Safe depth for drill/tap on 12 ga, 20 ga barrels?

[jkpq45]

Hello All,

Looked through the FAQs and couldn't find any info--leaning towards using the Loctite 380 BlackMax vs. drilling and tapping for a scope, but would like the added strength of screws.

Any opinions on max safe screw depth on the 12 gauge and 20 gauge barrels?

Thanks,
jkpq45

[quickdtoo]

Screw diameter deep on a 20ga is fine, ify on a 12ga, most gunsmiths won't D&T a 12ga for that reason. H&R solders steel bases on their 12ga barrels (except USH).

Tim

[jkpq45]

Thanks for the input, quick.  Kinda what I figured.

[jkpq45]

As an aside, am I going to booger up my 12 ga chamber if I heat it to ~400° F to get the steel base soldered on?

[quickdtoo]

I've not done it, but I'd say no, lots of sxs barrels are soldered together, read about em when I was learning how to blue a barrel.  I've soldered forend lugs on with no problem tho, it didn't affect the blueing, I use low temp(450º) high strength silver solder I bought on ebay, see soldering shims in the FAQs barrel fitting info. Epoxy has been used too, good surface prep is imperative tho, I think I'd D&T one hole for a recoil lug, I used one blind hole on my M1908 peep sight along with Black Max Loctite.

Tim

[gcrank1]

Gunsmiths wont D/T  12ga. due to the dreaded liability. Point of fact is there are a bunch of rifles that have had scope mount holes accidentally drilled through and a lot of them people dont know about. A properly snug fitting screw (When using a taper tap one should 'stay in the taper' rather than just running all the way up onto the major tap dia. right away and check the screw fit as you carefully go deeper in). with a full to chamber flat end when tightened down wont blow out.
As to depth other than a through hole: If you calc. the wall thickness and only drill in 2/3s deep it may give you a full screw diameter, which, as said, is sufficient. I tend to like a bit more, if I can get it and not exceed the 2/3s. It gives a little more depth for going from a plug tap (a taper tap likely wont even start a thread) to a bottoming tap as well as that thread engagement.
BTW, with a Dremel and cutoff wheel you can make a taper tap into a plug tap into a bottoming tap. I use a magnifier too. I greatly suggest using at least a well set up drill press as a straight guide with the tap handle head centered by a chuck mounted center. Bench vise/hand drill and hand turned D/T is for mechanics, not gunsmithing.