How do you lighten a single trigger?

[recurve]

I had a new tumbler put in a lock now the trigger seems  heavier than I would like. How can I safely lighten the trigger pull on single trigger?

[rich pierce]

Not easily. Usually you’ll need to re-position the pivot pin.

BUT if your harder pull only occurs with the new tumbler it is possible the full cock notch is at a bad angle that traps the sear nose. The angle of the notch should match a radius from the tumbler axle to the notch edge.

[Daryl]

Exactly - if the pull is harder with the new part, the geometry (or engagement) has changed.

[Pete G.]

Polish the top of the trigger where it contacts the sear.

[Scota4570]

1.  IF the the hammer is being cammed back by the sear you can alter the angle of the sear and tumbler to be neutral.  The new angle will follow the arc created by the sear nose on it's pivot screw.  The sear and the notch need to mate 100% ( or real close).  Judge this with with cold blue or marker pen.  Never round the sear nose or tumbler notches.  Retain the original depth of engagement.  I now do sear and tumbler work with diamond laps.  The lap is jigged as is the part being worked on.  No sear and tumbler notch angle work should be done free hand.   I do a single strop of 2000  grit  on the nose of the sear to just break the wire edge on the nose.  Same with the tumbler notch.  I finally strop with rouge in leather, just a couple of strokes.  A properly set up lock will reset to full sear engagement after a partial pull.   

As and aside I just examined a rife of mine with a top quality lock.  The hammer creeps forward when you move the sear.  This is overcome with a heavy sear spring.  This  is wrong and unsafe, I will need to rework the angles.

2.  Assuming correct sear and tumber engagement, you can remove material from the sear spring to lessen the pull. 

3.  Moving the pivot pin will increase or decrease the trigger pull.  A longer pull will be lighter.  A shorter crisper pull will be heavier.  A trade off. 

4.  Never touch a sear or notch with a file or dremil tool.  IF you can file it it is too soft.  Dremil tools ruin parts fast. 
 

[D. Taylor Sapergia]

Recurve:  I have no idea what your skills are.  You need serious attention to detail to make the alteration on the tumbler, not to mention the correct tools.  The seat of the full cock notch must be at ninety degrees to the axle of the tumbler, as does the sear's nose.  Also, the depth of the full cock's engagement is critical, both for a light crisp trigger break, and for SAFETY.  So, in one sentence, to lighten the trigger pull by adjusting the lock, reduce the sear's engagement on the full cock notch.  All bets are off 'til I see what your abilities are.

[Scota4570]

I would proceed with caution when reducing the depth of a full cock notch.  Several problems can come up.

First is safety.  You need adequate area of contact between the sear nose and the full cock notch .  IF you reduce it too much the parts will not last because there is too much pressure per square inch.  The steel will not be strong enough.  I have seen this on brand new modern locks that have a knife edge on the sear nose and a shallow notch  ...very dangerous.  Accidental discharge is possible when it fails. 

Another issue that comes up is that the sear nose crashes into the half cock notch if you reduce the full cock notch. 

Another way to get the same result would be to put a bevel on the underside of the sear nose.  Sears are easier to replace when it goes wrong.

Excessive pull is mostly due to the angle of the full cock notch causing the hammer to cam back.  Once it is corrected to not cam back the hammer, the pull is as light as it can be made safely, regardless of the depth of the notch.  Reducing the dept of the notch is a way to cheat by eliminating the long cam back. 

The full cock notch must hold the hammer with no sear spring installed. 

The depth of the notch determines creep.  If the notch and sear are properly finished, and there are no burrs it will feel good and it will be safe, regardless of the depth of the sear notch.   

Once the hammer does not cam back you can reduce the sear spring if needed.  Be sure the sear spring nose is as long as possible for a smooth non stacking action. 

Really, attempting to get a safe, creep free, light pull is impossible to do safely with a single trigger.  That is why they used set triggers.  That is why we have over ride multi lever triggers in modern  bolt actions guns.  The old military triggers with cam lumps were safe because there was plenty of engagement.  Trying to make a crisp short trigger by reducing sear engagement is a similar recipe for disaster. 

I'd be interested in a similar long 2-stage trigger pull scheme on a ML.    A 5# trigger that has a 4# take up and a 1# second stage feels like a 1# trigger.  At the same time it is safe.   It might be possible to have a cam arrangement on the trigger in a plate.  A roller bearing on the sear lever?.  The cam could be arranged to get the long pull with a crisp wall at the end of the pull. 

Somebody must have invented it already because I rarely have original ideas in such matters.  : )


When I specified diamond laps before, I meant diamond sharpening stone made with diamonds bonded to a sheet of steel. 



 

[recurve]

Thanks for all the replies I've decided to leave well enough alone. I would rather have a heavy safe trigger than risk a unsafe rifle

[smokinbuck]

I'm not a gunsmith, or much of a builder, but have always been under the impression that if all else is good with a lock that the trigger pull weight on a single trigger is most dependent on the pivot pin location.
Mark

[Scota4570]

I'm not a gunsmith, or much of a builder, but have always been under the impression that if all else is good with a lock that the trigger pull weight on a single trigger is most dependent on the pivot pin location.
Mark

See item #3 of my first post.

The second post was dealing with the lock itself and modifying sear notches and noses. 

[gonetocamp]

Scota4570 regarding bevel on the underside of the sear nose. Do I presume correctly this would be done to reduce creep in the trigger pull; or shorten the length of the trigger pull; or both? I have stoned such a bevel on 1911 pistol sears to reduce creep. I am aware that this is a go slow and test frequently process.

[Scota4570]

It reduces the depth of engagement.  That shortens the sear travel.  That produces less creep.  It avoids compromising the tumbler.  It maintains the strength for the sear nose.  I am talking about a steep bevel, say 45*.  I would only do this if the tumbler notch was way too deep. 


That said it is not reducing the trigger pull in the best possible way.  The best way is to use appropriate angles, plenty of engagement, and a smooth finish.   

[gonetocamp]

Thanks Scota4570.

[longcruise]

I think leaving well enough alone is a good idea.   Give it time to settle in and it  might improve.  Even if it doesn't, if it still shoots well maybe it's just one of those little things to adapt to.

[Dphariss]

You need professional help. It's actually pretty complex to do right and too complex to cover in a post here. You need the sear nose and the notch "adjusted".  Maybe the sear spring as well. Its possible to have a very safe light single trigger. It also possible to have a heavy trigger that is unsafe.
Dan

[Dphariss]

Try putting a **light** coat of grease, GOOD EP stuff, on the full cock notch and the tip of the mainspring where it bears on the tumbler.
Dan

[utseabee]

I would take it to Brad Emig or someone who tunes locks. It's well worth the money spent.