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Discussion Starter · #1 ·
Okay Guys I have a question about internal brass capacity, for the past few years I have been using BH Match brass for my Savage .308 bolt gun that has had all the work done to prep it like primer pocket uniforming, flash hole uniforming and all trimmed to 2.007" and neck sized only until the bolt get's tight then I bump the shoulder back .002", I have the load worked out using 42.0g of RE-15 and it will do under a 1" grp at 100yrds if I do my part well the brass has reached it's life's end and the Mrs. gave me 200 Lapua cases to replace them, well my question is the BH Brass weighs in at 155g and the Lapua comes in at 175g and they are identical in size (2.007") well I filled each case to the top with RE-15 and the BH holds approx 2g more the the Lapua.

My question is do I reduce the load by 2g and come up or go all the way to the min and rework the load, will be using a SMK 168 (this is what I had been using)

Thanks
 

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Discussion Starter · #4 ·
If you want to measure internal volume your going to have to use a liquid like water. It's a pain but that's the only way to get an accurate volume measurement.
I played around with the cases again last night and I am seeing that using powder is not a good idea so I guess water or alcohol is a better bet.
 

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A friend has been helping me try to figure out some unexpected results using Vihta Vuori N-135. After sending him "comparable" data for the N-135 and H-4895, I realized that I'd used Winchester 7.62 Nato "white box" cases for the N-135 but used new Winchester .308 cases for the H-4895.

The following is for cases that were reloaded, fired, re-sized, trimmed, and then primed with spent primers (anvil removed):

Average weight for new .308 cases was 161.1 grains with 55.9 grains of water capacity.

Average weight for the Win white box 7.62 cases was 181.6 grains with only 54.2 grains of water capacity.

According to my friend's software, the difference in case volume would increase chamber pressure a few hundred PSI and muzzle velocity only 30 fps. Honestly, I would have expected a bigger difference due to the more than 3% change in case volume. My next testing will include using the same load of H-4895 in both case types to see what the results are in my rifle(s).

While you're thinking about case volume, remember that if you measure the water an empty case can hold, then part of the volume you are measuring will be taken up by the portion of the bullet that is inside the neck. IOW the percentage change of case volume is actually larger because the bullet occupies a fixed volume in the neck of the case.

BTW yes, I learned that just because a case is made by the same manufacturer doesn't mean that it's the same damned case. Stupidly, I figured that Winchester used the same cases for all of its .308/7.62 Nato applications even though the headstamps are different. Not too bright of me, eh?
 

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Panther: measure the capacity of a few FIRED cases of each type, and get 2 averages. Easy process, just takes a few minutes.


I can then plug those capacities into Quickload and give you some results.
 

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Use the water volume method, it's more accurate. Also, check the volume before the case has been resized, the expanded case more closely represents how much volume there is just as the powder ignites. I've found that the volume will change by about one grain of water if you compare before and after resizing. Some people allow the water to have a small curve at the top of the neck and others don't, whichever way you choose to do it be consistent. I also prefer to use filtered water, I don't know if it makes any real difference but I figure that regular tap water has so much stuff in it the weight will be slightly different depending on where the water comes from.

I use Lapua cases and, compared to all the other brass that I've checked, the Lapua brass has the largest volume except for BH brass, which is slightly larger. The Black Hills brass is only a couple of tenths of a grain more than the Lapua so for all intents and purposes they are the same. My list of case volumes include Federal, WCC, Winchester, GGG, LC, CAVIM, R&P, Nosler Custom, and Hornady Match (Black Hills).
 
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Here is link to a list by manufacturer of case weights and capacities. Unfortunately the author used resized cases and for my QuickLOAD software I have to add about a grain of case capacity in order to get closer to real life results. Regardless, the relative differences between cases will help you get an idea of how the pressures and velocities would relate if you only changed cases when you hand load your ammunition.

http://riflemansjournal.blogspot.com/2011/01/cartridges-1000-yard-308-case-capacity.html
 

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RAM: FYI. I get 55.7 gr H2O for Lapua, and 57 gr for Federal cases.

Fed seems to have the highest capacity in my shop. And, there are 2 different fonts used on my fed cases, so I sort by that. I forget if the capacities are different. Fed Match vs Fed regular, maybe ???
 

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Mine come out to 56.3gr for the Lapua cases with a Trim-To-Length of 2.007". My FC cases average around 54.0gr. with an avg. TTL of 2.010". My records are several years old now because I settled on using Lapua cases for all my accuracy work and WCC cases for most of my general shooting needs. Since the accuracy isn't the focus for my general shooting I don't bother measuring the volume on the WCC stuff any more, but I still check the Lapua cases from time to time.

The differences could be an issue of TTL or measuring technique or both. I also know that, depending on the lot and date of manufacture, cases will vary in volume even with the same manufacturer; that's why I re-measure the capacity when consistency really counts.



RAM: FYI. I get 55.7 gr H2O for Lapua, and 57 gr for Federal cases.

Fed seems to have the highest capacity in my shop. And, there are 2 different fonts used on my fed cases, so I sort by that. I forget if the capacities are different. Fed Match vs Fed regular, maybe ???
 

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Discussion Starter · #14 ·
Panther: measure the capacity of a few FIRED cases of each type, and get 2 averages. Easy process, just takes a few minutes.


I can then plug those capacities into Quickload and give you some results.
Can't measure capacity of the Lapua cases they are new unfired
 

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Discussion Starter · #15 ·
Have to work a few nights but I am thinking that maybe I can F/L resize one of the new unfired Lapua cases and also one of the BH cases and use either water or rubbing alcohol to see what volumes I come up with, a friend of mine suggested just drop the charge by 2g and work back up to the most accurate load he said 2g is about as far as I would have to go but my OCD kicks in and won't go with that
 

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maybe I can F/L resize one of the new unfired Lapua cases and also one of the BH cases and use either water or rubbing alcohol to see what volumes I come up with
I would only run them thru a neck sizer die to take out any dents in the case mouth and not full size them because you arent gonna make them smaller than new virgin brass size (does that make sense?)
 
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