what is the safest depth to drill scope mounting screws

[LAGS]

You should measure the barrel WIDTH at the part right below the front of the sight Dovetail with a Dial Caliper or Micrometer.
Then measure the Barrel Width right below the Rear of the dovetail.
Then subtract the .312 BORE diameter from those two numbers, and then devide each of those numbers by 2.
That will give you the barrel Wall thickness at the front of the dovetail, and the rear of the dovetail.
And that is the area you will be drilling to mount your base.
Your mount has set screws that Pinch the scope base on the dovetail , correct ?
Leaving the set screws and drilling and tapping the Base, so you can add two more set screws going Down may just keep your mount in place without having to drill into the barrel.
And you can install the mount with the top set screws tight, then remove the base, Look for the set screw marks on the flat of the dovetail top, so you can drill two Detent dimples in the top of the dovetail to help front and rear movement.
Then if that doesnt work, you can drill the base out thru the same holes for a screw to pass thru, Then, drill and tap the barrel in the same detents, for the new screw to thread into the barrel.

[corey012778]

I measured from the point of where the mount meets under the dovetail not the width of the flat point of where the mount sets on top. using a caliper and micrometer to confirm my measurements.

[LAGS]

You want to Measure th Round part of the barrel.
You do not measure any part of the dovetail or any where near it.
It is like drawing a Circle in a circle.
The outside circle is the Barrell Diameter.
The Inside Circle is the diameter of the BORE
Barrel diameter, minus Bore diameter, Devided by 2 equals the wall thickness on one side of the barrel.
But that wall thickness is the same all around the barrel, unless you have a Fatter part like on top of the barrel from the dovetail being on top of the barrel.

[corey012778]

ok, had to reread the last 2 or 3 post. got kinda confused.

did find my first slug for these barrel. have a .312. barrel is .757 so it is one side thickness of .2225. remember with out scrolling back. need half of that as the safe depth is half the thickness of one side of the barrel so that is .111. I have an 91/30 that has a sight pin that go thru barrel, I was able the measure the depth of that I beleave ( no notes being pulled up) .110.

I got hung up on the dovetail. lol

[LAGS]

You have got the Math Correct.
The only thing I question is the Barrel Outside Diameter. and that is only because i do not have a 91/30 to measure and compare it with, and the closest thing I have right now is my M-44 which measures .720.
But you may be correct for your model.
I don't want to seem too picky, but I really want to make sure you are understanding what I am trying to explain.
I can not post pictures, but I can on regular Email if that helps you out or is needed.

[LAGS]

BTW
You might consider trying Slow rust Bluing on some of your small parts like the Magazine and such or small parts for your other rifles.
You can boil them on a Kitchen stove in a pan like a old Bread Loaf pan ( steel of corse )
Then you can decide later if you want to buy a Larger Bluing Tank to do the whole barrel and action, or have a tank made at a sheet metal shop near you. Do not make a tank out of Galvanized metal or Aluminum they wont work.
I can fit my Bluing tank on the kitchen stove actoss two burners, if it is too cold or raining outside to do it on my gas burner. ( Yep, you guessed it, I am not Married, I can get away with that kind of stuff in the kitchen , and hanging the parts to rust in the spare bathroom shower stall )
Contact Andy about the acid to use, and there are plenty of things on the net if you need instructions.

[corey012778]

next thing is on my list is finding the center of the scope base and marking that. all the practice. did not like any of the drill presses the local hard ware stores had so I ordered one, wait for that to come in.

[LAGS]

Lacking the machinests centering Tools. I suggest using a Combination square and some Dye Chem.
If you dont have DyeChem, then you can use a Black or Blue Felt tipped Marker to darken your dovetail flat for clearer marking.
To use the combination square, measure the width of the dovetail Flat.
Devide that measurement By 2.
Now lock your Combination square at thar measurement.
Place the square on the side of the Dovetail, and Mark a line in several spots with a scribe or razor knife along the Flat.
NOW
Put the square on the other side of the dovetail, and make a centerline, without changing the Combination square adjustment.
The Lines may not come out exactly the same, but that is OK.
The space Between the lines will be the exact center of the dovetail flat.
The ink makes your marks more visable when you scribe the lines.
Or you can use the square to mark your sight base for centerline, drill It, then mount it on the barrel and mark the holes on the dovetail flat thru the holes in the scope base.
I drill the base, then drill one hole into the barrel.
Then I mount the base with that screw to hold it in place, Mark and drill the second hole.
Doing one hole first also lets you make any right to left adjustments you need to make Before you drill the second hole.

[NoAngel]

One thing to remember when drilling and tapping ANY hole, anything over one and a half times the diameter of the thread is a waste of time. Threads deeper than this give zero advantage.
A half inch bolt threaded in 3/4" deep is at its maximum strength.

[LAGS]

You are correct for Pull out.
But if needed, and metal Permitting, the extra depth can add Lateral stability, even though the sheer strength remains the same.
Lateral stability is Not needed for mounting Scope Bases.

[corey012778]

problem is, is with my mount, I have a set hole but it is going to be 10x or more bigger then I am planning on using so setting center on it will be hard. the other. it is still new, crisp black coating dont know if it is a paint or a powder coat. so I would need a color other then blue or black. white grease pencil or a silver marker would work well. worst case, I could just strip the finish and powder coat i after I drill it.

the dovetail of the gun I am going to clean the old silver solder and dirt and grim off before I do some drilling.


the blue on the magazine is in great shape. I don't see even a scratch on it. the barrel look horrible. going to have to think of something other then the blue i bought already (nu-blue off fleebay). reblued the trigger guard on a inline muzzleloader. coming out looking pretty good. I strayed a little from there directions. first time I seen someone write use paper towel to apply anything. I used my favorite thing to apply some type of solution with, a cotton makeup pad. took me an hour to apply the first treatment took an hour second and third was an hour total. half hour to hour between. it is a instant blue. seeing if it will darken anymore if I let it set overnight and then do the last two steps.

[LAGS]

When i said use a Black or Blue Marker to marl your holes, I neant.
The Top of the dovetail on the Barrel.
You are going to clean off the silver solder off the flat surface right.
Then you color The top of the dovetail base with Ink, so when you scribe your lines, you see Silver lines from scribing in the black or blue inked surface.
Now if the hole in the Mount is way larger diameter than say a 6/48 screw , you can always make a Sleeve or Bushing that fits into the hole in the scope base, and that has a hole thru it that the 6/48 can pass thru.
i use Brass tubing from local Hobby shops , Model Shops like for Trains , Planes or R/C cars.
Find the size that fits in the scope base, and if the inner diameter is still too large, then insert the next smaller size tubing into the first tubing.
Then if that hole is Too small to fit a 6/48 screw thru, then you just drill out the hole.

A Tip; If you have to use a Tube in a tube to make the right size tube, then solder the tubes together when you slip them together. Then they wont come apart, and are esentually one thbe or bushing.
A Bushing is better than using too large of screw just to fit the hole.
And the screw is holding Down, the tubing only centers the scope base to the hole.
To mark the hole, wither With or without the bushing, Take a peice of round rod that fits thru the hole in the scope base. If you dont have one, Make one with your Poor Mans Lathe and a file.
Then put a Slight point on the rod using your Poor mans lathe.
Now, with the flat Inked, you install the scope base on the dovetail, then insert the pointed rod down thru the hole in the base, and tap it a few times Lightly straight down into the hole.
When you remove the scope base, you will see a shiny mark from the point of the rod in the inked surface.
That is the Center of the hole, and will be centered on that hole no matter if you use a 6/48 or a 10 screw.
Now they make Punches called Transfer Punches just for this type of work.
But I cant see you buying a whole set of punches just to do one scope mount.
I have transfer punches, but most of the time I have to make one like I described, because of Odd Hole sizes or holes being Metric or something.

[LAGS]

When i said use a Black or Blue Marker to mark your holes, I meant.
The Top of the dovetail on the Barrel.
You are going to clean off the silver solder off the flat surface right.
Then you color The top of the dovetail base with Ink, so when you scribe your lines, you see Silver lines from scribing in the black or blue inked surface.
Now if the hole in the Mount is way larger diameter than say a 6/48 screw , you can always make a Sleeve or Bushing that fits into the hole in the scope base, and that has a hole thru it that the 6/48 can pass thru.
I use Brass tubing from local Hobby shops , Model Shops like for Trains , Planes or R/C cars.
Find the size that fits in the scope base, and if the inner diameter is still too large, then insert the next smaller size tubing into the first tubing.
Then if that hole is Too small to fit a 6/48 screw thru, then you just drill out the holein the tubing.

A Tip; If you have to use a Tube in a tube to make the right size tube, then solder the tubes together when you slip them together. Then they wont come apart, and are esentually one tube or bushing.
A Bushing is better than using too large of screw just to fit the hole.
And the screw is holding Down, the tubing only centers the scope base to the hole.
To mark the hole, with or With or without the bushing, Take a peice of round rod that fits thru the hole in the scope base. If you dont have one, Make one with your Poor Mans Lathe and a file.
Then put a Slight point on the rod using your Poor mans lathe.
Now, with the flat Inked, you install the scope base on the dovetail, then insert the pointed rod down thru the hole in the base, and tap it a few times Lightly straight down into the hole.
When you remove the scope base, you will see a shiny mark from the point of the rod in the inked surface.
That is where you will Center Punch a dent and drill your holee into the top of the barrel.
That is the Center of the hole, and will be centered on that hole no matter if you use a 6/48 or a 10 screw.
Now they make Punches called Transfer Punches just for this type of work.
But I cant see you buying a whole set of punches just to do one scope mount.
I have transfer punches, but most of the time I have to make one like I described, because of Odd Hole sizes or holes being Metric or something.

You can clean the ink off the barrel with Alcohol or Acetone, and even Nail Polish remover you sneek away from your wife.

[corey012778]

I have alcohol (a staple in most of my cleaners from guns to bowling balls. sometimes the same cleaner hehe). and acetone. just reminded me, need to stop by the hobby shop and order my dermal workstation. owner is a friend of the family. one hole is drilled in the mount for a set screw so, I should be able to take a bushing/metal pipe, solder it in place. silver solder?
I would have to pick up a small enough rod, was going to ask if a nail would work, but I don't think I have one on hand long enough to work.

I did buy a punch set. not for these project. either misplaced, lost, or let people barrow some of the ones I had. I was needing a new set.

[LAGS]

To solder the sleeve or Tubing together, all you need is regular solder either plumbers or electrical solder.
Heck, I even Crazy glue one brass tube inside the other, and have even Glued the busings into the parts so they didnt come out and get lost.
Now , you are Getting A Dremmel work station ?
Now remember, A Dremmel Tool is "Bubba Gunsmith's" Best Friend, and also his worst friend.
Do not resort to using a dremmel for everything, Think the project thru, an look at all options, rather than grinding and cutting with a Dremmel to save time, or get things done faster. They are a Precision tool in the right hands, but also a great way to screw up a project in record time.
I think you can make a transfer punsh out of a 16 penny framing nail.
They are about 1/8" shank.
Just cut off the head of the nail with a saw or dremmel tool, then chuck it in your drill or drill press and spin it and run a file on it Flat to bring it to the Diameter you need, then while it is spinning make a shallow Point on the end.
It doesnt have to be tempered or anything for what you are doing, you will probably throw it away when you are done marking the scope base hole.

[corey012778]

I do a lot of polishing with a dremmel a lot for polishing, getting the work station for an extra hand.

[LAGS]

I have three Dremmel's or rotary tools, so I dont have to stop and change tips when I am doing something.
I even have a Air Die Grinder for that heavy stuff, like Rasping a stock to shape.

[LAGS]

I noticed something in the pictures of your scope base.
Basicly your base is a groved peice that Slides onto the dovetail on the barrel like a 22 scope rail, then is held by 4 Pinch screws on the sides.
Or do the lock screws hold on Side plates that do the tensioning, ( There are so many different models )
If the base is sliding front and back or coming loose, then you might have an easier option than drilling into the barrel and tapping it, if it has the set screws that pinch against the barrel.
You just have to make Detent notches in the area of the dovetail for the lock screws to lock into.
Just look for the marks left on the barrel where the lock screws marked the bluing or dovetail, and use a 1/8" Ball cutting point on your Dremmel to maks a depression for the set screw point.
No Tapping required.
Then you can also possibly put the sight retaining pins back in thru the barrel, If it is the model that has side plates to retain it and make notches in the scope base side plates for the pins to go thru.
Also , If the Base does now fit really tight to the dovetail on the rifle, You can put release agent on the barrel, then smear the inside of the scope base with JB weld after you clean it with Acetone or Alcohol and Glass Bed the scope base to fit your dovetail on the barrel.
It will come off after the epoxy hardens if you use release agent on the barrel.

Try the other Options First if you can.
I believe in the K.I.S.S. principal.
Keep It Simple Stupid.
Do not always jump to the most Radical option First.
Try the others, and you can still upgrade later.
But once you drill things, you are stuck with that.

[corey012778]

Then you can also possibly put the sight retaining pins back in thru the barrel, If it is the model that has side plates to retain it and make notches in the scope base side plates for the pins to go thru.

may take a closer look, may not be an bad idea, I don't think the sight pins are long enough. may have buy some or custom make them. doing a notch should not be hard. done that for a few other type project.

I most likely switch out the screws all around. I have found on these type scope set ups. that the screw are not the best. and the heads round out easy. nothing I done.

on mounting plate, I wanting to put long screws and tap the whole base out. they used almost the same length (just a hair longer) for it as they did ring screws. found I switched the ring screw and the plate screw.

may still work on drill and tapping barrels start with the metal stock I have and then with pipes. then hunt up or when I honed some skill and do a barrel change on the mauser I was give. and use the old barrel as a drilling practice for firearms.

[LAGS]

Try the pin thing first, and yes you can make the right diameter pins in your drill, with a file.
I too change out the screws on the " Less Expensive Mounts "
Be carefull, the threads may be Metric.
I have Two old Mauser barrels that I practiced cutting Dovetails or Stamping Calibers and such.
I also have two servicable Mauser barrels , One off a 98k and one off a Yugo Mauser, plus the Husquvarna sporter barrel in 8x57