Guidance To Reshape Sear Spring

[jm190]

Hi All,
   This sear spring is in the lock for a Brown Bess kit that I have. The shape is off and the trigger pull is horrible. I've attached a picture so you can see how the geometry is off. As you can see it's not close enough to the pivot point and it is actually gouging the sear.



   I believe the gap at the bend has to be opened a little and the leg to the sear straightened a bit. I've never attempted to reshape a spring so I'm in need of a little guidance.

   I did find this discussion and I think it points me in the right direction. https://americanlongrifles.org/forum/index.php?topic=3171.msg30127#msg30127

   This spring is 1/16" of an inch thick; will heating it till it turns blue be sufficient to bend it? I'm thinking will it require annealing, etc. to reshape it. 

   I have MAPP, propane, and digital temp lead pot if any of this is what you would suggest to use.

   Looking forward to hearing your guidance to accomplish this.

Thanks!
John

   

   

[rich pierce]

A couple things come to mind. The sear spring should be softer than the sear arm and shouldn’t gouge it.

I’m not thinking you’re going to gain enough length by re-forming the sear spring. But you could try. To change the sear spring shape you will need to heat it to red hot. Tempering temps won’t do it. Then you’ll need to re-harden it by heating to bright red and quenching in warm canola oil or other options. Then it needs to be tested to see if it’s glass hard. Then it needs to be tempered. Lots of ways to do that. I use molten lead with a thermometer and rest it on the molten lead at 1100 degrees for 10 minutes or so then allow to cool. Others place a hardened spring in a tuna or sardine can and cover with motor oil and burn the oil off. Messy but works great.

I’d probably buy or make a new spring and also check the hardness of the sear arm, and re-harden and re-temper the sear. Sear springs are the easiest springs to make and seldom fail as they don’t get compressed very far in use.

[Bob Roller]

The lower limb is too short and if it's gouging the sear that is the real problem.If you have no experience with making or altering springs then find someone to harden the top of the sear after it has had the gouged are removed to the extent possible.I have had no experience with any big locks but the same thing can happen to to the small ones and I have made a LOT of these.
Bob Roller

[Daryl]

These responses all seem spot-on to me.
Too  muskets didn't need or have good trigger pulls throughout history..
I fully understand the desire for a decent trigger pull.

[mgbruch]

Start with the simple things first.  Round and polish the end of the sear spring.  Then polish the sear where the spring bears on it.  Both surfaces need to be polished anyway... so start there.

[Dphariss]

Like Daryl said they were not designed to have a trigger pull. Military did not WANT a nice trigger pull. Causes ADs when people are under stress. Just a fact. And many of the people making these parts are just making a part with no actual contact with the finished mechanism.
I personally would case harden the sear, then draw it back the 375-390 degrees. Perhaps to dark straw color infront of the screw hole.
The spring needs to be flattened or rounded where it bears on the sear, i.e. any sharp edges cutting the sear removed, this alone will help. Then thin it to a taper thinnest just short of the contact with the sear and thickest at the bend. “Buggy Whip” taper. This will lighten the spring and should improve the trigger pull. This can be done with one of the sanding drums on a dremel tool. Use the finer grit. Smooth taper no edges across the spring. These cause breaks.
DO NOT THIN TOO FAR. If you do pitch it in the trash. Spring needs to be strong enough and lively enough to make nice “clicks” as the lock is cocked.
You should be able to reduce it by 20-30% or so at the sear end. This is a carefully grind, cool the part in water, try, grind etc operation. DO NOT OVER HEAT. Thus the water for coolant.
Use a high tech modern gun grease on the bearing surfaces. Just a small amount. Excess is a waste and will get into the stock wood. I use M Pro-7 grease on ML sear noses and where parts rub on springs ect.

[Jim Kibler]

As others have mentioned, it really needs to have the contact point closer to the sear pivot.  This requires a new spring or moving the existing hole.  The spring is also probably a little heavy.  You can very easily thin the lower limb.  In the absence of moving the hole or a new spring, you could try just thinning it.  This might be good enough to get you where you want to be.  It's a very easy thing to try.

Jim

[smart dog]

Hi Jim,
I fix this all the time on Pedersoli and Miroku Bess locks.  It appears you have a newer Pedersoli with the stupid curve in the sear.  I assume you can harden and temper the spring?  Heat it red hot and straighten the lower leaf.  Then open the bend just a tiny amount.  The lower leaf will be much closer to the sear pivot and approach the top of the sear at a lower angle making less abrupt contact.  Harden and temper it and then check it.  If still too heavy grind the bevel on the lower leaf a little bigger.  Also polish the end of the spring and the top of the sear.  It does not need to be a mirror just nice and smooth.  The photo below shows a Bess lock with a good fitting sear spring.


dave

[Gaeckle]

Out of curiosity, whose lock is that anyhow?

If it were mine,  I  would simply heat, re-bend, mount it up and check for fit. If it fits good I would then harden and temper.

You should be able to file a spring with a good file to reduce thickness

[kutter]

If you heat the spring up red hot...
Straighten out the entire lower arm....it will have more than enough length to reach the pivot point.
That current Arch takes up a lot of length.

Then open the V in the spring itself to bring the tip into position with the Sear a bit of pre-load.

File/polish the spring a bit thinner perhaps on the lower arm.

Polish over all.

Re-heat Red and harden

Temper in a Lead Bath at 730F
 

[jm190]

First of all thank you all for your input. I'm going to address your suggestions in order from first to last except to say up front this is a Pedersoli lock.

Rich and Bob: upon further examination the sear appears to be a metal injection molded part by the circular impression on the underside, minor grinding marks and a mold line on the arm. I don't know if you can harden MIM metal.

Daryl: I don't don't plan on experiencing the stress of defending against attacking Native Americans or rebellious Colonists so I'd like something lighter than a 12 plus lb. trigger pull.

mgbruch: Polished both as you suggested including removing the sharp corner on the end of the spring. No real improvement.

Dphariss: I think you're correct; it appears each individual part was made in a separate shop and assembled by someone down the street. There are several other minor issues to address but this is the biggest. I have a spare coming from DGW should I manage to bungle this little project. My Dremel is waiting for me on my workbench. My goal is as you suggested to straighten and thin as required.

Jim: I'll start with straightening and thinning.

smart dog: Stupid wasn't the word I used when I saw the sear spring. I don't know much but I knew it wasn't a good geometry. It is a new Pedersoli and there's a first time for everything including hardening and tempering a spring. Thanks for an image to work towards.

Gaeckle and kutter: Pedersoli. Any suggestions on time in the lead bath?

Again, thanks to all of you for confirming I was heading in the right direction and the tips and techniques on how to get there.

John

[smart dog]

Hi John,
I fix many of those locks and the sear spring is very often an issue.  Let me give you some help with heat treating the sear spring.  After annealing it and shaping the lower leaf and bend, then polish up the spring a bit and heat it bright red with a torch and quench in about 3 cups of canola oil.  That will work for Pedersoli springs, it does not work for springs on India-made guns.  Then clean up the spring until it is shiny clean metal.  Very slowly heat it with a propane or butane torch constantly moving the heat around.  The spring will turn pale yellow, then bronze, then purple, then deep blue and then a light blue color.  Keep heating a little longer after it goes to light blue and stop.  Let it air cool slowly.  That should do it.  Let me warn you, however, about lightening the trigger pull too much.  Your lock does not have a fly detent to prevent the sear from catching in the halfcock notch of the tumbler when fired. The lock requires a substantial trigger pull so your heavy finger pressure keeps the sear away from the tumbler on firing. A light pull risks allowing the sear to engage half cock on firing.  The diagram below explains why there can be a problem.   
 


The length of line C-A (from the spindle center to the lip of the half cock notch) must be equal to or less than the length of line C-B (from spindle center to lip of full cock notch).  If it is greater, the sear risks hitting the half cock notch upon firing shown in the next diagram.




Your Pedersoli tumbler likely will violate those requirements and risk catching half cock on firing. I can usually get trigger pull down to 4-5 lbs on Pedersoli Bess locks by modifying the sear spring (as you intend) and polishing the lock internals as well as the top of the trigger lever.  However, to go beyond that, I have to reconfigure the tumbler notches and that often requires welding.

Good luck and I hope this helps.

dave

[J.D.]

John, a word of caution when thinning that spring. Thin from the  width and not the thickness. Thinning from the thickness will reduce the strength of the spring 7X more than removing the same amount from the edge of the spring.

[Leatherbark]

Before I would apply heat, I would round the end of the sear spring and polish it like a mirror.  Then polish the top of the sear arm so they will have some "give".  Then narrow the width of the sear spring a little.

Bob

[jm190]

Success! 



Last night I straightened the lower leg and expanded the V using lines I drew on the lock plate as a template. Only had to make one correction by closing up the V slightly. Left just enough tension on the spring that with the cock down and sear in place I could push the tab on the spring into the slot my fingers. Reshaped the tip of the spring where it contacts the sear and then thinned till I didn't break sweat moving the sear.  Straightening the lower leg moved the contact point about  1/16" forward towards the pivot; not ideal but the trigger pull is MUCH better.

This morning I assembled the lock and installed it in the stock to check for trigger pull and what Dave cautioned about too light of a trigger pull on lock without a fly. The trigger pull is now firm but very smooth and the sear never caught the tumbler in half a dozen pulls. Then I followed Dave's directions for heat treating the spring and actually saw all the colors exactly as he described! Polished the spring and all the necessary contact points, reassembled the lock and installed it back in the stock for a final ops check which was good!

Many thanks for the support and all the advice!

Take care!
John

[rich pierce]

Great job!

[smart dog]

Hi John,
Well done indeed!  I am always excited when someone figures out how to help themselves in these situations.  I have way tooooo much experience with these locks from early production to the latest versions. I'll offer up a few tidbits.  Often on the later Pedersoli locks, the hole in the bridle for the tumbler is oversized.  I believe it is because the tumbler holes in the plate and bridle are not on center so they drill the bridle hole a little larger to compensate. The resulting wobble in the tumbler can create a mushy feel to the trigger pull.  The sear pivot screw also often pinches the sear between the plate and the bridle when fully tightened.  I often correct these flaws by welding the bridle hole shut and redrilling it for the tumbler as well as making a replacement sear screw with proper threading so it cannot pinch the sear.  If your trigger pull is fine and the lock works satisfactorily for your purposes just ignore those issues.  The Pedersoli and Miroku locks are significantly smaller than the original Brown Bess locks.  This is particularly true of the frizzen, lock plate, and flint cock.  Consequently, I urge you to use flints that are smaller than historical musket flints.  Use 7/8" to 1" wide flints not the big musket flints.  Big musket flints are wider than the battery face on the frizzen and often just contact the edges.  Smaller flints will produce more sparks particularly as the face of the battery gets worn.  Polish the upper surface of the frizzen spring (traditionally called "feather spring" ) where the frizzen rubs against it. Then apply grease on every surface over which something slides (e.g., toe of tumbler) and lightly oil every surface that rotates (e.g., sides of the tumbler). 

dave
 

[Bob Gerard]

I love happy endings 
It's a wonderful forum with so many guys here who really know how things should be done and help us out.

[Dphariss]

I write the newsletter for The Montana Historical Gunmakers Guild and just did a column on sear nose and notch angles. But I went with the safer idea of working on the spring first.
The sear notch and sear nose should not have an identical angle. The notch angle should have, IMO, an angle that will “trap” the sear nose slightly. Just enough that the sear will stay and position under mainspring tension with no sear spring pressure. This makes the lock safer. But it need not have a “hook” stops the sear from smoothly coming out of the notch. It is not unusual to find such things.
If the angles of teh sear nose and notch are exactly the same the lock may be safe enough but it may result in a long “drag” to get the seat out of the notch. Especially if the trigger pivot is too close the the sear contact point.. If the angles are slightly different as show in the “ok” drawing the sear will stay in position until some pressure builds and then tend to “pop” out of the notch giving a quick “break” with no feeling of movement of the trigger.

The 1/2 cock issue. I used to work at a place where the machinist/took and die maker owner had “fixed” the lock by greatly deepening to full cock. If the notch was brought down to the proper depth the sear would hit the 1/2 cock. So to fix this on the rifles I did for me I added metal or a screw to the tumbler to stop the seat from going to deep.
As a side note I used to do gun work for a country music singer. I rebuilt a hammer on a pistol and it workd fine, for me. Sent it off and he immediately called about the trigger hitting the 1/2 or 1/4 cock. I told him it had worked fine for me.. He said “you are not a guitar player”. He could stop the trigger when the sear cleared the notch, no over travel.  He sent it back I welded up the full cock, again, and recut it. The difference was very slight. But… So this is a very real issue if one starts to play with notches on the tumbler.
This is my two cents worth. To start playing with the full cock notch requires the proper tools and some thinking.
Fly/detent…
You should not rely on the fly to compensate for a “goofed” full cock notch. Yes it will “lift” the sear over the 1/2 cock.
HOWEVER, it can cause wild variations in hammer fall if too much mainspring energy is used doing this. To this day there are dedicated unmentionable target rifles of 19th c design with NO 1/2 cock for this very reason and it was done “back in the day” as well. And I have done this. One in particular is very sensitive to this and the resulting accuracy “errors” are so extreme as to be hard to believe. While it may not cause ignition issues with a flintlock or even a percussion it can cause damage to the sear nose. So all these things must be balanced and work smoothly together. And there were late percussion era locks with no 1/2 cock. Cheaper to make…..

[rich pierce]

Good diagram and explanation.

[Bsharp]

For best results, the two pivot angles should form a 90 degree surface for the sear.