AR15 upper assembly what do I need

[laurencen]

Hi all, putting together a AR15 upper from parts off EE, finally had all the parts but the front sight, anyway picked up a sight and was not aware there were 2 styles, the one I have is too long, example the cross pin holes on barrel are 20mm centers and the sight is 36mm centers, the hand-guard is correct everything is fitting as it should but I have to figure the sight deal,

thoughts? should have just got hold of a complete upper

 

[CraigNConnor]

so if I am understanding you correctly you are looking for the correct FSB (Front sight gas Block)?

 

[Suputin]

There is not standard for front sight base cross pins. Each sight is drilled and pinned in place. You will never find a sight to match your barrel. This is why we have clamp on gas blocks.

 

[laurencen]

There is not standard for front sight base cross pins. Each sight is drilled and pinned in place. You will never find a sight to match your barrel. This is why we have clamp on gas blocks.

a clamp on come with the sight or switch to a red dot sight?

 

[sky52]

Depends on what u do, if u run a red dot then you dont need a FSB. U need a low profile or a railed gas block. Some people co-witness their redot with the FSB. So figure out what your plan is cause we dont know what you bought on the EE