Upper ejection port opening

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Upper ejection port opening

Postby Aztrooper » Thu Dec 29, 2016 11:58 am

Somewhere, I think on this list, I saw a diagram with the measurements that the ejection port had to be milled out to so the spent case would clear it properly. Does anyone know where that post is and could copy and past it here? I have done a search but couldn't find it.

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Re: Upper ejection port opening

Postby plant_one » Thu Dec 29, 2016 12:04 pm

did you incorrectly buy an upper that is standard that you have to make work?

or are you doing it just for the exercise of being able to do it because you want to have the skills to do so.

there are lots of uppers on the market specifically geared toward big bore calibers that would preclude the need to mill your port and get a modified ejection port cover to successfully work on the 450 bushmaster.
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Re: Upper ejection port opening

Postby Pig_Popper » Thu Dec 29, 2016 3:09 pm


I went ahead and bought an upper receiver that didn't have an ejection port cover to ease the process.

Also don't take the measurements to seriously , carve away and when you can easily toss a case back and forth through the hole then you're there.

I was a couple thousands less than the stated measurements and all ejects fine.
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