Half cock failure

[Relicman]

I have a model 1873 trapdoor that has been sporterized and has a mixture of parts ,which is typical, my problem is this , at half cock ,when trigger is pulled, it will drop , it has the 3 position tumbler, is this a typical problem that shows a part is worn past tolerance, if so , what so I look at , visually, all looks good, but I am not experienced enough to recognize a worn part , any help is appreciated

[Dick Hosmer]

Is it that it won't hold at all, or that it can be pulled off? Sears and tumblers need to match. A 2-notch sear will not engage properly in a 3-notch tumbler. Post some good high-res photos of the interior of your lock. We might be able to spot the problem.

[Relicman]

It sets, but drops when trigger pulled , i will post the pictures of lock later today as I am not home at the moment

[Tom Trevor]

Just to add be sure to cock lock for spring to clear wood at 6:00 and back the tang screw out a couple of turns to take pressure off lock plate. A little lemon oil around lock may help stop splintering wood around plate.

[Dick Hosmer]

Tom is dead right on this. It is VERY important to cock the hammer before plate removal. Also, if you've never taken a lock out before, do NOT just remove the screws and wrestle the plate out by pulling on the hammer. Undo the screws a couple of turns and tap the heads with a soft mallet to be sure you aren't stating a chip. Repeat as required. If you are lucky it will be loose and just come right out, but don't just assume it will.

[Tony Beck]

If this is a shooter rifle and not particularly collectable, Dixie has 2 notch tumblers and sears for reasonable prices. Usually when this happens you will find that either the stock wood is swollen and won't let the sear drop into the half cock notch (which is easily fixed), or the overhanging part of the notch is broken off (and you need to replace the tumbler).

[Tom Trevor]

Tony He mentioned it was sporterized usually some ham handed individual get to grinding on parts to lessen trigger pull. If it gets to light then it will fall into the lower notches and break them out.

[Tom Trevor]

I wonder what he found? I can not count the times questions are asked and some answers provided and they never report back as to the results.

[Relicman]

I have not found the issue yet , I am sure , it's gonna be a mismatch in parts , or maybe a out of spec part in the lock , only way is to start replacing something, I will probably replace the sear first and see how that does , it has a 3 position tumbler, so it could be the sear is incorrect, just my thought

[Dick Hosmer]

The nose of the 3-notch sear is quite slender and should seat like a glove, perfectly, in the finer notches of the 3-notch tumbler, The 2-notch sear is noticeably thicker and blunter when seen side-by-side, giving the appearance of trying to force its' way into a place where it doesn't belong.