Why more powder for 223 than 556

[triggerjerk]

Hornady 62gr website download data shows more powder in 223 for 2230 and xbr than for 556 and equal max loads for TAC. Emailed em and they simply said lab said that where pressure got high.

Would someone explain to this fudd how that works? Did I just get complacent and not notice that 556 doesn't always have more powder than 223 at max? Below are powders listed in common:

556
AR-Comp 17.6 gr.-24.6 gr.
H322 20.0 gr.-23.3 gr.
Accurate 2230 20.5 gr.-23.6 gr.
H335 21.2 gr.-25.4 gr.
IMR 8208 XBR 21.8 gr.-24.4 gr.
TAC 21.4 gr.-24.7 gr.
NORMA 201 21.9 gr.-25.6 gr.
Power Pro Varmint 22.9 gr.-26.9 gr.
WIN 748 22.5 gr.-25.7 gr.
CFE 223 23.5 gr.-27.7 gr.
BL-C(2) 23.6 gr.-27.9 gr.

223:
H335 20.1 gr.-22.9 gr.
H322 20.7 gr.-23.1 gr.
Accurate 2230 21.3 gr.-24.8 gr.
TAC 21.6 gr.-24.7 gr.
AR-Comp 22.2 gr.-23.4 gr.
WIN 748 22.1 gr.-25.5 gr.
NORMA 201 22.8 gr.-24.2 gr.
IMR 8208 XBR 23.0 gr.-25.3 gr.
Power Pro Varmint 23.6 gr.-26.1 gr.
BL-C(2) 23.1 gr.-27.7 gr.
CFE 223 24.5 gr.-27.4 gr.

Thanks and best to all in these trying times.

Edit: Accurate lists same max weights as Hornady for 2230, but the higher weight is 556 and the lower is 223....

[mRad]

I believe this is because they are referencing a .223 Bolt-action and not a .223 Rem AR. Bolt rifles can take significantly more pressure than ARs.

Also, it may have something to do with lawyers


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[T2C]

A quote from the Hornady Reloading Manual 9th Edition - "The main differences between the 5.56 NATO and .223 Remington is the operating pressure and chamber throat. SAAMI (Sporting Arms and Ammunition Manufacturers Institute) maximum pressure for the .223 Remington is 55,000 PSI. The 5.56 NATO is loaded to 60,000 PSI. Chamber throat for the .223 Remington is shorter than 5.56 NATO chambers as well."

Military 5.56 mm cases are thicker than .223 Rem. commercial cases, which may also play a role in the difference in listed data.

[markm]

Military 5.56 mm cases are thicker than .223 Rem. commercial cases, which may also play a role in the difference in listed data.

No they aren't. Most mil brass and commercial weigh the same. (7.62 is a different story.)

[T2C]

No they aren't. Most mil brass and commercial weigh the same. (7.62 is a different story.)

The walls at the case mouth of my Lake City 5.56 cases are 0.0015 thicker than my commercial Winchester cases. Federal .223 cases tend to be thicker than most commercial cases, but the brass is much softer and they are not suitable for comparison to military cases.

I've cut cases in two with a band saw and observed the web on military cases thicker than commercial cases I cut in two.

What cases are you comparing to Lake City 5.56 mm cases?

[DG23]

The walls at the case mouth of my Lake City 5.56 cases are 0.0015 thicker than my commercial Winchester cases. Federal .223 cases tend to be thicker than most commercial cases, but the brass is much softer and they are not suitable for comparison to military cases.

I've cut cases in two with a band saw and observed the web on military cases thicker than commercial cases I cut in two.

What cases are you comparing to Lake City 5.56 mm cases?

There is a water capacity chart floating around somewhere where about ten or so different cases were tested / compared. Will try to dig it up and post it...

ETA:

http://i2.photobucket.com/albums/y17...iesresized.jpg

[T2C]

There is a water capacity chart floating around somewhere where about ten or so different cases were tested / compared. Will try to dig it up and post it...

ETA:

http://i2.photobucket.com/albums/y17...iesresized.jpg

I used Isopropyl alcohol to measure case volume to develop .30 caliber 1,000 yard loads. Loss of liquid when dumping into and back out of the case made it less accurate than I anticipated. I weighed cases, both .223 and .308 cases, to sort them and found that sometimes a case with thinner brass thickness at the case mouth weighed more than a case with thicker brass at the case mouth due to differences in head thickness, web thickness and other factors.

[RedTeam98]

Yes 5.56 is thicker brass thus holds less powder but pressures rise quickly !

[s4s4u]

No they aren't. Most mil brass and commercial weigh the same. (7.62 is a different story.)

Oh there are differences in case thickness in 5.56/.223 all right. My pet load that will fill a Remington .223 case up to the neck was nearly overflowing one 5.56 case, IIRC PPU, and varying levels in other brands. None exactly the same, although all cases within a brand seem consistent.

[mRad]

If you compare 5.56 data from Sierra vs .223, it seems the opposite if I remember correctly.


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