7400 barrel converted to 7600 barrel NEED MORE INPUT HERE GUYS!!

trapoholic

trapoholic

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I already did it but haven't fired it yet. Here's the full story below.

I went on a hunt for a blued 7600 barrel in 308 or somebody who had and would change the bracket from 30-06 to 308. No dice on either; I'd still prefer a 7600 308 barrel but nobody has one.

So a member here told me a guy had a 7400 barrel for sale that was 308, told me to just convert it to a 7600 barrel. Made sense they're the same gun minus the action. So I bought the barrel, heated up the gas block and knocked it off. Crazy the size of the gas port in the barrel it's 1/8" or better.

Member I was talking to said just weld the port hole closed and Bob's your uncle. In my haste and excitement of my quest for a barrel I thought it was a hell of a idea.

So I took the MIG and welded the hole closed, settled on MIG cause it was the least amount of heat to get the job done. Now my question is to all you real gunsmith fellas; am I good to go or was misinformed? Inside the barrel is clean and shiny, no heat marks even around the hole; just a neatly plugged hole. As you know it's not at or just ahead of the chamber it's just under the front of the forearm.
 
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I had a .308 742 barrel converted to be use on a 760 ( same principal ) removed the gas block and welded up the port. Upon firing the gun at the range the weld blew out and destroyed the pump forend, if the gun wasn't on a bench sitting on a bag it would have taken my hand with it. Be very cautious of this, I think along with filling in the hole a patch should be welded in place for added security.
On a side note I replaced the barrel with a 760 barrel in .270 cal.
 
Just my opinion, but I would suspect that threading the hole and using a set screw would be more secure than trying to weld closed an 1/8” hole. You’ve likely got very little actually penetration into the barrel.

Again, that’s all my opinion and I’m curious to hear what others with actual experience have to say.
 
smokeeter said:
On a side note I replaced the barrel with a 760 barrel in .270 cal.
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"I wish I knew what I know now when I was younger" comes to mind. That was the original idea. Unfortunately I can't find a 308 barrel anywhere, things aren't as available as they once were that's why I went this route.

Wellse said:
Just my opinion, but I would suspect that threading the hole and using a set screw would be more secure than trying to weld closed an 1/8” hole. You’ve likely got very little actually penetration into the barrel.

Again, that’s all my opinion and I’m curious to hear what others with actual experience have to say.
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If I had the grubbers and a small enough tap I'd drill it out and re-do it then zap the grubbers in place, unfortunately I lack both.

gunrunner100 said:
I've done this a few times. Had the hole Tig welded, headspace checked and no issues.
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I didn't go the Tig route cause I didn't wanna heat up anymore than necessary. I don't own a Tig but I do have access to one and am quite proficient at the work. As it is now it loads and ejects every dummy I've got made for 7 different 308's no problem at all.
 
Tig would use the least amount of heat and get the best penetration also the most controlled.

The barrel will be fine to shoot and not explode. Ideally you would have put a set screw in the hole the covered the head with weld.

But as long as you have no weld going into the bore of the barrel and just did a normal little 1 second tack on the hole it would be ok. With that small of a hole there won't be much force pushing on the weld
 
Evanguy said:
Tig would use the least amount of heat and get the best penetration also the most controlled.

The barrel will be fine to shoot and not explode. Ideally you would have put a set screw in the hole the covered the head with weld.

But as long as you have no weld going into the bore of the barrel and just did a normal little 1 second tack on the hole it would be ok. With that small of a hole there won't be much force pushing on the weld
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I gave it 2 small zaps to fill it, ground it down and gave it a couple more zaps on any outline I could still see. I think I still have a small tap set I could drill it out and tap it if need be. I had a jag in the barrel at the port to catch any stray slag that might have popped in, barrel looks clean and shiny; I also pretty much destroyed a brush on it when I was done to make sure it was squeaky clean
 
I would warm the area gently with a propane torch until the colors of the freshly ground steel just start to fade towards blue. This will reduce the hardness of the brittle zones that always happen after welding on high carbon steel.
The color will start as yellow, then brown, then purple, then blue. If you're going slowly, you can stop at purple and it will probably peak at blue before it starts cooling down.

After that, a long string, a tire, and a "blue pill".
 
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Ok so I've overthought this far too much at this point. Should I drill out the weld, tap and plug the hole then secure the screw with a bead of weld? Or leave it as is?
 
trapoholic said:
Ok so I've overthought this far too much at this point. Should I drill out the weld, tap and plug the hole then secure the screw with a bead of weld? Or leave it as is?
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Lol You're right about the overthinking part. You don't gain anything by messing with it more; the only purpose of weld or a set screw is to plug the hole. The hole is currently plugged. Any damage you may have done by welding/overheating is already done. If you develop a gas leak maybe revisit, but for now, you're trying to fix something that isn't broken.

Also, definitely DON'T heat the barrel up til it turns blue, lol. That's a terrible idea.
 
Scotty454 said:
Lol You're right about the overthinking part. You don't gain anything by messing with it more; the only purpose of weld or a set screw is to plug the hole. The hole is currently plugged. Any damage you may have done by welding/overheating is already done. If you develop a gas leak maybe revisit, but for now, you're trying to fix something that isn't broken.

Also, definitely DON'T heat the barrel up til it turns blue, lol. That's a terrible idea.
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Definitely didn't turn blue, it was still shiny steel inside same as the rest of the bore after the weld. I was more concerned about the amount of heat it took to break the solder on the gas block honestly. Had to get it glowin before it'd break off. That silver solder is some tough ****!
 
trapoholic said:
Definitely didn't turn blue, it was still shiny steel inside same as the rest of the bore after the weld. I was more concerned about the amount of heat it took to break the solder on the gas block honestly. Had to get it glowin before it'd break off. That silver solder is some tough ****!
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Actually I think it’s silver brazing.
 
I would shoot the gun, ensuring my hand wasn't in the way of the port just in case. Then inspect after 1, a few, and a bunch of rounds. If everything still looks good after a bunch of rounds I'd stop thinking about it and move onto other things.
 
Suther said:
I would shoot the gun, ensuring my hand wasn't in the way of the port just in case. Then inspect after 1, a few, and a bunch of rounds. If everything still looks good after a bunch of rounds I'd stop thinking about it and move onto other things.
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I like your advice, got a bunch of loads made up for it
 
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