"Back on Face" Problems

[Cold Spring]

I've rejointed a number of guns, and I concur that the back ends of the barrel breeches should never be filed, They were contact fitted when the gun left the factory, and there's no need to try filing them to get new contact with the standing breech. When re-doing a barrel hook by welding, the EXACT original X and Y axes must be maintained. Even a .002" difference in location in either axis will make a huge difference on the fit of the barrels against the standing breech. And a compound error (both axes off center) is a MAJOR problem. Trying to do it without a witness location (pre-welding) and with files is just asking for big trouble. I do it on a vertical mill equipped with a digital readout (DRO). The hook axis center is located before welding, barrel removed for welding, then replaced on the holding fixture on the mill, with adjustment made using the DRO for the off-face dimension plus a thou or two for fitting. New hook radius is cut with an end mill ground to the exact diameter of the hinge pin. Readers please note I only work on my own guns, no exceptions. I am not posting this to solicit work.

It's just my opinion but soldering or gluing a shim to the hook radius may apparently get the barrels back on face but it usually results in "point contact" at the top and bottom of the shim because the hook radius is then smaller than the hinge pin diameter. The hook radius is usually not worn uniformly round. Short term fix only.

All that doesn't help you now with the Flues. Best you might do IMO is to reweld and just work the hook radius only, being careful not to make its diameter any larger than the hinge pin. That can easily happen and you'll end up with very limited bearing against the hinge pin. Work very-very slowly while watching what's happening with the barrel contact. Once you get it very close (touching at the bottom of the barrels, maybe .001" off face at the top) you can soot fit the back end of the barrels which you said you've already filed. Keep in mind that will likely tighten the headspace and the rim cuts will probably have to be redone with a rim cutter. One last tip, the oil lamp soot tends to build up and it should be wiped off each and every time you check for fit, then resooted. Otherwise you'll get erroneous readings of " good fit" because the soot is so thick.

[Eldon Goddard]

Thanks for all the info guys. I did not file on the breech face. I just sanded down the barrel faces very lightly to get it to contact the breech face. I bought the gun for the specific purpose to learn how to fix it. I figured that you had to clean it after smoking it but now i know for sure. The pin should be round as my first attempt at fixing it was to replace the hinge pin, only to find that the hook was to worn down even to contact the new pin, so I decided to weld the hook. I have never tried this before so I did not expect to get it right the first time.