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Merkel Rear Trigger Problem I hope someone has a solution to this problem…

Subject: Merkel 140AE double rifle. I posted in the more frequented shotgun forum since this is a trigger problem.

Problem: Double trigger boxlock ejector Merkel 140 AE rear trigger increases from 6 pounds to almost 12 pounds after a few shots. I fire this gun by alternating the barrels right to left. On my 16th shot (attempt) I could not pull the trigger.

I took the gun to my gunsmith who disassembled it and set the triggers to 4 and 6 pounds.
Next time shooting with less than another 15 rounds, the rear trigger suddenly increased to almost 12 pounds.

Back to the gunsmith who disassembled and inspected it for a possible cause to include possibly the stock binding. He could not find anything.
Reassembled and return to range. Once again after relatively few shots fired from each barrel, the rear trigger suddenly increased to almost 12 pounds.

Has anyone seen this problem before in any boxlock rifle or shotgun?

Mark, not familiar with Merkels or boxlock guns but I still think it is a sear problem. I agree to what Rainey states, disconnect the safety as I think the recoil has something to do with it. Reading up on a few sites the only thing I saw on this model was "doubling. I would contact Merkel and asked them.
Why it only happens after 12-15 shots is the $100 question.

I am curious as to whether the problem arises with snap caps or only when firing live ammo An experiment with snap caps would reveal if it is recoil related or not.

The stock is fastened with transverse stock pins. Something tells me that the problem is related to a change in internal geometry brought on by stock flexing.

I sure cannot even guest, but if GSI is still the importer for Merkels, I would give them a call for starters. Long ago I had my nearly new Merk doubling on me and they took it back and did a little work as well as replaced some parts which solved the problem.they may have some ideas.

Well, there’s definitely something causing some gas to escape and leave marks on your breach and action face. You’re right, that’s definitely no Bueno. Next thing I would do is check the condition of the tumbler to see if there’s any signs of that gas making it back into the action….if it is, the face of the tumbler will also be scorched.
You said the trigger wiggles and isn’t tight when it switches to its 12 lbs pull phenomenon……has your gunsmith checked to see that the tumbler is at full cock or is the sear resting in the intercepting/safety bent instead of being in the bent at full cock? If that’s the case, somethings gotta be causing the tumbler to come out of full cock and resting in the intercepting bent which would definitely explain the heavy trigger pull.
If the tumbler and sear are dirty, I’d highly polish them both, reinstall without lube and try and see if you can see any abnormal drag/friction marks. It would explain a lot seeing where the parts are resting when the 12 lbs pulls are happening.

Just FYI….JJ Perodeau is a very good mechanic when it comes to issues like this. The escaping gas on the left barrel is fairly concerning.

I could see that it is chambered for a belted cartridge case.

When I chamber double rifles, I measure the rim and/or belt thickness of maybe 20 new cartridges and I also refer to the cartridge original design specs and then I chamber the cartridge for only a couple of thousands of an inch clearance between the back of the cartridge and the barrel flats. Then after shooting if I see that another thousand or so of clearance is needed I increase the depth of the cartridge rim into the chamber. This is a very critical clearance on a .375 belted magnum as the pressure of this cartridge is significant (max 62,000psi) versus the .375 flanged cartridge of 47,000psi.

I suggest to you that you measure the depth of the belt cut from the face of the barrel flat in the right barrel and do the same for the left barrel and compare the two measurements. Check to see how close the chamber cut is to the standard of the .375 belted mag which I believe is about 0.220 inch thickness. You can look up the standard for the brass on the web.

I just went back and looked at your photos again and I can see just barely an imprint of the cartridge rim of the left barrel against the action flat. Therefore my previous thoughts may be wrong about why there may be some gas escaping from that barrel---if there is any excess escaping.

Stephen Howell

Mark,
I've had Del Whitman do work for me that was excellent. Also, Steyr Arms is handling the Merkels after GSI stopped. My contact at Steyr was Einar Hoff and they have an Austrian trained gunsmith who services the Merkels.
Hope this helps,
Karl

Having just returned from the hospital, I haven't seen this thread before. The 375H&H is really a little too powerful for the typical 16 ga frame size many are made on. They pass proof testing, usually, so are considered safe. Continued use may bring up otherwise not noticed problems. Raimey's idea of disconnecting the safety makes sense, to see if recoil is causing the automatic safety to partially reset to "safe". Bushveld's discussion of chambering belted cartridges is great if you are building a new rifle, but the one under consideration is already chambered. For many years, I set the headspace in my loading dies by smoking the neck and shoulder of a case fired in the particular chamber and set the die to just "kiss" the shoulder of the fired case. This causes the handloads to headspace on the datum line rather than a belt or rim. On the other hand, I think this is a different problem having little to do with the heavy trigger pull. LeFusil's idea of recoil causing the sear to fall from full cock to the intercepting bent is worthy of consideration also. BTW, if setting the cartridge headspace with the sizing die, for a double rifle, the shortest chamber should be used to avoid having to load separate cartridges for each barrel.
Mike

Thanks for the good thoughts and prayers everyone.
Mike