Is “Once Saved, Always Saved” Biblical? Can a Christian “Lose” Their Salvation?

As I see debates over this, the thought that comes to mind for me is that whether friends of mine were saved or not, they formerly were in the fold (if not the flock), but now are not. So are they saved backsliders, unsaved from the start, or???? I am reminded of the old Marines T-shirt that says "kill them all, let God sort them out." I am not of course endorsing mass murder, but the place I've got to be is to offer them the Gospel, and let God sort them out as they pass across Jordan.

For reference, I do tend to the doctrine of perserverance of the saints, but I think that too rigid a position can distract us from the reality that people need the Gospel, especially when they are walking in a way that does not reflect Christ.

Better ; perseverance of the saints

I think it is pretty clear that if you have been justified ("saved") you are eternally secure in Christ. 100% Rom 8:30.

Assurance of Salvation is a different matter and when I teach on this I show how assurance is based on three legs -- promises of God (objective), one's perseverance (subjective), and internal testimony of the Holy Spirit (subjective). In our circles, we tend to emphasize the promises of God, OSAS (once saved always saved), but the other two legs should not be ignored, and if you do ignore them you can't really have assurance. The Bible is pretty clear that those who exercise saving faith will persevere in the faith. It doesn't say you will never have ups and downs in your faith or your relationship with God, but there are many strong warnings about failing away from the faith and if you stay in that position you will not ultimately be saved. True faith perseveres and God promises to chastise true believers when they go astray. I also believe that these warning passages are used by God to keep true believers from ultimately falling away. If you emphasize OSAS to the exclusion of perseverance, you run the risk of giving false assurance to the unjustified and rob backsliding believers from a tool that God uses to bring them back into full assurance of faith.