Brass capacity...

[270WinDude]

I'm under the impression that the best way to reduce spread in velocity is to sort by capacity. Trying to figure this out... If 2 loads are exact same except 1 has a bit of room left in the case even though powder weight is same and the other case is packed to max and compressed, which case would have higher pressure. If anyone can help explain a bit to me or point me towards some reading on this, I'd appreciate it.

 

[dcali]

A smaller chamber volume with an equal powder charge will result in higher pressure. Think of it as the powder turning into a fixed amount of gas that is proportional to the powder charge. If that gas has a smaller volume to occupy, it must do so at a higher pressure. That's oversimplified, but it's more or less what's going on.

 

[jepp2]

Ideal gas law: PV = nRT

 

[retired]

internal combustion engine....smaller combustion chamber, higher pressure.

 

[Ned Ludd]

Ideal gas law: PV = nRT

This brings back memories of the time I went barhopping with Amedeo Avogadro. The guy COULD NOT hold his liquor...kept on talking all night about burrowing rodents.

 

[270WinDude]

This brings back memories of the time I went barhopping with Amedeo Avogadro. The guy COULD NOT hold his liquor...kept on talking all night about burrowing rodents.

Strange... I remember him talking about some really esoteric deep state guy who was talking to the press a lot back then.

 

[Homerange]

I'm under the impression that the best way to reduce spread in velocity is to sort by capacity.

Not in my experience.

More so; good case prep, good powder weight consistency, consistent neck tension, 90%+ case fill and it must be found by trial and error once you meet the previously listed requirements.
In short, some recipes work, some don't !

The best one I have I stumbled upon wanting to push some 130's @ ~3000 in a 308.
Max listed load of ADI 2208 (Varget) and very nearly full to the top of the neck resulting in a moderately compressed load provided the expected velocity and only 6fps spread. Shoots ~1/2" from a sporter.
Pure dumb luck !
Brass sorting.... none, just fire formed once fired range brass and LCD neck sized only.
Cases, just what I was using at the time....can't remember, (in my notes somewhere) maybe Federal M1 or something ex AR15 range pickups.
No special case prep except, inside flash hole chamfer !

 

[Bart B.]

I'm under the impression that the best way to reduce spread in velocity is to sort by capacity.

Or compensate for it with a tuning weight on the muzzle to make slower bullets leave at a higher angle than faster ones.

 

[270WinDude]

Or compensate for it with a tuning weight on the muzzle to make slower bullets leave at a higher angle than faster ones.

I'm just getting started really so haven't done that yet. I am pretty excited to do testing with a barrel weight so thanks for the tip!