Gunsmithing Adhesives

I was first introduced to epoxies about 1957 and thought they were the best thing since sliced bread. I used them to try and fix everything, from a broken bed frame and a broken exercise bike, to even damaged ski boots… and more! Well, they were better than most "glues" of the day and were waterproof as well. And, of course, some of these projects were successful, but many were not. Most of the problems were probably due to improper or general lack of surface preparation, which I still had to learn about.

About nine years later, an off-the-wall experience gave me a something akin to a "bachelor’s degree" in surface preparation! Note, this was decades before high grade cyanoacrylate adhesives (popularly known as "super glue") were available. More about them later. Back in 1966 at a cocktail party near Pittsburgh, the home of the Alcoa Corporation, I happened to strike up a conversation with a scientist with that aluminum giant.

At the time, I had a 375 horsepower (which was a lot in those days!) ’63 Corvette with a leaky aluminum radiator. I explained to my new drinking buddy how I couldn’t find a radiator shop anywhere that would work on it because, unlike most cars which had conventional brass or copper radiators that could be soldered, mine was aluminum. Replacing it would have been pretty pricey and I was interested in any viable alternative.

To my good fortune, he was excited about this as his boss had been pushing Chevrolet to switch to aluminum radiators for all their models but the company was resisting due to an "insufficient" amount of real-world testing and real-world repairs. He insisted that I bring my Corvette into his laboratory at a nearby Alcoa facility, pronto! The next morning I visited Alcoa where two white-coated, $100,000per-year scientist/mechanics pulled out my radiator and taught me how to epoxy aluminum components.

First, they pressure washed the radiator and then filled it with water under pressure to find the leak. Next, they wire brushed the area around the leak and then etched it with hydrochloric acid. Following this, they scrubbed the area again with distilled water to remove any trace of acid, dried it with a heat gun, and washed the area again, this time with a solvent like carbon tetrachloride ("carbon tet" as it was known then, which was a great product but is no longer available today, due to dangerous fumes.

More about that later). Drying the radiator again, they applied an epoxy mix over the leak, put the radiator into a warm (about 90 degree) oven, and we went out to lunch. They wouldn’t let me pay for any of their work, but they did let me buy lunch. After along lunch the epoxy had cured, so they pressure tested it again. Success! Then they reinstalled the radiator and attached a metal tag with their phone number, saying that anyone working on the radiator again should call the laboratory.

I sold the car years later, but don’t think anyone ever had to call the lab. I know I didn’t! That experience at Alcoa helped me again eight years later. I was a crew chief for a small sports car racing team running a Datsun 240/260 Z. We were having a great weekend, qualifying second overall against some big names. However, just hours before the actual race, I noticed a small oil leak coming from a hairline crack in the aluminum transmission case.

We had no spare and obviously had no time to locate and install a replacement gearbox. Having no other choice, I grabbed some J-B Weld epoxy from a toolbox, plus my old faithful (and still available) carbon tet. With a 1/32" drill bit I slightly enlarged and roughened the crack for more surface area, wire-brushed it with probably a pint of carbon tet, then forced the J-B Weld into the crack with a flat blade screwdriver.

With our fingers crossed, the epoxy was probably still curing when we pushed our race car onto the starting grid. Fortunately it was a warm summer day. How’d we do? We won some money after finishing in second place and had no leaks, which was critical as leaking oil on a race track will get you disqualified in a heartbeat! Here’s a more extreme case.

About 1980, my stepson, driving without permission, somehow managed to get my wife’s turbocharged, grey-market BMW 745 airborne, landing with the oil pan and intercooler on a large boulder! A friend of mine with a tow truck got it off the boulder just before the police arrived. While there was no apparent damage to the boulder, things didn’t work out so well for the cooling system as it turned out. On the way home, it overheated, of course, and blew the head gasket.

Far The grooves in the outsides of the pillars virtually double the surface area, adding significantly to the strength of the bond. The inside and top of the pillars, as well as the action and screws, have all been coated with mold release; part of the scheme to avoid permanently bonding the stock to the receiver or even the stock bolts. Ordinary children’s modeling clay from Walmart and masking tape are used to keep excess Acra Glas from intruding where we don’t want it.

Again, a good mold release is applied to the top and insides of the recoil lug itself, as well as the front assembly bolt. The modeling clay is easily removed after the Acra Glas hardens. Anew gasket would have required removing the cylinder head, timing chain, water pump, intake and exhaust manifolds, the intercooler and the turbo. This would have been about $6,000 in labor in 1980 dollars. No, I couldn’t afford it.

So, with nothing to lose, I scraped around the existing gasket junction with a screwdriver, wire brush, and lots of carbon tet. Once it dried, I forced J-B Weld into the crack and let it cure. The next morning, I refilled the "bimmer" with antifreeze and water. (Bimmer? Yep. A little known fact: According to the BMW Club of North America, "bimmer" is slang for a BMW car while a "beemer" is a BMW motorcycle.) I had a friend of a friend TIG weld the intercooler as that was too damaged to repair with the epoxy.

Even after a number of years later, and despite thousands of miles with all the associated heat, vibration, and turbo pressure, the gasket never leaked! The above anecdotes weren’t about guns, obviously, and this is a gun magazine. Yes, I, Les Baer, and probably many of you, enjoy fast cars as well as guns.

Like RK Campbell’s "Stuck Parts And Extreme Measures" article in the June 2022 issue showed, many of us learned welding, machine work, spring making, adhesives, etc. from other trades and sometimes before getting into gunsmithing. So now, here’s the gunsmithing side of this: Until something I think is better comes along, my go-to adhesive for pillar bedding and glass bedding rifles is Acra Glas Gel, the epoxy from Brownells listed as number 081-014-007.

This can be stained and various shades I’m showing it front and rear to prove its age; note the number of members are about half of today’s membership number. Shortly after I bought it, the hook in the buckle that snaps into the holes in the belt broke off flush. I drilled out the base of brown or black, and where necessary strengthened with atomized steel. What I like most about Acra Glas is that as a gel it doesn’t sag or run; it just stays where you want it then hardens predictably.

Once hardened, instead of becoming brittle like some of the others, it can "give" just enough to avoid breaking due to age while under recoil and other stresses incurred by firearms. When working with adhesives it’s important to note three important points: Surface Preparation, Surface Preparation, and Surface Preparation!

Here’s the part about carbon tet: All surfaces must be clean and dry with zero traces of oil, including the oil off of your skin! of the broken hook, just partially through the buckle, thoroughly prepared the surfaces, and used J-B Weld to "glue" in a small sheet metal screw as a replacement for the hook. Before the epoxy cured, I added a small washer over the screw to enlarge the surface area. I’m still wearing the belt, 43 years later, and that’s with a "little" extra tension in my beltline!

Notice, with pillar bedding I’ve skipped the acid-etching for fear of damage to the action but I still clean the heck out of the pillars, assembly screws, and action with a good brake cleaner available at most any auto parts store. In my opinion, this is as good as carbon tet but without the associated EPA problems. Of course, remember to next use a good mold-release on the screws, the tops and insides of the pillars, contact points of the action, etc. to avoid epoxying the whole rifle together!

Brownells now offers two versions of mold release: # 081-028-000 and # 081-007-004. I’ve also tried Dev-Con and Marine-Tex epoxies; both are good, but for our purposes, I still recommend J-B Weld and/ or Acra Glas where appropriate. Note, in my article "AR-15 Recoil Pad" (March 2021) I also used J-B Weld where I had to fill a "honeycombed" portion of a buttplate on a 450 Bushmaster AR-15 so I could drill and tap it in order to attach a recoil pad.

And, where heat might be an issue, J-B Weld is already steel-impregnated and can handle heat better than any other epoxy I’m familiar with. Always, as with any two-part adhesive, measure your portions carefully and blend them carefully. Stir thoroughly but don’t whip the mixture lest you incorporate air into the mix, which will weaken it. Incidentally, for something great in which to mix your epoxies, see if you have a Gordon Food Service (GFS) store in your neck of the woods.

They’re basically a restaurant supply, yet open to the public. They’re a fun place to visit and while there, I found a bag of little half-ounce plastic cups, 100 for about $3.00. They’re probably made for salad dressings, catsup, or whatever, but they’re perfect for mixing gunsmith-sized portions of epoxy! Lastly for epoxies, there will be times that you have an odd-shaped piece of metal that you need to machine but is tough to clamp.

For those situations I choose a lowcost "five minute" epoxy from Ace Hardware or Harbor Freight. Use it to epoxy the darn thing to apiece of aluminum or steel scrap you can conveniently clamp in the mill vise or lathe chuck. Once the epoxy cures, clamp it and machine where you need to. Afterward, a little heat with a heat gun or propane torch will allow you to separate them when you’re finished. Earlier, I mentioned cyanoacrylate adhesives.

There may be some job where they can help, like maybe an irreplaceable cracked plastic trigger guard, revolver stock, or butt plate, however, a recent development called Black Max from Loctite is a whole ‘nother animal! It’s a proprietary formula combining a cyanoacrylate with rubber. Black Max may be a little hard to find and it’s a little pricey, but it’s amazing for the right application. It’s great for attaching and repairing shotgun sights, sight ramps, and vent ribs and beads.

I also use it when replacing screwon front sights on heavy-recoiling handguns like .45 caliber or 10mm Glocks. With proper surface preparation, its hold is more or less permanent, yet the rubber in it absorbs shock Since it’s already black, it hides the tiniest gaps, like just under the rear of the front sight. Lastly, here’s an unexpected one, but to my knowledge, nothing else compares to it for certain jobs. Shoe Goo as available at Ace Hardware or elsewhere is amazing!

It’s tougher than two-for-a-nickel toilet paper and it stays flexible. In fact, it’s almost as strong as J-B Weld but it adheres better to plastics and rubber compounds. Available in clear or black, the black version of the product is the answer where older black recoil pads start to delaminate or get torn. Put it where it’s needed, then clamp everything together appropriately. About 12 hours later, sand the edges lightly as otherwise it will dry and glossy, exposing itself.

Of course, as the name implies, it also fixes damaged shoes of all kinds. That’s it for now. Hope I’ve been some help to the fraternity. For any questions or comments, please email me at CBgunsmith@ verizon.net. AG