full cock and the
engagement area of the sear.

Bob Roller

Should I be making that engagement smaller?
Kevin

No,only smoother. Does that trigger have a good strike or a light tap?

Bob Roller

[Bob Roller]

The untapered mainspring has to be putting a heavy back thrust on the sear at
full cock.If possible,use a 3 cornered whet stone and clean the full cock and the
engagement area of the sear.

Bob Roller

Should I be making that engagement smaller?
Kevin

No,only smoother. Does that trigger have a good strike or a light tap?

Bob Roller

Looked at you first post and that is NOT a single set trigger.It's a
double set that must be set for every shot. The strike area of this
trigger must be JUST behind the lock up area of the rear trigger.
Any farther back on the release bar may be the problem.

Bob Roller

[WKevinD]

[/quote]

 Does that trigger have a good strike or a light tap?

Bob Roller
[/quote]

I have tightened the trigger mainspring and it gives a good solid hit just behind the lock-up notch in the center of the sear bar. With the sear spring removed it fires every time. I am aiming at lightening the sear spring engagement and polishing the sear/tumbler engagement.
Sorry for the confusion, I thought the single bar trigger was a single set.

[Bob Roller]

 Does that trigger have a good strike or a light tap?

Bob Roller
[/quote]

I have tightened the trigger mainspring and it gives a good solid hit just behind the lock-up notch in the center of the sear bar. With the sear spring removed it fires every time. I am aiming at lightening the sear spring engagement and polishing the sear/tumbler engagement.
Sorry for the confusion, I thought the single bar trigger was a single set.
[/quote]

The single set trigger is a single trigger that must be pushed forward to set it and
a good one will fire set or unset. In German it's a"Franzosicherruckstecher "
or a French push forward trigger.I have been told by my German friends that
the very best ones were made by watch makers in the French speaking part of
Switzerland

Bob Roller

[Ian Pratt]

Anybody else have one of these locks to compare to his photo? Hard to tell for sure since the picture isn't taken square to the sear / spring area but it looks like the sear bar is arched. Seems unusual unless something has been heated and bent, but I'm not familiar with this particular lock and this may or may not be normal.  The lower limb of the sear spring seems like there's a bunch of preload on it and curved up to the tip.  Maybe a poorly formed sear spring with too open an angle at the bend, or possibly an incorrect (or improperly bent) sear causing too much spring compression?

Again, hard to tell from the photo angle but also looks like the sear spring tip is not very close to the pivot which doesn't help your trigger release

You probably have checked already, but is the lower limb of the sear spring contacting the plate?     

You mentioned that the lock fires fine with the sear spring out - just to be sure of what you're saying, this was with the mainspring installed, or by applying force to the hammer and the mainspring removed?

[WKevinD]

Anybody else have one of these locks to compare to his photo? Hard to tell for sure since the picture isn't taken square to the sear / spring area but it looks like the sear bar is arched. Seems unusual unless something has been heated and bent, but I'm not familiar with this particular lock and this may or may not be normal.  The lower limb of the sear spring seems like there's a bunch of preload on it and curved up to the tip.  Maybe a poorly formed sear spring with too open an angle at the bend, or possibly an incorrect (or improperly bent) sear causing too much spring compression?

The sear bar does look arched and the lower limb of the sear spring is hard loaded against the top of the sear, I polished the mating surfaces and polished and tapered the plate side of the spring, I also slightly shortened the lower part of the sear spring when I polished it. It helped a little.

Again, hard to tell from the photo angle but also looks like the sear spring tip is not very close to the pivot which doesn't help your trigger release

You probably have checked already, but is the lower limb of the sear spring contacting the plate?

No see above    

You mentioned that the lock fires fine with the sear spring out - just to be sure of what you're saying, this was with the mainspring installed, or by applying force to the hammer and the mainspring removed?

No this is with the mainspring and all other parts in place.
Kevin

 

[Mark Elliott]

Like Ian said, a photo square with the sear pivot would be helpful.   There is one thing I have run into that nobody mentioned, but I can't tell from the photo if it might be the case.  That is, that the end of the sear spring is binding against the pivot point of the sear.   You want to make sure that you have enough of a gap (a very small gap) between the end of the sear spring and the sear where it intersects the round area for the sear screw so that spring doesn't bind up when you raise the sear.    I also stone the end of my sear spring rounded so that it slides smoothly.   If I thought that the sear spring was preloaded too much,  I would reshape it rather than grind it.   Of course, you need to be able to properly heat treat the spring afterward.   

[WKevinD]

Mark, when I polished the leading edge of the sear spring I shortened it so that it is not pushing on the pivot point.
I'll get some better pics tomorrow.
Kevin

[WKevinD]

Sear spring and sear.
The "dirt" is inletting black used to make sure there were no hang-ups.
Kevin

[smylee grouch]

Do the triggers trip the sear now?

[Ian Pratt]

Much better angle, thanks - Kevin you'll have to take this with a grain of salt since I am unfamiliar with the internals on that particular model, but a couple things I'm seeing are that yes it looks like there was too much preload on the sear spring, the tip of the spring is sitting farther back from the pivot than ideal (although too close may cause the problem Mark described), and really the spring looks to me like either it is too long for the lock or was mounted too far back on the plate - the bend looks awful close to the edge of the plate.     

I'm not knocking L&R's locks or assembly, I am sure most of these work fine but obviously your has a problem.  Also looks like somebody may have wallowed out the slot in the plate for the tit on back of the spring, maybe in an effort to raise the spring and let some tension off - ? The sear bar looks less arched to me in this shot, and again maybe this is just the shape of the part to begin with, but perhaps somebody heated and bent it. Did you buy this lock new?

If you're positive that the spring isn't dragging the plate (with the spring mounted, a thin piece of paper should slip behind the lower limb, and bending the shouldn't force it over to contact the plate) then modifying or replacing the spring seem the logical next step.  If it was mine and I was sure the spring was the culprit, I'd close the bend slightly and re- harden and temper it. If a replacement is no different than this one, modifying may be the only option .

The reason I asked if you had tripped the lock with the mainspring installed, or if the mainspring was out and you were just pushing on the back of the hammer - sometimes when it takes excessive force to raise the sear it's because the relationship between the sear nose and full cock notch is out of whack. Without getting too involved here, a situation can exist where in order for the sear to drop out of the full cock notch, the tumbler has to rotate back slightly first which means you're fighting mainspring tension to release the sear. Makes for a very stiff trigger pull no matter how well you do everything else.  A quick check for this is to take the mainspring out, pinch the lock plate nose in the vise with the tail straight up, cock the lock and very slowly trip the sear. If the hammer raises upward  even a little bit before it drops, you have a notch / sear nose geometry issue.   

[WKevinD]

Ian, I think your observations are correct. It looks like the whole drilling template was rotated up causing the need to "wallow out the plate" and shifting all other components up in too high a position causing that preload.
I do have plate to spring clearance and I polished and relieved the sear spring to be sure of it. I can see a hairline of light when held to a lamp.
Closing the gap, annealing, hardening and re-tempering will wait until I get the replacement sear spring from L&R. I don't trust my abilities with springs beyond polishing and slowly removing material.
Yes it was a new lock (TOW) and before this was completely unfamiliar with it.
I'll check the notch/ sear/ geometry.
Kevin

[rich pierce]

The sear arm is quite high above the lockplate lower edge, supporting the idea things got rotated a bit.

[Bob Roller]

NOW it's clear. That lower limb of the sear spring is too far back and
exerting unneeded pressure on the sear .Quality control is definitely
a problem here.I have used these plates with another hammer on
a group of locks for Helmut Mohr in Germany and still have 4 to finish
for him long with a Swiss styled caplock for a Weber&Reusch (Veber und Roysh)
31 caliber pistol.This goes back to 1978 when he was using a modified
T/C Cherokee lock remodeled externally to give a Swiss look.The Schwartzpulver
Abteilung**Deutsch Schuetzen Bund told him the days of the coil spring locks were over and no more
guns with coil springs would be allowed.Gunter Stifter told him about the work I was doing and about
poor sales in America on gun locks.A sample was sent to Mohr and it kept my shop going for
quite a while from his orders alone.I enjoyed making locks and did other things like car parts that
could be done on common equipment.I found that there was a good interest in a shop that did
NOT tell callers "You have to buy 50"of whatever.I told a Packard parts man that I can't make less
than one of anything.He wanted bronze bell housing bearings for the Packard Ultramatic and he
bought 12 at once.Stator supports for GM 350 to recondition were another good item.Simple,easy
job for sure.I also made special tooling for a transmission shop that specialized in rebuilding
front oil pumps for a Japanese car that is still popular.I had a hard time teaching one of those
rebuilders how to read a depth micrometer to a critical depth.
Enough for now.

Bob Roller
** Black Powder Division of the German Shooting Association.

[P.W.Berkuta]

Sear spring and sear.
The "dirt" is inletting black used to make sure there were no hang-ups.
Kevin

From what I am seeing - the sear spring is your problem - the arm of the spring that is resting on the sear has no room to "flex". When the sear is being tripped it starts to compress the sear spring lower arm and then the spring contacts the top of the sear all along the springs surface which in turn "stacks up" the spring and stops the springs compression.