AJMD429 wrote:
OK, what is a "Wilde" chamber...???
A SAAMI spec .223 Rem chamber has a shorter leade with a sharper angle to the leade and a shorter amount of effective freebore than a 5.56mm NATO chamber. The freebore itself is also narrower in the .223 Rem chamber. This helps the .223 Rem chamber shoot more accurately than the 5.56mm NATO chamber. The 5.56mm is a higher pressure/velocity cartridge, but it is made to a military standard, with different test methods, (and therefore is not easily directly comparable to .223 Rem pressures). The general spec for US 5.56mm ammo is 58,700 psi max, measured at case mouth. Note this is a different method than SAAMI transducer or copper crusher, as used on commercial ammunition. 5.56mm ammunition spec results in ammunition loaded to a higher pressure level than commercial .223 Rem, but the test methods specified are different.
In short, you can safely fire all 5.56mm AND .223 Rem ammunition in a gun properly chambered for 5.56mm. You MUST NOT fire 5.56mm ammunition in a .223 Rem rifle. Tests have shown that XM193 5.56mm ammunition fired in a .223 Rem test barrel averaged pressures of 72,550 psi, and peak pressure registered at 76,250 psi. Since the SAAMI MAP for the .223 Rem is 55,000 PSI, that puts XM193 fired from a minimum spec .223 Rem chamber at 17,550 PSI over the maximum. Because the .223 Rem chamber has a shorter and sharper angled leade compared to the 5.56mm chamber as well as a shorter effective free-bore, the bullet engages the rifling sooner in the .223 Rem chamber than it would have in a 5.56mm chamber. This causes the pressure to rise faster, peak sooner and reach a higher (and per SAAMI, unsafe) level than it would have if the round had been fired from a 5.56mm chamber.
The Wylde chamber was developed to attempt to gain the increased accuracy of the .223 Rem chamber while still allowing the use of the higher pressure 5.56mm NATO ammo safely. The Wylde chamber has a longer leade / freebore dimension than the 5.56mm as well as the and the same leade angle but a tighter neck than a 5.56mm chamber. However, the .223 Rem Wylde chamber is not the same as .223 Rem chamber because it has the longer leade / freebore dimension similar to the 5.56mm. Therefore, you can shoot the higher pressure 5.56mm ammo safely in a Wylde chamber but also enjoy most of the benefits of the .223 Rem's better accuracy. So, in theory you'll shoot tighter groups using a Wydle chamber with better accuracy than a 5.56mm chamber while safely shooting both .223 Rem and 5.56mm NATO ammo.
a rifleman can never have to many options.
. I'm going on a prairie dog hunt this weekend and the AR is coming along, I should have a couple of hundred more rounds through it come Sunday afternoon and will know more then. Good luck with yours. Oh by the way, mine has a 5.56 chamber so most of the brake in ammo has been cheap milsurp stuff.