I'm looking for input from the resident gunsmiths here. Your suggestions would be appreciated.

Buddy broke the 6-48 front base screw on his 700 in .308 Win, and took it to a gunsmith. Gunsmith drilled the fastener threads out of the action and did a sloppy job of converting to 8-40, with the barrel installed. More importantly, he drilled into the barrel. I believe that the gentleman that did this work was competent in his younger years, but in his advanced age it seems like he might have lost his edge.

Anyway, it appears that the hole is ~0.3" deep, measured from the top of the receiver. If my math is correct, the gunsmith drilled into the barrel ~0.156". That should leave ~0.138", between the chamber wall and the bottom of the botched hole job.

I understand that there are minimum chamber wall specs, but these are for the entire circumference of the chamber. Are there any specs for the minimum amount of material between the chamber wall and a blind hole?

I see some references to 0.1" as a rule of thumb, but don't know where it comes from or how accurate that information is. And some gunsmiths have mentioned that this only applies to the barrel, forward of the chamber.

Is the barrel usable or should it be scrapped?

Deeper then it needs to be, but not unsafe.

I would have pulled the barrel, but that's me, should be safe

I would have no issue with it.

Ditto to all above this...

Just out of curiosity, does the gunsmith even realize he did it?

I had a guy bring me one once where he’d drilled all the way into the chamber, like a pressure barrel for a copper crusher. His complaint was that ever time he shoots he has to put a new screw in the front base hole because they fly out and hit his scope! And the brass has a hole in it for some reason.

I put a new barrel on it and ran the base screw holes out to 8x40s and had a customer for life.

I don't think he did, but didn't talk to him.

Thanks for the feedback guys.

For anyone curious, the images below show the hole.

some ugly work there.
as to a hole into the chamber , if the screws have good threads they wont blow as one post says. and the brass usually only has a pimple on it , making extraction hard.
had a 257 Roberts in a 98 mauser with that condition. finally got a screw the right length, honed the chamber and cured that. no more pimple.

Fu ck that chit. You didnt pay to have a hole drilled into the chamber. You need to find a real smith and not someone that hangs his shingle out claiming to be one.

Very interesting. I figured that the brass would flow into the hole, and completely prevent extraction.

The gunsmith didn't drill into the chamber on this rifle, but I've wondered what could happen if he did.

I've never met the gunsmith. It's a cheap rifle, and lessons have been learned by my buddy. Water under the bridge.

Yeah, it sucks but at the same time I think this gunsmith was well regarded years ago. He's just lost his mental capability, and doesn't appear to have anybody to keep him pointed in the right direction. Bigger problem than the botched hole job in this rifle.

I hope the old man can find a way to walk away from his old profession. Must be a hard thing to do, when it's been your career for so long.

If I am reading and understanding correctly, the hold didn't go through into the chamber. It's just into the barrel threads over the chamber and left a wall thickness of .138".
Correct?

If that's so I think the work was not done as carefully as it should have been, but it's not unsafe. The cylinder walls on a 454 Casull are thinner than that, and the 454 runs a higher chamber pressure then a 308 rifle. So .138" may seem thin, and it's far thinner than the standard wall thickness, but not too thin to be safe.

You said he drilled into the barrel. How could he *not* drill into the barrel if he was enlarging the hole diameter? Then you ask whether the distance from the bottom of the hole to the chamber is safe. Then you show us a hole right into the chamber. I'm confused.

Did you look at the picture ? Its off center in a ripped up hole that needs spotted with an endmill and then tapped,

I agree, I think you are confused

A Remington 700 receiver has four 6-48 holes for the base screws. All four of the tapped holes are thru-holes. The forward most hole, closest to the receiver lug, appears to be a blind hole. It appears blind because the barrel is at the bottom of the hole! You don't drill and tap the barrel for that base screw.

The barrel in that area does not normally have a hole drilled into it. It should have unmolested threads on this shank region. With the botched job, the gunsmith drilled a blind hole over the chamber.

Make sense now?

Yes, that is correct. He did not go through into the chamber.

I assumed that the receiver wall is 0.144" thick. The hole, made by the gunsmith, measured from the top of the receiver is 0.3" deep. So, I figure the depth of the hole, into the barrel, is 0.3" - 0.144" = 0.156".

I also assumed that the diameter of the barrel shank is 1.062". And the diameter of chamber (.308 Win) to be 0.474". So (1.062" - 0.474")/2 = 0.294" for the chamber wall thickness.

The material between the blind hole, made by the gunsmith, and the chamber proper, would be 0.294" - 0.156" = 0.138".

If anyone sees a problem with my math or assumptions, please let me know.

Jason

I've never understood the boneheads that wouldn't set the depth stop on the drill press/mill so that kind of thing doesn't happen. Unless I'm drilling a thru hole, I ALWAYS set the depth stop !

szihn,

I thought that the 454 and 480 cylinders use different steel, and/or heat treatment, than the common 416 stainless in a 700 barrel? I was under the impression that it could handle much higher pressures due to higher strength material?

Jason

The pictures are too close. Everything looks ugly when magnified that much! Anyway, a hole that small with anything over .1" of chamber wall thickness, isn't going to be a problem. Homely, but not unsafe. Broken screws are often a real problem because they break off when they bottom out on the barrel threads. The remnant is torqued down tight so it is locked in place. In addition, it has already deformed the barrel threads and will deform them even further if the barrel is unscrewed without removing the screw. If the screw has broken off from simply being over torqued, the remnant will be loose once the head is gone and can usually be winkled out with a scribe or punch. A bottomed out screw usually has to be drilled out. When I have to drill one out, I usually use the Forster jig and a carbide bit.
I have seen a couple which have been drilled through. One was a Savage 99 in 308 which , when fired, blew the scope off. The other was a 22. The owner shot it until the little brass discs filled the hole and kept right on shooting it.
By the way, I'm getting a little sensitive about "advanced age" comments! There are an awful lot of us well past retirement age. GD

Thanks for the comments, GD.

Jason

Think about it. If the barrel is on and the rifle needs to be drilled and tapped, you will need some room to run in the tap. It ain't practical to tap it all the ways with a bottoming tap. Just don't go to far.

As I figure it, it's a matter of hoop strength. Stress will flow around the hole, that's how drilling a hole stops a crack. It spreads stress around the diameter of the hole instead of focused at one point. A I read it there's plenty of metal there to handle the extra stress, Gunsmiths here say it's safe and I think that's why.

Very true 4th point.
17-4 Stainless is used by Freedom Arms. (I don't know what is used by Rossi My 92 lever actions , Ruger in both the Super Redhawk and the #1, and TC in their encore) In the case of the Rossi 92 you should measure the wall thickness of their barrels at the dovetail cut. The sight is down the barrel so the pressure is lower there, but it's only 4.5" down the barrel from the chamber yet I have never seen one or heard of one letting go or bulging there.

So you are correct. But factor the wall thickness in the full length of a shell of a 454 running pressures far higher and then factor the pressure you'd need to press a dimple into a hole only .120" at it's base and that hole having a point which would act somewhat like a load bearing arch. Like this>>> V so the max pressure is on the smallest area.

I was alarmed is times past working on factory Ruger #1 barrels when I found how thin the spots were under their quarter ribs where the mounting doles were drilled and tapped on such caliber as 7MM Mag and 300 Win mag. Some were as thin as .058" and yet I have never seen one dimpled (or bulged from the inside.)

As I said, I think the work was a bit sloppy and I sure would have only set my drill to penetrated the full receiver and then into the barrel threads about .020. Just enough to get full threads in the receiver ring. But that being said, the wall thickness is adequate to hold the pressure (IF those measurement giver were indeed correct.)

Just as a possible point of interest:
I got out my Freedom 454 and measured the wall at the 12:00 position of the chambers. It's.126" That a 5 shot cylinder.
I know the Ruger SRK is a 6 shot and I think the walls of that gun are even thinner, but maybe one of those reading along has one? If so, can you measure the thickness of the walls between the chambers and tell us all?

Consider the expected failure mode, It's in tension in the chamber annulus. An axial split - hoop strength failure. A weak spot will go elastic first transferring tension around the defect. Which, of course,, we expect to be strong enough to handle the extra stress. So you can't really go by the thickens of an annulus without a defect. No? Except, of course, it's definitely safe if the thickness at the defect is at least a thick as a sufficiently thick n unaffected annulus, all else being equal.

Interesting info, szihn.

I don't have the Ruger or know about the dimensions, but the Carpenter metal company lists the alloys used. I didn't know that the barrel material was upgraded, as well as the cylinder.

https://www.carpentertechnology.com...revolvers-get-lift-from-aerospace-alloys

When this problem was first presented to me, I looked for the minimum chamber wall specification and found that C.I.P. specifies 3.3 mm to 4.7 mm for the .308, depending on category of steel used. So 0.130" to 0.185". However, with the 700 we have the action surrounding part of the chamber, and the area in question.

Although I have a background in product test and development, the areas of material science, structural dynamics, and fatigue behavior are outside my realm of knowledge. In my ignorant perspective, a rifle chamber is essentially a simple pressure vessel but adding a blind hole is something that I don't pretend to understand in terms of design limits. I am very happy to say, "I do not know and will ask people that do!"

Gunsmiths here say no problem, don't worry about it. I'm just looking at how could that be. In my weirdness I find such questions interesting. I'm just following the stress which is not the same as a chamber of homogeneous wall thickness. Don't need to be an engineer to do that.

I have rebarrelled many rifles a suprizing number of them hav at some point been drilled into the barrel...none of them had a problem....I wouldn't worry about it...
How I would have done it was pull the barrel and drive the screw out shearing off the threads...brownells has a kit that you then just tap that hole and use the oversize screw....no walking around drill bits and offset holes...

I know of gunsmiths who relieves the barrel threads under the base hole in the receiver on purpose.

I was wondering who drilled them. Factory, owner of the firearm, or gunsmith.

David Miller does it as a matter of course.

I may do that one of these days. Anyone check out the thread depth of the front 2 scope base holes on a Browning X-Bolt receiver. You have about 2 usable threads on those 2 screws. Recommended torque on those 2 front screws is 10 inch pounds, not much. If you used a smaller than tap drill size centering bit first, going less than .2" deep, followed by a tap drill, you should be fine, Then tap the threads all the way to the bottom of the holes. With the X-Bolt scope base holes being on the sides of the receiver you would not get too close to the chamber. RJ

Update on this, for anyone curious.

My buddy didn't want to spend more money at a gunsmith. And I sold my action wrench and barrel vise several years ago, so we couldn't take the barrel off to clean up the threads. Nobody close with tools that we could borrow either. The hope was that we could clean things up a bit, and put it all back together.

I didn't have an 8-40 tap, and was planning to modify it anyway, so I got one from Amazon. I ordered a plug tap, and ground the tip down shorter in stages. Basically run the tap, then shorten to get full depth threads at the bottom of the blind hole.

I think it cleaned up pretty good, but the hole was butchered by the gunsmith with a lot less thread engagement between the fastener threads and receiver threads. Basically the minor diameter in the receiver hole was oversized. The 8-40 hole also seemed way off center, but I don't know if the gunsmith did that or if it came that way from the factory.

Not a gunsmith.

Agreed, based on the work done. And this is no attack at you, since there is some back story, but I think he was actually really well regarded for many years. Many decades actually. I know people that have had really good service from him, and see a lot of online discussion about his quality work and knowledge from a few years ago. Especially older rifles, and Mausers in particular.

When my buddy last talked to him regarding the sloppy threads, it seemed like he wasn't at the same level, mentally.

I know that some people think that the gunsmith screwed up, which he obviously did, and others are upset about my opinions on his declined ability. I'd like to state that we are not interested in pestering this gentleman for a refund, but also hope that he hangs up the apron. Advanced mental decline, which is what we think is happening, needs support from caring friends and family. Much more important than a buggered up hole in a cheap rifle. It's not age related, per se, but when you can't perform at the expected level then something needs to happen. And as far as I know, he was really good at his profession until recently.