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Posted: 5/4/2013 4:56:21 PM EDT
[#1]
thanks for posting this, seems to come up a lot
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Posted: 5/4/2013 5:39:45 PM EDT
[#2]
Quoted:
Every reloading book in print contains incorrect information about 5.56X45 brass. Whether it does or not isn't relevant anyway, we all have to check and confirm the details for ourselves. Reloading is all about the details. By far the best summation about reloading, and the funnest part, IMHO. |
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Posted: 5/4/2013 7:26:24 PM EDT
[#3]
Thanks for clearing up my fuzzy posts in that other thread.
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Posted: 5/5/2013 6:47:54 AM EDT
[#4]
I ran across this last night loading up 9mm.
I was weighing each case before dispensing powder into it, then re-weighing it to double check my new powder dispenser (RCBS Uniflow). Seems that there is a +/- .8 to 3.4 grain weight difference in my mixed lot of 9mm cases. I kept having to re-zero my digital scale almost every time. I'm not loading anywhere near max powder charge so I'm not too worried about it, or should I be?? |
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Posted: 5/5/2013 7:59:48 AM EDT
[#5]
Quoted:
thanks for posting this, seems to come up a lot Thanks AeroE. |
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Posted: 5/5/2013 8:30:10 AM EDT
[#6]
Quoted:
I ran across this last night loading up 9mm. I was weighing each case before dispensing powder into it, then re-weighing it to double check my new powder dispenser (RCBS Uniflow). Seems that there is a +/- .8 to 3.4 grain weight difference in my mixed lot of 9mm cases. I kept having to re-zero my digital scale almost every time. I'm not loading anywhere near max powder charge so I'm not too worried about it, or should I be?? Are those numbers for the charge weights or case weights? If it's the powder weight, which gunpowder are you loading? If it's Unique, you'll have to do everything you can to kill static charge on your powder measure, and then it will throw pretty well but not great. The only straight wall cases I've weighed are for .32 ACP, due to the tiny charge weights and warning in some data to use exactly the published charge weight, plus or minus nothing. The difference from heavy to light was a little surprising in those tiny cases. |
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Posted: 5/5/2013 4:44:02 PM EDT
[#7]
Quoted:
Quoted:
I ran across this last night loading up 9mm. I was weighing each case before dispensing powder into it, then re-weighing it to double check my new powder dispenser (RCBS Uniflow). Seems that there is a +/- .8 to 3.4 grain weight difference in my mixed lot of 9mm cases. I kept having to re-zero my digital scale almost every time. I'm not loading anywhere near max powder charge so I'm not too worried about it, or should I be?? Are those numbers for the charge weights or case weights? If it's the powder weight, which gunpowder are you loading? If it's Unique, you'll have to do everything you can to kill static charge on your powder measure, and then it will throw pretty well but not great. The only straight wall cases I've weighed are for .32 ACP, due to the tiny charge weights and warning in some data to use exactly the published charge weight, plus or minus nothing. The difference from heavy to light was a little surprising in those tiny cases. The cases are +/- .8 to 3.4 grains difference in weight - uncharged. Instead of using the cup on the scale, I'm using the case and re-zeroing the digital scale every time. that's where I noticed the weight difference between some cases. I'm using Power Pistol. My RCBS Uniflow is doing a pretty good job dispensing powder. It's with in .1 most of the time. I get an occasional .5 low or .3 high, but I think I should chalk that up to the powder not the dispenser. |
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Posted: 5/5/2013 5:09:57 PM EDT
[#8]
What are the weights of 5 to 10 of the cases? +/- .8 to 3.4 grains difference doesn't make sense.
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Posted: 5/6/2013 4:06:02 AM EDT
[#9]
Quoted:
s. Every reloading book in print contains incorrect information about 5.56X45 brass. Whether it does or not isn't relevant anyway, we all have to check and confirm the details for ourselves. Reloading is all about the details. All but one, Sierra #5, page 176. The conventional wisdom to reduce loads with military brass is familiar to most reloaders and is generally good advice. The rationale here is that the military cases tend to be somewhat thicker and heavier than their civilian counterparts, which in turn reduces capacity and raises pressures. This additional pressure normally requires a one or two grain reduction from the loads shown in most manuals or other data developed with commercial cases. While this is most often the situation with both 308 Winchester and 30-06 cases, it is less true with the 223 brass. We have found that military cases often have significantly more capacity than several brands of commercial brass. Again, take the time to do a side-by-side comparison of the cases you are working with and adjust your load as needed. There may be no need for such a reduction with the 223. Know your components and keep them segregated accordingly. |
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Posted: 5/6/2013 6:36:28 AM EDT
[#10]
but why are they different?
I can only think of two possible reasons: * .mil wants higher chamber pressures * thinner is cheaper (ie: less material cost for the manufacturer) for the commercial market |
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Posted: 5/6/2013 6:47:44 AM EDT
[#11]
Quoted:
but why are they different? I can only think of two possible reasons: * .mil wants higher chamber pressures * thinner is cheaper (ie: less material cost for the manufacturer) for the commercial market 7.62X51 brass is heavier for operation in machine guns. The chamber pressure expressed in CUP or piezo measured pressure expressed as psi is slightly less than for the SAMMI .308 Winchester. But not as much as the difference between CUP and piezo measured pressure seems to indicate. SAAMI .223 Rem pressure is less than for 5.56X45 ammunition, but again, we have to be careful to compare them using the same measuring stick. I'll make a wild guess that the pressure level for .223 Rem ammunition was set at that level to accommodate firearms that might not be up to 5.56X45 pressure. Maybe someone has access to original sources that lay out the reasons either pressure was chosen, but I expect the 5.56X45 pressure was selected in order to extract as much speed out of the cartridge as possible to partly compensate for the poor mid range ballistics of the original bullets. Excerpts from the quality requirements for 5.56X45 ammunition; pay close attention to the chamber pressures required: http://www.ar15.com/content/page.html?id=434 http://www.ar15.com/content/page.html?id=473 Info from 6mmbr.com: http://www.6mmbr.com/223Rem.html The Ammo Oracle: http://www.razoreye.net/mirror/ammo-oracle/AR15_com_Ammo_Oracle_Mirror.htm |
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Posted: 5/6/2013 6:07:11 PM EDT
[#12]
I recently read the pressure difference was from when they switched from 55 to 62 gr projectiles which, due to different ogive contour, necessitated a different freebore. The longer freebore allowed higher pressures.
IDK the source and don't quote me on that. 
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