Mounting Sling Studs and Flush Cups in Foam Core stocks

Litehiker

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When I was working in a ski shop one of my jobs, besides being a ski salesman, was mounting bindings on XC skis.
Most skis had either wood or foam cores that required "potting" the screws in epoxy glue.

"Potting" is the art of making an inverted cone (^) in the foam or wood with an awl. The inverted cone was filled with foam-friendly epoxy and the bindings were mounted on the skis with the supplied screws.

Once the epoxy had cured the skis were ready. The screws would not pull out.

For foam core fiberglass or carbon fiber stocks this method is what I recommend to keep the studs or flush cups from pulling out. Remember, ASK the stock maker what epoxy to use. Usually Marine Tex is "neutral" with most types of structural foam. That's my experience.

If you don't do this "potting" then basically you have mostly the fiberglass or carbon fiber shell to do the work of holding the stud in place, not a good idea as it can easily break under strain.

I would not recommend using a drill for potting as you ned to keep the entrance hole an exact diameter for strength and good looks when the stud or flush cup is mounted. An awl will work for potting but you need to vacuum out or knock and dig out the debris you create when making the inverted cone.
Eric B.
 

jrock

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Thank for sharing your thoughts. I am working designing my own carbon fiber stocks and debating about ways to provide attachment. Especially for flush cups since they don't have much length for bonding.
 

Litehiker

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rock,
I'm buying some flush cup swivels and sling studs for my Browning X-Bolt Pro. I will replace the existing studs with flush cups. Then I will put more flush cups on the left side of the fore arm and stock so I can carry the rifle flat on my back using this special sling that permits a "biathlon carry".
I can use either restricted term cups or 360 degree cups. I'll have to unstitch my sling to install the sling studs and have my shoe repair shop re-stitch with a bar tack on the nylon webbing sling. Likely all cups will be the restricted rotation type to avoid a twisted sling.

** Be careful when installing "restricted turn" cups that they are permitting turning ONLY in the direction you need and then are aligned properly before the epoxy dries.
If they end up restricting turning in a needed area because they were not properly aligned they cannot be easily removed to correct them! (Don't ask me how I know.;o)

Eric
 

jrock

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I would be more worried about a restricted rotating cup twisting out. Seems best to use a 360 one. I'm moving to side cups for guns with longer DBMs and I don't like swivel studs for shooting off bags.
 

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