I've got a 7MM Rem Mag. New to loading for rifles, I figured there was nothing to worry about since it was a modern gun and all. Today at the range I had a case head fall off on me.
Here's what I've got.

Brass is about 6-10 times loaded.
60gr of H4831 with 175gr Sierra.
I've always full length sized because it's a hunting rifle. (been told that's a good idea)
.016 length expansion
.005 head expansion

From what I've been reading that's too much slop. So is just a partial size the fix or am I looking at something else?

Advice?

It sound like when you full length resize you are pushing the shoulder back this will change your head space try backing your die
up so you only resize the neck this should fix it

Guntoter,

What Paul told you is right and partially incorrect. 7mm Mag headspaces on the belt, not the shoulder. However if you are full length sizing your brass the pressures involved can seperate the case head in as few as two loadings.
When I first got into reloading, the rifle I was loading was a 7mm Mag, and I had the same problem. I solved it as Paul suggested, backing of the resizing die to barely touch the shoulder.
Got as many as 10 firings out of a case which is excellent (in my opinion) for a magnum cartridge. Might have gotten more but the rifle was stolen and I sold all my 7mm Mag stuff. :-(

------------------
Surely we must all hang together, for separately we will all surely hang.

On any belted magnum you are reloading, two things are essential that you do for safety. First, run a dental pick, or a bent paper clip, in the inside of the case where it separted. When you feel a ridge or bump in there that is the signal for the case starting to separate. Second, check the outside. When you see a slightly discolored line in that area, your are past the point of separation. Throw those cases away.

You describe the classic result of excessive (full length) resizing multiple times.

Once a case is fired in a given chamber, it should never be resized more than is necessary for it to re-enter the chamber easily. This is equally true of belted cases, which, even though they can initially headspace on the belt, have infamoulsy sloppy belt dimensions; therefore they need to headspace on the shoulder on subsequent firings to avoid repeated case stretching and thinning in the web area.

Just start sizing your brass only enough to readily chamber -- any more sizing will not increase dependablility, it will only make for a sloppy fit. You should be able to load such properly-resized brass without a case head separation far more times than the necks will hold out without splits.

10 reloadings out of a high pressure case like a 7mm Mag is too many. Buy some new cases.
I limit my .308 loadings to 4 in USGI cases as I get case head separations on the 5th loading. But this is brass that has been fired in oversize machine gun chambers the first time.
Still, 10 loadings is a bunch...

Thanks dudes. I was worried there was more to it than that. As soon as my new "headless case yanker" comes from Brownell's I'll get right on that sizing.

I've looked all my brass over very carefully, and on some of them I can see a slight, bright ring. Those are the ones that I can feel the groove in the most. Some of them don't have a detectible ring, but I can still feel a groove. I think the probe test will be a routine for me... and that, OF COURSE, will be on my NEW BRASS.

Thanks again.

For safety consideration [as you've no doubt found] full-power reloading of magnum rifle cartridges should be done carefully and held to a minimum. Personally, i wouldn't fire a belted mag case w/ a full charge of powder more than 2 or 3 times before retiring it [the difference being inspection. i certainly wouldn't full-load these types of cases if they show any noticable amount of bright ring near the head. It could be that i'm paranoid but in 10 years and thousands of rounds of loading and firing my own ammo i've yet to have a problem or failure of any kind].

Does the same load in new brass give you any indication of excessive pressure?

-Catter

Guntoter. Try this. Take a new broze cleaning brush and run it into your rifle from the receiver to just past the stuck headless case. Then pull it back out. The case should come out with the brush.
For those who feel magnums should not be loaded more than three times, I have one box of Federals in .375 H&H that I'm shooting to destruction. I neck sixe for five reloadings anf then anneal the necks prior to a full lenght resize. These rounds have been loaded twenty times and are still going strong. Rifle used is a Ruger #1 single shot. I think my shoulder will give out before the brass does.
Paul B.

Thanks, Paul B. I just had to bite my tongue on that comment on throwing away brass after 2 or 3 loadings. Appreciate your setting things straight. Magnum brass can be loaded as many times as rimmed, rimless, or rebated. All depends on the care one takes.

[This message has been edited by Stonecreek (edited 10-17-2001).]

For those that doubt you, Paul B, I have a set of 338 Win Mag case with 18 reloads still going strong. I do exactly the same thing. Neck size, 5 or 6 reloads, anneal and keep going. I got rid of the initial stretch problem by sizing down 358 Norma Mag brass to a close shoulder fit rather than those horrific .015" to .025" initial stretches on most new cases. No sign of separation yet. With domestic 338 brass, separation comes at between 10 and 15 reloads for me.

Thanks Paul... That brush trick was a snap. I can't beleive I didn't think of it. I mean, I'm an ex grunt, and I can't tell you how many times I saw some bolo get is bore brush stuck in his M-16.

Thanks.