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Flush Cups? How well do you trust them?

Archangel01

Private
Full Member
Minuteman
Aug 6, 2010
129
27
38
Arizona
How much faith do you guys running flush cups put into them? would you say $2500 worth of faith? I question how secure they will hold so i don't drop my optics down to the ground and break it. I plan on using a TAB biathlon sling to carry my rifle and am just not sold on the detente balls and grove holding capacity to hang my 16+ lb rife only relying only on them. What are your guys experience with them? Anyone have a flush cup slip out and drop there stick? Please give me all the pros and cons of there reliability.
 
If a flush cup is mounted too deep in the stock it will not lock up solid. Test your setup by pulling on it and visually inspecting it. If it is correct it is a very strong connection.
 
Ive seen two types.

Uncle Mikes that just glue in and Grovtec that screw in.

I have only used the Grovtec along with some epoxy. They havent moved in a couple years.
 
Ive seen two types.

Uncle Mikes that just glue in and Grovtec that screw in.

I have only used the Grovtec along with some epoxy. They havent moved in a couple years.

The epoxy version doesn't sound too promising. Why would someone build a 3k plus rifle and then cheap out on using epoxy?
 
Epoxy is used like loctite or a thread locker. These are the grovtecs.

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These are the others and they have to be epoxied in.

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I have installed 100s of flush cups and never had a single issue. I use Marine Tex epoxy and they are all installed in fiberglass or carbon stocks, so the interface is solid and no chance of the flush cup failing. The flush cup swivels use a ball bearing system similar to a socket wrench, but there are 3-4 ball bearings under spring tension. Basically, you don't need to worry about it failing, there may be the occasional story.
 
I had flush cups installed on my stock. I don't worry about them failing but, in hindsight, I wish I would have chosen a different setup.
I don't like the fact that they spin around and twist my sling all to hell.
 
I'm not really concerned with the flush cup itself actually being pulled out of the stock. But the male end accidentally uncoupling itself from the cup. I know that high quality products have much better quality control and tighter tolerances. I guess I've always steered away from the ball detente cup type connectors just because of smaller shitty connectors like car key connectors for example. Granted i know that they are not in the same ballpark as the flush cups for firearms. but i couldn't help my concern for there holding power.




I have hung from mine. They are solid if the cup is installed correctly.
t-payne this is good news! Exactly the stories i feel i need to hear.
 
I had flush cups installed on my stock. I don't worry about them failing but, in hindsight, I wish I would have chosen a different setup.
I don't like the fact that they spin around and twist my sling all to hell.

There are anti-rotation / limited-rotation bases available that prevent sling twist.
 
after installing mine i put one qd in it and it yanked out. i put the one that came with the cup in it. it will not pull out. the cup was to deep in the stock so it could not lock up all the way. cup locked up i bet you pull the cup out of the stock before you break it. i epoxied mine and put a screw in it.
 
If you're terrified about using flush cups, just use a 3/4-1.5" wood screw on the inside to secure it to the stock even better. I believe that's what the hole in the bottom is for anyway. You have to use a flat screw though, otherwise it takes up too much space and your cup won't fit. Drop a screw inside and make sure you can still get the swivel in.

My dad has a really crappy 788 stock that the sling studs pulled out of 4-5 times. I replaced them with grovtec cups, epoxied them into the wood, and secured them again with a 1" wood screw just for extra piece of mind since the wood was pretty crappy anyway.
I highly doubt they will ever move.

His rifle is only about 8lbs, but my 7mm Rem Mag is 22lbs when it's loaded and the suppressor is on it. I have no fear about the cups coming lose. None at all.
 
Watch out for the male swivels also, I've got some that got a little rusty and the balls didn't spring back out all the way and would let go if I pulled on it. Once I oiled it back up they worked fine, just watch out.
 
I've used them a lot over the past five or so years in various setups and haven't had a single issue. I find they are a rather sturdy setup and have no concerns that they have an increased likelihood of failure vs. other setups.
 
Considering that a Fortner action uses the same principle (bearings in a groove) to hold an action together during firing, I think QD sling swivels are more than up to the job... :)
 
I use the limited-rotation cups installed by Manners in my T4A stock...16lb gun and haven't had an issue.
When installed correctly and using a quality QD adapter and cup, they are a solid system.
 
I felt the same way you did. I tried the DIY version with the grovtech flush cups. The rear on that went into the butt stock went in without a hitch. The other one on the forgrip got fucked up a little and the hole widened up. I used JB and epoxied the hell out of it, then touched it up later and all was right. I have a 16lb gun with a 4K S&B on it and it's never been a problem.

If you have doubt about doing it yourself then pay a smith the $50 to do it for you and never worry about it.
 
im still wary of using them in the HS precision stock. I drilled the butt for a karsten. its dense foam. Id glue & screw it, and trust the rifles weight on it. but being foam, I don't think id hang from it
 
Considering that a Fortner action uses the same principle (bearings in a groove) to hold an action together during firing, I think QD sling swivels are more than up to the job... :)

No, not all QD sling swivels are the same. Some are absolute junk (uncle somebody or other comes to mind).

Give all your sling connections a good test before trusting them in the field.
 
oh yeah, like he said, don't buy a cheap one for $5 off ebay an think its going to be worth a crap. ask me how I know, lol
 
Only problem I ever had with my flush cup wasn't with the actual flush cup. The part that goes in the cup unscrewed from the rest of the sling while I was at a match two years ago. Got some lock tite on it and haven't had a problem since.