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I recently had a significant issue in my reloads that I posted int he reloading section. I thought I might post here about belted magnums for any additions insights or just to relay my issue. I see some previous related discussions. Gun - brand new Ruger American Magnum in 338 WM Brass - Hornady Load - 210 TSX, 66 gr H414 (0.5 off max), 2795 fps Dies - Lee full length resizer I loaded new brass to find my load. I then full length resized and reloaded. In the second fire, I had one crack that went unnoticed at the bench and then a full crack. I measured the brass and bought factory Barnes ammo for comparison. I used a Hornady collet system to measure off the shoulder datum. The new brass and Banes brass measure the same. The Lee die does not reset the shoulder in the first resize. The fired cases grew by 0.013". A ring about the case head can be seen under a magnifying glass, but I honestly did not notice before reloading. Primers appear OK and I am off book max with expected velocity. The Lee die sets the should back off the fired size about 0.003" when set up per the instructions (bottom end of the recommended 1/4-1/3 turn after touching shellholder). Case head separation occurred on this second firing. I looked up max cartridge / min chamber in SAMMI. It appears form my measurements that the ammo and chamber are in the middle of the tolerances. At the outside edges of tolerance, a difference of 0.026" at the shoulder datum is allowable. I am in the middle of that. My initial thoughts were excessive headspace. But the belted mags headspace off the belt and the gages are the same for all. I am trying to find gunsmith to check, but I suspect my issue is the chamber dimensions, not the belt headspace. This was quite eye opening. This is my first foray into reloading a belted magnum. I don't think I am overpressure. I think my gun and ammo is within spec. This leaves me to believe I can only get one shot out of the brass. My questions are, if anyone care to answer, : - what shoulder datum dimension do you chamber 338 WM for ? - If tolerances stacked, wouldn't 0.026" allowable per SAAMI be in danger of case head separation in the initial fire? - Should I be having visible issues with a 0.013" stretch? - I assume the issue could be on the belt end, which I cannot measure without a gage? - Am I missing something in my though process? | ||
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You might be diluting your responses because the same guys read reloading too., The shoulder length is not germane; if the belt is held in place, then the shoulder will just blow forward and the head end will not be affected. Experienced reloaders will not set that back at all, just enough to chamber the cartridge. So, the shoulder to bolt face difference is not relevant to the "headspace" on a belted cartridge, Until you make it so and treat it like a belt less cartridge. That does not cause the head to separate. Then it is important and you can remove the belt completely. Take your brass and put some masking tape on the head, and close the bolt. Keep putting layers of tape on it until you can't close it. Measure the tape thickness; that is how much longer your chamber is than the brass, regardless of what the actual dimension is. Buy a gauge for $30. Cheaper than sending your rifle out. Or do what everyone has already said; forget all this; treat your rifle as a wild cat and form brass accordingly. Or send it back to Ruger and complain and see what they do. Post or send a picture of your "ring around the case head". Did you have a separation? Stop adjusting your die so far down; just barely enough so the case can be chambered. Or send it to me and I will make your chamber to minimum specs. Cost more than the rifle. If your headspace is good, then the shoulder to belt length will not cause case head separations; the shoulder just gets blown forward; I might have already said that; but in any case you want to minimize that. | |||
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What are the actual, real world measurement and tolerances for belt thickness? | |||
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Take a fired case mark the neck with whatever, I use a marks A lot most of the time..then I back off the die a good bit and run the case in the die, then the chamber, and note the mark on the neck which is generally half way..then take turns on the die as I resize until I make connection with the shoulder with a ever so slight tightness and make note of the marks a lot in relation to the shoulder. then my die is set to the chamber of that particular gun..You can do this same thing with a rifle that has headspace..I do this with belted or unbelted cartridges, especially on some European calibers. Then just neck size until case won't chamber then repeat the process from a full length resize. The process is no more than matching the die to the chamber, headspacing on the shoulder only. I believe I just repeated DPCD sorta. Ray Atkinson Atkinson Hunting Adventures 10 Ward Lane, Filer, Idaho, 83328 208-731-4120 rayatkinsonhunting@gmail.com | |||
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It needed repeating. First, realize that SAAMI standards are Voluntary; unlike in Europe, our government does not get involved in firearm dimensions, and that is a good thing. Having said that, though, our makers of rifles, brass, and dies do a great job. A belted cartridge can be from .220, to .212 head to belt. A belted chamber an be from .220-227, so you can see the potential for a minimum piece of brass and a maximum chamber, both within specs, having a big, (.015 or so) extra space to float around in. Firing one factory round; no problem. Reloading them? Might be an issue, as the OP knows. In factory brass and chambers, they usually fall well into the specs. Reloaders often compound the problem too; not saying that the OP is doing that, at all. Deal with it, as Ray said above. | |||
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I have never seen a piece of belted brass which measured more than .216" from base to belt. I cut all my belted chamers to .220 which is the saami minimum. So, even with the minimum chamber dimension, the very best I will see is .004' head clearance and usually there will be up to twice that much. This why everyone who has figured it out, sizes belted mag brass to headspace on the shoulder after the first firing. Regards, Bill | |||
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Size to the shoulder and you'll be much happier. | |||
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Yes and do that BEFORE you ever fire the brass. | |||
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bottom line is neck size magnum cases until they will barely chamber and your off the belt and cases will last many rounds. You may end up with a double shoulder in the worst of chambers, but it won't hurt a thing. I seen some German firearms and doubles wherein Im sure the ran the reamer in until it just looked good..Had to load them accordingly to fireform to the off chamber, and they worked fine when reloaded as such to fit THAT chamber. One was a nice old 10.75x 68..You should make the case fit the chamber on any rifle. Most of todays factory US chambers can be full length or neck sized and work fine..The US problem is the throats and magazines seldom match in length and that's a pain in the kazoo as the magazine determines the OAL of the round, and the chamber is long so the bullet has to jumps sometimes a bunch,and sometimes its visa versa. Ray Atkinson Atkinson Hunting Adventures 10 Ward Lane, Filer, Idaho, 83328 208-731-4120 rayatkinsonhunting@gmail.com | |||
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Everyone else has covered the reloading aspect, so that you treat the cartridge as if it doesn't have a belt. That's the best solution. I've never seen a piece of magnum brass that the belt comes anywhere close to the minimum chamber headspace dimension. So, when I chamber a magnum cartridge, I chamber it so it will "ALMOST" take the go gauge. Then, I check it with several pieces of factory brass. Every piece of factory magnum brass I have ever measured had about .010" of "headspace" in a minimum chamber. It sounds like yours has about .013" from your case stretch measurement, which is about right if it was chambered to take the go, and not take the no-go. Belted case headspacing as it has been applied by rifle and cartridge manufacturers is totally garbage for those that intend to reload the cases. | |||
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That is good practice; I should have said that my "GO" gauge is actually a piece of belted brass cartridge head. I do not even own a real go gauge. | |||
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