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I have a lower that I put a fostech echo sport binary trigger in. It seems to function correct on semi and on binary. The problem I’ve got is putting the upper and lower together. I’ve seen videos on YouTube that make it look like no big deal. I’ve had the trigger pulled and held with the parts inside as far out of the way. I’ve had the selector on semi, and on binary. I can take the upper and put it on another lower and goes right on, so it’s not a defective upper. The lower is just a typical Anderson. Have any of you had a problem mating the upper and lower and what did you do to fix it?

Try E Harmony.

They didn’t have an idea how to fix the problem

Possibly the binary trigger is interfering, try taking the bolt out see if it works, see if it's closing all the way, try pulling both. Pins and closing , then push them both in, don't rock it as normal, sometimes buffer is in the way

I was talking with someone about these a while ago and not sure which version they had but were having a similar issue of the upper not wanting to close all the way. If I remember correctly their fix was once the upper started to hang up and not close they would pull back on the charging handle just a little bit and the upper would finish dropping down, sounded like the bcg was hanging up on part of the assembly.

This is the most craziest thing I’ve ever delt with. If the bolt is out it still doesn’t want to close.

Also, I tried to pull the charging handle and still nothing.

When the bcg was out were you able to see what it was hanging up on?

I’m not sure what the hang up is. I could take the upper and it matches up any other lower without problem. I sent a video in to fostech but they have not gotten back to me.

Was this upper/lower combo functioning prior to the installation of the trigger? If this is a complete new build perhaps something is out of spec. Do you have a different upper you can try on this lower, I see you’ve tried the upper on a different lower but try it the other way around if you have one. If not I’d take the trigger out and see if the upper/lower will go together correctly, this way you can identify if it the trigger causing the issue or perhaps the lower itself.

It is a complete new build. I tried a different upper on it and got the same result.im afraid I’m going to have to start over with it on the trigger.

My buddy was having issues with the binary trigger as well. He just ended up removing the trigger. Get a lightweight upgraded trigger. You can do the same thing imo w/o the binary

Try taking the replacing the binary with a normal trigger and let us know if that works.

Let us know how it goes with the milspec trigger

You stated this was a new build.. Check to see if the buffer tube is not screwed in too far.. I have seen one like that to where it was almost closing on the back pin but not quite making it..