H&A underhammer trigger problem

[theDuck]

I put together a H&A underhamer using Deer Creek hammer and trigger. The problem is I keep breaking the sear on the trigger. I talked to the nice lady at Deer Creek who says that I have to continue the pulling the trigger after the sear lets the hammer go to avoid breaking the sear. I do that and it the hammer still catches and breaks the sear on the trigger.
I'm wondering if the hole spacing for the pins holding the trigger and hammer are too close. They are 1.1" centre to centre. Can someone who has a H&A underhammer do me a favour and measure the centre to centre distance of the pins on the non screw slot side of the action. That would give me a place to start. Thanks.
If anyone has built an underhammer using Deer Creek hammer and trigger parts what distnace did you set the pin holes?

 

[Ian Pratt]

sometimes this can be fixed by rounding off the outside edge of the half cock notch, works if the two moving parts are just contacting at the outer edges. If they are hitting more square, the tip of the half cock notch may need brought down in height slightly to make clearance - if that is taken down too far it becomes next to impossible to cap the gun at half cock.
Depending on what work is done re-heat treating might be needed afterwards.

 

[Tinker2]

“Can someone who has a H&A underhammer do me a favour and measure the centre to centre distance of the pins on the non screw slot side of the action.”

I checked three of mine, a rifle, pistol, and shot gun.
Two were 1.1 and one was 1.087

No matter what I did, springs out, the triggers on any of the three I checked would not have hook on the half cock notch and broke the trigger.

Take the spring off and work the action, it may show you what’s wrong.



Tinker2

 

[theDuck]

Thanks. I shortened the half cock notch and will see how that works. If not I'll order more triggers and keep trying. I had left the half cock notch as cast. Maybe that is the difference. Anyone else with H&A's have ideas?

 

[BS]

I also try to angle the front of the sear and angle and shorten the half cock.

I make the so that as you let the hammer down, it will not hook, unless the trigger is released.

 

[Ed Wingenroth]

OK !!!

Here I go again but I gotta ask !!!

What good is the half-cock on a U/H ???

Ya never charge the cap until your ready to fire and until that, ya leave the hammer down on the empty nipple...

Ya think ??? :surrender:

 

[theDuck]

Picture is worth a thousand words BS. Thanks for your help.

 

[MRW]

Well i disagree to point here How many hunt with a capped nipple on a traditional design like TC Hawken or Lyman GPR do they immeadiatly uncap them if they turn then upside down I doubt it! While I don't agree with marching all over woods with a capped gun on half cock I can't imagine anyone setting on a stand with a capper at the ready position ready to cap that nipple as soon as a trophy 8 pointer walks into range or trying to stalk a deer using the same logic. I think one has to approach this problem the same as with a loaded cartridge gun if you are crossing fences, ditches etc. where you don't have good control of your gun then yes uncap it just as you should unload your cartridge gun OR make up a positive hammer block like this BETTER then a half cock and about 90% foolproof and will allow you to carefully carry one capped.

 

[MRW]

Forgot to mention that gun doesn't have a half cock just full cock with a hammer block as the safety

 

[Ed Wingenroth]

Great Idea !!!

I hate getting into debates about safety but in this case, my only point is the U/H design just begs for something like yours has”¦ Good job !!!

Apple’s and Oranges to compare a U/H “cap” to a cartridge gun for safety.. A cartridge won’t fall off leaving the powder to run down your leg”¦..

Don’t think I would hunt with a U/H anyway, Target only, for me”¦