Surefire m73 shifting POI

[andy t]

I recently installed surefire M73 rail on my RRA 16" M4 profile upper. When I got to the 50 yard range on Saturday, I noticed that i had to move the rear sight one click to the right to center my group. Is this expected behavior? Will there be any long term effects on the barrel?

Thanks.

[R.D.]

FWIW I also have a M73 on my RRA upper with a customized 14.5 heavy barrel. I also had a small shift in my zero most likely due to the method the handguard mounts to the barrel/upper receiver. I have had no shift in zero since sighting in after installing the M73 that can be atributed to the rail. Also I have noticed no loss of accuracy since the install. I have just shy of 2000 rounds through the upper since the rail was installed.

[-H-]

What is happening is the different Railed Handguards are effecting your barrel harmonics differently than your stock HGs.

POI may change if you mount a Forward Grip, Flashlight or Bipod etc..

This is why many prefer Free-Floated Handguards.