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Some history on the gun, bought new, had trigger job done about 20 years ago, set @ 2 lbs. Worked great for all these years. The other day it doubled twice after shooting about 60 rds. I cleaned it, paying special attention to hammer sear area, breech face and chamber. When back, out after about 40 or so rds. it doubled again. This was with federal lightning. I swiched to winchester X-pert and shot around 100 rds. with no problems. Today I took the hammer and sear out, they looked fine under magnafication. Hammer still falls a little over 2 lbs. During reasembly I could feel the hammer bump the halfcock notch when lowering it with my thumb, so I backed out the trigger stop to allow the sear to disingage more. Am I on the right track or could this be some kind of slamfire issue? I've used both the above ammo for years with no problems. It only seems to do it with H V ammo. Also the firing pin, spring and chamber are clean. I'm running out of ideas. Thanks,
Steve

Adjusting the trigger stop would be a logical first step. If the stop is bumping the half cock notch it can over time wear the sear face's break away angle too much and cause a hammer slip (bump fire). It is harder to visually inspect the engagement angle without some stand off pins. The hammer and sear faces may not be cut square anymore and that could mean slippage too. Hard to make a call in this situation, there are lots of variables to consider. I may be able to see more with a clear picture of the hammer and sear engagement with the grips off.

R,
Bullseye

What are "stand off pins"?

They are pins that fit on the outside of the frame and the hammer and sear can be placed on them to check engagement angles.

R,
Bullseye

I see. This sorta answers a question I had a few weeks ago. I was bored and looking at gunsmithing tools on Midway, I came across this: http://www.midwayusa.com/viewProduct/?p ... ber=388128

No two frames are drilled the same, so I was wondering how a fitting block like this would really help. When I was looking at the fitting block I was wondering why one wouldn't use the stand off pin method (though at the time I had no name to give this idea) that you have describe.
The only thing I could come up with for a use for the fitting block is if you were mass producing sears like VQ.

That fixture can work but I was talking of a set of pins like these.



They fit into the pin holes on the outside of the frame. By using a set of these you can see the actual engagement angle of that particular frame.

Brownells has a fixture that you can adjust the pins to match the holes in the frame.



R,
Bullseye

Thanks for all the info, Bullseye. Messing with the engagement of these parts is way beyond me -- but it is something I'd like to, one day, be able to do safely.

I took a picture of the hammer sear engagement from the left side of the frame with the thumb safety removed. took some time figuring out how to get a picture on here, hope it works.

Looking at that picture I see the sear's break away angle is quite significant on that face. A Model 41's hook engagement is normally small but that one appears a little smaller than usual. There's very little actual engagement holding that hammer hook on the sear. I could see that hammer slipping off of the sear when higher recoil ammo is used. Especially if the sear spring has lost a little tension over time and not getting the sear under the hook fully in time to catch the hammer during normal cycling.

R,
Bullseye

Your right, it does'nt look like a lot of engagment. I think I'll replace the sear spring and stick to SV ammo and see how it does before I get a new hammer or sear. Thanks Bullseye

The trick is to catch the second case when the gun doubles. My IZH was doubling and I thought I incorrectly adjusted the trigger, but the shell landed in my gun box and didn't have a firing pin mark on it.

Incidentally, Federal ammo was quite a bit more prone to doubling due to head space than anything else I've tried.

Just my experience,

Steve.

Funny that you mentioned Federal ammo, that's what it's been doubling on. I replaced the sear spring and dropped in a buffer, will be trying it out this weedend.

SShearer, great picture, sounds like you have are on the way to a fix! I'm blessed with the time to shoot thousands of rounds of 22RF a year and the difference between "good" and "bad rimfire ammo even within the same lot continues to amaze me. I'm lucky that both of my 41s love CCI SV. I rarely have any drama. I have been next to new RF shooters with a new pistol and a box of ?? and watch them be frustrated thinking they bought either a jamamatic or poor grouping pistol. I'll let them load a full mag of CCI SV and both troubles disapear. The last guy was the range owner who was testing two new pistols. He is a believer now.

Yea, I hope I'm on the right track, I've shot these Federal Lightnings for many years with no problem and they group well if I do my job. I sure can't complain about the price. I guess I was being spoiled until this stared happening.
Steve