223 and 5.56 ?

rebs · August 7, 2012, 06:40 AM

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 ?

Adamantium · August 7, 2012, 07:43 AM

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.

wncchester · August 7, 2012, 08:03 AM

"... 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!

Marco Califo · August 7, 2012, 08:46 AM

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".
http://thefiringline.com/forums/atta...4&d=1336880187
http://thefiringline.com/forums/atta...2&d=1326064897
http://thefiringline.com/forums/atta...3&d=1326064897

**Unclenick** · August 7, 2012, 01:23 PM

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.

m&p45acp10+1 · August 7, 2012, 02:35 PM

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.

jepp2 · August 7, 2012, 04:47 PM

Quote:

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

August 7, 2012, 06:40 AM	#1
rebs Senior Member Join Date: January 10, 2012 Posts: 3,881	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 ?

August 7, 2012, 07:43 AM	#2
Adamantium Senior Member Join Date: June 6, 1999 Location: El Paso, TX Posts: 1,021	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. __________________ New gun, same ol' shot.

August 7, 2012, 01:23 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	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. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

August 7, 2012, 02:35 PM	#6
m&p45acp10+1 Senior Member Join Date: May 3, 2009 Location: Central Texas Posts: 3,930	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. __________________ No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.

August 7, 2012, 08:03 AM	#3
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"... 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!