Questions about an underhammer project.

[Ponstre]

Hello,

I am a french muzzleloader and I have two questions for the US experts.
I have a steel checkered buttplate in a as cast finish, I wonder how to polish it without rounding all the checkering.

The project is based on an hopkins and allen style underhammer action, on it the breechplug is secured inside the action using 3 set screws, unfortunaly hex set screws are not considered period correct for the competitons here in France.
I thought about making the link with a conical pin like it was made on the originals but I dont know how to do it right (I don't want any play or a loose barrel-action junction)

If you have any idea...

Thanks a lot for such a wonderfull website.

Regis

 

[paulvallandigham]

To polish that steel checkered piece, try using a wire brush on a motored arbor, to take off the rust. The brush will get down into the checkering, and remove any surface rust. It should not be hard enough to actually damage your steel plate, however. If any doubt, then use a bronze bristle brush to clean it. If you have a power grinder in your shop, you should be able to find these other attachments at your hardware, or equipment supply stores.

Without pictures of that barrel/action joint, its pretty hard to advise you as to what you can use. Can you find screws to replace the Allen head screws, that have standard screw slots in the heads? That should meet the rules.

If you could put in a tapered pin, it would require a drill press at least, and some real skill to make the holes correctly to use the tapered pin.

 

[bingo1952]

This is how I attached my barrel to my action. I used a straight dowel pin to hold the breech plug in the action and then fit the barrel to the pinned in plug so that when everything was torqued the breech plug goes tight in the barrel and the barrel goes tight against the face of the action at the same time. Doing it this way makes it so it is difficult to swap out barrels but it is very solid with no discernable accuarcy robbing movement. Now I just have to think about the stock/action connection some more.

Welcome To The Forum.

 

[Zonie]

re: Welcome to the forum.

I have no fast, easy way to clean up your buttplate casting.
Were it me doing the work I would use various grades (or grit) of Silicone Carbide sandpaper to sand the plain, uncheckered areas down to obtain a smooth flaw free surface.
This sandpaper is commonly called "Wet/Dry" in the U.S. because the adhesive that holds the grit in place is waterproof. It is colored black but should not be confused with "Emory Paper" which is also black but has a much softer abrasive.

As for the checkering, I would use a 3 Point or triangular file to file each individual line of the checkering. This would maintain the typical 60 degree angle that most checkering is done with.
Jewelers files can be purchased and the bend that some of them are made with would be a benefit in getting into some of the small areas.

As for the attachment of your barrel, if suitable straight slotted set screws are not available for your purpose you could perhaps go to an automotive supply store and buy several high strength bolts in the correct thread pitch and size.
These are very tough steel but they can be cut with a metal cutting hack saw to a suitable length.
To form the slot, after squaring up the cut surfaces with a file use a 3 cornered file to lightly make a notch across the center of the end of the screw.
Using this notch as a guide your hack saw can then be used to cut a slot for the screwdriver.

If you have access to an electric drill, you can hold the short set screw you are making in the chuck.
While the drill is running, use a flat file to file the end opposite the slot to a 120 degree cone.

If the 3 holes for these screws are drilled while the barrel is in place, run the drill bit in until it makes a full conical impression in the barrels breech plug. This impression should only be the size of the drill and not actually create a hole in the barrels plug.

Screwing the coned set screws in until they bottom in the 3 coned impressions will not only hold the barrel in place by faying friction but the mechanical interface between the screw points and the breech plugs "impressions" will prevent the barrel from moving in any direction.

If you want the three cone ended set screws to do double duty, rather than actually creating the three cone points in the breech plug stud while the plug is mounted in the receiver, just run the drill bit in until it lightly touches the breech plug stud.
Remove the barrel and breech plug from the receiver and note the three marks.
Using these as a guide, make a dimple or dent using a center punch at each mark however, make it about 0,5 mm (.020 inch) closer to the barrel breech face.
Using these center punched marks as a guide, drill the drill point only into the breech plug stud.

Now, when the three cone point set screws are installed they will not only hold the barrel and breech plug stud in place but they will actually create a force which tries to cause the breech plug stud (and the barrel) to move tightly against the receiver assuring a tight joint for years.

 

[kansas_volunteer]

My 1970s version of the Hopkins and Allen underhammer rifle has a slightly tapered pin holding the breech plug and barrel in place. I suppose a skilled machinist could come up with several ways of creating the tapered hole. Left to my own devices, I think I'd use a thin coat of epoxy to hold the breech plug in place on the frame, then drill a hole and ream it with a tapered reamer to match my pin. The epoxy could be heated and removed after the work was through.

I don't like the look of the screws holding the barrel on my more recent underhammer kit.

I agree with Zonie on polishing the buttplate, if you're just trying to remove the casting texture.

You might consier this rifle for inspiration:
http://trackofthewolf.com/(S(mxxo2...catId=12&subId=78&styleId=266&partNum=AAG-556

 

Regis,
I have several of the H&A type underhammers that I have modified. The simplest way I have found is to drill a horizontal hole from side to side and through the breech plug stud. Once the hole is drilled, and true, take a slotted roll pin and drive it through all 3 holes. It makes a very tight fit but can be removed. The third, top, hole can be fitted with a guard screw and then the head filed clean with the top of the action. Reblue and you won't even notice the guard screw.
Mark

 

[Ponstre]

Thanks a lot for all the infos.
My project is a long range underhammer,it will be used for shooting in the prone position with sling as a rest.
As you know when shooting that way you can apply a great stress to the rifle due to the sling tension.
So I need a very tight fit, all your ways of doing it are great, I think I will go for a mix of them.
I allready have a dovetail on my barrel, so I think I will gently screw the breechplug, make the holes for the pin in such a position that I can add 1/8 or 1/16 turn to the barrel once the breechplug is pinned.
I hope that whith the additional torque the barrel will be held tightly in front of the action.
I am in the process now of finishing the buttstock,the final sanding has been done and I just have put the second layer of lineseed oil/turpentine/drying agent mix.
Next will be the finish of the buttplate.

Thanks again.

Regis

 

[kansas_volunteer]

Re, if you're going to be shooting the rifle prone with a sling, you might be able to take some stress off the barrel-frame joint by mounting two sling attachment points to the barrel, then slinging-up the way British snipers and target shooters have done, with the Lee-Enfield series of rifles, just using a simple strap for a sling. With the sling attached at two points on the barrel, one forward and one to the rear, all the sling stress would be on the barrel, the most rigid part of your rifle, and none of it putting strain on the joint.

Are you familiar with the British way of using a sling?

 

[ghostdncr]

I suppose a skilled machinist could come up with several ways of creating the tapered hole.

Check out any edition of "The Machinery's Handbook" and you'll find that those tapered dowels are standard purchased items, as are the reamers that cut the corresponding holes. Really common stuff on machinery such as lathes and mills. MSC Industrial Supply should carry both tapered dowels and reamers,if I remember correctly.

For "our" use, shoot for an earlier edition of the Handbook as that would cover stuff like blacksmithing that in the later editions has been replaced by metric and CNC (computer) info.