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…
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.
But… Really depends on the actual chamber. Just being marked a particular way only tells you so much.
Just because you have max 5.56 loads that fire fine in one 5.56 marked barrel does not mean they will be fine in a 5.56 marked barrel manufactured by someone else.
Same with respect to .223 chambers. They are not all the same.
FWIW - Best accuracy does not always come from the hottest round you can send downrange.
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?
Something to consider is that the leade (free bore) makes a difference in chamber pressure spike and how quickly pressure spikes with a given load. That may account for the difference in chamber pressures when Hornady tests loads in their laboratory and their recommendations for maximum charge weights.
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…
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.
Case capacity also varies pretty drastically year to year, lot to lot. I seem to recall back in the mid-2000s a guy on a precision shooting forum measuring differences in LC stamp and seeing a .2 gr capacity difference from one year to the next. That’s over 5%.
Anyone who has ever wet tumbled will know that ‘it takes a bit to get all of the water out of the case’. You are not just going to turn it over and the case be completely empty and dry.
That’s what I found out. I also tried measuring case weight, then adding liquid while the case was on the scale. Problem was that I could not see air bubbles inside the spent primer and primer pocket. Isopropyl alcohol was more consistent than tap water or distilled water, but you still had to wait a considerable amount of time to see if you had to add any liquid to the case. If you tried to measure the liquid by volume as it went into the case, it was difficult to do it consistently enough to reduce error.
I marked twenty cases and tried to measure case volume twice a day, five days in a row. I left the electronic scale on the entire week, so there would not be issues with warm up error. Out of ten readings for each cartridge case, I saw three to four different values for each case.
I gave up on measuring case volume, because I was not seeing higher scores at 1,000 yards. I focused on sorting cases by headstamp, case wall thickness, trim length and number of times fired.
Back to the original concern by the OP. Hornady has chamber pressure and temperature measuring equipment most people do not. A lot of testing goes into their research before they publish reload data and comments for each cartridge. I base my reloading on what Hornady suggests and group sizes. If they say there is a difference between 5.56mm and .223 Rem. chamber pressures, I’ll take their word for it.
I’ll be posing the question to the powder manufacturers later today after a couple more football games have been played. With luck, we’ll have their feedback sometime next week…
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.
The Hornady 9th and 11th editions have similar data sets as the data sets you are using, the 8th doesn’t have 556 listed. I looked at XBR for 55 grain bullets.