Buffer tube question

[EWB_TUS]

I built an LR308 rifle initially with a carbine configuration and am trying to switch it to the rifle configuration. I bought an AR-Stoner rifle buffer tube but it doesn't thread far enough into the upper to retain the buffer retaining pin. I included a picture. Is there a rifle length buffer tube that will thread farther into the upper. Had no issue with the carbine one but it has many more threads and a castle nut.

Thx

[EWB_TUS]

PS - meant lower, that's where the buffer tube threads in as I am sure the rest of you know 🙂.