FSP = jargon. I assume it means a front sling point? Using an acronym just left 50% of the readers out of the question poll. It's the first I've seen it, and I surf 5 or 6 AR forums.
Rest the barrel on a solid surface, it can shift the point of aim, whether a sandbag, door frame, etc. Pressure will exert a bending moment on just about any barrel light enough to be carried by a single user. The effect on accuracy is relatively minimal, as a combat rifle with a sling attached to the barrel is generally 2MOA, not 1/2. Most weapons are designed for minute of soldier at 600m, largely because most soldiers will only attempt shots up to that range at best.
Using a sling to make more accurate shots at distance is common, but on combat rifles, it's common for the swivel to be attached to the barrel. That, right there, makes the technique invalid. It's a precision target shooting technique that obviously doesn't translate. So, marketing came up with the $200 solution, add a free float, and while they're at it, lots of rails to mount stuff. The sling can be mounted to it and won't bend the barrel.
Very few just don't use a sling, for some reason that's not considered an option - and yet that solves the problem, too. It's also a lot cheaper. With single point slings being attached to a slider at the back of the lower, it get it out of the way of mag reloads, too.
The point is - do you want ( I won't even ask need) the added accuracy of a free floated barrel? Competition shooters demand it, long range shooters insist on it, OK. If the barrel you use is actually that good, and you are, too, why not?
It's the free floats on GI barrels - with rails and no accessories - that make me think it's more fad than worth it. A 2MOA barrel with a free float is still that, and a 2MOA shooter behind the charging handle is likely going to hear more feedback than see it on a target. Too many post about their new AR with the caveat "I haven't taken it to the range yet." Or, "I've got 200 rounds thru it this year and it's flawless." I'm not impressed with the reliability or the users ability in either case. It most likely just another tricked out AR, a male enhancement therapy.
I would certainly give some thought to the fact that most free float makers will not give a guarantee of improved, measurable accuracy for their product. Barrel makers can and have, take it under consideration where the advantage is.
