Breach plug trouble. Anyone else have this problem. (Must be hawken season)

[Thawk]

I was convinced to building a hawken for a friend of mine.  I ran into a problem with breaching the barrel. 

I screwed the breach plug in and of course it was too long.  So I started shortening it.  Got to the point where it came flush with the back of the barrel but it needed to turn 180 to put the barrel markings on the bottom.   (or at least where they won't be seen.)  No problem right, just shorten the barrel a touch and go back and forth between the barrel and the plug till everything comes up flush and tight. 

Then the problem.....  The plug would not longer sit flush with the back of the barrel.   I thought it must be time to shorten the plug a little.  So I do....  Still not flush we're talking a 64th of an inch here. 

hmmm I think, got to be something going on.  Look for messed up threads..  nope all good. So I measure the plug and the depth of the breach.  Plug is shorter than the depth of the breach.  uh-oh not good.  Finally I think to cover the plug with Dykem.  Where ever it is scraped of should be where it's stopping.   Took me a few times to see it.

There is a slight flare at the base of the plug where it was machined and apparently originally there was a small cone at the base of the barrel that accepted this flare.   When I shortened the barrel,  I filed off the cone....   So I put a slight cone at the base of the Barrel and...  Bingo we are flush again.   

I'll get back to it tonight but I may have to order a new breach plug.  I might have made it too short.  It's going to be close.  I'll measure it up and figure out how much a quarter turn of the plug will get me.  I'm hoping I'll be ok.

Has anyone else had this problem and what did they do to solve it?

[Don Stith]

THe countersink is the right approach. Depending on who's breech you used, it may still be all right
 Some makers of  Hawken breech plugs use 1/2" and some 5/8"depth.

[smylee grouch]

I might be looking at this wrong but a 1/4 turn of the plug-and if your plug is tapped 3/4-16-you would be moving the plug about 1/4 of 1/16 inch. Does that sound right?

[David Rase]

I might be looking at this wrong but a 1/4 turn of the plug-and if your plug is tapped 3/4-16-you would be moving the plug about 1/4 of 1/16 inch. Does that sound right?

A thread pitch of 16 to the inch would be .062" (1/16")per revolution, which ends up being 1/64" per quarter turn, if my math is right.
David

[Thawk]

Ha!  I was really dreading doing the math.  I kept looking to my left and right for a smart kid to copy off of.      I'll let you know how it goes.  I really wished I had figured the counter sink on the barrel before I took that last 64th off.  It's going to be close.   Those Hawken breach plugs ain't cheap but better than ruining a Rice barrel.

[flinchrocket]

1000/ treads per inch-will give you distance of one turn in thousands

[Herb]

Thawk, go to Tutorials, Metal Shaping, near the bottom of the first page.  Post by Herb on July 07, 2010, "Fitting a Hawken Breech Plug by Hand".

[Thawk]

Thanks Herb.  That will help finish it off for me!

[Thawk]

I'm .01 inches short on the breech plug and 1 flat past the top one.  If I go another flat then I have to file of the markings.  Any suggestions?

[Herb]

I knew a good gun builder with a similar problem.  He took a dime and filed it flat on both sides, and fitted it in front of his plug as a shim.  He turned his plug up against it.  I think a dime would be near the correct size for a 3/4x16 plug.  Just measured two new ones, .701 diameter and about .050 thick.  The metal does not rust.  If too small in diameter, the dime could be peened to flatten it and this would increase the diameter.  That would be a lot easier than turning the plug in another turn.  Of course you would have to keep filing it thinner to a little over .010.

[Thawk]

I knew a good gun builder with a similar problem.  He took a dime and filed it flat on both sides, and fitted it in front of his plug as a shim.  He turned his plug up against it.  I think a dime would be near the correct size for a 3/4x16 plug.  Just measured two new ones, .701 diameter and about .050 thick.  The metal does not rust.  If too small in diameter, the dime could be peened to flatten it and this would increase the diameter.  That would be a lot easier than turning the plug in another turn.  Of course you would have to keep filing it thinner to a little over .010.

I have a piece of .016 brass.  I was considering that but was worried about corrosion. Dime might work better.

[flehto]

Have only done 2 Hawkens and both req'd larger ctsks at the thread lead-in on the bbl to accept the radiused base of the threaded plug.  Luckily I saw it right off w/ both and because I have a free standing drill press to accept the bbl length, was able to rig up a crude fixture to ctsk the bbl. Don't know why the manufacturers  of the breechplugs think they need such a large fillet....Fred

[Thawk]

OK Breach plug is in.  I made a washer out of some thin sheet steel I had for practicing engraving.  Drilled a half inch hole in it.  Then put dykem on it.  Measured the inside diameter of the breach.  Subtracted .5 from that measurement then divided by two.  Set the digital calipers for that measurement.  Then used the calipers to scribe a circle by placing one side of the calipers on the edge of my .5 inch hole and dragging the other through the dykem.  Used my small belt sander to grind it down to that line.  Smoothed it out and cleaned it up with a fine file.  Repeated the process to take the .5 in hole out to .54.  Once I had a .54 circle scribed in the dykem.  I used my dremel to widen the circle to .54.  Easy peasy.   20 minutes after the washer was in,  I had her breached to the top flat.   All is well that ends well. 

I was going to try and use a dime but I dropped it and it landed near that piece of steel and the proverbial light bulb went on.  Sometimes you just have to walk away for a day.   Oh and aways check if your barrel needs to be counter sunk.

 

[bgf]

I think the same thing happened to me on a Green mountain barrel with 5/8" thread depth and a patent breech with 1/2" length.   I countersunk the barrel as I shortened it and made sure there was a slight relief at the bottom of the plug threads.

I put a .50 caliber Rice barrel on the same stock recently and didn't have even half the work, since the thread depth was 1/2", exactly the same as the breech plug.

Not a hawken, but a chunk gun based on a SW VA. Rifle that had a flint patent hooked breech adapted to it at some point.  It has 50 and 40 Cal barrels, now.