Another 5.56 vs .223 question

KDX

KDX

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I just measured some .223 Winchester (fired) brass and it was 0.0135 at the troat. I measured some 5.56 9(fired also) that I recieved on a trade (much of it wasn't boxed), and the measurement was the same. Can I conclude that the .223 brass and the 5.56 are the same dimentions and I would not have to make allowances for smaller volume in the 5.56 brass?
 
I would say that measuring the neck thickness alone is probably not a reliable indicator of the internal volume of the cartridge. It's generally accepted that military 5.56 brass is thicker, I would suspect in the web and head area where it really matters. If you want to get a more reliable comparison of the case volumes, you could fill each cartridge to the mouth with water, dump it on the scale and weigh it. A simple calculation would yield more or less the exact case volume that way, no guessing. I believe the rule of thumb that most go by though, is to start loads with 1 grain less powder in mil brass. Don't quote me on that.
Drew
 
The external cartridge dimensions are the same, it's the chambers that are cut slightly different. The measurements you took would be the same if both cartridges were fired in similar chambered guns.
The water test above will tell you the volume.
 
I generally have to drop a grain of powder in the NATO cases. They are thicker. The same charge from the commercial cases will blow primers in the military cases I've played with over the years. Some lots of IVI cases came out the same as commercial cases. It's hit and miss.
 
OK. I tested one of each, both fired, and they were 29.4gr of water. Should I test a few more or just assume thay are the same? BTW, thanks for the excellent advice.
 
I will try some 25.5gr loads because that is below the 26gr max an this site.

Cartridge: 223 Remington
Load Type: Rifle
Starting Loads

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Maximum Loads

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Bullet Weight (Gr.) Order BW Powder Bullet Diam. C.O.L. Grs. Vel. (ft/s) Pressure Grs. Vel. (ft/s) Pressure

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  • 40 GR. NOS BT 40 Benchmark .224" 2.280" 25.3 3404 39,600 CUP 27.3 3666 51,000 CUP
  • 45 GR. SIE SP 45 Benchmark .224" 2.240" 25.3 3327 41,100 CUP 27.3 3554 51,100 CUP
  • 50 GR. SPR SP 50 Benchmark .224" 2.210" 24.0 3139 38,600 CUP 26.5 3396 50,400 CUP
  • 53 GR. SIE HP 53 Benchmark .224" 2.200" 24.0 3102 39,900 CUP 26.0 3308 49,800 CUP
  • 55 GR. SPR SP 55 Benchmark .224" 2.200" 24.0 3113 42,600 CUP 25.6 3264 50,000 CUP
  • 60 GR. HDY V-MAX 60 Benchmark .224" 2.250" 23.0 2913 42,500 CUP 24.6 3086 49,900 CUP
  • 63 GR. SIE SP 63 Benchmark .224" 2.200" 22.0 2845 41,800 CUP 24.2 3066 50,500 CUP
  • 69 GR. SIE HPBT 69 Benchmark .224" 2.235" 21.5 2770 39,700 CUP 23.5 2970 49,700 CUP
  • 70 GR. SPR SP 70 Benchmark .224" 2.140" 20.5 2665 45,200 CUP 22.8 2869 51,000 CUP
  • 75 GR. JLK VLD 75 Benchmark .224" 2.250" 21.5 2610 41,900 CUP 23.5 2829 49,400 CUP
  • 77 GR. SIE HPBT 77 Benchmark .224" 2.260" 20.5 2523 27,400 CUP 22.8 2763 50,000 CUP
  • 80 GR. SIE MK 80 Benchmark .224" 2.550" 20.5 2525 43,900 CUP 22.5 2700 49,600 CUP

NEVER EXCEED MAXIMUM LOADS

http://data.hodgdon.com/cartridge_load.asp
Click to expand...
 
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