what happend ?

[hoz53]

i am sizing brass to the bolt gun . the trying it in AR was to find if the same sizing of the brass was going to work in the AR. then try'ed a factory loaded one ,the AR set it back .003

nothing new for an AR to push the shoulder back some. Ive had it happen to me.

here i am loading some 223, bolt gun. i checked to sure that i had the die set correctly . i sized a case and slipped the brass into the chamber , needed just a bit more force on the bolt handle than it should take . then adjusted the die for perfect fit . removed and measured the brass at the shoulder and slipped it into an AR carefully closing .worked as it should . removed the brass, remeasured it, its was the same . put it back into chamber and did a free drop of the bcg as hard as it would go . removed the brass and it had shortened .007 ......i'm confused

 

[Bill K]

I would say your AR chamber length is slightly shorter than the bolt chamber you are testing this drop, etc with the case. So it is pushing the shoulder back to fit the AR chamber.

 

[gunsandgunsmithing]

On a stripped bolt gun, barrelled action, two things can stop forward bolt travel...the bbl OR the bolt handle. On an AR, just the bbl, assuming no charge handle etc...may not matter. Bottom line, the .007 is a pretty typical amount of bolt to bbl clearance number and stands to reason that it's what stopped the bolt from going even further. I'm curious if the brass has been annealed.

 

[divingin]

Just so you know, the 5.56 nato chamber has different headspace specs than the 223rem.

Have any sauce on this? AFAIK, the external cartridge dimensions are identical (as would be the chamber specs.) The difference is in freebore (with 5.56 having a longer spec.) The chamber on NATO firearms may be cut a little sloppier, but the headspace spec should be the same.

 

[Coyotefurharvester]

Chambering empty brass doesn't have the mass to resist forward bolt movement and become in full contact with the bolt face BEFORE the round chambers. So the brass is forward(at a slight angle) makes contact with chamber shoulder. BCG is still travelling to go into battery, brass deforms slightly(shoulder) as bolt stops.

 

[Zero333]

Have any sauce on this? AFAIK, the external cartridge dimensions are identical (as would be the chamber specs.) The difference is in freebore (with 5.56 having a longer spec.) The chamber on NATO firearms may be cut a little sloppier, but the headspace spec should be the same.

Dimensions of the brass are the same. I'm only talking about the chamber headspsace

 

[divingin]

Dimensions of the brass are the same. I'm only talking about the chamber headspsace

Bottleneck cartridges use the shoulder (usually measured to the midpoint) to the case base as the "headspace" measurement (incorrectly as there's no space there.)

Headspace on an action is that measurement, plus a thousandth or three (or more) to allow for ease of chambering (literally, "space for the head of the cartridge".)

Since the cartridges are dimensionally the same, headspace will be as well. The throat/freebore and radial measurements (diameter at wherever you want to measure) may be slightly different (and will be depending on how accurate the reaming job was), but that isn't headspace.

If you can provide some kind of documentation about differing headspace between .223 and 5.56 chambers, I'd be quite interested to read about it.

 

[Ajwilly96]

closing the bolt on an AR is a very violent process. If you use the same loaded round over and over you will notice marks on your bullet from it slamming into the chamber, as well as dimples on your primer from the free floating firing pin.

 

[Zero333]

Bottleneck cartridges use the shoulder (usually measured to the midpoint) to the case base as the "headspace" measurement (incorrectly as there's no space there.)

Headspace on an action is that measurement, plus a thousandth or three (or more) to allow for ease of chambering (literally, "space for the head of the cartridge".)

Since the cartridges are dimensionally the same, headspace will be as well. The throat/freebore and radial measurements (diameter at wherever you want to measure) may be slightly different (and will be depending on how accurate the reaming job was), but that isn't headspace.

If you can provide some kind of documentation about differing headspace between .223 and 5.56 chambers, I'd be quite interested to read about it.

5.56 x 45 (Nato) vs. 223 Remington; The Ongoing Saga

The subject of 223 Remington vs. 5.56×45 (5.56 Nato) is a popular source of discussion. Probably one of the best blog posts on this subject can be found at or PDF = 556vs223 One item this and…

gunsmithtalk.wordpress.com

 

[divingin]

I'd guess the added length in 5.56 is slop for dust/debris and crap to allow for positive operation in a battle rifle, or a bit of extra space for full auto operation. It has (AFAIK) nothing to do with the cartridges being different. Note that length difference only comes up when talking maximum allowed; min chamber lengths are the same for both. To paraphrase, NATO spec *allows" for a longer CBTD (base to datum in the chamber); it doesn't mandate it.

Regarding your inclusion of the pic of the Forster lengths, the article insinuates exactly the opposite: "Conclusion: Headspace gauges for the 223 Remington and the 5.56 Nato are identical."