So I bought a few green mountain blanks...

[jmorris]

After looking for "uppers" for one of my TC contenders for my Daughter and not liking the prices I decided to build them.


Started with the .22 blank and turned it down and threaded it for a suppressor.

While I was at it, I went ahead and machined a thread protector if it ever didn't have one on or a QD adapter on the threads.

After a little searching, I couldn't find any weld on lugs (one source for threaded) and machined my own just averaging the measurements from the TC barrels I do have.

Welded the first one together yesterday, chamber reamer is on the way now and after that will have to machine the slot for the extractor, finish and test. If it is a "winner", will do the next one the same way.

 

[4V50 Gary]

This is inspirational.

 

[tangolima]

Nice machining. I wish I have a lathe and a welder as you do.

But I am not sure welding a barrel is a good idea, as the heat will alter the heat treat. It is generally a no no according to the teaching at the school I go to. Same concern on the lug as it is a critical part bearing the blunt of recoil force. I wouldn't do it for myself, let alone giving to my daughter.

It was a 0.22 blank, but you didn't mention the exact cartridge type. It may be OK if it is a low pressure round like .22lr, but a TC usually does a much higher power round.

Well just be careful and good luck.

-TL

 

[jmorris]

That 3rd pic shows a factory TC welded barrel, that's just the way they do it. Weld then ream the chamber. That one is going to be .22LR.

There are some out there that have a radius machined into the lug then they fusion weld the lug to the barrel. They had the best intentions in that that wouldn't heat the barrel/lug as much as a "real" weld. Problem is that they don't get any penetration and things like this happen.

Silver solder would have been a better idea than that.

But not sure your understanding what the lug is actually doing, if it were recoil force opposite of the bullet leaving the barrel the breech face against the frame would take care of that. The lug is there so the breech face remains in contact with the frame instead of going down range.

 

[tangolima]

I see. I thought the picture was your finished work. Perhaps 0.22lr is OK to weld. But at least I would draw back the steel to blue in case the weld has made the steel hard and brittle.

-TL

 

[jmorris]

None of the contender barrels are machined from one piece, they are not the only firearm that has multiple parts to the barrel either.

Even the 300 win mag barrel for the encore uses a welded on lug.

Same thing with the handi rifles.

 

[tangolima]

Reheat treat after weld is how they are made.

I was incorrect about the function of the lock lug. It is not for bearing the recoil force directly, but to keep the action from opening while projectiles is traveling down the barrel. It is critical part in a pivot barrel gun.

-TL

 

[Clark]

I was with you on the first two pics.
I have threaded a Green Mountain muzzle in the lathe.

But at the 3rd pic, welding on the lug, you lost me.
I have $2k in TIG welding gear here and so far put one useful spot on a overground Mauser trigger.

I need to learn how to weld.

Jmorris says Silver solder. I have that stuff. The flux is corrosive. I should try again.

I drilled and tapped blind holes into the barrel, then fastened to the lug, with an epoxy to improve fit.

 

[ocharry]

nice job jmorris,,,,looks good

so before you ream the chamber are you planning to send it somewhere and get it normalised before you ream,,,to get the stress out where you welded??

ocharry

 

[FrankenMauser]

Sweet.


Everyone that I have seen successfully weld lugs to barrels (Handi-Rifles, in particular), has encountered enough warpage to be problematic unless they pre-heated the parts, TIG welded the lug/block on, and then put the assembly back in the oven to slowly cool.

But... I'm not a metallurgist. So all I know is what I've seen others do ... and the few failures people have been willing to share on the GBO and MO H&R/NEF forums.

I have been wanting to build a few barrels for my Handi-Rifle frame, for a few years now; and I'm not a fan of the ever-so-popular 'stubbing' methods (mostly due to the fact that an existing barrel must be sacrificed). So new blocks/lugs was the direction I planned to go when the time comes.

 

[Gunplummer]

I would like to think that the barrel is an undrilled bar before welding. Even a lot of the old S/S shotgun barrels were forged as one piece. I don't know, I have seen some dumb stuff come from the factory. Most barrels are 4140 that are pre heat treated to about 28 RC. When welding 4140, the parts should be heated up first. The problem with welding 4140 is it gets unstable. You cannot be sure what it will do. It may get softer, or it may get harder. I would not worry about a .22 or a low energy center fire. A round with some pressure would make me think twice.

 

[Unclenick]

This article on barrel making is an interesting read. Douglas draws back barrels at 1100°F (just 12°F less than the 600°C mentioned by Kolbe, so, close enough). This is done in a controlled atmosphere oven to avoid oxidation. I would be doing that after welding to stress-relieve the steel. You can wrap the thing in heavy stainless foil to prevent much oxygen getting at the surface, and then put it into a knife oven or kiln that has proper temperature controls and let it soak in there for an hour.

How much the welding will affect the properties of the barrel, I can't say. If you can at least rough the chamber in before welding, then pump a coolant like anti-freeze through it while you weld, that will go a long way toward keeping strength integrity around the bore and chamber. The cold bore and chamber surfaces will then cause a temperature gradient to develop between the bore and the weld site that will stay below 1100°F for some portion of the thickness to the weld. If the steel is half an inch thick around the bore, then about 0.2" will stay below that value. For 1/4" thickness between the bore and the weld, it will be about 0.1". In other words, about 40% of the thickness, whatever it is. On the assumption the barrel was drawn back at 1100°F originally, you should then not affect the temper inside that thickness around the bore and chamber. If you don't at least rough the chamber first, though, you may end up cutting through the preserved temper when you chamber.

 

[Gunplummer]

1100 degrees sounds about right. That would take it to 33 RC even if it was up at 57 RC to start, and all they are doing is stress relieving. The use of coolant while welding is a little dicey. The 4140 series of steel is oil hardening. Quenching it in water could bump it up to 70 RC. I have seen it done accidentally by people wanting to cool something off after welding.

 

[ocharry]

thats what i was thinking,,,i have done some welding of 4140,,,and the weld sight does get kinda hard,,,,without stress relieving or normalising you might wreck the reamer

good thought about roughing the chamber before the weld,,,,just make sure you leave enough to finish

ocharry

 

[Pahoo]

My compliments !!!

This is inspirational.

And then some !!!

Be Safe !!!

 

[Unclenick]

A quench could cause distortion and hardening, but if you run coolant through the bore and roughed chamber of that thick barrel, cooling from the inside out will be slower than a quench is at the weld sight. Whether or not it is slow enough that the surface cools itself faster by thermal diffusion than heat flow to the inside can, I don't know, but suspect that will be the case. Perhaps our resident metallurgist, Mete, will see this and know the answer. I can set up an FEA model to see, if I get time. In any event, doing the draw afterward should bring it back closely enough. Matweb has 25 mm 4140 oil quenched round bar drawing back as:

Rc 34 1000°F
Rc 30 1100°F
Rc 27 1200°F

Thinner stock will be harder after exposure to that temper because it is harder through and through to begin with as a result of quenching faster.

 

[Gunplummer]

I welded up a set of pie jaws once and the kid helping me had grabbed a slug (of 4140) and turned it while I was boring the jaws. I welded them up and about 5 minutes later he put them in a bucket of water to cool down. Could not split them with a band saw. 4140 is funny stuff sometimes. Who knows what the coolant would do? I used a brass bar to align two halves of a receiver together one time when gas welding. The brass acted like heatsink and I could not weld it.

 

[Unclenick]

It's a question of proximity and the thermal properties of the material and the ability of the welding system to supply Btu's fast enough. In this case I am counting on the thickness of the steel to have enough thermal resistance to allow heat build-up for the same reason you can weld a piece of steel without heating the whole piece.

 

[Gunplummer]

Instead of just talking about it, try it.

 

[jmorris]

I used LA-CO Block-it (same product I use when I TIG weld brazed heat exchanger cores to tanks without damage) when I welded the parts together and the reamer arrived yesterday so I was able to test fire it a dozen times today and it all works. After I get it drilled and tapped and figure out what optic I am going to put on it, I'll post back accuracy results.