223 vs 5.56 accuracy - Page 3
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Old 05-30-2014, 06:22 PM   #21
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my three Ar-15's are chambered in the .223/5.56 Nato with 1/7 twist which will stabilize the heavier gr. bullets. I am changing out one barrel to the S/S match shieln with 1/8 twist in hopes of improved accuracy. I like the ability to shoot mil surplus 5.56 nato rounds and still be able to hand load the .223 rounds which gives me the choice of the 55gr thru 77 gr loads.


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Old 05-31-2014, 05:18 AM   #22
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Quote:
Originally Posted by 303tom View Post
You have Sizer Set`s for individual chambers ?................
Not exactly. Just an extremely adjustable set. I use Redding type S competition neck bushing and seating dies. Shoulder length, neck diameter and depth of neck sizing can all be set individually.

The Colt has .002" more head space than my match rifle so I don't bump the shoulders back as much. It also has a longer lead and shoots better with more neck tension so I size the necks down very close to the shoulder. The match rifle has minimum head space and a shorter throat, and shoots better with minimal case neck tension.

I do shoot them both in matches, otherwise I wouldn't bother trying to squeeze every little bit out of them as I can. The M4 clone on the other hand only gets fed surplus 5.56 NATO ammo or handloads thrown together on a LEE press. Nothing special.


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Old 05-31-2014, 03:19 PM   #23
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Quote:
Originally Posted by Highpower View Post
Not exactly. Just an extremely adjustable set. I use Redding type S competition neck bushing and seating dies. Shoulder length, neck diameter and depth of neck sizing can all be set individually.

The Colt has .002" more head space than my match rifle so I don't bump the shoulders back as much. It also has a longer lead and shoots better with more neck tension so I size the necks down very close to the shoulder. The match rifle has minimum head space and a shorter throat, and shoots better with minimal case neck tension.

I do shoot them both in matches, otherwise I wouldn't bother trying to squeeze every little bit out of them as I can. The M4 clone on the other hand only gets fed surplus 5.56 NATO ammo or handloads thrown together on a LEE press. Nothing special.
OK, I got what you mean now ................
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Old 05-31-2014, 05:19 PM   #24
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A helpful tool that I feel any hand loader will benefit from is the RCBS case micrometer. Check out the video for more info.

http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/rcbs-precision-mic-cartridge-headspace-tool-prod33476.aspx
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Old 06-05-2014, 06:15 AM   #25
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I have a 70's Colt SP1 with two uppers. One is .223 SP1 barrel in A1 receiver. You can tell there is more pressure from the short lead and slight chamber dimension. The leade is the biggest difference, I think. The A2 upper with .556 Military and equivilent has softer recoil with same buffers because the leade is longer or throat is longer. Longer bullets in the .556 loading and brass will generate more pressure in the .223 barrel. Some say the 5.56 can damage the .223 guns but I haven't seen anything. I have polymer lower too. I am concerned about recoil damaging it, if I put the SP! .223 upper on it with adapter pin of course.
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Old 06-05-2014, 07:08 PM   #26
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Originally Posted by montveil View Post
I realize the 223 case is slightly smaller than the 5.56 case.
With the 5.56 chamber being larger, how does that affect accuracy when the 223 is fired in a 5.56 chamber.
It would seem that the looser 223 round would result in poorer accuracy.
Also, if a 223 round is fired in the 5.56, does that case now not fit a 223?
No the cases are identical within standard deviation and have identical dimensional specifications. They are loaded and reloaded with the same dies.

Another myth is that 556 cases have thicker brass than 223 cases. They do not. Variations between cases marked 556 and 223 are no different than variations between different manufacturers cases.

556 marked rounds are loaded to higher pressure than 223 marked rounds. It is 223 +P and that is all. A 556 chamber has a longer leade to handle the higher pressure.
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Old 06-05-2014, 07:12 PM   #27
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Originally Posted by Axxe55 View Post
apparently from some sources the 5.56 operates at a higher pressure than 223 ammo does. some sources say the cases are externally the same but that the interior dimensions are smaller on the 5.56 vs. the dimensions internally of the 223 cases.

please don't quote me on that. this debate has been ongoing for years now and i don't have a clearcut answer yet on this. but my thoughts are this, i use what is marked on the rifle as to what i would fire in a particular rifle.
I have found that 556 cases have on average an insignificantly higher volume than 223 cases.
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Old 06-05-2014, 11:05 PM   #28
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Quote:
I have found that 556 cases have on average an insignificantly higher volume than 223 cases.
This is usually true. Some S&B .223 cases are very thick as are some .223 Lapua cases.

i've weighed the cases used for my accuracy loads since about 1968.


You will likely not get gilt edged accuracy from a MilSpec 5.56mm chamber or a SAAMI .223 chamber. There are at least a dozen different .223/5.56mm chambers.

http://ar15barrels.com/

Click tech
Click chamber dimensions
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Old 06-05-2014, 11:19 PM   #29
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Originally Posted by mboylan View Post
I have found that 556 cases have on average an insignificantly higher volume than 223 cases.
as i said, that has been debated for years now.

i will defer to my reloading manuals for information regarding the loading of 223 and 5.56mm ammo when i get to that point.

IMO, i would gather they are refering to military surplus 5.56. commercially available 5.56 cases are more than likely very much similiar to commersially available 223 cases. that is an opinion as i have nothing that supports that statement. just an observation on my part in regards to the debate on the differences between the two cases.

Edit: i have both 223 and some 5.56 mm ammo i have used in my AR. the 223 is PMC 55 gr. FMJ ammo, and the 5.56 NATO is 62 gr. Green Tip LAP BT ammo by PMC.

i weighed both cases and came up with these results.

223 case weights average 95.8 gr.

5.56 case weights average 96.4 gr.

so that is an average of about 0.6 gr. in difference.

i don't have any MilSurp 5.56 mm ammo to compare readings to.

Last edited by Axxe55; 06-05-2014 at 11:35 PM.
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Old 06-06-2014, 03:35 AM   #30
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Quote:
Originally Posted by 303tom View Post
There is NO difference in the two rounds, just in the chamber of the firearm !..........
5.56 mm cases tend to run a little long. Shooting 5.56 in a .223 CAN be problematic if excessively long.


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