What it is shorty, is that on Marlin Rifles the Company puts a plastic white ring along with a black plastic center dot in the buttstocks of their rifles. It is a trade mark thing of Marlin's called the "Bullseye" Marlin put them on to give the customers the idea that it is an accurate rifle, which most are that I have ever owned or fired, and especially smooth operating for lever guns with easy scope mounting to be had with the factory side ejection they have on them.
Puting a sling stud in that plastic Bullseye dot could make it pull out, along with your sling coming off when you are alonggg ways from your truck when out hunting if a person were to not drill through the dot deep enough etc, when installign sling swivel studs, since the dots are only glued in.
"If it burns Gunpowder, I'm all for it" Varmintmaster
