So I'm building a .308 AR and I would like to be able to use a standard USGI Garand/M14 1.25" web sling on it for sling assisted shooting. Its easy to find "wide" sling swivel loops that attach to a picatinny rail for the front, but I need to know whether the built in sling loop on the Magpul UBRs default strike plate is wide enough to take the fixed metal clip on the rear of the USGI web sling or if it isn't, is there a QD type sling swivel that attaches to the QD ports on the left side of the UBR that is wide enough to accept the USGI web sling metal clip? Ideally the rear clip should somehow be fixed as it is on an M14 or A2 buttstock so that it doesn't slop around when you try to re-attach the clip, but that might be difficult in the case of the QD swivel. The KZ QD swivels from Botach claim to be 1.25" but I've seen reports where some QD swivels are measured from the outside dimensions rather than inside... I need to know which definitely will fit the USGI clip.
Ideally I'd LOVE to have someone create a UBR strike plate insert that emulates the A2/M14 rear stock fixed sling swivel thats mounted perpendicular to the bore rather than parallel with the bore as most EBR collapsible stock swivels/sling mounts. Does something like that exist already? If not, I might have to talk to a machinist...
All of the push-button QD swivels that fit those sockets are 1 1/4", and will fit GI webbing just fine. If you use a push-button QD on the rear, you don't even need the metal clip on a GI sling. Just remove it and install the QD swivel in it's place. Functionally it accomplishes the same thing (being able to quickly remove and re-attach the rear end of the sling). Plus it makes a lot less noise!
I have to say, that's a wonderful problem to have.
I don't use the web sling clip on the front on any rifle, just the rear. And, if I have the QD option, I especially use it on the rear (front too, but much less reason to).
I just zip tied (3 zip ties) a quick release buckle clip (female end) to the UBR and put a male end in the loop instead of the metal clip. The UBR loop is too beefy to slide a clip over easily.
When you talk to your machinist, please get me a price. I'll need 3.
Having the rear of the sling attached vertically or to the side of the rifle is not an issue. It does not impact using the sling as a marksmanship aid or as a carry strap.
I have a RRA NM A4 on which I put a UBR stock. I did this because it is heavy and I thought it would counter balance the heavy barrel. I drilled a small hole on the bottom and installed a sling swivel that allows me to attach the USGI sling.
A couple of thoughts. Think about your stock selection in terms of your sights. You can't modify the UBR. It's critical to have your head upright and the same cheek weld and your sight choice is a big factor in that. I've gone from irons to scope to reflex!
Second, the sling. I'm still experimenting, but after doing a lot of reading and experimenting I am leaning toward a tactical type two point sling. The UBR is perfect as it has two QD mounts. I have developed a "shooting cuff" that stays on my arm all the time.