5.56x45 NATO in a .223 rifle (sort of long)

[cnjcomp]

A lot depends on the rifle. I have seen a Remington .223 Police 1/9 twist barrel blow off the extractor using 5.56 loads. For rifles marked .223 use .223 only.

[bigedp51]

"...sizing them in your .223 die..." No such thing as a 5.56NATO die. There's no 5.56NATO load data either.
Before there was an internet, .223 Rem and 5.56NATO(which is just a military standards designation) were the same thing. The cases still are. The only difference between .223 and 5.56NATO is the pressure. The 5.56NATO's being higher.
NATO has their own testing methods. The U.S. military follows SAAMI's method. That puts U.S. made 5.56NATO ammo at 55,114 psi. SAAMI max pressure spec for .223 Rem is 55,000 PSI. NATO says all ammo must test to 125% of the max of 62,366 psi which is 77,958 psi. The latter being a test max, not an operational max. Whole thing is about where the test sensor is on the case during the test.
The Wylde chamber just has a longer throat than a regular .223 chamber. The case is the same length. No need to worry about the higher pressure of 5.56NATO. No need to worry about using commercial .223 either.

Sunray, send a email to RCBS and tell them there is no such thing as a 5.56 die and there is no metric equivalent for a .223 cartridge.



The older M193 5.56 is loaded to 55,000 psi and the newer M885 round is loaded to 58,700 psi SAAMI testing standards. And this is why the SAAMI came out with their interchangeability warning in 1979 when the M885 cartridge was adopted by the U.S. military.

And the throat length of my two AR15 rifles are .0500 and the throat in my Savage .223 with a 1 in 9 twist is .0566 and "longer" than the AR15. It is the .223 rifles with a shorter .0250 throat with a 1 in 12 or 1 in 14 twist that will have a pressure spike when firing 5.56 ammo designed for a longer .0500 throat.



sunray, the link below was written just for you.

5.56 vs .223 – What You Know May Be Wrong
http://www.luckygunner.com/labs/5-56-vs-223/

Below the .223 is rated for 55,000 psi "BUT" the green bar on the far left shows you that the factory .223 ammo was only loaded to just below 50,000 psi.

[bigedp51]

I reload my buddy's .223 ammo from our varmint trips for him. Nothing fancy. I neck size or full length size each time with my Lee .223 Remington dies, trim to length, usually load 55 gr bullets and only use one of two different powders he buys (IMR 4064 and Varget). If it's stuff he fired through his .223 CZ bolt rifle, I usually neck-size only and label BOLDLY the boxes to be fired in CZ ONLY (and indicate how many reloads the brass has gone through). His other rifle is an AR variant with a Wylde chamber. So, that gun gets full length sized every time. It has, so far, fired all my .223 reloads without issue. Up until now he has only supplied me fired .223 brass. His last batch of 75 rounds was a mix of 5.56 and .223, but I didn't note the headstamp until I had full-length sized all the brass with my .223 Lee dies. The brass may now be the same on the outside as my normal .223 brass, but on the inside there is less volume due to more brass (or, so I have read). Thinking about holding back a half grain or so from the load with these 5.56 brass pieces. Does this seem reasonable? And, if so, should the 5.56 headstamped brass be designated to fire in one of these rifles only? In my thinking, I would lean towards the AR for firing these since the Wylde chamber can handle higher pressure rounds. Or, do I tell him to stick to .223 ammo purchases from here on out and scrap the brass (40 pieces). I feel I have created .223 profile brass that has a built-in chance of having higher internal pressure when fired than is normal for a .223.

I know I'll get wrist-slapped for this, but the education will be worth it.

Lake City 5.56 brass is harder in the base and not thicker like 7.62 Lake City brass. As you can see below the majority of .223/5.56 cases are close to the same capacity. But the difference between the older Lapua cases at 28.0 grains of H2O capacity and the Lake City cases at 30.6 capacity can cause 6,000 psi difference in chamber pressure with the same powder charge.



I buy bulk once fired Lake City 5.56 brass for my AR15s and bolt action Savage .223 because the brass is harder and a higher quality than commercial .223 brass.

How Hard is Your Brass? 5.56 and .223 Rem Base Hardness Tests
http://bulletin.accurateshooter.com/...ardness-tests/

223 Rem + 223 AI Cartridge Guide
http://www.accurateshooter.com/cartridge-guides/223rem/

[Sunray]

"...no metric equivalent for a .223 cartridge..." There isn't. Not that I said anything of the sort. However, .223" does not mathematically convert to 5.56mm for one. Converts to .218". (.308" doesn't convert to 7.62mm either.) And the 5.56NATO case is the same as a .223 Remington case.
Remington's marketing types agree with "The cases still are." anyway. Nor is the RCBS die set a 5.56NATO die set.

[RED]

This is the first instance where my buddy has brought me 5.56-marked brass, emmagee1917. We've been shooting over 10 years together. I suspect he has located a cheap source. If this is going to be a regular thing, I just wanted to get the scoop on the differences now. And I think I have. Also, I envy your brass source @ .10 per!

GI brass from Jeff Bartlett is $100/1000 deprimed, primer pockets reamed, and polished.

5.56mm NATO Just in: Recent shipment, once-fired, 95+% LC, a few SAWS (M249)
(223) brass, mixed dates, mostly LC10 and LC11. Nice brass,
Add $25/M to polish and process primer pocket.
Ttl Qty: 100 500 1M 5M
$ Cost: $10 $40 $75/M $350/5M

$.35/round for brass is crazy. Midway will sell you 420 rounds of IMI brass for $160 ($.38 ea.) and it comes primed, polished, and loaded with a 62 gr SS109 bullet, and postage paid in a metal can.

IMI Ammunition 5.56x45mm NATO 62 Grain M855 SS109 Penetrator Full Metal Jacket Boat Tail Ammo Can of 420 (14...
4.8 (45 Reviews)
Sale$159.99 & SHIPS FREE