AR-15 5.56 Questions
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Old 11-02-2008, 12:02 AM   #1
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Default AR-15 5.56 Questions

First time poster on Firearmstalk forums. Hi @ all

I am thinking about buying an AR-15 5.56 and I have some questions.

1) Is it legal for a civilian to have a barrel shorter than 16"?
2) Is it legal to hunt(Deer) with a small 5.56 cartridge?
3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly?

My next set of questions are more technical.

4) What are the differences between 1x7, 1x8 and 1x9 twist barrel?
5) What are the general purposes of these different barrel types?
6) What gain cartridge should you use for these different barrel types?

Thanks in advance!

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Old 11-02-2008, 12:19 AM   #2
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Default AR-15 5.56 Questions

I am thinking about buying an AR-15 5.56 and I have some questions.

1) Is it legal for a civilian to have a barrel shorter than 16"?
2) Is it legal to hunt(Deer) with a small 5.56 cartridge?
3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly?

My next set of questions are more technical.

4) What are the differences between 1x7, 1x8 and 1x9 twist barrel?
5) What are the general purposes of these different barrel types?
6) What gain cartridge should you use for these different barrel types?

Thanks in advance!

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Old 11-02-2008, 12:35 AM   #3
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Quote:
Originally Posted by rcb View Post
I am thinking about buying an AR-15 5.56 and I have some questions.

1) Is it legal for a civilian to have a barrel shorter than 16"?
2) Is it legal to hunt(Deer) with a small 5.56 cartridge?
3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly?

My next set of questions are more technical.

4) What are the differences between 1x7, 1x8 and 1x9 twist barrel?
5) What are the general purposes of these different barrel types?
6) What gain cartridge should you use for these different barrel types?

Thanks in advance!
1)you can get a shorter barrel legally...you just have to do some paper work, wait, wait, wait some more, then pay a $200 tax

2)sure why not? it'll be a little hard though haha
3)because the 7.62 round is longer than the 5.56 you'll need a special lower as well i believe
4)the difference is the rate of twist. the most common is 1x9 but it depends on preference
5)not too sure...i just know most people prefer 1x9
6)well for 1x9 barrel a 55gr works best not sure about the others

hope that helped even though i didn't answer all of them


welcome to the forum btw
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Old 11-02-2008, 12:39 AM   #4
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Originally Posted by rcb View Post
First time poster on Firearmstalk forums. Hi @ all
Hi and welcome!

Quote:
Originally Posted by rcb View Post
I am thinking about buying an AR-15 5.56 and I have some questions.

1) Is it legal for a civilian to have a barrel shorter than 16"?
2) Is it legal to hunt(Deer) with a small 5.56 cartridge?
These depend on your local laws. There are AR "pistols" with very short barrels.

It is not uncommon to have a 14" barrel with a 2" muzzle break to bring the total length to 16". That's the minimum here in New York.

As for hunting deer, it's a pretty light round to use, but it will take a deer down.

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Originally Posted by rcb View Post
3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly?
I believe so, as in this case.

Quote:
Originally Posted by rcb View Post
My next set of questions are more technical.

4) What are the differences between 1x7, 1x8 and 1x9 twist barrel?
Just the rate of twist the bullet has per inch. 1:9 is a full turn in nine inches, for example.

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Originally Posted by rcb View Post
5) What are the general purposes of these different barrel types?
To accommodate different weight bullets and probably different loads.

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Originally Posted by rcb View Post
6) What gain cartridge should you use for these different barrel types?
The 1:7 twist is standard military, I think. That's what's used for heavier bullets (75 to 77gr). Not sure about 1:8. 1:9 are very common for ARs and accommodate weights from 45gr up to at least 62gr. I've had very good results with both 55gr Remington (.223) and 62gr SS109 (5.56).
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Old 11-02-2008, 12:49 AM   #5
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3)because the 7.62 round is longer than the 5.56 you'll need a special lower as well i believe
A 7.62x39 is actually shorter than a 5.56x45.

You might still be right...not sure how a 7.62x39 would feed with a stock lower.
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Old 11-02-2008, 12:49 AM   #6
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Thanks for the post reply!

Quote:
Just the rate of twist the bullet has per inch. 1:9 is a full turn in nine inches, for example.
So, the projectile does one full rotation in nine inches? Or it rotates nine times per inch?
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Old 11-02-2008, 12:58 AM   #7
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Thanks for the post replies, This info has helped a lot!

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Old 11-02-2008, 04:34 AM   #8
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3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly?
5.56 lower will not accept 7.62(x51) mags
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Old 11-02-2008, 08:23 AM   #9
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1) Is it legal for a civilian to have a barrel shorter than 16"? yes, so long as there is a pinned and welded (permanent) muzzle brake or flash suppressor to bring total length to 16", or get an NFA weapon following the proper paperwork and paying the transfer fee.
2) Is it legal to hunt(Deer) with a small 5.56 cartridge? Depends on your local laws, for the most part, I don't think it's legal anywhere to use FMJ ammo for hunting
3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly? yes...you can buy a complete 7.62x39 upper for your lower and buy the correct magazines for it (DPMS I believe)....it won't accept regular AK magazines

My next set of questions are more technical.

4) What are the differences between 1x7, 1x8 and 1x9 twist barrel? the difference in twist rates pretty much dictates the accuracy and stability of the preffered bullet according to bullet weight. The 1/9 twist should stabilize most bullet weights you'll be buying commercially More info here: http://www.gunnersden.com/index.htm.rifle-barrel-twist-rates.html
5) What are the general purposes of these different barrel types? Please refer to the previous question/reply
6) What grain cartridge should you use for these different barrel types? Please refer to Q/A #4 and the link supplied

Thanks in advance! No problem.....you're welcome

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Old 11-02-2008, 08:27 AM   #10
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Thanks for the post reply!



So, the projectile does one full rotation in nine inches? Or it rotates nine times per inch?
1/9 twist rate will spin the bullet one 360° revolution in 9 inches.
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