Started a new build today. 300 AAC 8".

Upper: Aero M4E1 (M4 Feed Ramps)
Barrel: Ballistic Advantage (Aero) 8" 300 ACC barrel (M4 Feed Ramps)

As you can see in the pic, The feed ramps on the barrel overlap the feed ramps on the upper.

Is this going to be an issue? if so which is out of spec? Barrel? Upper?

I believe there is a thread (might even be a tacked thread) addressing the M4 feed ramp issue and the differences.

I don't have time to look it up right now but I know it is here on the site somewhere.

Can anyone else help the OP out with a link?

Hope this helps.

ETA: Grammar

OP different manufacturers use different tolerances and as a result, things don't always match up like they should. About 6 months ago I had the same issue with a Noveske Afghan and a Mega billit upper. I said fuck it and assembled it anyway despite the obvious feed ramp overhang. Long story short, I have yet to see a malfunction with the setup. My advice is to build it up and run it. If you start having FTF then consider a different combo or filing the feed ramps. I'm sure someone will be along with that stupid picture shortly.
 

ETA: What mine looked like

Since both the barrel and upper are AERO ,I say tell them to make it right.

OP - you have two ways to go with this. 1) you can send them back to Aero. 2) you can use a dremel by hand to make them line up right if you have a dremel.  Personally, I'd just do it myself with a dremel and then use the dremel to also polish it all up nice using the brushes in kit. I don't actually have a 'Dremel' - I have a Master Mechanic kit. Same thing though.

You can fix this by hand also with a round file. A chainsaw sharpening file would work well. File down the lip so that it mates up nice and then polish off will 0000 steel wool.

I like it all to mate up nicely and cleanly so I would make it do so. If the ramps in the receiver were a tiny bit higher than the ramps in the barrel extension it would really be a non issue since the cartridges would chamber without getting hung up. A lip with the barrel extension ramps being a tiny bit higher than the receiver ramps could catch cartridges where the bullet seats in the mouth of the cartridge and cause failures to feed. The solution would be to dremel out or polish out that extra tiny bit of metal at the edge of the feed ramp of the barrel extension.

I'd just do it myself because i do have the tools anyway. I wouldn't want the wait time involved with sending the parts back and getting them back.

The reason these things happen is because most companies don't make all the items themselves. Other companies make parts for them - like barrels.

Thanks guys. It appears to be an issue with the Aero M4E1 upper. Have ran across a few posts that involve this upper and the same issue.

I have cross posted in Aero forum and also sent an email. After I hear back from them I will decide what direction to go. Would rather not file anything but also do not want to ship this one out, wait for return... just to have the same issue and have to file anyway.