Barrel lug location and depth question

[sean69]

I have a 31" swamped barrel & was planning lugs at 3" from the muzzle 5" from the breech and finally 17" from the breech [about center of the barrel] so there is lots of material at the muzzle and breech for the dovetails [lots!!] but near the center I have a width of 0.900", a calibre of 0.620" giving me a wall thickness of 0.140".
If I were to cut my dovetail 1/16" deep [0.0666ish] that will only leave me with a final wall thickness at that point of 0.074" ~ish at that point.

1. What is safe here? How thick should the wall be at this point? 0.074" does not sound like a lot of leeway!
2. Is that center lug ~really~ necessary on such a short barrel? [also the lock bolt is running through the tang]
3. I'm assuming the barrel caliber is measured from the grooves, not the lands. Are my calculations correct?
4. can I get away with a much shallower dovetail & still have the lug be secure, say 0.0300ish?

Here is the barrel, just for reference:

http://www.trackofthewolf.com/Categories/PartDetail.aspx/0/1/RICE-62-J

-thanks
-sean

[Mike Brooks]

Reduce your lug thickness to 1/32" or less. Put lugs  (from the breech) 9" , 18" , 27".

[Mark Elliott]

Dovetail slots should be no deeper than 0.040"   You want to maintain at least 0.10" of wall thickness.      

Your locations don't seem quite right to me.     There is no need to put a pin 5" from the breech.   Usually it is more like 10-12".   The pin locations should be fairly evenly spaced.    3" back from the muzzle sounds reasonable.   So, that leaves you with 28" to divide up relatively evenly.   That gives you 9-10" between pins.    Since you don't really notice barrel pins,  I work them around the thimbles, but still try to keep the distance between them to within an inch.   Usually it works out pretty well.    

As to the important lugs,  that center one and the front one are the most important.   They are there to attach the forearm to the barrel, not the barrel to the forearm.  

Caliber is measured land to land.

[D. Taylor Sapergia]

This little Jaeger rifle has only two pins, but it has a sling swivel in the middle that does the same job, since its screw passes through a lug dovetailed to the barrel.  The barrel is a Rice 31" x .62 cal.  Spacing is as follows:  from the breech end of the barrel - 8 1/2", swivel 20 3/16", and second pin 2713/16".  The lugs are brass dovetailed .032".  Mechanical fit - no solder needed.  The swivel lug is placed so that when the rifle is standing on its butt plate for loading, the swivel lays against the middle rod thimble.

[Acer Saccharum]

If you have a thin barrel wall, consider soldering a lug to the surface.

I seldom go deeper than .03 for my lugs. The lug is merely holding a thin shell of wood to the barrel, and this thin shell carries a ramrod. There is virtually no load on these lugs, so shallow is best.

[Acer Saccharum]

For a front swivel, I use a block for the swivel screw to pass thru. This prevents the forestock from twisting if the sling gets yanked hard from the side.

The lug on the right is a regular one, and the sling mount is on the left. Yes, I'm cooking my barrel, an attempt to heat color it.

[sean69]

thanks all....

hmm both books I read were recommending dovetails 1/16 deep......  grrr.

anyway front and rear are done/cut  there is going to be a sling swivel. so soldering a lug for that sounds like just the ticket.

thanks again.
-sean

[Acer Saccharum]

Sean, so many things change over time. Gun building is one of them. With swamped barrels commonplace, and many of these thin walled at the waist section, many of us prefer shallow dovetails for the lugs. Much of the advice in older publications was written at a time when straight barrels were the norm, and barrel walls were thick.

The lugs don't have much strain on them, but the swivel lug will. Hauling a deer out of the woods with the rifle slung over your shoulder will put that lug to the test. If it were mine, I'd dovetail it .04 to .06 deep, and then punch down the dovetails to lock it in. I would not trust soft solder for this purpose, unless it's dovetailed AND soft soldered.

[David R. Pennington]

I soldered the middle lugs on a 44" swamped and dovetailed the two end ones. (I used four.) Didn't feel comfortable cutting any more metal away in that narrow wait.

[sean69]

Sean, so many things change over time. Gun building is one of them. With swamped barrels commonplace, and many of these thin walled at the waist section, many of us prefer shallow dovetails for the lugs. Much of the advice in older publications was written at a time when straight barrels were the norm, and barrel walls were thick.

The lugs don't have much strain on them, but the swivel lug will. Hauling a deer out of the woods with the rifle slung over your shoulder will put that lug to the test. If it were mine, I'd dovetail it .04 to .06 deep, and then punch down the dovetails to lock it in. I would not trust soft solder for this purpose, unless it's dovetailed AND soft soldered.

Point taken.

Though I believe that could be mitigated by providing more surface area for the lug to be soldered to, weld our lug to a thin sheet of steel say; the width of the barrel flat, about an inch long and 1/32 thick then solder that. Much like you see Mauser sight sleeves soldered to the barrels, lots of surface area = no move.  I suppose you could make the sheet a little thicker depending on your web thickness .

Sound reasonable?

[L. Akers]

What I do on thin wall sections of barrel is cut a shallow (ie .030 deep), square sided notch as you would before filing the dovetail angle.  Take a cold chisel and lay one flat of the tip parallel on the bottom of the notch with the cutting edge in the angle of the notch.  Strike the back end of the chisel with a hammer to cut and raise the "dovetail".  1/2 of the dovetail will be above the surface of the barrel but you can use your 1/16" thick base lug.

[Mike Brooks]

Sound reasonable?

No, listen to Acer.