Lock help - sear catches on fly

[pjmcdonald]

This is a Davis lock. When the set trigger hits the sear bar, the sear drops just enough to hang on the fly, in about the half cock position. In other words, the fly isn’t doing its job and allowing the nose of the sear to ride over the half cock notch. In fact, the sear catches on the fly.

Here are a few photos, showing both full cock and the tip of the sear caught on the fly. I took several, so someone might see something at a better angle.

I’ve tried stoning the fly. Made the problem worse. Broken one sear already. And replaced 2 flies.














Additionally, I’m using Davis double-set, double lever triggers. Front trigger works. Rear (set) trigger does hit the sear bar. I’ve tried a modified set trigger (made one), adjusting trigger placement, and adjusting the set spring. I think it comes back to lock geometry.

Bama, yes, this is the same one that was giving me fits in your class. Tried everything you showed me. Beyond my skill set at this point in my education.

Thanks for any input.

Paul

[Darkhorse]

I think the fly itself is perhaps a tad to long and may need to be fitted to the lock. Simple to do with a swiss file.

[smart dog]

Hi,
I agree with Darkhorse that the fly is too long and needs to be stoned smaller.  Perhaps you already checked these things off but make sure the sear screw is not binding the sear and make sure the fly can move freely and is not bound by the bridle. Given the length of the fly, I suspect you really feel the sear riding over that fly when pulling to full cock.

dave

[EC121]

Looks like the sear nose is hitting the straight part of the fly instead of the slanted part.  That will stop the tumbler and break the sear nose.  I would put more slant in the fly on the side away from the halfcock notch.  This will let the sear nose hit on the slant.  Try rounding the corner of the fly a little to reduce the  sharp angle.  Go slow.  It shouldn't take much. 

[Bob Roller]

The sear HAS to be hitting a vertical edge to stall the hammer fall.
The "fly" is simply an intercepting cam and it's now creating a second full cock position
and should be easy to fix.
Bob Roller

[smart dog]

Hi,
Yes, the sear is probably stopping the tumble dead in its tracks hitting the straight edge of the fly.  No wonder it is breaking.  The fly is too long and needs to have the rear slant intersecting the radius of the tumbler notch. It probably works when the trigger is pulled unset but not when the sear is just tapped by the rear trigger lever.  I used that lock on a recent English rifle.  It had to be completely worked over to bring it up to any standard approaching those great English locks.  On mine, the toe of the frizzen only touched the roller on the inside edge causing the upper leaf of the spring to angle outward and the snapping action to be very poor.

dave

[Dphariss]

Fixing a fly right takes more time than I have. Put a longer angle in the fly so the sear catches the "ramp". May need considerable reshaping, its relative since its a tiny part. BUT be sure that fly kicks forward AFTER the sear is behind the full cock notch or the rifle is VERY DANGEROUS.
Dan

[rich pierce]

All good advice and I agree with it 100%. But that you’ve tried multiple flies leaves my head scratching. So it’s not that one fly was “off”.

What does the sear nose look like now? Specifically where it interacts with the fly?

[Robby]

If you have tried two flys and modified another, my thought is the tumbler has been turned or ground too far down at the point where the fly projects from its slot, allowing the nose of the sear to hit the flat side. At this point I would try another tumbler.
Robby

[smylee grouch]

Could it be that the sear itself is too short? Like maybe it has been worked on or is the wrong sear in the first place.

[pjmcdonald]

Thanks for the suggestions. First fly, I took too much off. Tried two other flies straight from Davis. Have not touched tumbler. First sear, tip broke hitting fly in testing fixes. New sear straight from Davis. Will try to reshape another fly.

A better pic of what is happening.

[pjmcdonald]

Another thought is that the half cock notch was cut too deep. Spring pressure on the sear ensures the sear nose (or tip) follows the tumbler cam. As the nose is lifted out of full cock by the trigger hitting the sear bar, the nose drops back dives down toward full cock notch. I’ve been looking at it under 10x magnification. Even if I take fly all the way down to match tumbler, angle is wrong. Tip is still going to wedge into a corner.

[EC121]

You need to eliminate the corner by extending the ramp.  The fly needs to have the corner at or above the edge of the tumbler.

[Jim Kibler]

The geometry I see doesn't look too good.  You can probably get it to work by shortening the fly and adjusting the angled ramp, but things could have been designed quite a bit better.

Jim

[smylee grouch]

It almost looks as though the sear spring is too long and putting is force on that boss of the sear and the top of it too. I dont know if that is causing the problem but the end of that spring could be stoned ever so little as to only put its force on the top of the sear right at that juncture if that is the case.

[pjmcdonald]

Thanks all for the input. Success!

It took considerable reshaping of the fly. In order to get the ramp correct, I also had to slightly shallow the half cock notch. Checked for safety and half cock still positively engages. Also slightly weakened sear spring to allow a little more “float.” Again, checked for positive engagement in both half and full cock. Three swipes of the sear nose on 4000 grit hone to polish it. Finally, adjusted triggers to engage a little better.

Still need to adjust triggers to lighten pull weight. Currently pretty stiff - about 10 lbs. From many years with service rifles, I don’t mind a little on heavy side but these are still too heavy.

Thanks again for input. Think I needed most the positive reinforcement. I was so frustrated I wanted to scrap the whole lock.

Oh forgot to add the most important steps - blood sacrifice and communion whiskey! 😁

Paul

[Acer Saccharum]

I'm a little late to the party, but here's a sketch. When you pull the hammer to full cock, you want the fly long enough to have the sear nose to drop into the full cock notch.

You don't want to hear 'click-click', which is the fly flipping forward, then another click as the hammer is pulled further back, which is the sear dropping into the full cock notch. If you lend the gun to someone, they might think at the first click the gun is cocked, so they let go, and the gun fires accidentally.

[pjmcdonald]

Acer,

Thanks for drawing. That is essentially what I did. My tools are pretty crude for this sort of detail work. But I managed it.

Thank you,
Paul

[smart dog]

Hi,
Here is a post I made a while ago about this locks.  I describe the things I needed to do to make it work as it should.  I eventually also added a sole to the frizzen to thicken it and add mass.  That really turned it into a sparker.
https://americanlongrifles.org/forum/index.php?topic=53413.msg534024#msg534024

dave

[Joe S.]

Looking similar to L&R's fly can someone explain why these things are not made a little beefier, like double the thickness to engage more metal all the ways around.I'm far from an expert in all things muzzleloader but it just looks like an accident waiting to happen.

[rich pierce]

Looking similar to L&R's fly can someone explain why these things are not made a little beefier, like double the thickness to engage more metal all the ways around.I'm far from an expert in all things muzzleloader but it just looks like an accident waiting to happen.

It’s a stamped part. Probably cost or equipment is a factor.

That being said they can work great for a very long time. Like 40 years and counting.

[pjmcdonald]

Dave,
Thanks for the link. Now that I’ve got it to function basically, I’ll have to see about improvements. God help me, I could get into fiddling with locks. Fascinating mechanical problem.

Paul

[Joe S.]

I get all that,I have noticed that in extreme cold I had to change to a different lube for that part as the one I used would thicken up causing the fly not to engage properly on occasion. I would assume the same would happen if one got a little lax with proper cleaning/lubricating as well.My thumb doesn't leave the hammer till I feel/hear that thing click securely into half cock position,common sence I'm sure.Just my opinion that a thicker, heavier fly would work better than that dinky little chip of metal.

[EC121]

A thicker fly means a thicker tumbler and bridle to keep the same amount of notch engagement area.  The means more wood removal to inlet the lock.  The new Rice lock has the fly in the center of the tumbler for less wear and tear on the sear nose.

[Joe S.]

Wouldn't deepening the channel to accommodate a thicker fly work without doing any other modifications.