sight hole drilled too deep into bore

[roklok]

Doing a bit of gunsmithing on a Remington 760, getting ready to send it in to Black Ice coatings to get the metalwork including the original 30-06 barrel and a second JES rebored .35 Whelen barrel coated in their teflon treatment. I just finished shortening both barrels to 20 inch and remounting the front sights. I took great pains as always when mounting the front sights not to drill into the bore. Imagine my surprise when I discovered the FACTORY rear sight holes on the original 30-06 barrel broke through into the bore ! This is a 1960 production 760, and had certainly been shot a fair bit in the last 65 years. The rearmost hole is only 5.5 inches in front of bolt face ! The 6/48 sight mounting screws kept .30-06 pressures corked up without blowing sight off. I am a bit impressed. Not exactly sure the best route forward, thought about TIG welding a screw into holes, filing flush and drilling relocated holes. I guess I would probably be fine just using the holes as is as they worked so far, but kinda bugs me. Maybe this isn't as uncommon as I think, but first I have ever encountered it. I have seen a Swarovski scope with a small diameter hole blown clean through the objective bell when a screw let loose from a hole drilled into bore.

 

[Daggaboy375]

I had a Remington 660 that had the front sight holes bored through. Didn't adversely affect accuracy on a hunting rifle but the holes were only a inch from the muzzle.

DB

 

[BourbonTrail]

You may be able do a plug repair. At work we use a screw plug and red locktite to fill the dowel holes set in the wrong location (those holes get tapped for repair). Then we grind flush and re-drill. I don’t know if using a sub-flush set screw would allow you to reuse the holes, or you could step up a size and re-drill inside of the plug.

 

[Ontario Hunter]

You may be able do a plug repair. At work we use a screw plug and red locktite to fill the dowel holes set in the wrong location (those holes get tapped for repair). Then we grind flush and re-drill. I don’t know if using a sub-flush set screw would allow you to reuse the holes, or you could step up a size and re-drill inside of the plug.

I was thinking the same thing. Just make a very shallow threaded plug with slotted head. Problem is the holes are so far forward from the chamber. They are well into the taper of profile. I don't think there's enough metal left in the screw holes to do this and still get the sight screw on top of the plug to bite enough for proper torque. I would just plug the holes with blanks and move the sight back where it should be. I suggest buggering the threads a bit on the plug right at the top. That should help keep it from backing out. And of course plenty of LokTite.

Why in hell they would mount the iron sight that far forward is beyond me. Longer the distance between rear and front sights = more accuracy. Surely if someone is intent on mounting a long length big belled Hubble scope on the gun, they would just remove the irons anyway and plug the holes with blanks. It's what we all do. Here's where I mounted the rear sight on my Springfield 03A3 when I decided to add QD rings for optional irons in adverse conditions. That's a 3-9x Nikon with a relatively short tube. Anything longer would be a problem. But that gun and this guy really couldn't make any better use of a longer/greater magnification scope.

 

[Ontario Hunter]

Another thought. Can you plug the holes with blanks and add a rib or express type rear sight with a base long enough to cover them? That might allow you to move the rear sight back and conceal these holes without tig welding, turning/polishing, recoating/bluing, etc.

 

[roklok]

I did some measuring. As close as I can determine, the holes are .237" deep from barrel surface to bore. The sight mounting screws are only using the top .115" of the hole. I could run some small threaded plug screws down to bottom of holes with loctite or epoxy, and still have enough threaded hole above to secure sight. Or, I could just use longer sight mounting screws that utilize most of the .237". I could also plug and relocate the sight, but either way the holes will be filled primarily with a threaded screw, I am not sure how much additional strength a bit of weld at surface would add if I chose to plug and weld.

 

[farmer_john]

Doing a bit of gunsmithing on a Remington 760, getting ready to send it in to Black Ice coatings to get the metalwork including the original 30-06 barrel and a second JES rebored .35 Whelen barrel coated in their teflon treatment. I just finished shortening both barrels to 20 inch and remounting the front sights. I took great pains as always when mounting the front sights not to drill into the bore. Imagine my surprise when I discovered the FACTORY rear sight holes on the original 30-06 barrel broke through into the bore ! This is a 1960 production 760, and had certainly been shot a fair bit in the last 65 years. The rearmost hole is only 5.5 inches in front of bolt face ! The 6/48 sight mounting screws kept .30-06 pressures corked up without blowing sight off. I am a bit impressed. Not exactly sure the best route forward, thought about TIG welding a screw into holes, filing flush and drilling relocated holes. I guess I would probably be fine just using the holes as is as they worked so far, but kinda bugs me. Maybe this isn't as uncommon as I think, but first I have ever encountered it. I have seen a Swarovski scope with a small diameter hole blown clean through the objective bell when a screw let loose from a hole drilled into bore.

View attachment 735019

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Is this your barrel or a customers barrel?
If its a customers barrel I would tell them that its a liability and they will need to order a new barrel before work can continue.

If it were my rifle id order a new barrel.

 

[roklok]

It's my rifle, I agree if it was somebody elses I would be very hesitant to work on it for liability reasons.

 

[Ontario Hunter]

I did some measuring. As close as I can determine, the holes are .237" deep from barrel surface to bore. The sight mounting screws are only using the top .115" of the hole. I could run some small threaded plug screws down to bottom of holes with loctite or epoxy, and still have enough threaded hole above to secure sight. Or, I could just use longer sight mounting screws that utilize most of the .237". I could also plug and relocate the sight, but either way the holes will be filled primarily with a threaded screw, I am not sure how much additional strength a bit of weld at surface would add if I chose to plug and weld.

Option #1 is your best solution. Two screws in the same hole and it will be plugged solid. Loktite would be better than epoxy which could permanently seize both screws. I don't think you want that. You may need to redesign a screwdriver head so it slides into the screw hole to tighten the bottom screw.

 

[steve white]

Well, if you did TIG weld, and it extruded into the bore, how would you correct/smooth the disruption to the rifling? The temper of the metal will be affected, as well as the blueing. It has worked plugged, and could work again. I'd let the sleeping dog lie.

 

[farmer_john]

Well, if you did TIG weld, and it extruded into the bore, how would you correct/smooth the disruption to the rifling? The temper of the metal will be affected, as well as the blueing. It has worked plugged, and could work again. I'd let the sleeping dog lie.

Conversly what was done has been undone. With no assurance it can be redone without issue.

 

[Longwalker]

It's a Remington. About what I've experienced and expect from Remingtons. If it was mine I'd get rid of it (sold at a low price) with a full warning to the buyer.

 

[Grumpy gumpy]

Well, if you did TIG weld, and it extruded into the bore, how would you correct/smooth the disruption to the rifling? The temper of the metal will be affected, as well as the blueing. It has worked plugged, and could work again. I'd let the sleeping dog lie.

It is possible to anneal a piece of brass to dead soft and tap it into the barrel to act as a backing plug. If done correctly it will "form " itself into the rifling, you can then weld on that.
This is not a cheap or easy option nor is it a guaranteed method as it’s easy for it to go wrong if a lot of care isn’t taken. Financially it would be cheaper to fit a new barrel, at least down here it would
Gumpy

 

[Andrew NOLA]

Sounds like factory Magna porting. I pay to have that done

Put it back together and see if gas leaks around the screw. The rifle has been shot a lot just like it is so far.

I'm not sure this is actually an issue.

 

[AZDAVE]

Any time you are talking a major safety issue “hole drilled into the bore” on a bolt gun. I default to a new barrel every time.

 

[roklok]

I ran a bottoming tap to the bottom of the holes. After I did so, no light was visible as before when a flashlight was directed down the bore. Apparently when the holes were drilled they did not quite break through, subsequent firing ruptured the thin metal remaining. The tap pushed the metal back shut. I then ran plug screws slathered in red loctite down to the bottom of the holes. There are still enough threads to mount the sight above the plug screws. I am still undecided whether to weld over the top of the plug screws and relocate the sight mounting holes, or simply mount the sight and move on. I am leaning towards using the barrel, it had been fine to this point, and if I had not removed the rear sight I would be none the wiser.

742 barrels have been converted to pump action by plugging the gas vent, granted that vent is 3 inches further down the bore and smaller diameter than a sight mounting hole.