I'm working on a Ruger #1 and I'm drilling the barrel for #6 screws to hold down the scope bases. Two of the holes will be above the chamber, so I'm wondering how deep I can go. I figure I can go at least as deep as the tenon. Is there some rule of thumb on how much chamber wall should be left to the drill point?

DO NOT KNOW ABOUT DRILLING, BUT HOW ABOUT SWEATING OR SILVER SOLDERING THE BASES ON?

Minimum .125" wall but thicker better and on magnum calibers I'd go thicker still.

I found a serious mistake in a Riflesmithing book and it stated that the front receiver hole is the only hole that doesn't go through the receiver. (wrong you must correctly position the sight base as to not drill into the receiver lug surface) The depth is calculated as follows barrel diameter minus groove diameter divided by two minus .125" well if you did it this way you might drill all the way through the barrel wall over the chamber depending on where the hole lines up with the chamber.

So you one: Drill a very minimum depth. Or two: calculate the diameter where you drill will be over the chamber and subtract at least .125" preferably .187" for magnum calibers.

These are minimum depths, always drill only what is need to do the job. i.e. drill just deep enough to leave sufficient wall thickness or in the case of a very thick barrel drill just deep enough to get 2 X the diameter of the screw thread engagement.

One good rule of thumb is that a screw's threads are at maximum holding strength when their engagement length is as long as the screw's width, that is, about 0.120" deep for a #6 screw. The Ruger's barrel thread tenon measures 1.000", leaving a chamber wall thickness of ~0.240" when using a belted magnum case and even more if using a standard '06-head case.

Ackley tells us that a standard-pressure cartridge in a modern steel barrel needs AT LEAST 0.125" wall thickness over the chamber area; however this applies only to the overall wall thickness, not the small area encompassed by the body of a #6 screw.

In my experience I've found that 0.100" is a more-than-adequate wall thickness for the chamber at the bottom of a #6 screw hole, which means that you can make your holes ~0.150" deep with no problems and still retain maximum holding strength. Just make sure that your screws don't bottom out before they clamp firmly!

For very thin applications, I've ground special flat-end drill bits and taps so that I can tap clear down to the bottom of the resulting flat-bottomed hole; this gains an additional 0.020"-0.030" for those borderline featherweight barrels.
Regards, Joe

You might find this thread interesting, it was for me.

It appears the Flicks have "timed out" in the thread. And it seems the split began in the Flutes(maybe), but they went straight through the Scope Base Holes as the Chamber came apart.

Best of luck to you.

Thanks for the replies guys!