What causes mushy trigger feel?

[Tom A Hawk]

I decided to install a single trigger in my current Lancaster build since its primary use will be for deer hunting and a gloved hand is often needed. After installation, I'm noticing a very slight mushy, spongy feel leading up to a clean sear break. It's barely perceptible, but its there and its not sear creep. This trigger feel is not evident at all in my previous single trigger build which is of similar construction. The previous Lancaster build has an excellent trigger pull and I tried to duplicate the trigger placement in the new gun, however its feel is not the same. This spongy feel is also present in my TVM fowler and to a much greater degree. Any input regarding the cause and any cure for this characteristic would be appreciated.

 

[BJHabermehl]

I decided to install a single trigger in my current Lancaster build since its primary use will be for deer hunting and a gloved hand is often needed. After installation, I'm noticing a very slight mushy, spongy feel leading up to a clean sear break. It's barely perceptible, but its there and its not sear creep. This trigger feel is not evident at all in my previous single trigger build which is of similar construction. The previous Lancaster build has an excellent trigger pull and I tried to duplicate the trigger placement in the new gun, however its feel is not the same. This spongy feel is also present in my TVA fowler and to a much greater degree. Any input regarding the cause and any cure for this characteristic would be appreciated.

Trigger geometry is allways a bit of a compromise. A high pivot point yields a lighter pull, but reduces “crispness” somewhat. Especially if the pivot is a bit close to the the sear arm. If the pivot pin is even 1/6 inch further foreword the trigger finger feels less take up, but at the price of a slightly heavier pull. Allways there is some compromise, unless something else is adjusted too. Personally I’d rather have a bit of take up than have a trigger that is scary during our cold weather late season here in Pa. with cold impaired fingers. BJH

 

[Sam squanch]

Mushrooms are growing in the lock cavity. Better clean them out.....

 

[EC121]

Polish the fullcock notch and sear nose. You are feeling the sear pressure load up before the sear nose breaks out of the notch.

 

[Scota@4570]

Could be slop in the sear pivot hole/ screw. Same for sloppy tumbler fit. Super deep full cock notch (unlikely). Could be the trigger pivot is close the where it hits the sear bar.

There is a trade off on the pivot point of the trigger. Close, say 1/4", means more travel and a lighter pull. A loner pivot, say 1/2", will be crisp but a heavier pull.

All that said, I'll take a smooth long trigger pull any day. It means you have good engagement between the sear and tumbler (usually). And, that is an important safety feature. I now appreciate Mauser type double hump triggers. If the first stage is smooth at say 4# and the final step is a wall with no creep the breaks at 5#, you have a match grade trigger. The second stage feel like 1#. That is an excellent shoot able trigger, and it is a safe trigger.

Having a single stage, breaks like glass with no take up and no overtravel, can not be done safely with these types of locks and triggers. It can be done with a modern override trigger, this is not that. Do not expect to be able to achieve it.

 

[Col. Batguano]

What Scota@4570 said. A light "break like glass" trigger is a set trigger, or you can sort of have both with a Double Action Single Set Trigger. The only one I've found is a Davis, and I wasn't particularly impressed by it. Installing it was a real nightmare.

Wondering out loud now; I wonder if it would be possible to engineer in a modern override trigger that could be made to work beneath the exterior of a sidelock gun? I mean, they've done coil springs inside of wheel locks. Nobody would notice. We use modern glues and metallurgy all the time, so (if you want to) why not put a super hot rod engine under the hood of your Model A Roadster?

 

[Scota@4570]

"Wondering out loud now; I wonder if it would be possible to engineer in a modern override trigger that could be made to work beneath the exterior of a sidelock gun?" I've thought about that quite a bit. I am sure it could be done. My best solution would be to make the lock with the sear normal except deliberately set up the angle so that is does not hold full cock. The traditional sear would not have a tail for the trigger to press on. Then Install a second sear with the shallow sear engagement and minimal movement such that it engages the tail of the first sear. The pivot point of the primary sear might have to be moved. The tumbler would require a fly.

 

[Col. Batguano]

That's really cool. Of course, in a flint lock it'd be like trying to improve the engine performance of your 1929 Model A by adding gold plated spark plug contacts

 

[GoodRabbitPilgrim]

Trigger Creep is the term you're looking for. May help in finding more info

 

[BV]

"Wondering out loud now; I wonder if it would be possible to engineer in a modern override trigger that could be made to work beneath the exterior of a sidelock gun?" I've thought about that quite a bit. I am sure it could be done. My best solution would be to make the lock with the sear normal except deliberately set up the angle so that is does not hold full cock. The traditional sear would not have a tail for the trigger to press on. Then Install a second sear with the shallow sear engagement and minimal movement such that it engages the tail of the first sear. The pivot point of the primary sear might have to be moved. The tumbler would require a fly.

I suppose one could improve on a simple lever, but all you have then is a complicated lever.

 

[Artificer]

I decided to install a single trigger in my current Lancaster build since its primary use will be for deer hunting and a gloved hand is often needed. After installation, I'm noticing a very slight mushy, spongy feel leading up to a clean sear break. It's barely perceptible, but its there and its not sear creep. This trigger feel is not evident at all in my previous single trigger build which is of similar construction. The previous Lancaster build has an excellent trigger pull and I tried to duplicate the trigger placement in the new gun, however its feel is not the same. This spongy feel is also present in my TVM fowler and to a much greater degree. Any input regarding the cause and any cure for this characteristic would be appreciated.

Hi Tom,

That "Mushy or Spongy" feel comes from one or both of the following items, normally.

The full cock notch should/must be perpendicular to the center of the tumbler and it must be SMOOTH so as not to cause the mushy feeling. I smooth really rough ones with a medium India Stone and less rough ones with a fine India stone THEN polish with a hard arkansas stone. The Sear face may require this as well, though if the Sear Face is of a noticeably different angle than the Full Cock Notch Face when cocked, that will also cause a mushy feeling.

Another thing that WILL cause a "Mushy or Spongy" feel, even with a smooth and properly angled full cock notch, is if the Leg of the Sear is hitting/jamming into the wood inside of the lock mortise. This is a VERY common problem on Military BP guns, by the way. If you grease up the sear leg, assemble the gun/rifle and dry fire two or three times, it will transfer the grease to where it hits the wood inside the lock mortise. Just clear away where it hits, try again and if you didn't clear enough, the grease mark will show you where to clear more.

If the trigger pull seems to get HEAVIER as you pull it, the full cock notch is probably angled backwards, which means there is more pressure and trigger weight as you finish the trigger pull before the sear releases.

If the trigger pull gets LIGHTER as you pull the trigger, this is BAD JUJU as the full cock notch is angled forward and really is unsafe.

Other questions or perhaps something I wasn't clear about?

Gus

 

[ApprenticeBuilder]

In my case it's the result of fat fingers

 

[Col. Batguano]

Isn't a trigger creep a politician that wants to take your guns away?

 

[Scota@4570]

That's really cool. Of course, in a flint lock it'd be like trying to improve the engine performance of your 1929 Model A by adding gold plated spark plug contacts

Thanks.
Wheel locks used a sear that was pushed out of of the side of the wheel. It was prevented from doing so by an arrangement that worked like a showed above. I bet it was tried at some time in history on a flint lock or caplock.

 

[Col. Batguano]

I've been down the road inventing things I don't know how many times. Most of the time, I find that if I can think of it, somebody else can (or has) too. But occasionally, I've come up with things that are truly unique as a way to solve a problem. Getting it to a commercial application stage (so that it is financially viable) is the next step, and the hard part. And, with all the industrial espionage that happens (and foreigners being renowned for not respecting US Patents), a patent is only as good as your ability to defend it.