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one of us |
Interesting Scenario; loaded up a bunch of test loads using once fired Remington and Winchester brass for 300 H&H. Brass came from the same rifle. Cases were trimmed to SAAMI spec and neck sized. On testing, the velocities were extremely consistent and almost bang on what the book indicated. No pressure signs at all on the primers. We were not looking for extreme velocity, and want to push a 180gr bullet at around 2700-2800fps. Powder was norma MRP, primers are CCI Magnum, bullets Nosler partition. BUT.........after suffering from 2 complete case head seperations, and indications that a couple of the other fired cases were heading the same way we packed up, completely puzzled! This rifle has shot a lot of reloads without a hiccup. What comments and suggestions? | ||
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| one of us |
quote: I load for a old mod 70 in 300H/H and have not had a problem with it....the first thing that comes to mind is the die is setting the upper case too far back or that the chamber is too large for the die..this will let the shell case expand foreward and try to fill the larger chamber and the area in front of the belt area is where the brass flows from to expand to the chamber? this will cause seperation....you sure about the number of times the brass has been loaded and trimmed? and since you state that two different brands of brass are involved then it shouldn't be a bad lot of brass! a chamber cast of the guns chamber and then a precise measurment of the cast and compare it to unfired brass measurements....first compare a fired case measurement to unfired and then size the fired case and measure the difference...the strech has to be coming from the die or chamber....good luck and good shooting...with the case and your head still on...lol..! | |||
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one of us |
As the cartridge is headspaced on the belt, there is no specification for the shoulder on the brass. Some can be as much as .025" short of the chamber in a new case. When it's fired the first time, the initial stretch of the brass can be significant and commences the process which leads to head separation. If for some reason the chamber is a bit longer in the bolt-to-shoulder measurement, then that separation can be quick. It pays to check the inside of the case with a dental pick or bent paper clip after initial firing to check for the separation. A short case, or a long chamber can be the cause. | |||
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| one of us |
Unusual, indeed. You state that the brass was neck-sized only, so I've got to assume that the shoulder wasn't set back. The pressure for the load you were using has to be mild to only get 2800 fps or less with MRP and a 180 grain bullet, so it ain't excessive pressure per se. My best guess is that the brass may have been fired only once in YOUR chamber, but may have been reloaded several times by someone else doing the full-length sizing trick. Otherwise, I'm baffled. Only perhaps if the chamber's belt recess is cut grossly deep, and the chamber's head-to-shoulder dimension is also very long and therefore allowing extremely long headspace could a neck-sized case have a head seperation on the second firing. Is this a custom chambered (or rechambered) gun? Measure the head to shoulder length of a fired case (which ain't easy on a .300 H & H) as best you can and compare it to SAMMI specs. | |||
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| one of us |
While I could be off base here, I think the problem may rest with the way the die is set up. I'd check this out by using a Magic Marker pen and blackening the neck and shoulder are of the case, or smoke it with a butane cigaret lighter and run it through the die. The marks left by the die should indicate if the shoulder is being pushed back. While magnum rounds are supposed to headspace on the belt, measure a few with a caliper sometime. The results may surprise you as to how much leeway can be found on those belts. If my 30-06 were that far off, it would be considered unsafe. Paul B. | |||
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| one of us |
Belted Magnums, and the 300 H&H, is the worst. That long sloping body and neck is heck on stretch. When chambering for a Belted case, I use the "go" gauge as the NO GO, and a cartridge for the GO. That way the bolt will not close on the GO gauge, but will close on a cartridge. It is the only way I have found to combat the headspace on the belted cases. ------------------ | |||
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Thanks Guys, Thanks for the input! A lot of what you have suggested I have already covered, some not. I will have to sit with a batch of the cases and go through the full basics this weekend and try and get to the bottom of this problem. They are definitely once fired from this rifle and again definitely only neck sized. I will pull a cast from the chamber as well to see how it compares to SAAMI spec. | |||
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| <re5513> |
quote: The shallow sloping shoulder of the 300 H&H could be the cause of the problem on the first firing of the brass. You may be getting too much stretch on the case when the case goes from virgin to once-fired. One way to avoid this is to handload new brass with the bullet jammed into the rifling to keep the base of the case firmly against the bolt face. Naturally this can lead to a rise in pressures so the load needs to be construed with care. I'd check for imminant case head separation (using a paper clip or other appropriate tool) upon first firing of your brass. If that is what is happing, the second firing of neck sized brass is just exacerbating a pre-existing condition. Regards, | ||
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| <Reloader66> |
Even though belted magnums head space on the belt you should size them like an unbelted case. When you set your neck sizer die up you should have 1/16" space between the shell holder and the bottom of the die body when the ram is at full swing. By doing this you will keep your head space set on the shoulder of the case instead the belt. This is with once fired brass from the same rifle your shooting it in. If this does not solve your problem you should have a qualified gunsmith check your chamber to be sure it is within specs for that cartridge. | ||
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Trimming the cases too short... | |||
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With magnum cases after the first firing forget that forget that damn English invention we know as "the belt" & adjust your dies so that you maintain correct head space using the Datum line on the shoulder of the case. Neck size only, stay off the shoulder. If the head space in really bad in the first place you will stretch the web of the case head & that will also lead to head seperation. One trick is to straighten out one of those big paper clips & make a we- little hook on one end. Run that hooked end down the case mouth along the inner case wall. you will be FEELING for a bump when you reach the web area. The presents of said bump means that the case has been stretched. through those cases away! Excessive headspace = setting the barrel back a thread.  Shoot more & shoot more often! ------------------ [This message has been edited by Bear Claw (edited 11-04-2001).] | |||
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