Best shear strength epoxy?

safehunter

safehunter

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I've tried epoxying a weaver rail to a spare shotgun barrel just below the chamber using JB Weld. Holds for a while, but eventually breaks free even with meticulous surface prep.

I'm about to try Devcon's 5 minute gel but I thought I'd solicit advice about high strength epoxy and/or adhesive materials given the amount of time I've poured into this little project. I liked JB Weld because I could mold it to counter the barrels taper, but it just can't take the repeated shear stress of a 12 gauge with high velocity slugs.

I thought about silver solder, but the weaver base is aluminum, which as far as I can tell, does not solder well to steel.

I should probably get the shotgun drilled and tapped by a smith, but I'm stubborn and the bill would probably be more than the shotgun is worth.
 
safehunter said:
I've tried epoxying a weaver rail to a spare shotgun barrel just below the chamber using JB Weld. Holds for a while, but eventually breaks free even with meticulous surface prep.

I'm about to try Devcon's 5 minute gel but I thought I'd solicit advice about high strength epoxy and/or adhesive materials given the amount of time I've poured into this little project. I liked JB Weld because I could mold it to counter the barrels taper, but it just can't take the repeated shear stress of a 12 gauge with high velocity slugs.

I thought about silver solder, but the weaver base is aluminum, which as far as I can tell, does not solder well to steel.

I should probably get the shotgun drilled and tapped by a smith, but I'm stubborn and the bill would probably be more than the shotgun is worth.
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Two options:

1. Get the shotgun drilled and tapped by a smith.

2. Buy a barrel with the mount already attached.

Those are the only two reliable and permanent solutions. Metals do not like to adhere unless there is major interlock between the attached parts and the adhesive.
 
There are adhesives out there that will literally tear the metal before the glue joint fails.

The minimum qty buy price will make you run out and buy a brand new barrel with a mount already on it.

That does not include the required high temperature kit to cure the glue, either.

Rough rule of thumb as far as epoxy adhesives goes. If CTire sells it, it's pretty much crap. Good for filling dents, but not for structural integrity.

Cheers
Trev
 
One of the strongest epoxies is Devcon Titanium putty. And if you think drilling and tapping the barrel is expensive....
 
safehunter said:
I've tried epoxying a weaver rail to a spare shotgun barrel just below the chamber using JB Weld. Holds for a while, but eventually breaks free even with meticulous surface prep.
Click to expand...

I don't understand what you mean when you say "just below the chamber". Do you mean under the chamber? Anywhere on the barrel close to the chamber area will be dealing with violent barrel expansion and contraction each time it is fired. Hard to 'glue' anything of weight there.

Describe 'meticulous surface prep' please.
 
I learned the hard way many years ago that aluminum forms an oxide that gives up long before the epoxy will.

+1 details of surface prep. You may be able to treat the aluminum Weaver rail bottom with something after you have shaped it, and you may be able to roughen the barrel surface, but silver solder and steel rail sounds more likely to work. I am allergic to the idea of drilling into the chamber area near your face. Others might say "it's your face", but it might not be. The only thing worse than blowing yourself up is blowing up a friend or loved one, or the poor schmebe who buys this thing on the EE.
 
Surface prep consists of sanding both the barrel and the bottom of the mount, which includes removing the paint. I also ran a hacksaw perpendicular across the barrel and mount in a dozen or so places to give the epoxy some gaps to squeeze into as well as general scouring to roughen the rest of the surface. I finish off by cleaning with brake fluid, drying, then cleaning with alcohol and cotton swabs.

The mount starts about 3.5" from the top of the barrel, or about 1/2" away from the end of the chamber towards the muzzle.

These epoxies do get expensive, making drilling and tapping the receiver by a gunsmith more economical...

I could also get a steel base and silver solder, although the ones I found 5x the price of aluminum bases, again making the $25/hole + jig setup I've been quoted seem more feasible.

3M has some amazing products. I may try their panel bond if I can find a local distributor who doesn't charge through the nose for it.
 
fuser panel bond is avalable from lordco. bad news its about $40 a kit. done properly it will never come off . it can hold panels on vehicles. like roofs and quarter panels. the only way to release is to heat to several hundred degrees.
 
Try final cleaning with lacquer thinner or acetone. It is 'cleaner' than alcohol... but I think the violent barrel expansion and contraction each time it is fired is still going to affect the bond.
 
guntech said:
Try final cleaning with lacquer thinner or acetone. It is 'cleaner' than alcohol... but I think the violent barrel expansion and contraction each time it is fired is still going to affect the bond.
Click to expand...

What will affect the bond even more is the differential rates of expansion of steel and aluminum. It is important if an epoxy is used for bonding that the layer of epoxy is too "thin". It is the plasticity in the epoxy that allows some "give" between the two components.
 
metal prep (acid etch) the aluminum base follwed by MEK and water break test the item for cleanliness.
Surface prep the steel, clean with MEK and waterbreak test for cleanliness.
Mix magnolia structural adhesive and apply with directions on container and allow to fully set.
go on about your happy life

the water break test is the standard for surface preparation cleanliness, a clean surface will not bead water, only a contaminated surface will cause water to bead and drain. You should be left with a surface that holds a thin sheet of water. If it does, its clean enough. http://en.wikipedia.org/wiki/Parts_cleaning
Metal prepping or acid etching will deal with the aluminum oxide and you will seal the surface with epoxy not allowing it to re-oxidize.

Magnolia products are the aircraft structural repair go to adhesives and are called out in most engineered repairs if an adhesive is to be used.
 
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There is a Loctite product - BlackMax - that Brownells sells for attaching ribs to shotgun barrels. It might be worth a try.
 
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