arakboss

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First off, I would like to get the "why" out of the way for the imagination challenged individuals. The reason for building such a firearm would be because I can.


Now the what. I am thinking a person could make a shotgun utilizing a standard AR upper receiver and a fresh lower receiver. Since smoothbore AR barrels are a rare commodity, I believe that a rifled barrel could be drilled out to remove all the rifling. A 450 BM or 50 Beowulf barrel might work well for this given that they use nearly straight walled brass. The brass could then be loaded with shot or slugs for firing? Based on legal definition of shotgun this type of set up should be legal as long as barrel length minimum is followed?
 
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First off, I would like to get the "why" out of the way for the imagination challenged individuals. The reason for building such a firearm would be because I can.


Now the what. I am thinking a person could make a shotgun utilizing a standard AR upper receiver and a fresh lower receiver. Since smoothbore AR barrels are a rare commodity, I believe that a rifled barrel could be drilled out to remove all the rifling. A 450 BM or 50 Beowulf barrel might work well for this given that they use nearly straight walled brass. The brass could then be loaded with shot or slugs for firing? Based on legal definition of shotgun this type of set up should be legal as long as barrel length minimum is followed?
They make AR10 receiver based shotguns already in 12 gauge. Pretty neat, but spendy.
 

arakboss

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They make AR10 receiver based shotguns already in 12 gauge. Pretty neat, but spendy.
Those are sweet. I was thinking of a budget AR15 combo that would allow me to switch the barrel and bolt for some centerfire action if that is legal? In my case I would only need to buy the sacrificial barrel to build one as I have a fresh lower and all of the other parts. Harbor Freight sells long drill bits that might be useable to get rid of rifling. Not sure how hard that material would be to drill?
 
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Those are sweet. I was thinking of a budget AR15 combo that would allow me to switch the barrel and bolt for some centerfire action if that is legal? In my case I would only need to buy the sacrificial barrel to build one as I have a fresh lower and all of the other parts. Harbor Freight sells long drill bits that might be useable to get rid of rifling. Not sure how hard that material would be to drill?
You’re a tinkerer, I remember other project ideas you’ve shared. Seems like you could buy an upper in .410 for less than you’d be into it otherwise. But then there wouldn’t be any tinkering.

 

arakboss

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You’re a tinkerer, I remember other project ideas you’ve shared. Seems like you could buy an upper in .410 for less than you’d be into it otherwise. But then there wouldn’t be any tinkering.

I almost bought one of those 410 uppers on more than one occasion but now the prices have almost doubled. I would get more satisfaction out of something I did myself. I still want to do a slamfire version too.
 
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The ar15 magwell is only 2.4 inches long and .89 inches wide. Rounds like .50 beowulf and 450 BM are only possible in an AR frame because those rounds overall length of 2.12 and 2.26 respectively, with width below half an inch. Meanwhile there are very few 12ga shells that are shorter than 2.4 inches, and they have a diameter around .85.

It would be virtually impossible to feed 12ga shells through an AR-15 magwell... and even if you manage to get your shells into the gun you still have to figure out a BCG and tune it to cycle properly, as well as finding/fitting an appropriately large barrel.
 

arakboss

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The ar15 magwell is only 2.4 inches long and .89 inches wide. Rounds like .50 beowulf and 450 BM are only possible in an AR frame because those rounds overall length of 2.12 and 2.26 respectively, with width below half an inch. Meanwhile there are very few 12ga shells that are shorter than 2.4 inches, and they have a diameter around .85.

It would be virtually impossible to feed 12ga shells through an AR-15 magwell... and even if you manage to get your shells into the gun you still have to figure out a BCG and tune it to cycle properly, as well as finding/fitting an appropriately large barrel.
The plan was to make shot shells with the appropriate brass 450 BM brass for 450 BM barrel or 50 Beowulf brass for 50 Beowulf barrel. There should be no issues with BCG. The only difference would be a smoothbore barrel and the way the ammo is loaded.
 
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The plan was to make shot shells with the appropriate brass 450 BM brass for 450 BM barrel or 50 Beowulf brass for 50 Beowulf barrel. There should be no issues with BCG. The only difference would be a smoothbore barrel and the way the ammo is loaded.
IMO, making your "shot shells" based on 450BM or 50BW brass seems like a very difficult and potentially dangerous project...but its def an incredibly cool project too.
 

arakboss

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IMO, making your "shot shells" based on 450BM or 50BW brass seems like a very difficult and potentially dangerous project...but its def an incredibly cool project too.
There should be little difference between loading the 450 BM, 50 Beo brass compared to 303 Brit, 444 Marlin or brass hulls that are commonly used for shot loads. The 450 BM and 50 Beo brass will withstand much higher pressures too, as will the smoothbore AR barrels. This will give me more room to load up some smoking hot buckshot and slug loads.
 

arakboss

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Just had a thought, it can identify as a musket.
I am going to try a bunch of different projectiles including some muzzle loading projectiles before I do any drilling on the barrel. The 50 Beowulf brass is expensive and hard to come by so I am going to block the gas port on the barrel and run it in a manual loading configuration. That will allow me to get more reloads out of the brass and run some lower recoil loads. I don't want to bang up my shoulder either;)
 

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