OK
Ok
OK!
This is getting Strange....
Thanks for the Post,,PLM
Using commercial .223 cartridges in a 5.56-chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223-chambered gun due to the excessive leade. [3] Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice.[4] Some commercial rifles marked as “.223 Remington” are in fact suited for 5.56 mm, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition.
Bushmaster.com has this to say about it.
Question / Issue
I recently purchased a Bushmaster AR15 O.C.R my question is which is the proper ammunition for this weapon? The lower receiver is stamped as follows..CAL 223-5.56 MOD XM15 - E2S. I have Remington UMC 223 rounds I was wondering if I can fire 5.56 rounds in this rifle safely (I have read it can be dangerous if fired in a short leade ) also if 5.56 rounds can be safely chambered and fired what is the distinct difference between both calibers.. any information you can provide would be greatly appreciated as I would prefer an answer from the manufacturer then from an online forum.
Answer / Solution
All Bushmaster barrels are chambered to accept 5.56mm ammunition and always have been.
The NATO Spec 5.56mm chambers have a longer “leade” or throat than the SAAMI Spec .223 caliber chambers which have about half of the leade or throat of the 5.56mm chambering.
While it is safe to fire both 5.56mm and .223 caliber ammunition in our rifles according to SAAMI the 5.56mm ammunition should not be fired in rifles chambered in .223 caliber as they will develop very high pressures.
http://www.bushmaster.com/faqs/afmviewfaq.aspx?faqid=723