5.56 NATO ---.223


5.56mm ammo is loaded a bit hotter than 223 and should not be fired in standard 223 chambers. Several hybrid chambers allow use of the GI ammo, such as the "Wilde" chamber. Here is reply from Bushmaster regarding their CMP & fluted varminter bbls. which have a hybrid chamber.


Chambers, DCM/CMP & 24" Fluted Varminter

The DCM/CMP & 24" Fluted Varminter barrels have a custom match hybrid chambering that uses the tighter SAAMI Spec headspace from the shoulder of the chamber to the bolt face. It has the longer "Leade" or throat that will accommodate the 5.56mm ammunition so it can be used without developing higher pressures as in a .223 caliber chamber that have a shorter "Leade" or throat.

Both 5.56mm and .223 caliber ammunition can safely be used in the DCM/CMP & 24" Fluted Varminter rifles.

Regards,
hm
 
Many, many, millions of rounds are shot interchangeably every year with no reported problems. Some ammo is even labeled 223/5.56.

Jack
 

Way back, a long time ago we had what was referred to as the broken bolt
club. What the ammo manufacturers came up with was the higher pressure
5.56 could stretch the case neck into the throat of the shorter, tighter throat
of the .223 and pinch the bullet driving up pressures. True or not it sounded
plausible. Knowing what reamer was used on your gun is the key. There are
at least ten different chambers and only a few of the .223 match ones could
present a problem imho.(here are a few)

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Originally Posted By: hm1996
Chambers, DCM/CMP & 24" Fluted Varminter

The DCM/CMP & 24" Fluted Varminter barrels have a custom match hybrid chambering that uses the tighter SAAMI Spec headspace from the shoulder of the chamber to the bolt face. It has the longer "Leade" or throat that will accommodate the 5.56mm ammunition so it can be used without developing higher pressures as in a .223 caliber chamber that have a shorter "Leade" or throat.

Both 5.56mm and .223 caliber ammunition can safely be used in the DCM/CMP & 24" Fluted Varminter rifles.

Failed to mention this was Bushmaster's reply to question I asked after my grandson discovered several blown primers (4-5) after firing 100 (or so) rounds of Radway Green 5.56mm in his DCM/CMP rifle. He was not shooting rapid fire, but temperature was close to 100* which may have contributed to the problem.

Regards,
hm
 
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