Yes, the Magpul Industries PRS Lite Rifle Stock fits Mil-Spec carbine length buffer tubes as well as A5 buffer tubes.
The Magpul Industries PRS Lite Rifle Stock will work with a Mil-Spec carbine length and rifle length buffer tube assembly. The Magpul Industries PRS Lite Rifle Stock can also be used with all AR15 and AR10 calibers.
Answering my own question for posterity as combing YouTube and the internet reveals nothing and Magpul has no instructions. The circular covers for the QD cups pry and pop out to reveal the receptacle where you install the type 2 QD cup. Inside there is a screw and nut that can be removed. The nut is accessible from the receptacle opposite the one with the screw on the other side of the buttstock. Remove both. The type 2 QD cup is meant to be a tight fit and needs to be tapped in with a light hammer or rubber mallet. This takes quite a bit of force to get them to sit flush. The screw your removed can go back into the receptacle opposite the side you install the type 2 QD cup and will screw into the threads of the QD cup further securing it in place.
No, the Magpul Industries PRS Lite Rifle Stock is only compatible with Mil-Spec USGI carbine/SR25 collapsible/A5 extension tubes. It is not compatible with Rifle/A1 receiver extensions.
The Magpul Industries PRS Lite Rifle Stock features a 1.25" ambidextrous footman's loop in the rear, Reversible, rotation-limited QD sling swivel cup in front, and QD sling swivel cup in the rear.
The Magpul Industries PRS Lite Rifle Stock is not compatible with the ASAP - Ambidextrous Sling Attachment Point. You will need to use a flat sling plate with this stock. The stock itself features a 1.25" ambidextrous footman's loop in the rear, Reversible rotation-limited QD sling swivel cup in front, and QD sling swivel cup in the rear.
The Magpul Industries PRS Lite Rifle Stock will be compatible with the Ruger SFAR rifle. The SFAR will still accept mil-spec carbine stocks despite having an extension tube that is slightly longer than carbine length tubes.
The Magpul Industries PRS Lite Rifle Stock will not require any modification as long as you have a Milspec carbine length or A5 buffer tube/receiver extension.
The Magpul Industries PRS Lite Rifle Stock will not fit A2 rifle length buffer tubes. You will need either a Mil-Spec USGI carbine/SR25 collapsible/A5 extension tubes for it to work with that rifle.
Yes, the Magpul Industries PRS Lite Rifle Stock is compatible with your FN-15 Patrol Carbine Rifle.