I just filled the case with water, dumped it into a powder pan and weighed it. After doing this, I realized I should have weighed the case, filled it with water, weighed again and subtracted the difference. I actually doubt, however, that the wet walls would contribute even one grain difference. I can do this again if you would like.
My factory bbl has a 1/9.5 twist. Some of the factory loads run up to 160grns, so I think I am safe with the medium heavy bullets. The only drawback is the rifle has a 26" bbl.
The way I measured the capacity is just like you stated, weigh an empty then add the water, reweigh and subtract the empty weight. I also used a spent primer installed backwards, should have stated that before. I don't know if trying to put in a live primer backwards would be safe or not.
After reading Wayne's post with his weighing 116.1gr, I went back to look at mine, mine was also 116.1gr, not sure where I came up with 117gr. Maybe I figured when the necks lengthened back out to 2.720" they would be 117gr. They were all trimmed to 2.690" after fire forming and 116.1gr is wrote right on the side of them.
Wayne's case has a bit more capacity above the shoulder because his has a 35 degree and mine has a 40 degree, mine is a tiny bit larger in diameter below the shoulder though (.570"), which is why I think we have basically the same capacity in the two.
210 Bergers blew holes right through my 3/8" steel plate at 600 yards yesterday, and almost through the 1/2" plate. They're going 3200 fps. I've got a bunch of welding up to do on 'em now! [img]images/icons/grin.gif[/img] Going back out to try 800 and 1000 yards today, a few shots before it's dark anyway.
The water left in the case WILL add about 2-3gr in my experience. Even if you tap it out real well it will always weigh over by this amount. I weigh them first, primer upside down, fire formed, drop of dish soap in the eye drop bottle, top it off until the water is flush to the top. No big bubble on top, just flush so you can barely see the water looking at it across the case mouth from the side.
Tap every bit of water out of the case afterward to see what the difference in dry weight verses wet weight is.
Now there's a difference in the way your rifle is throated for long bullets, which could give an even bigger edge to the shorter fatter Lapua case design, that is if your magazine box doesn't allow the big bullets to be seated out in the Ultra's, it can using the Lapua case. The neck on the Ultra is real short, which also eats up more capacity when seating bullets when a chamber is improperly throated for them. If each is throated properly, the mag box will still limit the Ultra or Weatherby/Rigby case where as the Lapua will gain an edge on it as it won't have to be seated any deeper.
Loaded OAL at land contact for the 30-338 Lapua IMP with:
210 JLK....... 3.818"
210 Berger.... 3.741"
240 SMK....... 3.694"
200 Accubond.. 3.769"
178 A-Max..... 3.701"
I think I'm going to have to end this shooting with Michael, he pretty much wipped my ***** with his awesome shooting 308win yesterday! When I shot his 308, I found out his secret! It's a freakin 1 ton trigger pull!!! [img]images/icons/grin.gif[/img] Must be all of 10lbs anyway. He stacks 'em in there with it though, 3 different bullets too! You don't ever want to be in this guys sights!
Fired case, primer seated upsidedown, case neck sized a couple of thou, 393.2gr wet, 278.2gr dry = 115.0gr. Different case than the first however.
New case, primer seated upsidedown, 390.8gr wet, 278.7gr dry = 112.1gr. This is soft water, if that makes a dif. [img]images/icons/rolleyes.gif[/img]
Hope this helps,
After coming upon this forum, I found that you are trying do exactly what I have been working on for some time now. I currently have a rifle chambered for a .338 Lap necked down to 7mm. It is based on a Remington action, has a 28" Pac-Nor 1:9" SuperMatch bbl, blueprinted/trued action and bolt face, heavy recoil lug, Sako extractor, bbl is free floated and is glass/pillar bedded into a blue-laminate, tactical-style stock. It has an adjustable butt-plate with a kick-eeze pad installed. It is a hard-core powder burner. The cartridge is called a Big 7 TurnerBurner. It is one of the proprietary cartridges from a local gunsmith here. We decided we would try something new and build the rifle with a 1:9" bbl and take advantage of the 130, 140, and 154gr. bullets (which are perfect for Texas whitetail!). It loves the 140gr Ballistic Silver-Tips from Nosler and it burns about 109.5grs. WC872 with the bullet seat right at the lands. On lighter loads of about 100.0grs and the same bullet, chrono readings were 3685, 3649, and 3693 for three shots. With the heavier bullets, such as the 168gr. Sierra MatchKings, pressure signs become evident at 107.5grs. of H870. This appears to be the limit for this bullet / powder combo and would say the max safe load would be about 102.5 - 105.0 grs. I am currently working on developing more load data for the 162gr A-Max which is running pretty close to the same capactity as the 168 grainers. So far, H870 has had some problems with hang-fires at loads below 100grs. (tried two different primers, so detonation is more suspect since this cartridge seems to prefer charges > 88% with H870) Between 102.5 and 105grs. H870 looks like a good comfortable area for my rifle with a 168gr. Sierra MK and a Fed 215 primer. WC872 has shown VERY promising results without hang-fires also. Will report more on this later.
The cases are Norma .338 Lapua Mag and were made by necking them down in a two step process, fire-forming with a 140gr bullet seated on the lands on top of 17grs. Unique. After initial fire-forming, cases are annealed, and shot with a full load to complete the fire-form process. After this, cases are all trimmed to a length of 2.715", flash holes deburred, primer pocket reamed, and then, culled by weight. Final case capacity is 116.3grs H2O.
I am doing some final work on the stock, so I will be running some 130gr. MatchKings on top of 112grs. WC872 through the chrono some time next week when I finish. I will publish more ballistic/load data as I gather it. I'll let you know my results soon. Maybe some pics also.
One more note: When building this caliber, I have noticed that throat size becomes critical. Many times, with the 130gr. bullets, I am seating only .191" of the bullet in order to make contact with the lands. Usually, I seat right on the lands and drop my powder charges back, but I have had to seat at .005" - 009" off the lands with the 140gr bullets to maintain sufficient bullet pull. With this twist, the throat could stand to be .008 - .010" shorter for the lighter bullets. Have not really shot for accuracy too much yet, but 140gr. Nosler BT's were hitting at under 1/2" mark at 100yds. Seems to be an EXTREMELY flat, accurate shooter so far, just needs more time in development.