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Old August 7, 2012, 06:40 AM   #1
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223 and 5.56 ?

I am loading a 55 gr fmjbt with 24.5 gr of H335 in LC 5.56 cases and in Remington 223 cases and see no difference in accuracy. Both go under 1" at 100 yds. I expected to see some difference since the LC cases are supposed to be thicker brass having a lower capacity.
Why am I not seeing any difference ?
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Old August 7, 2012, 07:43 AM   #2
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In 5.56 the LC cases are not all that different from commercial 223 cases. In 7.62 the cases are thicker/lower capacity so sometimes people apply this idea to the 5.56 cases as well.
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Old August 7, 2012, 08:03 AM   #3
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"... LC cases are supposed to be thicker brass having a lower capacity. Why am I not seeing any difference ?"

Well, that does suggest much of what "everybody knows/conventional wisdom" often isn't ... don't it? Seems a lot of web gurus are eager to tell the world much more than they know!
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Old August 7, 2012, 08:46 AM   #4
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Accuracy is not an indicator of case volume.

There is no significant case volume difference in 223/5.56 anyway. There is a table I posted and others have too. Use search to find it. Get a copy of the Sierra 223 load guide (one for bolt; one for AR's). Also posted here. Use search to find it. "Supposed to" is very different than "Read in Sierra's manual".
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Last edited by Marco Califo; August 7, 2012 at 09:46 PM.
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Old August 7, 2012, 01:23 PM   #5
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As near as I can tell, these days only the .308/7.62 has significant case capacity differences between commercial and military. The new, never fired LC cases I have all present a very slightly lower weight and higher capacity than the Winchester .223 cases I have (all about 12 years old, now).

The factor that affects peak pressure is the capacity in the case when it is swollen out against the chamber under pressure. The chamber constrains all cases to close to the same exterior dimensions (except at the head, so double-check your lot in that regard). As a result, the weight of the case is a pretty good indicator of comparative water capacity it will have under the bullet. I find typically that each 1.5 grains less case weight indicates the need for about 0.1 grains more powder to keep performance identical. With some powders it's a little more or a little less, but the bottom line is that if two cases have less than about 4 grains brass weight difference, the chance of seeing the effect on your target, even without adjusting the load, isn't great.
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Old August 7, 2012, 02:35 PM   #6
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I have seen in my experience with loading .223 for over a year and half no big change in accuracy from one headstamp to the next as far as the group size in the target shooting a Savage Mod 12 with a bull barrel. Most loads give me well under a half inch group at 100 yards. If it is over that it was me not the loads, not the rifle. I am the weakest link when it comes down to it.
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Old August 7, 2012, 04:47 PM   #7
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I am loading a 55 gr fmjbt with 24.5 gr of H335 in LC 5.56 cases and in Remington 223 cases and see no difference in accuracy.
If you objective is to improve accuracy, you might consider weighing the cases of the same headstamp (LC, Remington, or whatever) and sort by similar case weights.

Other considerations for improving accuracy:

- uniforming the flash hole especially for ball powders like H335
- check bullet concentricity and see if your are running less than 0.002"
- find your Dan Newberry's OCW

as starters
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