is there a single shot action that will chamber a 12 ga  and have room to safely handle the pressures of shooting a slug   was thinking of making a 12 slug gun and using a falling bloch like a highwall type action  or would a rolling block hold this big of brass    any ideas would be greatly appreciated

FYI, a high-wall action has to be altered (slightly) to accept a 20 ga shell.  I believe that action should be elimintated from consideration if you want a 12 ga.   

I know Remington rollers have been used to make shotguns in the past, but I honestly can't remember whether they are big enough to make a 12 ga or not.  Strength would not be an issue with the Win or the Rem, but I believe size might well be.

I would tend to go with tar baby's suggestion to use a Greener Martini action.  This one has a tried and true record as a 12 ga.

Froggie

The Swedes made a lot of shotguns on rolling block actions some of which were specifically made to be shotgun actions.  Try this url for Simpson's::

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There are shotguns from 28 to 12 guage there.


Jerry Liles

I once owned a Rem Rolling Block in 16 gauge. It was an all original Roller. This was back when these were not collector items. I earned mine cleaning out a 100 ft long hen house two floors. Winchester  did make 16 Gauge Hiwalls also. I believe the issue was this was the biggest shell that would pass thru an  unmodified action. HTH Regards,
FITZ.

FITZ, the reason I don't have a shotgun barrel  on my takedown high-wall is that the rounded portion of the feeding passage was too small to allow passage of the 20 ga rim without alteration.  I had the original barrel to use, but couldn't bring myself to grind on that longsuffering action!  I can't see how a 16 ga could possibly pass through an unaltered action.   

Anyway, it seems like a waste of a good high-wall RIFLE action to make a clumsy shaped SHOTGUN out of it.    JMHO, of course.

Froggie

was looking for something with a hammer Actually I had planned to use a brass case 3 1/2 inches long loaded with  a slug and shot through a rifled barrel souped up 12 ga slug gun but with the class of a big falling or rolling block action

SAAMI Max Working Pressure for a 12ga today is 11,500 psi.  The service load of a shotgun in 1906 was about 8,000 psi.

There were literally hundreds of models of American made single shot shotguns produced from about 1890 to 1930.   Almost every maker had them.  These bicycle guns were very light, break action, most with a simple hammer.  They are called bicycle guns because most of the gun companies were also producing bicycles or parts for them, at the time.

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You will not be safe using commercially loaded ammunition.  Most shotgun ammunition today is loaded to properly cycle a semi-auto, so they keep the working pressures on the high side.   

The other issue is that these were not trap guns, but light utility guns that were cheaply made.   You will need a shoulder made out of granite to fire more than a few rounds with one of these guns.  With the properly tuned hand loads, you should be just fine. 

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Pete

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The gun in the middle is a Huskvarna Rolling Block in caliber 12, they were factorymade in large numbers here in Sweden actually a bit into early 1900.
This one has 65mm chamber, but i would not shoot hot modern slug loads in it.