The FSB on my LWRC carbine will rotate about 10 degrees about the centerline of the bore. Suprisingly, it still worked fine until I realized my sight adjustments were crazy and investigated more thoroughly. The taper pins are both still there (I can't tell if they are somehow sheared unless I take it off) but the FSP wiggles with just finger pressure. I notice DPMS sells oversize taper pins. Are these intended for just such a problem? I had never heard of this before. Any ideas or experiences out there? BTW, I don't recall ever really whacking the FSB against anything and I never ran a sling off of it.

Contact LWRC and they'll fix it.  The FSB should not be moving at all.  The front sight post does have a slight bit of movement on my AR's.  

Dorchester, thats not normal and we need to fix that ASAP. I've IMed you my email contact info.  Give me a shout, and I'll reply with a UPS shipping label - send it back and we'll take care of the FSB for you.
                                 Andy

To those who might be interested: Andy at LWRC contacted me promptly and by multiple venues, kudos to him for doing his job so well. I always knew I should just send the thing back but a long cold winter intruded and I just put this off. The upper is on its' way to be fixed (and upgraded with rails).

I'm curious what would result from shooting with a loose FSB besides having accuracy off.  If the FSB can move in both directions, it is still held in that spot on the barrel by the area where the pins were drilled in right?

To any who might care: I just got my LWRC upper back from the warranty repair, the new barrel they installed shoots straight, all is peachy. The issue turned out to be a barrel rather than a taper pin problem. Between, my procrastination and LWRC's moving the whole stinking factory it took a while. Excellent service actually, considering the situation. They include a BCG upgrade as a nice touch. I highly recommend the product.

Quoted: I'm curious what would result from shooting with a loose FSB besides having accuracy off.  If the FSB can move in both directions, it is still held in that spot on the barrel by the area where the pins were drilled in right?

It "could" rotate enough to act like a gas shut off and making your rifle a single shot. I think the taper pins would have to fall out of the FSB for this to happen.

Surely the fsb is also the front piston holder, part of the the piston system, maybe if that moves around it would bend the operating rod?