Replies

Let me quote this from the Speer reloading manual #13, Page #137.

“The 223 Remington resulted from the military development of a new service rifle cartridge. Adopted in “February, 1964 as the 5.56mm Ball cartridge M193, it was introduced as a commercial cartridge by Remington one month earlier.”

I checked each of the 13 reloading manuals that call my reloading bench home and each and every one of them say that the 5.56mm and the 223 rem are the same.
Still not convinced that my 25 years as a smith and my Dillon and RCBS dies for the 223/5.56 weren’t lying to me I called a good friend who is retired from RCBS and asked him if they had ever made separate dies that were dimensionally different for these cartridges. His answer was no.

There is always a difference in pressure/OAL (overall length) of cartridges between different manufactures on the 223 round and every other caliber I’ve ever seen. That is one of the reasons why the sell case trimmers to reloaders. The other reason any serious reloading bench has a trimmer sitting on it is that the chambers in different rifles vary in diminutions, not much but they are different. When you fire a 223 in one rifle the case expands and “fire forms” to that specific chamber. If the chamber is long or the headspacing isn’t right then the brass will “grow” a bit. The dies force it back into specs except for length and a reloader uses the case trimmer to take care of that.

Now to address the chamber pressures you were talking about. I have semi auto 223/5.56’s and in each of these rifles, AR types and my mini 14’s the chambers are very sloppy. The nature of the semi auto beast is that they do not lock up to the same exact point consistently. Because of this the chambers do not contain the ignition sequence as efficiently as a bolt action does. A bolt-action rifle, by the nature of its construction, is a very strong action. A bolt action locks up in exactly the same place every time, produces more consistent headspacing and is a stronger action than any semi-auto ever made. I can take that same 223 barrel/action on a bolt gun and rechamber it for any of the much hotter 22 cal rounds and it will hold the pressure without any problem at all. This is not true of an AR type action that is built for the 5.56 round. The bolt-action rifles are made to withstand higher chamber pressures than the semi autos can handle. That is a matter of physics and a well-established fact.

One of my blue progressive presses, a Dillon, stays set up with a set of 223 dies. We shoot several hundred rounds of 223 each month. I have two custom bolt guns that we shoot prairie dogs and coyotes with that are chambered for the 223 round.

I have carried the 5.56 M16 and several variants into combat. They served me well but there are better rounds out there for taking on people in a lethal situation. The new 6.8mm that they are working with now produces better impact energy on and in a body.