Originally Posted by TATELAW
I guess I should clarify that this is a bolt rifle, not an AR, not sure if that makes a difference in pressure tolerance.

Why are 5.56 loads hotter when it's essentially the same round? Never have fully understood the difference in the two.

I just PM'd the guy about buying the Lapua brass for sale in the classifieds. Gonna get me some CCI magnum primers to go with the quality brass and start over on my loads. Also think I'll get a pound of Benchmark.


This might help you some.

http://www.americanrifleman.org/articles/223rem-vs-556-whats-in-a-name

While the 5.56x45 mm chamber is slightly larger than the .223 Rem. chamber in just about every dimension, the primary difference is throat length, which can have a dramatic effect on pressure. The 5.56x45 mm has a longer throat in the chamber than the .223 Rem. The throat is also commonly called the leade, which is defined as a portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. Leade in a .223 Rem. chamber is usually 0.085 inches, while in a 5.56x45 mm chamber the leade is typically 0.162 inches, or almost twice as much as in the .223 Rem. chamber. Also, the throat angle is different between the two chambers, and that can affect pressure rise and peak pressure.


Swifty