So without a closer look at our rig, looks like semi extended M-4 feed ramps in the upper receiver, a non M-4 extended feed ramp barrel extension in the barrel.  The dead give away that it will be a problems, will be the start of the barrel feed ramps protruding above  end of the receiver ramps where bullet tip will snag on the ramps during loads.

You didn’t say which, but as long as you used a rifle receiver with a rifle extension or an M4 receiver with an M4 extension, barring a gross machining error somewhere, it’s good.

Even a rifle receiver with an M4 extension is OK.

The only combination that isn’t good is an M4 receiver with a rifle extension.

Colt M-4 barrel extension feed ramps will cut through the od of the barrel extension wall to create the longer needed angle to allow the rig to feed 69 grain ammo.



Then you have some craptasitic knock off of such, that the ramps do not cut through the od wall, and guess for uppers with shallower feed ramps instead.


Hence the whole reason for the extended ramps was so the rig could feed the longer ogive 69 grain ammo, so tend to favor true colt designs over knock offs.
Note, FN  may be making the M-4's for the government now, but colt is still getting 5% in royalitiy from the design of the M-4 system in the first place until 2050 for each rifle the goverment buys.
https://www.defenseindustrydaily.com/Colt-M4-Data-Rights-The-Individual-Carbine-Competition-06942/

So on that note, guessing that the shallower extension and receiver feed ramps that we are seeing in the civilian market place, are so these producers do not have to pay colt royalties on the M-4 system for using the correct specs.