doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Barrel Welding

There have been several threads on repairing barrel damage over the last year. Based on some of the posts by experienced people, I would like to hear if they encountered a similar issue.

I have TIG welded a limited number of barrels. All were of homogenous (not damascus) steel, all from the 20's-40's. I beleive these barrels were made of what we would call "chromoloy" composition today, or very similar.

The issue I ran into was that they all had sufficent carbon content to self-quench harden when welded at ambient temperature. The welding rod used was mild steel (low carbon). I even encounted cracking of the welds on my sleeve job from the shrinkage/hardening.

I had to anneal all the welds or they could not be filed. It wasn't the center of the weld bead where the filler rod was, but it was the edges and into the barrel parent material where it had hardened.

Anyone run into similar issues?

Chuck, I think you bring up a good point. I saw your pictures of the barrels you sleeved and of the cracking. I do believe that if the barrels have enough carbon in them, then these outer edges will harden because of said carbon content. Unfortunately, the only way to find out is to weld them since we do not have any idea what these barrels are made of.
I know some steels are better if they are heated before welding.

On the barrel that I had welded, an 1889 twist, The person who welded the barrel for me had me machine a tight fitting plug of copper to fit under the weld. After welding, it appeared that the bead and surrounding metal had the same hardness as the rest of the barrel. I was told that the plug was to keep the bead from entering the barrel, but did it also keep the welded area from becoming brittle by acting as a heat sink?

Abn Sarge, this has also been discussed before, and from what was stated that using a plug in the barrel is not such a good idea as this will not allow full penetration.

Hi Chuck,

I have seen this problem many times with. I have even had this accur on someof the recievers I have welded. I have found that making shorter beads sometimes helped to stop the hardening. I could not explain why it is only the edges of the bead and not the center. Could be that the filler material at the edges has has more material migration from the parent material which is a higher carbon content causing the hardness at the edges.

Bill G.

I am loath to enter a discussion on welding in case I attract the ire of anybody but in case this can be of help:
I know that the main barrel specialist who specialises in TIG sleeving always heats the tubes around the welded joint to normalisation temperature after the joint is welded. He can then strike off the weld and strike up the barrels. We welds using mild steel wire/rods.
He has said to me that he needs to heat up the tubes to 'allow the carbon the migrate and even up its distribution'.
I have never had any problems with hardness after this process but I will say that the zone along the weld joint (about 5-7mm wide) always polishes to a brighter finish than either side of it and doesn't black quite as darkly.
However, with the guns in my own modest collection, I have found that the darkness of the blacking evens out over 12 months or so and becomes pretty much invisible even after re-blacking.
The above are observations only. I leave the technical comments to any professionals watching.

I'd add one caviat to Toby's observation. That being, the cool down from normalization temperature would have to be controlled/slowed sufficiently to avert the air quench Chuck refers to. One method might be to immediately bury the barrels (especially the weld zone while still above normalization temperature) in sand and allow them to cool while buried. The elegant way would be to heat and cool in a temperature controlled furnace.

I'd add one caviat to Toby's observation. That being, the cool down from normalization temperature would have to be controlled/slowed sufficiently to avert the air quench Chuck refers to. One method might be to immediately bury the barrels (especially the weld zone while still above normalization temperature) in sand and allow them to cool while buried. The elegant way would be to heat and cool in a temperature controlled furnace.

Bill, the edges that harden are because the carbon content is higher than the filler wire and the same reason the center of the weld does not harden.
I'm sure that is why Toby suggested his welder heats the barrels to prevent this.

Chuck;

Cracking and hardness in the heat affected zone as discussed above can be caused by several issues, and a most common issue is lack of, or not enough pre-weld pre-heating. And of course if one does not know the exact content of the base metal selecting filler metal is a stab and if the selection is wrong cracking can occur. I have not seen any such problems with tig welding our typical English made barrels of the pre-WWII era, however they are very soft. I do not recall what "E" series steel was used on barrels of that time, but I will ask one of my colleagues who knows and get back to you. However, barrels of that time frame in England were not of chrom-moly, and I suspect that the barrels you reference must have been American made high strength barrels.

As to receivers cracking from welding(I assume that you are speaking of double gun actions that have been color hardened), it would not surprise me that they would crack if they had not been annealed prior to welding.

I spoke with one of my colleagues today about the issue raised above(he is a professional welding engineer with nearly 50 years experience) and he said that although he has never been involved in welding shotgun barrels, pre-heating to about 350 degrees F would be his choice on welding a tube that is as thin as a barrel.

I do know from some of the older Birmingham gun tradesmen( the one I am speaking of died in 1957) that they(he) learned to weld with OXY/ACL when it became commonly available to the trade around WWI. He welded actions and barrels much to the dislike of the proof house--but try as they may they could not get his welding to fail. Different era and different metallurgy though.

Bv