putting a 450 bushmaster upper on an AR-15 question (308, cheap, bullet)
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I'm debating on getting a 450 bushmaster upper for my Rock River AR. Having never tried to put a different upper on this rifle, I was wondering if it's a simple swap or if some mods would need to be done. I would like to be able to use both uppers at different times so it wouldn't be a permanent change.
It's about as simple as it gets. Push out the 2 small pins, pull the current upper off of it, install the new one in reverse order. Most all of the uppers come with the small pin uppers and lowers. The old Colts had some that are called large pin and won't fit. Your RR won't have that issue. Next time, consider building your own upper. Once you've done it, it's so easy you'll wonder why you haven't built one before. I have 5 uppers in various cartridges that I've built. You can also go full custom on the cartridge like a 6x 45 which is nothing more than the 223 necked up to 6mm. I can push the 70gr TNT just a little slower than a 243 but in an AR platform, as an example. My next one, if I can find the parts, will be a 30 AR Remington. You can push a 150gr at 2600'ps which is 200'ps slower than a 308 but in an AR15 platform rather than a larger AR10. LOTS of choices out there for the AR15 lowers.
If you don't have one yet, I'd strongly suggest getting an accurizing wedge for it. It's dirt cheap and makes the upper to lower fit a lot tighter. Here's one at Midway so you know what it looks like. It sits in the lower at the back of the lower where the receiver/upper sits on the lower. https://www.midwayusa.com/product/51...ng-wedge-ar-15
You don't have to swap out the buffer spring but expect full recoil. A 450 really should have it's own lower with a heavier buffering spring to take the recoil out. Once you've made the change to a heavier spring, you'll notice the difference first shot but it's not required. They also make a hydraulic buffer for the 450 and it is SMOOOOOTH! You'll want to buy Bushmaster 450 mags for it or expect feeding issues. The Bushy mags come with a blue follower that is made for the 450 and takes all of the issues out of it. Obviously, Bushmaster is in bankruptcy with Remington. I wouldn't wait if this is one you really want. You might find parts hard to come by, like mags.
I know that AR upper and lowers are pretty much interchangeable but what makes an AR 15 become an AR 10 ? Just anything with a larger caliber then 5.56/.223 ?
Also won't the OP need a heavier Buffer along with spring ?
An AR10 is a larger version of the AR15. No parts are interchangeable as such. The AR10 is designed around the 308 case. The 223/5.56 is a reduced or scaled down version of the 308. FWIW, all of the bullet makers use the 308 case in some form to test the accuracy of their bullets. They just neck it to the caliber they are testing. The 308, like the 223/5.56, is incredibly easy to get extreme accuracy.
I know that AR upper and lowers are pretty much interchangeable but what makes an AR 15 become an AR 10 ? Just anything with a larger caliber then 5.56/.223 ?
Also won't the OP need a heavier Buffer along with spring ?
10 and 15 are two completely different platforms. The 15 magwell is around 2.2 long while the 10 is near 2.8 inches The 10 is quite a bit heavier due to the extra material. Here is a pretty good list of total AR calibers but you can get wildcats too. They do make even bigger ARs based on the magnums too.
An AR10 is a larger version of the AR15. No parts are interchangeable as such. The AR10 is designed around the 308 case. The 223/5.56 is a reduced or scaled down version of the 308. FWIW, all of the bullet makers use the 308 case in some form to test the accuracy of their bullets. They just neck it to the caliber they are testing. The 308, like the 223/5.56, is incredibly easy to get extreme accuracy.
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Originally Posted by 1AngryTaxPayer
10 and 15 are two completely different platforms. The 15 magwell is around 2.2 long while the 10 is near 2.8 inches The 10 is quite a bit heavier due to the extra material. Here is a pretty good list of total AR calibers but you can get wildcats too. They do make even bigger ARs based on the magnums too.
An AR10 is a larger version of the AR15. No parts are interchangeable as such. The AR10 is designed around the 308 case. The 223/5.56 is a reduced or scaled down version of the 308. FWIW, all of the bullet makers use the 308 case in some form to test the accuracy of their bullets. They just neck it to the caliber they are testing. The 308, like the 223/5.56, is incredibly easy to get extreme accuracy.
So, your claim is that Sierra uses a .22-308 case to test their .224 match bullets?
From Rich at Sierra Bullet Testing Division, yes, they use the 308 case from .22 to .358 bullets to test for accuracy. You can call him at 1-800-223-8799. He's been in the Sierra Ballistic Dept the longest of the guys there.
Just for fun. Have you ever heard of the 22 Earsplittenloudenboomer? Try the 378 Weatherby Mag necked down to 22 caliber. It pushes a 45gr solid bronze bullet to over 6000'ps. While it has zero use as a hunting round, NASA uses it to test the shuttles components for small meteorite impacts.
From Rich at Sierra Bullet Testing Division, yes, they use the 308 case from .22 to .358 bullets to test for accuracy. You can call him at 1-800-223-8799. He's been in the Sierra Ballistic Dept the longest of the guys there.
Oh, this should be fun. I know a few of the guys at Sierra. What’s Rich’s last name? I’ve never met (or heard of him).
Quote:
Just for fun. Have you ever heard of the 22 Earsplittenloudenboomer? Try the 378 Weatherby Mag necked down to 22 caliber. It pushes a 45gr solid bronze bullet to over 6000'ps. While it has zero use as a hunting round, NASA uses it to test the shuttles components for small meteorite impacts.
P.O. Ackleys wildcat? Yeah, I’m familiar with it. The one that he was able to get about 4,500 - 4,600 FPS out of?
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I know a few of the guys at Sierra. What’s Rich’s last name? I’ve never met (or heard of him). 
