I know this has probably been discussed many times but how do you correctly measure the water volume and what tools do you need to measure it with? Doesn't the volume of the case have something to do with estimating pressure? I have a 270 Gibbs that groups 150gr NP's slightly less than .4" at 100yds with 60.5gr of H4831. I slowly worked up to this load which is .5gr over max according to what I've read but have no pressure signs yet. I suspect I have a chamber that's larger than normal because there's still a lot of room left in the case for more powder. I bought a reamer from Clymer and had a gunsmith ream a Pacnor barrel with it. When I started fireforming and reloading I found that my RCBS die was resizing the brass too much and I was afraid the brass wouldn't last very long. I called RCBS and they suggested I send them some fired cases and they'd polish the die to fit my brass so I did. I know it's a long story but I'm just wondering if knowing the water volume of the case might be useful information.

Knowing your case capacity can help sometimes. In your case if you are trying to compare to load data if you know the difference in your case capacity compared to the capacity of the test case it MIGHT indicate why your load is hotter or cooler than the posted. In most cases .5gr over max is normal easily within the lot to lot difference in powder burn rate.

If you are simply comparing to old published GIBBS max of 60gr of H4831 and you have worked up to 60.5 with no issue I would just go shooting.

Paul,
I was looking at the old Gibbs data. I have been shooting this rifle for several years and have reloaded some of the cases 4 times. I just like having the case full. I may play around with some slower burning powder. Do you have any suggestions?

Thanks,
Victor

Never played with the 270Gibbs but have burn a lot of powder in my 6.5PDK and 280PDK which are a Gibbs style case plus a couple grains.

Three powders are always on my go to list for that size case in those calibers. Norma MRP, RL22 and IMR 7828. With 150s MRP and RL22 will be in the 101-105% compression at max. 7828 will be closer to 109%. None of which sould be an issue.

"Doesn't the volume of the case have something to do with estimating pressure?" Yes, Less volume, more pressure. The water volume of the case will give info between brands/lots. When using brass of all the same lot/brand, the weight of each case will effect accuracy. A rifles chamber has a volume. This volume runs from the bolt face to where the bullet seals the bore. Anytime you place a different weight in the volume, pressure changes. So, going by weight of the brass is as accurate & less messy. IMO.

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So, going by weight of the brass is as accurate & less messy. IMO.

Case weight can indicate that one case, one load of cases, or a manufactures cases are heavier or lighter to anothers. With time this can probably give you an indication that you might need to back off a load for a heavy case. How much?? to me only comes with experience.

In the case of Silverado's 270Gibbs you won't find a factory case to compare to. While you might find load data it probably will have not reference to your styarting case. So many of us "die hards that don't shoot std" have to roll our own. Some of the loading programs now help but for years you had to formulate your own starting load data. So you either looked over your thumb and said well it is sort of 60% between x or y.

Or I always felt you got a much better starting point if your compared the actual case volume vs a std. Like my 280PDK compared to a 280 Rem. Since my case capacity was 10.6% larger than a factory case then I would ratio up published load data by that %. Perfect. Nope but to me better than a guess.

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Doesn't the volume of the case have something to do with estimating pressure?

Yes it does. I would be measuring CHE, which would tell me when to Stop adding Powder before I began making the Primer Pockets so loose that the Cases are worthless.

Knowing the Water Volume would not help me when Loading the Case, unless I was trying to "guess" at which Powder "might" work. I'd then have to compare it to other Cartridges I've Loaded for with similar Water Volumes. But, it would still be just a guess when there is no Load Manual for a Reference.

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I suspect I have a chamber that's larger than normal because there's still a lot of room left in the case for more powder.

Depending on all the Physical Dimensions of the Chamber and Bore, and all the variations in the Cartridge Components, that amount of Powder may be just right, too High, or too Low. Without watching the CHE, a person is just guessing at what is right.

Best of luck to you.

Thanks for all the good information. I don't plan on loading my Gibbs any hotter. It shoots great and I have a whole box of ammo already loaded for it. I'm pretty sure the load is ok since the primers don't flatten, there's no marks on the brass, it ejects easlily and the primer pockets are still very tight after 4 reloads. I don't have a micrometer that's accurate enough to measure CHE but I may get one. I'd still like to know how to correctly measure the water volume of cases. I used to CC the compression chambers of my hot rods so I'm guessing the method is similar.

Don't know what kind of brass you are using. Since it works well I would leave it be. Don't fix it if not broken. If youa re on your 4th relaod with no loose pockets you should be fine.

If you decided to go for higher velocity switch to Norma brass. It will give you an extra 3-4grs of capacity from the start.

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Originally posted by Silverado:
...I'd still like to know how to correctly measure the water volume of cases. ...

OK, you would probably want to use "Once Fired" Cases and do 5 or so then run an Average. Leave the Spent Primer in the Case, Tap it a bit to make sure the loose Residue is out, and Weigh the Case. Then fill the Case with Water(using a Syringe), re-weigh, subtract the empty Case weight and you have the Water Volume by Weight.

Or, you can use the Syringe and measure the exact amount of water which you insert into the Case by Volume(CCs). One of your Diabetic buddies who has to give himself Insulin Shots will be able to give you a Syringe, or you can buy them at a Drug Store for maybe $0.25.

The "Trick" is to get the Meniscus "Flat" at the Case Mouth when you add the water.

Using Once Fired Cases, or Neck Sized Cases that have been fired a few times in your chamber, gets the Case Expanded as Large as it is going to get. Just be consistent with which ever way you do it.

Best of luck to you.

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Using Once Fired Cases, or Neck Sized Cases that have been fired a few times in your chamber, gets the Case Expanded as Large as it is going to get. Just be consistent with which ever way you do it

I agree that will give you a good guess as to the fired case volume. What are you going to then compare it too? If you had to rifles same chambering same brass I could see if one was more water then larger case.

However comparing to various posted capacities a fired capacity compared to posted unfired capacities I don't follow how that will tell you anything.

As to measuring I agree I use several fired cases but I resize. Since I only measure as to my wildcats I's starting with custom dies anyway so I resize the body very little.

Hey RamRod, That is an Excellent Point - in comparison to what?

I seem to remember someone saying some of the Manuals(which are not ones I have) list Water Capacity of Cases. And, I'll "guess" some of the Software Programs list it. I'll also "guess" those would be done with New Un-Sized and Un-Fired Cases. But, then it would probably vary somewhat by the Case Manufacturer as well.

Sure glad I have CHE & PRE for new Loads.

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I'll also "guess" those would be done with New Un-Sized and Un-Fired Cases. But, then it would probably vary somewhat by the Case Manufacturer as well.

Yep QL list the capacity and on some more popular they list by case manufacturer. Loadtech simply listed capacity. As I understood LoadTech at least were new unfired. IN the ones I've actually compared to QL they appear to be new unfired.

Cartridge Case Capacity grs of wtr
.223 Rem (R-P) 31.4
.22-250 Remington (W-W) 44.6
7mm-08 Remington (R-P) 52.2
.243 Winchester (W-W) 52.8
.243 WSSM (W-W) 53.0
.308 Winchester (W-W) 53.5
6mm Remington (R-P) 54.6
.223 WSSM (W-W) 55.0
6.5x55 Swede (N) 55.0
7x57 Mauser (W-W) 55.6
8x57JS Mauser (W-W) 62.7
.240 Weatherby (Wby) 63.1
.25-06 Remington (W-W) 65.0
.270 Winchester (F C) 67.4
.30-06 Springfield (R-P) 68.0
.280 Remington (R-P) 68.6
.444 Marlin (R-P) 69.5
.35 Whelen (R-P) 72.6
.350 Remington Mag. (R-P) 73.7
.45-70 Government (F C) 75.5
.270 WSM (W-W) 78.9
.300 WSM (W-W) 79.0
.264 Winchester Magnum (R-P)81.5
7mm WSM (W-W) 83.0
7mm Remington Mag. (W-W) 83.2
.270 Weatherby Mag. (Wby) 85.3
.257 Weatherby Mag. (Wby) 85.6
.338 Winchester Mag. (W-W) 85.6
7mm Weatherby Mag. (Wby) 87.5
.300 Winchester Mag. (W-W) 90.4
.458 Winchester Mag. (W-W) 93.3
.375 H&H Magnum (N) 96.4
.300 Weatherby Mag. (Wby) 100.4
.340 Weatherby Mag. (Wby) 102.1
.416 Rigby (F C) 132.6
.460 Weatherby Mag. (Wby) 144.7

Hey Ray, Nice list. Plus it even tells who Manufactured the Case used for the measurements.

Hey Silverado, With the info Ray provided, how will you be using it?

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Hey Ray, Nice list.

+1 .30 Rem.AR@44gr- 308win@56gr In American rifleman magazine. I wonder how the different lengths of the necks play out in the water weights? Would case capacity be better measured by only filling to the neck/shoulder junction??

Some folks size the case, leave the primer out , seat a bullet to the OAL that will be used, weigh the result, fill the case with water using a syringe through the primer hole and weigh again. This method gives you the measurement of the actual powder capacity!

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Hey Silverado, With the info Ray provided, how will you be using it?

Hot Core,
I don't know that I'll try to use it at all. I did make a copy of it for future reference. I might compare the capacity of some of my fired .270 (FC) brass to my fired .270 Gibbs (W-W) brass just to see the difference. I asked the original question just out of curiosity. I don't have any reloading programs and just do a little reloading for hunting. I don't claim to be any kind of reloading expert but the more knowledge you have about anything the better. I don't appreciate your sarcastic question so I'll just put you back on ignore where you belong. I have no use for sarcastic know-it-all's. I appreciate all the good responses from everyone else though.

RD-Your method makes the most sense to me.

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Originally posted by Silverado:
... I don't appreciate your sarcastic question so I'll just put you back on ignore where you belong. I have no use for sarcastic know-it-all's. I appreciate all the good responses from everyone else though.

Wasn't intended as sarcastic, however you should do just what you said. And while you are at it - stick it!

Never thought of that method, thanks for posting.

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Originally posted by R D McMillan:
Some folks size the case, leave the primer out , seat a bullet to the OAL that will be used, weigh the result, fill the case with water using a syringe through the primer hole and weigh again. This method gives you the measurement of the actual powder capacity!

quote:

Some folks size the case, leave the primer out , seat a bullet to the OAL that will be used, weigh the result, fill the case with water using a syringe through the primer hole and weigh again. This method gives you the measurement of the actual powder capacity

I tried this way. I had trouble getting the measurements to repeat. I assumed I was getting air trapped. Done correctly it will give you your net case volume. However until some of the loading programs you had nothing to reference too because posted numbers were gross. Unless you had the other cases to test the same way.

Before QL I would simple take the gross and adjust it by removing the volume filled by the bullet. Simple calculation (bts make it a little harder). However if you are trying to compare a 270gibbs to a 270 and you load to the same OAL then the ratio of gross will pretty much equal the net.

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Originally posted by ramrod340:
I tried this way. I had trouble getting the measurements to repeat. I assumed I was getting air trapped. ...

That is correct. Plus you now have the Variance in Seating Depth, Variance in Bullet Shape(Boat Tail, Plain Base) in addition to the Variance in Volume among Cases from the same Manufacture within the same Lot.

It is as useful as knowing how many Hairs are on a Deer.

Here is an illustration of how to measure water capacity of a case. http://www.gsgroup.co.za/faqcasecap1.html

I used this method many years ago when I fire-formed some 300 H&H cases to fit my 300Wby. The seat-the-bullet-and-fill-through-the-primer-hole worked very well for me and I do not believe there would be enough difference in capacity due to variences in the length of the slug or manufacturers differences in the two different groups of cases to cause any concern. That said, I do not load to the extreme maximum, rather I load for accuracy first! Have a great day!