bbl staples not on centreline

[WadePatton]

I'm not sure where I first ran across the idea, but I've recently read a lot of threads about underlugs and understaples without seeing it mentioned again.  So i'm bringing it up here to ask if anyone does it this way.

The idea is that drilling a shade off-center (east or west of N/S pointed bore) can give substantially more metal for "margin of error" and resultant bbl thickness and bore preservation.  This avoids drilling at the absolute thinnest cross-section of the bbl. 

I haven't tried it, but do follow the logic. And still don't remember where i heard of it.

[galamb]

Never thought of that, and I do use staples whenever I can.

I have heard/read from numerous sources that you need to leave .05" barrel wall for safety - personally I won't go less than .08" just in case the drill runs a little deep.

If I can't leave .08" then I usually switch to tennon's and solder them on.

But the (kitty cornering) staples might solve that (self imposed) safe wall thickness issue. Can't see why it wouldn't work ()

[D. Taylor Sapergia]

Another two advantages to setting tenons off centre has to do with the slide or key, if you go that route.  If the slide enters the stock from the left side, setting the tenon's loop to lay right of centre means you don't have to withdraw the slide so far to release the barrel.  Thus, the slot for the keeper pin does not have to be as long.  All that being said, I haven't used that technique - yet!

[oldarcher]

I built a Hawken a year ago and used a NOS GR Douglas barrel and a partially finished stock that had been started and left unfinished 20+ years ago. I had to completely rework the previous builders work and in the process discovered that the patent breech had voids and had to be replaced. To keep the great stock I had to set the barrel back about 3/8" and could not use the staples that I had installed. I had to place the staples to either side of the centerline and it works great. I would not have thought to offset the staples if the barrel would not have had to be moved. I find NO objection to the staples offset and in fact I think that because of the additional metal off center it makes sense to do that! I also admit that I have not offset the staples in other builds that I have completed since I did in the GR Douglas rifle. The rifle shoots great, looks good and the offset staples are a non-issue.

[Acer Saccharum]

I would hazard a guess if you are concerned about the barrel too thin to staple on center, then it's too thin to staple off-center. You're not going to gain a lot of thickness by moving 1/8" off to one side.

Dimpling the bore is the biggest concern with staples.    Second is drilling into the bore. 

But the idea that the keys don't have to be withdrawn so far is wonderful. That advantage alone makes it worth offsetting the tenons.

[Herb]

I build all my Hawkens with the staples off-set from center.  There is a little more steel at the edge of the bore and a little more wood to the side of the ramrod groove.  But the biggest reason is that you don't have to pull the key as far to clear the underlug to lift the barrel out of the stock.  You can also make dove-tailed underlugs with the  loop offset to the side.

[WadePatton]

.... You're not going to gain a lot of thickness by moving 1/8" off to one side.

Dimpling the bore is the biggest concern with staples.    Second is drilling into the bore.  

...

I'm not concerned, I'm discussing technique.

Yeah, it's thicker 1/8" over for sure.  It gets thicker all the way to the corner.  

HAY, somebuddy with CAD program draw it up for us.  I don't has that right now.  But we only need 2 concentric circles inside an octagon.  The inner circle is the bore and the outer circle would be the groove depth (could get by with just this one).  The octagon is your bbl outside dimension, AT the point of attachment.  I'm interested to see what difference .125" from center of land/bore would make.  Maybe it should be 3/16"?

Is there an APP for that?  

Of course this assumes bore/bbl concentricity, margin of error should consider that.



Specifically the waist on a A-wt Colerain PA44 is listed as .668 and I'm working with a .40 which has round-bottom rifling at .012".  Of course we don't fool with the six inches of .668, but how far do we need to go into the flare to get certified "ok" wall thickness?  Do we go to .690 or .700 or more?

That depends, a dovetail is cut all the way across, thereby removing metal at the thinnest point of the cross-section.  A staple needs two holes.  Those holes do not have to be in the thinnest part.  A scalable drawing would be handy dandy-even for dovetails.

Yes, I'm being redundant, but just trying to catch the interest of a CAD person, so i don't spend all day looking up the software to do it.  

Here's a non-scaled section (quartz!).  With a CAD drawing/app properly scaled we might know just how far laterally to move the holes for a significant difference. But i've wasted enough time trying to dig up appropriate drawings.



The "thickness" diff between 12 and 3 minutes after looks significant to me.


along those lines: I did do some comparisons in published specs (not actual measurements) between my 40/A and 45/B to find that there's no appreciable difference in wall thickness.  The larger bore and the deeper rifling cancel out the heavier contour.  I'm going to weigh them to verify.

But then also, this is gun making not rocketships and traditional methods and considerations tend to work out just fine.  Methinks that staples give more chances for error, probably should be reserved for the less ham-fisted smittys.