water capacity of a cartridge?

[Sas874runner]

Is it as simple as simple as it sounds? Measure the weight of the water a fired case will hold?

 

[truck driver]

From what I under stand you use ionized water, I thlnk that's what I read not sure.

 

[jimbires]

I weigh a unsized fired case then I fill it with water and weigh it again . subtract these numbers and that is the water capacity . I've read that guys will add a little alcohol so the water will not be able to form a skin . I don't get that fussy . I fill the case and touch the water bubble with a paper towel to take the bubble off . I was weighing some tonight . here are my results .this is all Lapua brass . Jim

empty .................................. full ......................................water capacity
332.38.................................448.02.....................................115.64
334.04.................................449.50.....................................115.46
336.94.................................451.76.....................................114.82
338.64.................................452.68.....................................114.04
339.40.................................453.54.....................................114.14
339.88.................................454.08.....................................114.20

 

[Sas874runner]

So then putting a fired case on a scale and filling it with an eye dropper would probably work the same

 

[Antelope_Sniper]

technically you are supposed to let them set overnight, but I always say screw that, and just tap them a bit to make sure all the air bubbles are out.

 

[Sas874runner]

The reason i am asking is to see if the difference in ql data. Can it make that much of a difference?

 

[steve4102]

The reason i am asking is to see if the difference in ql data. Can it make that much of a difference?

QL recommends finding the actual case capacity in grains of H20 for better accuracy.

 

[DrMike]

The reason i am asking is to see if the difference in ql data. Can it make that much of a difference?

Yes.

 

[jimbires]

The reason i am asking is to see if the difference in ql data. Can it make that much of a difference?

yes , it can make a significant difference . the cartridge I was working with last night was maxing out at 96.x grains of powder , using the standard QL water capacity .so using the rule of thumb , by starting 4 grains under max , my charge range would be 92.0 - 96.0 grains of powder . since I've corrected the water capacity , QL max is now 100.x . since correcting , my velocity is just about the same as QL predicts . I think there is a 3 or 4 FPS difference now .

I'm working with very limited data , this is a new rifle and all new components . I have not messed with this cartridge before . Jim

 

[Sas874runner]

Thanks gents. I appreciate the input. I will have to do some water measuring

 

[SJB358]

I measure H20 capacity on all my cases. It usually gets very accurate data outputs from QL.