Thermal fit uppera++++ - ZEV Technologies AR15 Forged Upper Receivers

It’s interesting but it’s possible looking at a review that was from 2017. They didn’t understand the meaning of thermal fit that means you heat the upper so that it will let the barrel extension slide in and when it cools you get such a tight fit when the barrel heats up this will never developed slop therefore POI will never shift , due to too much slop between the barrel in the upper receiver not sure how one reviewer didn’t understand this. Also, if you have this upper, you should use their lower because their fit is absolute, do not use their upper with a different lower because it might not lineup because they’re tolerances are absolute… if you want to look at something that sloppy or has tolerances that are much higher than look at Aeroprecision for example they have much higher tolerances, so therefore, barrels will slide in upper and lower, as will slide together easily but yet there’s going to be much more wiggle and movement and you could say well that doesn’t affect barrel accuracy because the barrel is separate. Well, it’s really not harmonics are everything and if you’re not doing your own loads to account for this than different harmonics are going to change as slop movement and Cetra Cetra for the most part most people aren’t gonna care in their works or shoot just fine but if you’re looking for absolute accuracy and making sure that all else is zeroed out, then you wanna Zev upper and lower I know there’s others out there that also have tight torches, but this is the one I know of