I am about to invest in a rail for my bushmaster 16, and was looking at non free floated options. The RAS-II is out for a couple of reasons. I am looking at Surefire or KAC RIS to mount on the rifle.

I DO use the rifle for 500 yards. If I mounted a vert grip and a non free floated rail, would that change the POI at those extended ranges significantly? I think if I was pulling on the vert grip, it would be like sling tension on a non FF rifle and it would negativly effect the POI.

Also, after sept I am going to buy a 20 inch upper and a rail + grip. Would I experience similar problems?  

What do you guys think?

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Not even if tension is applied? They say a taught sling can change your POI on an AR15 (Non FF) but tension on a vert grip wont? Seems like its the same "theory", with the tension closer to the receiver.

Basically this thread is to justify the purchase of a new KAC or DD product.
Just dont want to take the FSB off unless their is a good reason. (POI shift is a good reason)

Thanks for the reply.