I've put together a bunch of SPRs and SPR uppers for individuals, as well as run them at various ranges and time constraints.
They are truly an excellent platform, and if I was in a static position such as on an embassy detail, where I knew I was going to be doing mostly roof top shots, I would take it in a heartbeat.
That being said, said for an all around weapon, I find that a 16" gun with match grade tube, free floated barrel/handguard setup and a proper trigger such as a Geissele Dynamic to ideal.
Top it off with a low powered variable such a 1.5-5 or 2.5-8 Leupold, or a Nightforce 2.5-10x24 and call it good.
Which buffer is best for an 18" set up?