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Scope Base Screw Hole Down Into Barrel
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Picture of Nitroman
posted
Had a 'smith drill out No. 6 screws and install No. 8x40's. I noticed when I got home he had drilled down into the barrel, just over the chamber for the forward base screw. Using my calipers I could get the feeler in for 0.091", which is not the actual bottom of the hole as he used a normal drill bit. I would say 0.10" is actual (or close to it) depth. The barrel shank is 1.115 just before the receiver ring. Using the base of the cartridge (0.473) this makes the hole within about 0.451" of the chamber. This is a 7x57 Mauser. I have seen much less metal on military rifles, I assume this is safe? I have not fired it yet and am going to ask for opinions from other 'smiths before I go forward with any questions to my 'smith. I will not quote any names but would like opinions.
 
Posts: 1844 | Location: Southwest Alaska | Registered: 28 February 2001Reply With Quote
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Picture of Paul H
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If you have a small ring action, it is 1.3" in dia, with .98" threads, so even at .10" depth, you wouldn't be into the threads, as you'd have to go ~.15" deep to hit them. On a large ring action, it is 1.4" at the ring, and 1.1" on most barrel, threads, though the Turks are .98". You would still have the same depths, .15" before hitting the barrel.

Personally I'd be comfortable with a depth that hit the base of the threads, though no deeper.

 
Posts: 7213 | Location: Alaska | Registered: 27 February 2001Reply With Quote
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Certainly not a cause for concern in my opinion. Regards, Bill.
 
Posts: 3534 | Location: Elko, B.C. Canada | Registered: 19 June 2000Reply With Quote
<allen day>
posted
I know this: If some jackleg gunsmith started drilling holes into the reciever of one of my rifles without properly removing the barrel first, he'd own the bloody gun. That is atrocious, unacceptable, incompetent procedure, and there's absolutely no reason to do things that way except out of laziness and ignorance.

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<Don G>
posted
Gee, Allen, don't hold back, tell us how you really feel about it!

You just turned a six-dollar hole into a $100 dollar one.

I have done it, and will do it again - to my own rifles.

Don

 
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Picture of D Humbarger
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Large M98 receiver rings are about .200 (two hundred thousanths) thick if they have not been ground on. I'm with Don, Bill & Paul on this one. I don't think there is a problem. As to what the limit is; it depends on several things. Magnums are a larger diameter than your 7x57 so naturally you wouldn't want the hole as deep. I set my drill stop at the thickness of the receiver of whatever i'm drilling.

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[This message has been edited by Bear Claw (edited 12-28-2001).]

 
Posts: 8346 | Location: Jennings Louisiana, Arkansas by way of Alabama by way of South Carloina by way of County Antrim Irland by way of Lanarkshire Scotland. | Registered: 02 November 2001Reply With Quote
<Kerry.S>
posted
It has more to do with the competence of the gunsmith then the procedure. If the smith takes his time and gets the measurement right, There won't be a problem. but if he just starts drilling well then he'll be lucky to get it right. To say that you must remove the barrel from a gun to drill and tap for a scope shows how little someone knows about gunsmithing. What do you do about a leaf sight base or a barrle mounted scope or a quarter rib, You can't silver solder them all on. I'll quote from the Gun Digest Book Of Riflesmithing. "ALL BUT THE FORWARD HOLE OVER THE CHAMBER MAY BE DRILLED COMPLETELY THROUGH. THE FORMULA TO DERTERMINE THE SCREW HOLE DEPTH OVER THE CHAMBER IS: BARREL DIAMETER MINUS THE GROOVE DIAMETER, DIVIDED BY TWO, MINUS .125 INCH."
So you can see that the minimum wall thickness is 1/8 inch for a 6-48 screw hole.
I would measure the diameter of the case where the hole would be, and use that diameter in the formula and not the groove diameter, unless the hole was in fact over the bore.
Allen come over to my place I'd be more than happy to take $100.00 of your money for a ten dollar hole. Hey the customer is allways right... Right
Kerry
PS being that almost all production rifles now come drilled and taped, Then for the most part the only guns that would need to be drilled are military actions, Hardly worth the expense to remove the barrel.
"lets see sir... You paid $250.00 for this P17 enfield.... with the holes that will be a total of $400.00.

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If you can't hunt, fish. If you can't fish, Hunt

 
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Picture of Nitroman
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Gentlemen,
Thank you for your opinions. This rifle is the Brno I bought for my wife. VZ-24 action that has been ground to remove the crest off the receiver. The original screws were very small and hardlt any meat was holding the front base screw in. Now these No.8 screws are substantially larger and will definitely do the trick.
To address Mr. Days concern; the screw is longer than the original. What the 'smith did was drill out to size and then tap. Since the ring was relatively thin this is why I believe he drilled into the barrel a little. The threads go right to the bottom of the hole so it is apparent this is what he intended. This cost me a total of $186.00. The rear bridge had been drilled with the holes too close (he told me how much but I forget). He used his vertical mill to make sure all things in alignment and re-drilled then tapped. All-in-all this is a bomb-proof arragement on a 7x57 holding a Leupold 1.5-5x.
Now I need to attach everything and go sight in. The best part!!
 
Posts: 1844 | Location: Southwest Alaska | Registered: 28 February 2001Reply With Quote
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Picture of D Humbarger
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Roger i'm confused. Did he charge you $186.00 to re drill those holes?? Hell I only charge $35.00 to drill & tap an action!

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Posts: 8346 | Location: Jennings Louisiana, Arkansas by way of Alabama by way of South Carloina by way of County Antrim Irland by way of Lanarkshire Scotland. | Registered: 02 November 2001Reply With Quote
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