Catching in half cock

Well I was planning on shooting my SMR for the first time this weekend but when I went to put a flint in the cock and check function, the cock stops at half cock every time I pull the trigger. If I pull the lock out of the stock it fires fine every time and if I actuate the sear arm with it in the stock it seems to work ok. I'm guessing there is something going on with the trigger but there doesn't seem to be much adjustment where I need it. Any advice?

Sounds like you need to clean out some wood around that sear arm. Or the trigger is touching it once it’s assembled.

Wondering if the sear arm is binding on something in the lock mortise?
Maybe even the tumbler is binding.
Loosen up the lock screws and see if that helps.
You can also dab the sear arm with a sharpie or something similar to kinda ink it up.
Reinstall the lock, cock the hammer and pull the trigger.
If the sear is hitting any wood, the ink will mark the spot. You can do the same for the tumbler.

If this is a Kibler SMR, it sounds like your lock is missing the fly. Did you disassemblie the lock at some point?

Jim

Please see Jim Kibler’s post right above mine.

If you activate the sear with your finger, a screwdriver, or whatever, or a simple, single trigger, you are holding the sear arm up and the sear nose cannot engage the half cock notch in the tumbler. Set triggers just knock the sear arm up, and it then springs right back. Without a fly, the sear nose will engage the half cock notch as the tumbler rotates.

If you have double-phase set triggers and they allow the lock to be cocked with the triggers unset, try just pulling the front trigger as you would a simple, single trigger. See if the cock stops halfway or if it drops as it should.

Good luck!

Notchy Bob

comment withdrawn

It would appear that I am missing the fly...

I had the same problem with a rifle several years ago. All it took to fix it was just a "very small amount" of wood removal. But when I had a similar problem with a pistol that had a single trigger I removed the fly, problem solved.

I have a similar problem with an L&R Manton lock. If I keep good sharp flints in the lock, it is very reliable and fast. The screw that holds the sear in place on the bridle will back out. When it gets loose enough, the sear will drop into the half cock notch. Tightening the screw solves the problem. I didn't want to do it, but I have applied blue Loctite to the screw. It shouldn't back out under normal use, but the screw can be removed for a full cleaning.

Grenadier1758 said:

I have a similar problem with an L&R Manton lock. If I keep good sharp flints in the lock, it is very reliable and fast. The screw that holds the sear in place on the bridle will back out. When it gets loose enough, the sear will drop into the half cock notch. Tightening the screw solves the problem. I didn't want to do it, but I have applied blue Loctite to the screw. It shouldn't back out under normal use, but the screw can be removed for a full cleaning.

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I have two Mantons that do the same thing. I called L&R to try n get a longer shoulder sear screw to fix this problem and they sent me a duplicate of the ones i have. The shoulder on the screw is not long enough to bottom out on the lock plate when tightened. I put the blue locktite on mine also and seems to work.