Montrala for your response. I don't think I have an OTB barrel that I can tell but glad I have the bolt. I didn't see a stud in the extension that I can tell. Im wondering if having a non OTB barrel would make a difference in wear. I see now about the sling loops being cut off for the hand guard, Pretty sure mine happens to be the larger one. Thanks again for your response. Looking forward to how this whole thing turns out.