Monday, March 27, 2017

Tips & Tools with Fred Stutzenberger – Part 9

Tips & Tools # 9: Bedding the Barrel

The process described below will invoke the rending of garments, gnashing of teeth and tearing of hair by the die-hard traditionalists. On the other hand, those of us who consider the strengthening and sealing of the fragile fore end to be advantageous may read on. If you are unfortunate enough to be working with a piece of wood with poor grain integrity (Fig. 1), it would be wise to bed at least in the breech area where the shoulder of the inlet must take the shock of recoil.

Tips-&-Tools-#9-Fig.1

Fig.1.
Soft, crumbly wood such as this behind a breech needs some sort of bedding reinforcement.

 

If you are considering bedding the barrel with one of the commercial epoxy preparations, now is the time to do it before adding pinning tenons (also called underlugs) sling tabs or other protuberances to the underside of the barrel. Epoxy is really tenacious in its grasp, particularly on anything protruding from an otherwise smooth surface.

Tips-&-Tools-#9-Mirror Image of Stamping

If your bedding material can reproduce a mirror image of the stamping of the barrel, you know you will get a good fit of the barrel in the channel.

Now that you see how closely AcraGlas or other barrel bedding epoxies will conform to the barrel surface, you should also realize that all contact surfaces (bottom 5 flats, breech end and tang) of the barrel must be smooth…really smooth! Otherwise you will have a difficult time removing the barrel from the stock after it sets up. Draw file the flats and sand them smooth to at least 150 grit abrasive using aluminum oxide or preferably silicon carbide paper. If you are unfamiliar with draw filing, see reference below. Draw filing is a method of smoothing metal by holding a single cut smooth bastard file in both hands and pulling or pushing at right angles to the metal surface while pressing it only lightly on the surface of the barrel. It is relatively easy but tedious. Just make sure that no particles get embedded in the file (embedded metal will score a smooth surface quicker than anything…practice on a scrap piece of metal to get the feel of the file). Rubbing some chalk into the teeth of the file will prevent metal sticking.

Before going further, it should be emphasized that barrel bedding is no substitute for good tight inletting. Although epoxy compounds can be stained to just about any hue and color to try to match the wood, the difference between the two is instantly apparent to the experienced eye. The final layer of bedding in the barrel channel should be, and appear to be, no more than several layers of carefully applied varnish.

Tips-&-Tools-#9-Fig.2

Fig.2
This pin, which should be a snug fit in the tang bolt mortice, will aid in lifting the tang clear of its bedding after the resin has cured.

Tips-&-Tools-#9-Fig.3

Fig.3
Every nook and cranny of the breech must be filled with melted beeswax of modeling clay to prevent seizure of the exposed threads by the epoxy.

Before mixing the resin and hardener, it would be wise to drill a hole in the tang mortise and tap in a snugly fitting steel pin (I use a #29 bit and a 8 penny nail, Fig.2) through the stock. The pin can be tapped to lift the tang out of its bed after the epoxy sets. Also, be sure to fill any exposed threads at the barrel/breechplug juncture (I melt beeswax to seal off any troublemaking exposed threads, Fig. 3). Drive a wooden plug into the muzzle to keep any epoxy from entering and to act as a handle.

Clamp the stock in the vise with the muzzle end slightly higher than the butt (you want the epoxy flowing to thoroughly coat the breech end). Coat the barrel with the release agent according to the manufacturer’s instructions…very important…you don’t want the barrel permanently fixed to the stock.

Make sure the tang lift pin is securely in place. Mix the hardener and resin plus the appropriate colorant slowly but thoroughly to achieve complete homogeneity without creating bubbles. My rule of thumb is to use one milliliter of mix per inch of barrel (on a carefully cut channel with good wood-to-metal contact, you could use a lot less). Some overflow from the sides of the channel is desirable, but no need to be excessively messy (spread some newspapers on the floor to catch the overflow).

Starting at the tang mortise, pour the mixture carefully into the bottom of the mortise and then move carefully toward the fore end, trying to keep the mixture in the bottom of the channel to avoid trapping air bubbles along the sides. If you run out of mixture before reaching the muzzle end, no problem; it will spread along the bottom as the breech settles into place. You can move it along a bit  with a popsicle stick cut square on the end, but keep it off the sides. You want the mixture to move up the sides on its own, forcing out the air pockets to prevent voids in the bed.

As the barrel settles into place, tap on the muzzle plug to keep the breech firmly against the shoulder of the channel as you start adding clamps from the tang forward. Since the fluid epoxy acts as a lubricant, the barrel may settle into the channel lower than you might expect. That’s good—you want to squeeze out all the excess bedding—so keep tightening the clamps until each is under firm pressure.

It may be that most of the bedding has now been squeezed out from the channel. So be wisely foresighted and line up a bunch of projects amenable to epoxy-based repairs. Catch the overflow in your mixing cup that usually comes with a bedding kit. If the excess mixture starts to set up too fast, set the cup in a saucer of cold water. Don’t hurry…haste makes waste…plan ahead and visualize each stage of the process. I have bedded dozens of barrels for myself and others, have never had an OMG moment, and have found that AcraGlas is pretty forgiving in the fluid state. Clean the epoxy off your hands with vinegar.

Barrel bedding and other operations on the fore end go best when the stock is left “in the square” during the early stages of construction. Beginners make the mistake of randomly moving from spot to spot, taking off wood in a haphazard fashion when working from the blank. Resist that. Those who try to bed the barrel in a shaped kit stock have a more problematic situation on their hands since the fragile fore end tends to twist under clamping pressure and the sharp edges of the ramrod channel are susceptible to crushing. Protect those delicate edges with the ramrod placed in the groove. Fortunately, high quality kits have well cut barrel channels, but they could still benefit from bedding a bit at the breech end to strengthen the stock against recoil. In #10, we’ll talk about pinning/keying the barrel in the stock.

Suppliers:

Brownells.com, 800-741-0015 and MidwayUSA.com, 800-243-3220 for a wide selection of barrel bedding compounds

References:

Photos taken from Epoxy Resins—Asset or Abomination Part I, Muzzle Blasts, July 2008, p.53.

Draw Filing Do’s, Don’ts and Nevers, Muzzle Blasts, Mar. 2006, p.55

 

 

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