Hodgdon 223 max pressure compared to 5.56 max pressure .

Metal god · June 1, 2015, 05:35 PM

Yep this one again

So I'm looking at the Hodgdon 223 data for 55gr bullets and they all have them maxing out at 52,000psi-ish . How ever I read elsewhere that the 5.56 maxes out at 62,000psi . Does this mean I can go over the 223 max data when loading for a 5.56 chamber ? If so is there a calculation to figure what the new max would be ?

I'm asking for a few different reasons but one of the main ones is . I've been loading for my AR's for a little while now and I can't get anywhere near the velocity's of the Federal 5.56 nato factory ammo when shooting my reloads and staying at or below max published data .

Yes two of my books have AR data and that is what I've been using . I still don't get anywhere near 3100fps+ from a 16" barrel like I do with 5.56 NATO ammo . I don't have my notes in front of me but I think 2850-ish is as good as I get

What gives ?

Clark · June 1, 2015, 05:52 PM

An AR can take a lot of pressure.
223 case heads can take a lot of pressure.
I would focus on getting the brass to eject 5 feet.

With Blue Dot and 35 gr bullets, an AR will not cycle, even with brass destroying peak pressure. The area under the pressure time curve after the bullet passes the gas hole is not enough to cycle.

Metal god · June 1, 2015, 07:15 PM

Well my Sierra book has 223(AR) IMR 4320 starting where Hodgdon maxes out with there 223 . So It looks like the 5.56 does handle more powder . I'll see how 4320 works with the 55gr bullet but it appears it will be better with heavier bullets . I'm only trying 4320 to have a back up powder that is around more then the more used powders . This will just be for plinking and general use . Although I may give it a try in my NM service rifle with the 77gr smk . I've heard a long time ago it was quite a good powder for that before all these newer powders came along .

FWIW , I do use LC 5.56 brass so the cases should handle the 5.56 loads

June 1, 2015, 05:35 PM	#1
Metal god Senior Member Join Date: April 10, 2012 Location: San Diego CA Posts: 6,875	Hodgdon 223 max pressure compared to 5.56 max pressure . Yep this one again So I'm looking at the Hodgdon 223 data for 55gr bullets and they all have them maxing out at 52,000psi-ish . How ever I read elsewhere that the 5.56 maxes out at 62,000psi . Does this mean I can go over the 223 max data when loading for a 5.56 chamber ? If so is there a calculation to figure what the new max would be ? I'm asking for a few different reasons but one of the main ones is . I've been loading for my AR's for a little while now and I can't get anywhere near the velocity's of the Federal 5.56 nato factory ammo when shooting my reloads and staying at or below max published data . Yes two of my books have AR data and that is what I've been using . I still don't get anywhere near 3100fps+ from a 16" barrel like I do with 5.56 NATO ammo . I don't have my notes in front of me but I think 2850-ish is as good as I get What gives ? __________________ If Jesus had a gun , he'd probably still be alive ! I almost always write my posts regardless of content in a jovial manor and intent . If that's not how you took it , please try again .

June 1, 2015, 05:52 PM	#2
Clark Senior Member Join Date: December 4, 1999 Location: WA, the ever blue state Posts: 4,678	An AR can take a lot of pressure. 223 case heads can take a lot of pressure. I would focus on getting the brass to eject 5 feet. With Blue Dot and 35 gr bullets, an AR will not cycle, even with brass destroying peak pressure. The area under the pressure time curve after the bullet passes the gas hole is not enough to cycle. __________________ The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought?

June 1, 2015, 07:15 PM	#3
Metal god Senior Member Join Date: April 10, 2012 Location: San Diego CA Posts: 6,875	Well my Sierra book has 223(AR) IMR 4320 starting where Hodgdon maxes out with there 223 . So It looks like the 5.56 does handle more powder . I'll see how 4320 works with the 55gr bullet but it appears it will be better with heavier bullets . I'm only trying 4320 to have a back up powder that is around more then the more used powders . This will just be for plinking and general use . Although I may give it a try in my NM service rifle with the 77gr smk . I've heard a long time ago it was quite a good powder for that before all these newer powders came along . FWIW , I do use LC 5.56 brass so the cases should handle the 5.56 loads __________________ If Jesus had a gun , he'd probably still be alive ! I almost always write my posts regardless of content in a jovial manor and intent . If that's not how you took it , please try again .