measuring case capicity/load density

[SPAK]

Hey guys, quick question. Do you measure your case capacity with your bullet seated in the case to the length that you've chosen? I'm trying to find out what the usable case capacity is without the trouble of powder going every where.

I've read some folks use water and a needle through the flash hole with the bullet seated and measure the difference in weight, and that would be close to the usable weight in grains of the case with teh bullet seated. Is this accurate going from water to powder?

Thanks. I hope I explained my question right.

 

[Victor N TN]

Re: measuring case capicity/load density

I like to choose a powder that the volume brings the level up to the shoulder area. Sometimes it makes it to the case neck. A couple of my benchrest loads are compressed charges.

 

[918v]

Re: measuring case capicity/load density

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body">Do you measure your case capacity with your bullet seated in the case to the length that you've chosen? .</div></div>

Yes.

 

[918v]

Re: measuring case capicity/load density

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body">
I've read some folks use water and a needle through the flash hole with the bullet seated and measure the difference in weight, and that would be close to the usable weight in grains of the case with teh bullet seated. Is this accurate going from water to powder?
</div></div>

Water is used to determine case volume for the purpose of pressure calculation, not load density. You don't have to use a syringe, just reduce the flow from the tap to a useable stream.

 

[SPAK]

Re: measuring case capicity/load density

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 918v</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body">
I've read some folks use water and a needle through the flash hole with the bullet seated and measure the difference in weight, and that would be close to the usable weight in grains of the case with teh bullet seated. Is this accurate going from water to powder?
</div></div>

Water is used to determine case volume for the purpose of pressure calculation, not load density. You don't have to use a syringe, just reduce the flow from the tap to a useable stream. </div></div>

So seat the bullet, then run water through the flash hole, take the difference between dry and wet = case volume at 100% non compressed. Correct??

 

[918v]

Re: measuring case capicity/load density

No.

You fill the case with water to the top of the neck leaving a round meniscus. You su btract the weight of the empty case and that gives you the case volume. You then subtract the volume occupied by the bullet seated in the case at whatever seating depth you are using.

 

[SPAK]

Re: measuring case capicity/load density

Total Case volume using water weight is the difference between dry weight case and a case filled to the mouth. check.


how do you determine the volume occupied just by the bullet to subtract it from the case volume?

 

[918v]

Re: measuring case capicity/load density

Ypu have to figure how much space the bullet shank is occupying in the case neck. This is easiest to do with a flat base bullet. Just figure out the volume of the cylinder that is the portion of the bullet shank inside the case.