5.56 in .223

270 win. · 05-21-2006, 10:11 AM

I am wondering whythis bad because I have a friend that has put thousands of rounds of5.56 inhis .223? And it still shoots the exact same the day he got it. Just curious.

Ridge Runner · 05-21-2006, 10:19 AM

the 5.56 and the 223 are exactly the same size, the difference is in the lead (throat) the 5.56 has a lead about .080" longer, since the bullet has that much jump the bullet is out of the case another .080 before pressures peak, the 5.56 is rated higher by saami specs, so a higher pressure round fired in a 223 chamber, is over pressure to start with, then without the bullet jump in the lead, runs pressures farther up and in some cases could create unduly high pressures that could possibly damage a firearm.
Basicly its like taking a over-max load in another rifle and jamming the bullet into the lands. one time may not hurt anything but that stress on the rifle on a regular basis takes its toll.
RR

sandilands · 05-21-2006, 10:25 AM

556 is the military deignation for the commercial .223. Its the same thats why he hasn't had any problem. Another way to look at it is 5.56 mm is the metric name and .223 is the imperial way.

Ridge Runner · 05-23-2006, 12:58 PM

another thing, GI brass is thicker having less case capacity, if you start using GI brass for reloading even your tried and true safe loads could develope excess pressure.
RR

AmericanPioneer · 05-24-2006, 12:57 AM

The cartridges are close but not the same. This is from Winchesters site. http://www.winchester.com/lawenforcement/news/newsview.aspx?storyid=11