.223 Rem vs. 5.56 NATO Chambers/Overpressure Issues?

[Metal god]

Clark :

You've blown up a gun or two right . Any chance you have some pressure numbers or likely pressures you started seeing primers popping out , extractor marks etc ??

I personally have never pushed anything real hard to see how hot I can go . .5gr maybe 1gr over max . Reason is simple . I've almost always found an accurate load below max .

Steve :

I realized I did not give you the bullet type . I get them at the gun show from the large powder vendor . When I ask what they are they say , we think they are Winchester ( not kidding ) So I'll say they are Winchester 55gr FMJ-BT . FWIW . They appear to be the same as Hornady's 55gr bullet . But the Hornady's take .5gr less of some powders to be more accurate which leads me to think they are not Hornady bullets .

 

[JeepHammer]

Now you guys are cookin with gas! (Pun intended!)
Can't wait to get home and read it on a screen I don't need a magnifier for.

I'm with Metal God, my best accuracy usually come in under maximum,
If it doesn't it usually involves a poorly cut chamber and/or crown, or a 'Choke' in the rifling in my experence.

I was wondering, can someone run Win Small rifle primers, military cases, 26 grains Benchmark, and 55 grain Hornady V Max?
I'm not seeing overpressure and I'm finding good accuracy in AR & bolt rifles without overpressure signs... Except ONE AR that likes to leave primer rings...

 

[Clark]

Metal god
Clark :
.. you have some pressure numbers or likely pressures you started seeing primers popping out , extractor marks etc ??

I have over load work up in 19 Bagder, .223, .243, 25acp, 257 Roberts AI, 260, 270, 7mmRemMag, 32acp, 32sw, 32S&WLong, 32-20, 7.62x25mm, 7.62x39mm , 308, 7.62x54R, 8x57mm, .380, 9x19mm, 9x23mm, 357 Sig, 38 sp, 357 mag, 38sw, 40sw, 10mm, 10.4mm, 45acp, 45Colt, .410, and 45/70.
~ 10 years ago I asked another engineer [better at challenging Denton than me] who did Von Mises calculations for work and gun hobby if he would also do 223.
https://en.wikipedia.org/wiki/Von_Mises_yield_criterion
I was getting a good match with the QL prediction of pressure at the point where primer pockets failed, and his calculation. Not perfect.
I find the weakest to the strongest for pressure vs primer falling out:
*10mm
*25acp
*Mauser large Boxer
*Belted magnum
*223
-----------------
Then there are the cases so strong the primer pocket does not matter
*Mauser small Boxer
*rimmed cases in general [but not Norma 7x57 rimmed is as weak as good brands of 7x57 Mauser large Boxer]

My personal work up system in strong rifles is to work up until I find the threshold of extractor groove diameter change anywhere around the groove. This is not a loose primer pocket, but a much more repeatable threshold than loose primer pockets. Then I back off 4% for temp compensated powder and more like 6% for other powders, to find a usable load that I produce in quantity for myself.

If you look at my post last year, the 223 extractor groove starts to change between 80kpsi and 92kpsi. That does not mean the primer pocket will get loose. But it is a predictor of enough shots and it would:
http://thefiringline.com/forums/showthread.php?t=561516&highlight=h335
That was in a Ruger #1 that has a breech face devoid of extractor or ejector cuts.

This is Blue Dot and 35 gr Vmax in one of my AR15s at 4200 fps.
It shows the extractor, ejector, and stretch marks.
The pressure has no meaning, the brass is destroyed. The same load will often produce 4100 fps and no change in the brass. Blue Dot is the wrong powder for high pressure in 223. It works best at 35kpsi. The 4200 fps load would not cycle an AR15 nor would any lessor load of that powder and bullet.

What does it all mean?
1) I want loads that are tuned to make my AR15s work.
2) I can take advantage of the large safety margins in 223 case head strength [compared to 55kpsi SAAMI] in my bolt and single shot 223s if I want to.

Chart below is Von Misses calcuations