Win. 66 / 73 hammer hanging up on the half-cock notch?

[hornady308]

I've got an Italian reproduction model '66 that fires 100% of time when firing quickly, but only 50% when truly squeezing the trigger as slowly as possible. I use Federal large pistol primers since they are supposed to be the softest, and make sure that I am seating against the bottom of the pocket. I've ruled out every other problem I can imagine, except for the possibility of the hammer momentarily hanging up on the half-cock notch. I've attached three photos showing the area and would appreciate any suggestions. I'm not a SASS competitor. I just like shooting old guns and would like to solve this problem so I can use this 45 Colt for hunting in close quarters.

[Bent Ramrod]

Did you buy your rifle used? Just a WAG, but if somebody tried to pull the trigger with the gun on half-cock, and stopped short of actually breaking the sear notches, it could result in bending the half-cock notch wider and bending back the trigger sear. This change in geometry would allow the half-cock notch to catch the trigger as it comes down, if you don't pull the trigger back far enough.

Alternately, shortening the trigger sear too much in an attempt to lighten the trigger pull could also result in the sear not being far enough out to miss catching the half-cock notch.

i don't know how well things would bend or peen back/longer without weakening or breaking. A gunsmith could fit the hammer with a fly which would ride the notch away from the trigger on the way down, but allow engagement on the way back.

If the gun is new, I'd alert the manufacturer and let them handle the problem.

[square butte]

Did you check for excessive head space or frame stretch

[Deadeye Bly]

This is usually a situation where most of the trigger pull comes from the trigger spring and not from the friction on the mating surfaces of the trigger/sear and the hammer. With a good balance of the forces involved when the trigger breaks the finger pulls the trigger out of the way of the hammer half cock notch. If most of the trigger pull is the spring then the finger does not pull the trigger clear when it breaks. It looks as if the half cock notch in your hammer is cracked. I think you need the services of a good gunsmith.

[John Taylor]

When things are working properly the trigger should clear the half cock. There are a few ways to check to make sure the full cock is at the same distance from the pivot screw. I get these in often where someone has tried to lighten the trigger pull and messed up the hammer. Most of the time the hammer gets a little weld and re-shape.

[fourarmed]

I think Deadeye is right. I had a highwall replica that did that. The previous owner had lightened the sear engagement to a hair trigger without changing the very heavy trigger return spring. Unless you jerked the trigger violently, the sear bounced off the half cock step and didn't hit hard enough. I made a lighter spring out of music wire, and the problem went away.

[hornady308]

The rifle was purchased new and I have not done anything to smooth out the trigger pull. When I noticed the misfires while squeezing the trigger I then tightened up the hammer spring as far as possible (it was already close) thinking that it was a problem of the hammer not hitting the firing pin hard enough. It may be that I need to lighten the spring to keep the sear from hitting the notch. I may have done the exact wrong thing to start with. Btw, I noticed what looks in the photo to be a crack, but it turns out it is just an imperfection at the very edge.

[IrishFritz]

There is a relationship between the height of the full cock notch and the half cock notch. This has little to do with depth of the full cock notch. When the trigger is pulled to the rear, the the top of the full cock notch acts to kick the sear nose outboard of the hammer and to hold it out long enough to bypass the safety notch. If the height is too low then the sear will tend to follow the ogive of hammer and to hang up in the safety notch. So if you pull the hammer hard, you are kicking the sear outboard, if you pull it soft, then you are letting the sear nose ride the ogive when the full cock height is too low. Having said all of that, I doubt that the sear is dragging all that much as you would quickly see deformity on the tip of the safety notch that would get progressively worse until the sear nose would drop into the safety notch breaking either the sear or the notch itself. I think the advice you have been offered to see a gunsmith would be well taken- Good luck!