Revisiting: sorting cases by weight

[Buster Hemlock]

I think we are trying to ultimately achieve the same barrel time from shot to shot.
I think consistent neck tension (annealing), sorting bullet bearing surface and/or bullet weight sorting and exact powder charges may make more of a profound influence on barrel time than measuring minute differences in case volume BECAUSE until the bullet has left the muzzle the space from the end of the flash hole to the end of the barrel becomes the actual chamber.

Powder doesn't completely burn inside the case! It burns all the way down the barrel.

I'm with you on all your saying but I think that all the things you have mentioned as well as case capacity would effect the initial uncorking pressure needed to release the bullet from the case mouth and would effect barrel time. Which of these factors makes the biggest difference I don't know so like most I try and uniform them all to the best of my ability. Now your going to make me delve even deeper into this whole mess and spend more time experimenting. Darn you TBrice! Lol

 

[Mikecr]

tbrice23, barrel timing is heavily tied to powder burn rate -which is significantly affected by variances (like neck tension) early in the burn. Volume & chamber fit are as much or more a part of this than your comparative potentials so far.

What every reloader needs to understand is that variances do not affect pressure without also affecting powder burn rate. Higher intial pressure, causes higher initial burn rate, causing higher pressure per some amount of time.
With a forgiving load (some might call OCW), an early spike can be countered further down a bore, but this contributes nothing good to consistency in barrel time (too late).
This is part of why OCW loads are not usually the most accurate loads. They're just forgiving.

 

[DUSTY NOGGIN]

i think most of the weight differences come as , flash hole burs still hanging in there , primer pocket depth( a uniforming cutter will show big difference in amount removed of cases) and then case length trim , once all those are perfected to the best your tools can do , your internal volume may still be off but once fire formed to a consistant shoulder and shoulder corner , all should be good.. water weight test really shoudl be done after all prep has been done


does someone sell a rubber primer pocket plug with a nipple on the end ???

 

[tbrice23]

does someone sell a rubber primer pocket plug with a nipple on the end ?

Seat a spent primer uside down.

 

[DUSTY NOGGIN]

Seat a spent primer uside down.

i was just thinking that the nipple on the end would assure there was not a bubble in the flash hole

and if the primer pocket diameter was long enough you could just pull them out by hand when you are done

 

[ntsqd]

Could likely make such a plug with some of the molding silicones out there. RTV might work, but probably won't be terribly robust.

A non labor intensive method for sealing the primer pocket would be very desirable when using water to get case volume.

 

[DUSTY NOGGIN]

Could likely make such a plug with some of the molding silicones out there. RTV might work, but probably won't be terribly robust.

A non labor intensive method for sealing the primer pocket would be very desirable when using water to get case volume.

but that bad is

youll end up weight sorting those too ... **** this road to precision never ends ..

 

[tbrice23]

---- this road to precision never ends ..

I spin my wheels constantly on this sh!t.
Then I ask myself if the ME or barrel can shoot the freaking difference.

 

[ntsqd]

Maybe:
http://www.xxicsi.com/primer-pocket-plugs.html

 

[Mikecr]

21st century offers a plug for H20 capacity checks

 

[Buster Hemlock]

Seat a primer upside down is what I do. Weigh cases and write the weight on the case. Put a splash of rubbing alcohol in your water to minimize surface tension. Allow the water to sit for a little while for the air to dissipate. I use a syringe and put the needle directly into the flash hole for the first few drops to make sure it's not holding a air bubble and then fill the case and let it sit again to allow any air bubbles to dissipate, top off and weigh. This is done after brass has been fully prepped and once fired.

 

[ntsqd]

That sounds like several hours of work to get the volumes of 100 cases, which is what I was trying to find a way to reduce. If bare case weight could cull out the extreme deviant cases then you wouldn't need to spend as much time on them. Based on what has been posted here and my own research I'm not confident in that approach.

One thing I did discover in researching aspects of this topic is that cartridge brass weighs almost exactly 8.5 times* more per volume than water. This tells me that a small burr or deviance in dimension will cause a much larger delta in case weights than it will in the weight of water displaced or added by this deviation. Thus all of the case prep needs to be done before weighing the case for any reason.

*http://www.matweb.com/search/DataSheet.aspx?MatGUID=8cfc8c6ae39449039af46d6a70493d22&ckck=1

 

[Buster Hemlock]

My method does take some time but it's a lot of down time waiting for the water to settle which I fill with mowing the lawn and other such chores and prepping stuff for other rifles. I haven't been doing every case but a smaller sample from the batch, usually 10, but I'm planning on doing all within a 50-100 lot batch to confirm I'm not missing something and confirm for myself that my method is doing what I'm intending and not missing out.