Hello everyone!

I have a very weird problem. I recently acquired all parts needed to complete my upper. I have Spike's Tactical lower that is completely assembled (furniture, trigger, buffer) and all. But when I tried putting my new Aero precision stripped upper on it to see how it looks, I noticed two things: Firstly, the upper is EXTREMELY tight. To a point where I needed to use a plastic mallet to smash it down. And even after that, I never go the rear takedown pin to go in. The front one kind of goes in and out (gets a bit stuck). Furthermore, I noticed the upper, when Installed on my lower is shifted to the left a bit. So, if you are looking at it from the top, it sits like 0.5mm to the left, causing a noticeable indent on both sides. If you drag your fingers from the lower up to the upper, you feel a fall on the right side and a "wall" on the left. So it's definitely not completely flush. When I removed it, I also noticed deep scratches on the top of the ring thing where the buffer tube screws in. Where the upper makes contact with the lower. Yes, I made sure the hammer was cocked back and all.

I borrowed my friend's PSA Assembled upper a few months ago and it went on my lower beautifully and functioned!! So I have no idea what could be the problem. Any help would be appreciated.

Specs:

Lower: Spike's tactical punisher lower
Upper: Aero Precision stripped uper.

Thanks!

How did you tighten the barrel nut? Brand new upper?

Edit. Reading is fundamental. No barrel installed and new and stripped. Email aero. They will take care of you

Aero has had a few problems here and there lately, they will make it right.

Yes, brand new upper out of the box. I have not installed the barrel yet. In fact, it is a completely stripped upper (except for the dust cover and forward assist). So there is no chance it's the BCG or hammer. I don't know what's wrong. Here's a picture. Should I contact Aero?



Here's a pic. As you can see, the edges of the upper are like 1mm off center.

Thanks!

Ok, so...

I took my entire upper and lower to my gunsmith. He also said they were un-conventionally tight. He then took a fresh lower out and tried my upper on that and it fit well. I couldn't see if it had been canted like with mine but it definitely went on there. He told me that I should try sanding out the inside of the cavity where the rear takedown pin is.
So, I did. I sanded off basically just the paint.
The upper now actually goes into the cavity but I STILL can't close the rear takedown pin. The left side of the receiver is flush and the rear takedown pin is ready to go into the left side of the upper but the right side is weird. It isn't flush at all. In fact, there is a noticeable gap between the lower and upper. More so than on the left side. And that "cant" is still there. The upper is still shifted to the left as on the picture posted above. I don't know what to do. I figure I'd either grind down the left side of the upper take-down pin hole and basically compensate for that cant. Basically just grind down the left side so that it can be pushed to the left and then closed with the rear takedown pin.

I don't know what else to do. Has anyone heard of anything like this before? Please let me know, I've been scouring the forums like a madman. It's a shame, because I've been building this AR for the past year.

I'll also take out a caliper and measure the thickness of my lower's walls of the rear takedown cavity. So I can confirm either side isn't too thick/thin.

Anything helps.

Thanks!

I would contact Aero and tell them it seems out of spec. I haven't had any problems myself but I imagine they would replace the defective part.