Ar front rail alignment expectations

[OB_WAN]

Hi. I'm somewhat new to the ar platform so bear with me.

I'm curious what expectations are for front rail alignment with the upper receiver rail.

I have a ar-15 with a basic non free float quad rail on it and it looks like it lines up fairly well. Maybe 10 thou off.

I recently picked up the aero precision m5e1(308) complete upper because I like how they reinforced the barrel support and integrated the front rail to make it free float and more stable(and I was hoping seem less alignment between upper and rail for optic alignment)

Unfortunately the front rail alignment is poor from a gunsmith fitment perspective(my personal opinion). It is raised about 30 thou above the receiver rail, is canted slightly to the left, and tapers down towards the end of the barrel. So that the end of the 15" rail looks to be slightly lower than the receiver. I would think this would make for quite a challenge for consistency when mounting optics. But don't have enough experience.

if you run free float rails on the ar platform I'm curious if you have similar alignment discrepancies or have feedback on fitment.

[brando]

for optics, it's a long standing issue when installing a mount across the upper receiver and top handguard rail, though this is mostly applied to scopes and not RDS.

That's specifically why the PRI top rail was made for the early SPRs back about 15 years ago.