Anyone using flush cup sling swivels?

INSTALLATION TIP (for foam filled stocks):
1.) drill proper size hole for mounting the cup
2.) using an awl make a "cone" shape in the foam
3.) Be sure the "cone-shaped" area is clear of all debris
4.) fill the"cone-shaped hole" with a good bedding epoxy or JB WELD
5.) insert flush cup and wipe off excess epoxy after the cup is fully installed
** If the cup is a limited swivel type (i.e. not 360 deg. swivel) be SURE it swivels in the correct arc and if not then turn the cup until it is properly lined up. (Do NOT ask how I know this.) :eek:

Making a cone in the foam stock is a way to make the epoxy wider than the entrance hole in the shell material so the epoxy anchor cannot easily be pulled out. It makes the shell material (carbon fiber, fiberglass, Kevlar, plastic) a "wall" against which the cone can bear instead of relying entirely on the shell material to hold the cup threads.
When I was a ski shop tech this was how we mounted ski bindings in skis (XC and alpine) if they had foam, balsa wood or honeycomb cores. Believe me, ski bindings put FAR more torque and pulling force on these holes than your sling should ever do and they hold very well.

You can use this technique if your flush cups ever pull out and need to be replaced. AND you can further strengthen repairs by using a thread-mating HeliCoil insert then screwing your cup base into the HeliCoil. This is when the cup pulls out and enlarges the shell material too much. It is a very common solution to this problem with skis and it is amazingly strong. Just be sure the HeliCoil or similar insert has inside threads that match your flush cup! Usually these inserts use an Allen wrench (that's larger than your flush cup threads) to insert them.

Is thisTMI?
 
Carrying my 338 LM last season on a sling with flush cups. The top flush cup swivel pulled out while carrying the rifle slung. Glad it was soft soil when the barrel hit the dirt. This IMO is the weak point of carrying using those swivel studs in the cups. The actual stud came apart in the center. Obviously defective but all the same didn't make me feel any better. Unfortunately I don't have any standard studs screwed in so I'll be trying the flush cup stud again next year.
 
VLD, what make flush cup was this? I used the grov tec HD on my 16lb 338 edge for years and never had issues.

To anyone who is planning on having flush cups installed by a smith, check them before you take them to the field. I had a new build done, took it out to the field and while hunting with my rifle slung over my shoulder. The top qd stud popped out and my muzzle hit the dirt, luckily mine was soft soil as well. I took it home and inspected it to find a very small dot of bedding material inside the cup recess where the bearings lock in place. Before I removed the debris I put the stud back in and had to pull pretty hard for it to come out but it would eventually. It's worth taking a quick look and at least pulling on it to make sure everything holds.
 
That looks like great advice but my cup did not pull out. Excess bedding material from installation inside of my cup was not allowing the ball bearings in my QD swivel to protrude out all the way in the cup and seat in place.
 

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