The QD cups on my URX4 seem to have issues. It seems like it might be a tolerance stacking thing. I was just wondering if anyone else had experienced this and if there's anything to be done about it.
If I use a magpul, gg&g or a couple other unknown swivels in the QD cups, they won't stay locked. There is one unnamed swivel I have laying around that seems to lock just fine on the URX4, and the ones that don't lock up on the URX4 work fine on other QD sling cups.
It's almost like the ones that won't lock aren't quite inserting deep enough to fully engage the grooves. If I insert and twist to make sure the bearings aren't on a rotation stop, then it seems to lock into place, and will survive a quick tug, but if I really pull on the sling it will pop out. Additionally, as soon as I twist the swivel at all, it's like the antirotation tabs inside act as ramps that allow it to pop right out. I can twist it either way and it will pop out.
I thought it might just be the gg&g swivel (I have 3 of them, which all have the problem), so I bought a couple magpul swivels. They both do the same thing. None of them seem to be bottoming out in the cup. It happens on both sides and on another URX4 I have. URX 2, 3, and 3.1 work fine. BCM mlok antirotation cup works fine. Midwest industries QD sling mount works fine. I mean, it seems like these sling swivels lock up tight in every other sling mount.
I really like the location of the URX4 QD cup so I'd prefer not to mount an Mlok QD mount. I also don't know what brand of swivel is the only one that seems to actually work, so I'm not sure what to buy that would fit, but it really seems like I should just be able to use any quality QD swivel without headache on a KAC rail.