Underhammer action questions

[Coffeecup]

In the other current underhammer thread, I mentioned an action I have that I am trying to puzzle out how to set it up. This action currently lives on my desk, and is a constant puzzle to me--I'd appreciate any thoughts. (I apologize for some of the pics being upside-down).

First shot (hammer down all the way):
59953

Second shot (hammer at full cock):
59954

Front view (where the barrel goes):
59955

Bottom view (where the priming set up goes):
59956

Has anyone ever seen an action like this? Anyone know the maker (it is unmarked) or recognize the design? I thought I had it figured out--I was way wrong! I can't figure how to set it up with a barrel.

First question: Does it look like the barrel directly threads into the action body (so there would be threads on the outside of the barrel), or like the threaded portion of the breechplug extends back into the action?

Second question: How in blazes does the primer set-up work? That hole (in the last photo) is 2 diameters, with different threading in each. Is this some kind of sealed ignition, where the actual nipple or "primer holder" is threaded into the smaller diameter (and possibly into something similar to a patent breech in the breechplug) while some other part covers the primer and transfers the force from the hammer?

Thanks,
Jim

[tacklebury]

It appears to be missing the breechplug piece that threads in the nipple also. If you had a smith make a steel plug and thread it to match the large hole in the bottom there, then have them drill and tap a 1/4-28 or similar for a modern nipple, you could then purchase a barrel with the appropriate thread to go into the action. Once seated tight, you would mark the barrel threads where they align with your bottom hole and drill a priming hole into it to access the firing chamber. Then thread in the big plug and finally screw in the nipple. You should then be able to test fire. You might be able to make a stock from an existing savage or H&R piece with a bolt on from the rear type mount. Sights can then be cut to match or a scope mount base added to the barrel you've chosen. Hope this makes sense and helps some. 8)

[bob208]

by the looks of it. it was made to use a sealed primer system. which was common on the old bench rest guns.

[pietro]

I would machine (or have a machinist make) a two-diameter plug with two different threads/diameters to match what's in the action underside, ending with the big end flush or slightly proud of the action bottom, and the small end's center even with the bbl threads minor diameter - which I would then install in the receiver bottom.

A "freshing" or "chasing" of the receiver's bbl threads with the proper tap should clean up the proud edges of the plug's smaller diameter, AND hold the inner face of the plug tight against the installed barrel.

I'd then thread (or have threaded) a bbl to match the receiver, and install it.

The last step would be to center drill the two-diameter threaded plug, first with a flash hole, all the way through to the bbl interior, then enlarge & thread the outer end of the flash hole for a nipple, either with or w/o shield.

The hammer should imping directly on the cap/nipple.

Then, sights, stock, etc, of course.

A nice little project, IMHO - worthy of a picture tutorial posted here later.

.

[Coffeecup]

Thanks guys! If I ever get around to doing anything with this, somewhere I've got (I think I still have it) a heavy barrel w/false muzzle that would match up well. No half-cock, so definitely a bench action. Probably stock it in walnut, because I've got plenty on hand--adapting a stock would take too much money from the powder fund.

Threading a plug and putting in a nipple the hammer could reach would result in a flash channel over an inch long. It seems it would result in some significant delays in ignition.

Bob, the sealed ignition idea was something I suspected, but only because A) I'd never seen a breech setup like this; and B) I've never seen a sealed ignition so I have no idea how it works. I just did some digging online and found some pics of one in place but not disassembled to see how it was made. I'll keep looking. . . . Somewhere there have to be drawings of this or a similar action so I can figure out the sealed ignition.

Meantime, I'll look around some more online for photos.

[Bent Ramrod]

You might post the picture and question on the Wyoming Schuetzen Union web site. Some of those guys are big into slug guns and may be able to recognize the maker by his work.

[Plastikosmd]

Here is a pic of one of my sealed actions, hammer up, hole for cap in center and action block or whatever to left
http://i76.photobucket.com/albums/j5/plastikosmd/f05cdeae.jpg
Sealed and capped
http://i76.photobucket.com/albums/j5/plastikosmd/616b71ac.jpg

[Tatume]

The interrupted thread design is nicely done. What is the advantage of the sealed breech?

Thanks, Tom

[Plastikosmd]

I imagine less erosion and more safety. That one is a .62 and I usually shoot it with about 220 ffg or more. My .69 275-350g

[Coffeecup]

Plastikosmd, thank you very much for the pics. I can kinda see how it works now. A few follow-up questions:

What type of primer or percussion can is your action set up for? If a primer, does the primer sit in a recess?

Is the rod that actually strikes the primer retained in the removable piece, or is is free-floating?

I like the interrupted thread, looks like a great idea.

Thanks!
Jim

[Plastikosmd]

cap is #11, fits over nipple, for easier loading it drops into recess by moving the firing pin into the protruded or fire position.

Just push pin back, put cap into block/holder, drop holder into barrel and give it 1/2 turn to lock


pin can be removed for cleaning by just pushing it out the other way, so free floating

1/2 the time the cap will extract after firing from the block making it easy, the other 1/2 it stays on the nipple. I have a small tool to grab the flange and remove a stubborn cap if needed

[Coffeecup]

Thank you very much for that explanation--I actually understood it! [smilie=w:

Given that, and your pictures, getting this action up and running may actually get done at some point, instead of serving as a paperweight. Thanks again, to everyone.

Jim

[Plastikosmd]

No worries, I have a project or 2 waiting myself
http://i76.photobucket.com/albums/j5/plastikosmd/2b6cf228.jpg

[Coffeecup]

Oh, that is nice--who makes it?

[Plastikosmd]

I cant remember, but it came out of Mr. Briesen's shop as he got out of making guns. I dont know if he had a hand in making it. Generally his actions seem to use the triggerguard as a spring. This is more similar to the RL Morris actions that I have.

[Hanshi]

Those are the strangest actions I've seen yet for underhammers. I like UH rifles and still treasure mine. It's nearly a half century in age but still does fine. I took the worn out forend off and like mine even better, now. Sorry for highjacking the thread but I love these guns.http://i599.photobucket.com/albums/tt74/hanshi_photo/PICT0655-1.jpg

[Plastikosmd]

nice gun. I dunno, I seem to run into these a lot, I have maybe 5-6. I think I posted this before this is a breisen 69 using the trigger guard as the spring, similar to yours and the OP gun. It still uses the sealed ignition however. It is also close to 80lbs in weight
http://i76.photobucket.com/albums/j5/plastikosmd/eb3fc9ad.jpg
That compared to a one of my Morris guns. This is a bit lighter at 35lbs. It is the one I took a pic of in the response above. You can note the different hammer configuration. The stainless action
still retains the more curved hammer (Breisen)
http://i76.photobucket.com/albums/j5/plastikosmd/91c1dde3-1.jpg