Drill & Tap Barrel

[dannylj]

I need to cut off, redrill, and tap a barrel for new breech plug (long story). I have bits, taps, and dies but have never done anything that large. I realize I will have to have a shoulder tapped to the bottom to refit the plug. Should I attempt this or find a machine shop.  Dannylj

[Larry Luck]

Good question.  I'm looking forward to the answer.
Larry Luck

[billd]

Since I work in a machine shop, I would say don't do it your self.  I would reccomend putting it in a lathe to drill and start the tap.  It shouldn't cost much to have done.  I would guess an hours labor at most. Tell the shop you can supply the drill and tap. Most shops won't have the correct tap on hand and will add the cost of the tap to the job.

Where are you from?

Bill

[Charlie B]

I would agree with billd if you don't have a lathe wouldn't do yourself. Not difficult but needs precision.

[dannylj]

I appreciate the advice guys - I may have to find a shop. It's just that I have built 3 rifles and was hoping I could add to my limited abilities. Bill, I am in West Monroe, La. (northeast part of state).  Dannylj

[Dphariss]

Best to do the boring in a lathe to make a flat bottomed hole.
Trying to drill it without some serious support might be a PITA.
Be careful with the tapping you will need to regrind the tap so it cuts to the bottom of the hole. Need not be more than 5/8" long.
Dan

[billd]

Danny,  If you were close I was going to offer to help you out but it's about a thousand miles.
Bill

[rich pierce]

At the museum at Bolton, PA where the old Henry shop once was there are some great old tools.  Included were gun barrel taps that had a pilot that went into the bore.  Maybe they did the breech threading before they rifled the barrels, I don't know.

I have drilled and threaded breeches on a drill press before and made the end of the plug mate the angle of the drill.  No problem.  Just get things really lined up using a drill or rod that is as near bore diameter as possible before proceeding.  I unbreeched a 1978 rifle of mine so breeched last year and it was clean as a whistle.  On the other hand I don't shoot that much.  If I had a lathe and knew how to use it, I'd use that.

After reading the cautionary notes below, I got lucky I guess.  Would hate to have someone try based on my luck and cob up a breech.

[longcruise]

I did this once and don't recommend it!!!  I used a slightly undersized drill to allow for my sloppy drilling.  Started with a through tap and gradually ground it down till it was a sort of bottom tap.  Did this with a hand drill and a bench vice.

Will never do it again!

[Acer Saccharum]

Drilling a large diameter hole by hand in steel is one of the worst scenarios in the world. Once the drill grabs, either you or the barrel are going for a spin. There is no doubt that the drill will grab many times during drilling, and trying to keep thing straight is secondary to keeping you hands and wrists intact.

During the above scene, you will also get the hole out of round and oversized.

Similar situations encountered while standing on a step ladder, drilling floor joists for 3" waste lines.....someone is going to go for a spin, and it ain't the house.


Now Rich mentions a piloted drill, as seen in antique gun tools. This would be a lot safer tool  to use by hand. the pilot keeps the drill centered, and straight with the bore. Who has tools like that anymore?

Take it or send it to a shop that knows what they are doing.

Acer