Need some help with 30" Macon Conversion

[Maillemaker]

I'm working on making a 30" "Macon Conversion" of an Armisport M1842.

I have had a gunsmith use a lathe to shorten the barrel.
https://i.imgur.com/hTRFVzcm.jpg

He pointed out before he started that he often discovers that the bore is not concentric to the barrel after doing such things, and this barrel was that way. You can see that the bore is no longer centered on the new muzzle.

https://i.imgur.com/KoIUbmjm.jpg

The first challenge is now that the barrel is short, the new muzzle end of the barrel is thicker than the original muzzle end. Consequently, the front barrel band loops don't fit the barrel:

https://i.imgur.com/EauSoaLm.jpg

Since this is a cast piece, I don't want to just try hammering into shape for fear of cracking it.

So, I presume I will need to heat the "bridges" to glowing with a torch and then use the wide end of the old cut-off piece of barrel as a forming mandrel to re-shape the "bridges"?

https://i.imgur.com/MG0H9mJm.jpg

Full-size pictures here: https://imgur.com/a/3UGAJRz

[John Bly]

It is cast steel not cast iron. You can hammer it into shape over a mandrel and it won't break. Best of luck to you.

[bobanderson]

I heated mine and used a vise to bend it to fit the contour of the barrel. A gap under the front band can help solve elevation issues.

I'd shoot it before you do anything else to see where it's hitting. You don't care what it looks like if it shoots straight. I also remember ALL Armisport front sights were made a bit off center. You'd want to find out where it's off and fix everything at once. When I made mine, I ground off the sight blade and brazed on a new one out of brass. (SAC allows that as long as the new sight is the same size and shape.)

[Maillemaker]

Well, before I can shoot it, I have to get the stock cut and shaped to hold the front barrel band on. And to do that, the barrel needs to fit into the barrel loops.

The biggest problem is the sides of the loops are hitting. So it's not that the loops need to come down, so much as the entire band needs to get wider. I think I need to heat the sides and belly of the part, but not the loops, so that I don't cave in the loops but rather the sides bow out slightly.

[John Bly]

You don't need to heat it just hammer the dxxx thing into shape on a mandrel. It is so much simpler. It is mild steel, not tool steel and is quite malleable.

[Maillemaker]

I think some heat is going to be required, because the loops are starting to cave in from beating on them.

The problem is that the barrel is too wide to fit up into the loops, as the barrel is hitting the "shoulder" where the loops flare out for the stock.

The part is too strong and/or springy to widen out from hammering on the top of the loop. It's just flattening out the loop.

[Jim_Burgess_2078V]

Probably not a good idea to use the barrel as a mandrel as you could risk damaging it while hammering. You need something solid to pound on that is the same diameter and taper as the barrel.

Jim Burgess, 15th CVI

[Maillemaker]

Probably not a good idea to use the barrel as a mandrel as you could risk damaging it while hammering. You need something solid to pound on that is the same diameter and taper as the barrel.

Jim Burgess, 15th CVI

I am using the scrap cut-off portion of the barrel as the mandrel. The area near the cut is close to the diameter needed.

[Maillemaker]

No pictures tonight, but a little heat and it was a snap.

I'm no blacksmith, and not even hardly an armourer, but I've learned a thing or two with metalwork making medieval armour. Hot work lets you move the metal you want to move a lot easier. Not saying that this could not have been done cold, and I've done a lot of cold work, too. But 60 seconds heating the sides and belly of the band with a pair of MAPP torches until it was glowing, slide it over a mandrel and one good POP and it was done. Had to to a bit of back-tweaking on the rear band due to over-doing it just a hair but the front one was a snap. And of course it's far easier to narrow up the band than to flare it out.

It now fits the barrel almost perfectly. Might do a little final file work.