Home Forums Hunting & Shooting Hunting Optics Should I epoxy scope bases to receiver?

Lotta good info here. I'm taking my time, learning all the while. Going to put it all together and may even shoot a bit before final assembly. Likely going to epoxy the base at that point, and as said, keep it out of screw holes. Right now I'm thinking Loctite on all screws. I don't shoot a lot, at least as I would define that, and am too old to be very rough on gear anymore.

I had never thought of welding but duh! That is a super idea. It is beyond my personal skill and tools, and my second rate method should hold minute of deer.

My initial reflex was to dismiss this idea; but given inevitable production variances in contact surfaces between rifle receivers and mounts, I'd probably give it a try on any rifle/scope combo I expected absolute precision from.

I don't think epoxy is necessary, just make sure things are in line, clean and you properly use loctite.

Stick, where is the photo of your rifle submerged in a stream and the rifle drug through the rocks and mud.

That would really prove you are quite a guy.....

Okanagan;
Good afternoon sir, it's been too long since we've touched base and I hope all is well with you and your wonderful family.

If you were still on this side of the medicine line and if you were so inclined to bring a rifle here for me to work on, then I would ask you if you DID NOT want your bases epoxied down onto the receiver, otherwise all the rifles which come through my shop get glued on.

Why is a good question and I'll do my best to answer as follows.

When I started fooling with horses more than a quarter century ago, I found that they'd loosen pretty much anything off given the opportunity, scope bases included.

I'd recalled reading a story by an old time Montana packer Ed Nixon who'd gone on an Alaska hunt and had epoxied the bases down onto his custom BSA - I think it was a BSA - action which had been barreled to a .338 wildcat which was very close to the .338 Win Mag.

Then after experimenting successfully with epoxying bases on - and not having them come loose on horse hunting rifles, a buddy informed me that some accuracy gurus did that because it takes up any space between the mount and the receiver....

The light went on for me and I began to check the fit of the contour of the base as it related to the receiver and it was seldom the very same. When it isn't, the screws will hold it in place after a fashion if the contour of the base is smaller than the receiver, but less well if it's the opposite situation.

When I was doing millwrighting, we'd use epoxy - JB weld or what have you, when we had slightly worn surfaces which we needed 100% contact on and it worked there too.

My way is as you mentioned - no glue on the screws - so they can come out with moderate pressure. However, in having glued bases onto rifles which are now in use across 3 western provinces, I've not had one person say that the bases loosened off on them. That's with folks who hunt with small planes, horses, quads, jet boats, back packing and just general knock around hunting of course.

Anyways sir, lots of roads lead to Mecca of course - not that we'd go there now or ever, but I digress - however, that's what I do on rifles running through my shop and why.

Hope that made sense and was useful. All the best to you all and we'll be in touch.

Dwayne

70 years ago my father at paccar used gallons of epoxy in his M55 design and follow on contracts for the M107 and M110 mobile artillery.
It is in the pendulum of the equilibrator to position Mercury switches that turn on hydraulic valves to balance the 20 ton barrel from swinging down hill and balance barrel elevation.

At Boeing a tooling machinist can walk into the epoxy shop and be handed a cup full of just mixed Devcon.

In my humble shop where I build myself 3 or 4 rifles a year, I can mix epoxy as fast as some people can mix a drink.

Probably the easiest way to get things right wit 2 piece bases. https://www.24hourcampfire.com/ubbt.../tps-basebed-alignment-tool-arrived#Post

The only deviation from TPS's instructions is, I would use JB Weld ( much stronger), instead of 5 minute epoxy supplied with the kit and use headless base screws for the bedding process, holding the the alignment tool/bases on the receiver with loops of surgical tubing or large rubber bands. RJ

I worked at a place where we had over a dozen different industrial epoxies, mostly in 55gal drums. We used the exact epoxy that JB Weld is marketed to for consumers (there are only a small handful of epoxy mfg's world-wide). I found it was far more "brittle" than other epoxies, and when heated seemed break its bond more quickly. It was primarily used to be mixed with fine silica to use as a trowel-on for industrial-chemical settings to cover and protect concrete from erosion. I call it "weak" (a simplistic term obviously) because it is more brittle and its bond breaks quickly when heated, which makes it ideal for bases/screws. Personally, I wouldn't use it for bedding due to to its brittle nature, but obviously it works fine. IMO Devcon Marinetex and Acraglass Gel are better epoxies for bedding.

Just one man's opinion based on industrial use...

Brad, I hear what you're say'n, but tell me how brittleness would matter when the epoxy is sandwiched between a base and the receiver? Brittleness only matters when you need the material to be flexible. For bedding purposes, you damn sure don't need or want flexibility. RJ

Not true
You don’t want anything brittle when you we dealing with impact/recoil forces

You're dealing with shear forces here. I'll bet 80-90% of the shear forces are taken by the 4 (typically) scope base screws and the rest with the static friction between the base/epoxy bedding and the receiver. The shear forces are in the horizontal plane - please tell me how the epoxy is transferring these shear forces.

Epoxy is good for about 4500 psi in shear.
We covered some of the force last month.
https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/14868946/1

Heck. You don’t need a 55 gallon drum of it to bed with.


Happy trails

Bob

😂😂

Say what you will, but epoxy brittleness will have absolutely no effect on epoxy bedded scope bases. RJ

I have never glued a base mount on a receiver but I can see the purpose, In my mind the epoxy is not so much to hold the base to the receiver. It is to give the base almost 100% contact with the receiver. The bolts or more appropriately, screws hold the base on the receiver. But the epoxy gives it almost complete contact with the receiver giving it a more steady platform which will prevent movement and secure alignment. There's a certain percentage of contact without the epoxy or else all mountings would require it. But the epoxy will increase the contact area from probably 50%-70% upwards to almost 100%. Brittleness isn't so much a factor. Percentage of contact, or how much of each piece is touching the other is what is needed here. The more the base contacts the receiver the steadier the mounting will be which translates to strength and accuracy.

Did it years ago on a 700 with a NF rail and NF scope. That rig had a tendancy to work things loose. Little JB fixed that completely.

Updates:

Got some excellent help via private messages from a couple of men who mount a lot of scopes. Thank you.

Second, re brittle epoxy: Golf club glue. There is an epoxy specially formulated for high impact strength. It retains a bit of elasticity rather than becoming brittle. It is designed to glue golf club heads to shaft, etc. I ordered some. Brampton and GolfWorks seem to be the two main brands of it. Impact of a golf club face on a ball should be somewhat similar to recoil.

Oh yeah, I remember that thread:

"A #6 screw tightened to 18 inch pounds with dry threads will make 640 pounds of clamping force.With 4 screws this is 2560 pounds of clamping force.
If there is no oil between the receiver and scope bases, the coefficient of friction is 0.8. That would be good for up to 2048 pounds of scope acceleration force.
But if there is oil, then the coefficient of friction is 0.16 and only good for up to 409 pounds of scope acceleration force, and the scope zero will be lost."

So, that static coefficient of friction (0.8) is steel/aluminum (scope base) on steel receiver? I know it's an assumed value , but there would be a good difference between an hi-gloss blued receiver and a bead blasted stainless, no?

If there is a layer of bedding compound installed, how does change coefficient of friction value change when you have epoxy/metal contract? It's still unclear to me Clark, how much of that 2,000 lbs of shear force is distributed between the (1) screws and (2) friction between the scope base/receiver.

I certainly see why increasing the contact area of the scope base/receiver takes the shear load off the screws. And I definitely see why roughening up the receiver (gasp) would make things even better.

You'da' thunked,that someone woulda said something about a clip slotted and double-lugged Marty rail. Hint.




I mean if only for conversation. Hint.



Pardon my having all the T-shirts and BT/DT for decades.....................(grin)

I'm not sure that I follow that logic, using a flexible epoxy, unless you simply want to seal out moisture.

That product is used in a different application. Since there is no fastener holding the golf club head to the shaft, flexible epoxy must fix the golf head to the club by adhesion. Impact and peeling resistance are very desirable. But our scope bases are held in place with fasteners, which provide a clamp load. I don't want a flexible spacer, between the base and receiver. Just like I don't want a flexible washer in a bolted joint, unless it is required for vibration isolation or some other special application.