What is needed to convert an ar15 receiver to 450?

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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What is needed to convert an ar15 receiver to 450?

Postby BIGDH0ward » Sun Oct 30, 2016 6:07 am

Hey guys, so I've done some rebuilds for 5.56/223 which came fairly easy with thanks to YouTube and some common knowledge. I've been think about doing a 450 bushmaster recently but have some questions in which I can't find answers. My friend recently bought a fully assembled 450 and he already had a stainless bull barrel which I had placed on his gun for him. He had the stock bushmaster 16 inch barrel and flash hider which came off the gun. I have a 450 bolt, low profile gas block, and carbine length gas tube in which I can use. My questions are can I use a standard 556 carrier group, do I need a heavier buffer spring, and can I use a standard 556 upper receiver for a build? Thanks in advance and have a good one.
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Re: What is needed to convert an ar15 receiver to 450?

Postby Hoot » Sun Oct 30, 2016 8:08 am

Welcome aboard Howard.

The short answer is yes. You may have to open up the ejection port a little depending upon how it arrived from the manufacturer. Some have more clearance but most dont. There are articles and IIRC a youtube video or two about how to do that.

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Re: What is needed to convert an ar15 receiver to 450?

Postby BayShoreBallistics » Wed Dec 21, 2016 5:30 pm

Can you use a standard 5.56 bolt carrier, yes. Just swap out the bolt and you are good to go.

Do you need a heavier recoil spring, no. It should run fine with the standard spring installed. Carbine gas length will make it run a bit on the harsh side of ideal but still functioning fine. Standard buffer weight is the best place to start and if needed you can go to something heavier.

As Hoot mentioned, you will probably need to open up the ejection port for it to allow the brass to even pass through at all. I have never had to open one up so large that the standard dust cover won't cover the entire port though. If you have ammo and a stripped upper it will seem obvious when you put the two together in your hand.

Those were some good questions that I am sure many newer members and casual readers will like to see answered.
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Re: What is needed to convert an ar15 receiver to 450?

Postby plant_one » Wed Dec 21, 2016 11:12 pm

i installed one of Hoot's CCWS in my BCG to add weight and its quite nice on my 20" upper with a standard carbine buffer and spring.

buddy of mine just got his factory upper and is building a regular lower with a normal carbine buffer. I'll be curious to put it side by side and do a recoil test to compared weighted carrier vs non and also my ross break vs just a flash hider
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