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7.62 ar question

Old 10-28-2013, 12:15 AM
  #1  
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Default 7.62 ar question

Ik you can put a 7.62x39upper on a 5.56 lower. But can you put a 5.56 upper on a 308/7.62 lower
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Old 10-28-2013, 04:56 AM
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NO!

The upper for a .308 AR is LONGER than the upper for a 5.56 AR. Say you were able to pin the two together at the forward pin:

1. How is a 5.56mm magazine going to stay inside a .308 magazine well?

2. What are you going to do to plug that gap between the rear of the 5.56mm upper and the buffer of the .308 lower? All those important parts like the hammer won't line up, either.

3. And worse, the bolt won't be under the influence of the buffer spring - therefore, will not properly return to battery even if you were able to get it to fire once. But with no pin to line up at the rear of the .5.56 upper and the .308 lower, that bolt will probably just fly out and into your eye on the first shot anyway.

Edit: Maybe you don't realize this, but the 5.56 AR can handle most cartridges up to the same length as a 5.56x45mm round (which is indicated by the LAST number: 45mm). That's why the 7.62x39 is offered in a 5.56mm-length rifle. Maybe you need to convince one of the many manufacturers that there's a market for a custom (longer) upper in 5.56mm for a .308 lower? Until then, the 5.56mm upper will always be too short to fit to a .308 lower.

Last edited by homers brother; 10-28-2013 at 05:01 AM.
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Old 10-28-2013, 06:18 AM
  #3  
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There is a special AR made, can't remember the name right off hand, that is convertible, the front part of the lower is pinned and can be swapped and work as an AR10. Think its called the Hydra or something like that. Can't remember who makes it though.
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Old 10-28-2013, 08:29 AM
  #4  
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Simply put, no, you won't be happy with an AR-10 that converts down to 5.56. It has been done, and can be done, but you will spend far far more on that set up than you would have spent on an AR-15 and an AR-10. It's just not worth it to hybridize an AR-15/10

That said, there are certain rounds available for the AR-15 that you would be happy with for big game hunting.. .243wssm, .25wssm, 6.5 Grendel, .458socom, 6.8spc, etc

I'm not sure I'd be interested in a 7.62x39mm AR-15, there are better cartridges available.
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Old 10-28-2013, 07:05 PM
  #5  
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I knew the 5.56 and 7.62x45 was the same and the 308 was longer. Just wondered if it had been done. I do see some benefits to it but not much outside of ammo cost. No i got little interest in a special converted ar10.

I like the excuse of i need another one cause ammos cheaper lmao

I figured the mag would be the easy part since they have 22 mags for them. Unless im mistaken cause arent there 22 kits to make a ar15 22cal
Originally Posted by homers brother View Post
NO!

The upper for a .308 AR is LONGER than the upper for a 5.56 AR. Say you were able to pin the two together at the forward pin:

1. How is a 5.56mm magazine going to stay inside a .308 magazine well?

2. What are you going to do to plug that gap between the rear of the 5.56mm upper and the buffer of the .308 lower? All those important parts like the hammer won't line up, either.

3. And worse, the bolt won't be under the influence of the buffer spring - therefore, will not properly return to battery even if you were able to get it to fire once. But with no pin to line up at the rear of the .5.56 upper and the .308 lower, that bolt will probably just fly out and into your eye on the first shot anyway.

Edit: Maybe you don't realize this, but the 5.56 AR can handle most cartridges up to the same length as a 5.56x45mm round (which is indicated by the LAST number: 45mm). That's why the 7.62x39 is offered in a 5.56mm-length rifle. Maybe you need to convince one of the many manufacturers that there's a market for a custom (longer) upper in 5.56mm for a .308 lower? Until then, the 5.56mm upper will always be too short to fit to a .308 lower.
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Old 10-29-2013, 07:03 PM
  #6  
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Sure you just have to buy a Colt LE901 and the conversion kit and you will be GTG. Oh don't forget all the extra cash.
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Old 10-31-2013, 07:23 AM
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Originally Posted by Nomercy448 View Post
Simply put, no, you won't be happy with an AR-10 that converts down to 5.56. It has been done, and can be done, but you will spend far far more on that set up than you would have spent on an AR-15 and an AR-10. It's just not worth it to hybridize an AR-15/10

That said, there are certain rounds available for the AR-15 that you would be happy with for big game hunting.. .243wssm, .25wssm, 6.5 Grendel, .458socom, 6.8spc, etc

I'm not sure I'd be interested in a 7.62x39mm AR-15, there are better cartridges available.
Don't forget the .450 Bushmaster.......LOL
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Old 11-10-2013, 05:35 PM
  #8  
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Originally Posted by Primitive Weapon View Post
Don't forget the .450 Bushmaster.......LOL
+1 for the 450B

Inside of 200 yds or so the 450B is hard to beat.. Factory Hornady ammo is available and under $30/box these days..

Sighted in correctly it is +/- 3" all the way out about 200 yds..

the 7.62x39 is more or less comparable to a .30-30 - not that there is nothing wrong with a 30-30..

Brian
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Old 11-10-2013, 08:29 PM
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Originally Posted by thatguybme View Post
+1 for the 450B

Inside of 200 yds or so the 450B is hard to beat.. Factory Hornady ammo is available and under $30/box these days..

Sighted in correctly it is +/- 3" all the way out about 200 yds..

the 7.62x39 is more or less comparable to a .30-30 - not that there is nothing wrong with a 30-30..

Brian
Only issue with the 7.62 is the type of bullets loaded for it. Need to use the correct type for the game you are hunting, and it must feed thru the gun reliably. That could be a problem for some. Your 45 caliber rifles are some real thumpers too.
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