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| Click on image to enlarge - M16a4 |
The M16a4 has a caliber of 5.56x45mm. It is a standard issue in the front-lines of the Army and Marine Corps. This gun is a military assault rifle.
The AR – 15 fires a .223 shell and is not an assault
rifle. Rather, it is officially labeled a “sports rifle.”
A primary difference between the two rifles is on
the inside of the barrel of each gun.
The twist in an AR – 15 is 1.2;
the twist in a M16a4 is 1.9 and uses.
Ammunition for each has the same caliper, a .223 and a 5.56 shell will
fit and fire from either rifle - but no one advises that you do so. The outcome is potentially dangerous for the
shooter.
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| A custom AR - 15 is only a sports rifle, seriously |
The AR-15 is a “recreational” rifle, and its ammo is designated “.223/SAAMI” while the M16a4 is chambered differently,
uses ammo designated “5.56 mm/ NATO” and is the military preference, of the
two. One rifle is for fun, the other is designed for deadly, long range, accuracy.
Understand that both guns are semi-automatics. Each comes with a 30 shell clip. Each will do a lot of damage, but one is a military weapon, and the other is not . . . . . . and for good reason.
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After notes:
This article will be of great value to those who care about the difference between a fun gun and a serious NATO weapon: http://www.thegunzone.com/556v223.html
Also, this is to the point, as well.
I am a 5.56mm ballistics technician. In a nut shell:
At one time the 223 and 5.56mm were identical - back in the 1950's to 1970's when the standard barrel was a 1:12 twist and the standard bullet weight was 55gr tops. When they US military adopted the 223 Rem and made the 5.56mm they went with a slightly faster 1:10 twist that optomized the M16 for 55gr bullets since lighter weight ones would never be used.
When the US military adopted the SS-109 62gr green tip ammo and moved to the 1:9 twist barrel for this heavier bullet the two calibers diverged and went their own ways. Barrels with a 1:9 or faster twist are branded 5.56mm while the slower twist barrels - used for long range varmint shooting will have a 1:12 or slower twist.
Although you can swap and fire each in each other - the results will never be good. Shoot a 40-55 grain 223 bullet in a 1:9 twist AR-15 (1:8, 1:7 and even faster 1:6.5 are available) and the spin rate of 226,000+ rpm will tear the soft copper jacket and the lead will spew out like water. Called 'bullet failure' - you shoot at the target and sometimes there is no hole! LOL.
Likewide, load a 69gr match 5.56mm round in a 1:12 twist 223 Remington barrel and the bullet will exit, loose balance, and end up hitting the target someplace sideways. This is called a 'keyhole'. If the target is more than 200 yard away good chance the bullet will miss it totally - even a 4' by 4' target! (Source site: http://answers.yahoo.com/question/index?qid=20081006114322AAG0da1)
At one time the 223 and 5.56mm were identical - back in the 1950's to 1970's when the standard barrel was a 1:12 twist and the standard bullet weight was 55gr tops. When they US military adopted the 223 Rem and made the 5.56mm they went with a slightly faster 1:10 twist that optomized the M16 for 55gr bullets since lighter weight ones would never be used.
When the US military adopted the SS-109 62gr green tip ammo and moved to the 1:9 twist barrel for this heavier bullet the two calibers diverged and went their own ways. Barrels with a 1:9 or faster twist are branded 5.56mm while the slower twist barrels - used for long range varmint shooting will have a 1:12 or slower twist.
Although you can swap and fire each in each other - the results will never be good. Shoot a 40-55 grain 223 bullet in a 1:9 twist AR-15 (1:8, 1:7 and even faster 1:6.5 are available) and the spin rate of 226,000+ rpm will tear the soft copper jacket and the lead will spew out like water. Called 'bullet failure' - you shoot at the target and sometimes there is no hole! LOL.
Likewide, load a 69gr match 5.56mm round in a 1:12 twist 223 Remington barrel and the bullet will exit, loose balance, and end up hitting the target someplace sideways. This is called a 'keyhole'. If the target is more than 200 yard away good chance the bullet will miss it totally - even a 4' by 4' target! (Source site: http://answers.yahoo.com/question/index?qid=20081006114322AAG0da1)
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