223 and 556 accuracy differences
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Old 05-10-2013, 02:40 AM   #1
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Default 223 and 556 accuracy differences

Because of the scarcity of ammo I have to just buy what I can find when I can find it. I have both 223 and 556 of different brands all 55gr. I am going to the range tomorrow to sight in a new set of iron sights and scope. Which should I use to sight in? How much of an accuracy difference can I expect to see between the two? I would expect whichever one I sighted in with the other would be off at least a couple inches, am I correct? I know the obvious answer is to sight in with the one I plan on using the most, but right now, for a while at least I am just going to get what I can get.

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Old 05-10-2013, 02:45 AM   #2
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Originally Posted by ccase39 View Post
Because of the scarcity of ammo I have to just buy what I can find when I can find it. I have both 223 and 556 of different brands all 55gr. I am going to the range tomorrow to sight in a new set of iron sights and scope. Which should I use to sight in? How much of an accuracy difference can I expect to see between the two? I would expect whichever one I sighted in with the other would be off at least a couple inches, am I correct? I know the obvious answer is to sight in with the one I plan on using the most, but right now, for a while at least I am just going to get what I can get.
Accuracy is going to depend on your twist ratio to ammo. If you have a 1n7 anything 55 grain is going to be a little off. Now if your barrel is 1n12 you'll be alright. The 5.56 is going to have a little more velocity then the .223 so it will be a little more off in the 7 twist but it will be tighter in the 12 twist then the .223.

So what's the twist ratio
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Old 05-10-2013, 04:26 AM   #3
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1 / 12 means one full rotation every 12 inches. Suitable for shorter (and therefore usually lighter) projectiles. This is the ideal twist rate for 36 and 40 grain projectiles.

1x9 is most suitable for 55 grain projectiles.

1x8 and 1x7 are suitable for longer projectiles like 75 gr and 80 grain vlds.

I know of a chart that acts like a good guildeline to help you understand let me see if I can dig it up.

But please remember, twist rate is just one of MANY factors. A well made barrel being much more important than just twist rate. Consistency of rifling, an even crown, an in spec chamber, barrel profile and more must be considered.

The most important thing for accuracy in my humble opinion is as follows #1 shooter, #2 ammo, #3 gun. If your ammo is only capable of doing 3 moa, it doesn't matter if your gun is able to do 1/4 moa. If the shooter is only capable of 3 moa, the best gun and ammo ain't gonna change that, so practice practice practice.

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Old 05-10-2013, 04:28 AM   #4
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http://www.firearmstalk.com/forums/f20/ar15-primer-beginners-guide-59600/

check out post # 32.

Cheers!
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Old 05-10-2013, 05:37 AM   #5
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So if I set my sights using 556 rounds how far off would they be if I switched to a 223?

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Old 05-10-2013, 06:46 AM   #6
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Quote:
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So if I set my sights using 556 rounds how far off would they be if I switched to a 223?
What's the ratio on your barrel
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Old 05-10-2013, 05:10 PM   #7
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What's the ratio on your barrel
Honestly I dont know. How would I find out?
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Old 05-10-2013, 05:18 PM   #8
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Quote:
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Honestly I dont know. How would I find out?
I have a stag arms upper and it is stamped right behind the comp. On the top of the barrel
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Old 05-10-2013, 05:53 PM   #9
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Honestly I dont know. How would I find out?
Top of the barrel behind the comp or sideways going towards the comp
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Old 05-10-2013, 06:58 PM   #10
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stag makes primarily 1x9

Notable exceptions are the 3gun 18" 1x8 twist and their milspec models IIRC are 1x7. Not sure on the milspec models I've yet to meet someone's that's had one.

twist-chart.jpg  
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