308 question

[G0nefishin]

Internal capacity sir. If you develop a load that is pushing pressure limits in a Winchester brass ( large internal capacity ) and transfer that data to military brass , you will likely have a problem with over pressure. How big of a problem depends on a lot of things...... could be case head separation ..... could be barrel separation . It's the most important thing to know if your loading for 308 ..... if your looking for precision , even mixing 308win stamped brass will give you fits ..... because internal capacity varies that much from manufactures

I don't really

Not being standing there in your shoes, I can't imagine what kind of 7.62 cases you are reloading - but most 7.62x51 is, as you might imagine, military, and the vast proportion of that is Berdan-primed.

In any event, as it has already been done to death a gazillion times, the internal volume of ANY case will vary from brand to brand, and .308Win usually has a larger volume/capacity than military brass. The military brass usually has LESS capacity than civilian, as the material at the base of the case has to withstand not just ejection from a regular machine gun at around 700-800 rpm in the case of the GPMG/MAG59, but the MG3, which churns 'em out at 1100 rpm. All small cheese compared with the GE/Westinghouse Mini Gatling gun, at 4000 and 6000 rpm. Anything less than a VERY substantial base is going to get torn off.

Civilian ammunition doesn't need that property, so the volume is greater by about 10%, simply because the interior of the case is flat, and not concave. Expanding propellant gases in a greater volume act substantially differently to the way they propagate in the smaller case - NATO spec ammunition is also pegged at 150gr, whereas the civilian can be shooting anything between 120gr and 200gr.

The bottom line is that civilian-spec .308Win shooting a 150gr bullet is operating at ~2000 psi MORE than milspec stuff, and you can take that to the bank.

tac

I'm not reloading 762 brass just civilian 308 for deer season & maybe poking holes in paper if I can find 200 yards + around here. Anyway thanks for all the helpful advice much appreciated.

 

[tac]

Duly noted, but I might moon you from 2000.

If your butt is big enough to gleam at me from 2000m, I'd go for it.

Using practical geometry. I reckon that a nine-inch diameter head looks about the same at 1000m as an 18 inch (or bigger) butt does at 2000m.

tac

 

[G0nefishin]

Thanks everyone for the info much appreciated.

 

[P7M13]

If your butt is big enough to gleam at me from 2000m, I'd go for it.

Using practical geometry. I reckon that a nine-inch diameter head looks about the same at 1000m as an 18 inch (or bigger) butt does at 2000m.

tac

Wide ride. It'll look like a Chinette dinner plate from 200. But there will be a methane thermal updraft from my vicinity that will deflect the downward trajectory of your salvo.

 

[Goosebrown]

good luck reloading!

 

[Lazyfaire]

Wide ride. It'll look like a Chinette dinner plate from 200. But there will be a methane thermal updraft from my vicinity that will deflect the downward trajectory of your salvo.

No tracers please

 

[DizzyJ]

Internal capacity sir. If you develop a load that is pushing pressure limits in a Winchester brass ( large internal capacity ) and transfer that data to military brass , you will likely have a problem with over pressure. How big of a problem depends on a lot of things...... could be case head separation ..... could be barrel separation . It's the most important thing to know if your loading for 308 ..... if your looking for precision , even mixing 308win stamped brass will give you fits ..... because internal capacity varies that much from manufactures

This right here. Internal capacity will be different, therefore pressures will be different, therefore speeds will be different, therefore harmonics will be different,

I think you get the idea.