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12/26/2016 2:23:35 PM EDT
My uncle decided to come over to the EBR side and wants me to build him an upper for deer and bear hunting. He wants a 450 but I have no experience with that round. I'm assuming it fits and functions in a standard upper but Tromix has a dedicated 450 upper with an enlarged ejection port. Is an enlarged port necessary or can I go with a standard Aero upper?
12/26/2016 2:31:08 PM EDT
[#1]
Pretty sure an enlarged port is required for the .450.


12/26/2016 3:43:19 PM EDT
[#2]
Yes the enlarged port is required for reliable ejection.  It is required for all big bore ar15's.

I have 2 tromix uppers for 458socom.  I say go for it.
12/26/2016 4:00:08 PM EDT
[#3]
.450" Bushmaster uses .451" bullets up to 330 grns or so, requires a special magazine, factory ammo is available.  .458" SOCOM uses .458" bullets up to 600 grns or so, standard GI mags, factory ammo is rare, you can handload heavy subsonics.
12/28/2016 6:30:22 AM EDT
[#4]

Large port upper.

ar15 large port upper
12/29/2016 9:59:39 PM EDT
[#5]
If you are handy enough to build AR-15's, you probably have the skills needed to open up the ejection port on a standard upper.  
The process and dimensions are readily available on the web (http://450bushmaster.net/viewtopic.php?f=2&t=12877)  &  (https://www.youtube.com/watch?v=IhLkrtymmoI).
It takes about 30 minutes and only requires a hand grinder, some masking tape, and a few small files.

Good Luck,
JW
12/29/2016 10:38:04 PM EDT
[#6]
Quote History
Quoted:
.450" Bushmaster uses .451" bullets up to 330 grns or so, requires a special magazine, factory ammo is available.  .458" SOCOM uses .458" bullets up to 600 grns or so, standard GI mags, factory ammo is rare, you can handload heavy subsonics.
View Quote


450B does not use special mags.  You can use reg GI mags, you may have some feeding uses depending on the follower.  Best way is standard mags with a signle shot follower, which can be found cheap.


To OP, take a look at factory busmaster uppers, they usually mark them down significantly this time of year.
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