I need a little input on how I am troubleshooting my issue. I have fire formed 20 pieces of brass, and would like to fire 5 of those pieces a second time, but without touching the shoulder during sizing. Just setting up my Redding full length die to only resize the neck so that I can reload the brass so it can be fired a second time, to assess if the brass grows even more after a second firing. I am taking the gun to a gunsmith in a few days and would like to be able to give him as much data as possible on what exactly is happening, how much case growth etc. I have spent hours studying this issue online, I don't need any advice on what causes this phenomenon, that is very clear. I would just like to know if those of you with experience feel that this would be safe. The gun is a Sako A7 in 7mm mag. I only push my shoulders back .002 but am getting dramatic case head separation after the third firing, including total separation where I end up with two pieces of brass. And I'm not firing hot loads. Thank you in advance.
Belted mag case head separation
- Thread starter Toemader
- Start date
WSnyder
Silver $$ Contributor
If you attempt to use a full length die to neck size only it probably won’t work as you envision. The body of brass will still get moved and it has to go somewhere so when you attempt what you are proposing the shoulder will usually move forward several thousandths and will likely be hard to chamber. Maybe this will work for you but maybe not. If you want to neck size only you will probably need a neck die.
I would try some different brass. Belted brass almost always grows quite a bit on first firing.
Thank you WSnyder, I was kind of wondering if that would be the case. And I just saw a 7mm mag neck sizing die at Scheels yesterday. I should have listened to myself when I thought about purchasing it. As for trying new brass, Walt, I'm pretty sure I could more easily find Jimmy Hoffa than a box of 7mm mag brass. Also, I really don't think it's the brass, I'm pretty sure it will happen regardless of what brass I'm using. But that said, you know what? I have three other types of once fired brass from that gun that I put on the back shelf as I only have 5-15 pieces of each, but they might be good for troubleshooting my issue.
No, it's not safe if you are experiencing incipient and most certainly complete head separation. The affected cases should not be used. Restart with virgin cases.
I don't own or shoot belted magnums, but I've assisted a few shooters with the problem you describe. Assuming the rifle has no mechanical or head space issues which your gunsmith should rule out, the following is a fix we used in the past. Run this approach by him to ascertain his thoughts on it.
First, start with virgin cases and fire formed in your rifle chamber. Measure the fired cases at a datum line on the shoulder with a bump gauge and caliper.
The FL sizing die should be setup for zero shoulder bump, so the die touches the shoulder but does not bump it back or extrude (lengthen) the case.
Check the first sized case to make sure the shoulder has not been pushed back and it chambers without issue - adjust if necessary. The idea is to have the case headspace on the shoulder, not the belt.
From that point forward, monitor fired case headspace via datum line measurements and bump only if necessary to allow issue free chambering.
I don't own or shoot belted magnums, but I've assisted a few shooters with the problem you describe. Assuming the rifle has no mechanical or head space issues which your gunsmith should rule out, the following is a fix we used in the past. Run this approach by him to ascertain his thoughts on it.
First, start with virgin cases and fire formed in your rifle chamber. Measure the fired cases at a datum line on the shoulder with a bump gauge and caliper.
The FL sizing die should be setup for zero shoulder bump, so the die touches the shoulder but does not bump it back or extrude (lengthen) the case.
Check the first sized case to make sure the shoulder has not been pushed back and it chambers without issue - adjust if necessary. The idea is to have the case headspace on the shoulder, not the belt.
From that point forward, monitor fired case headspace via datum line measurements and bump only if necessary to allow issue free chambering.
Gary in MD
Gold $$ Contributor
From what you are describing, it sounds like you are pushing the shoulders back more than .002”. Are you sure?
What brand of brass and was it only fired in this rifle?
What is your load?
What brand of brass and was it only fired in this rifle?
What is your load?
Couple points I didn't include in my previous post,
1. Cases must be dedicated to a specific rifle. Do not interchange with another rifle or use cases fired in another rifle.
2. Because neck sizing only sizes the neck, not the body of the case, it usually does not work very well with magnum cartridges because this creates chambering issues because of the radial dimension expansion that occurs which is magnified at the pressures generated encounter in magnum cartridges. The FL die even with zero bump, will size the radial dimension of the case which is often enough to allow issue free chamber.
3. Trying to neck size with FL die, as another has said, is not an effective approach. This invariably extrudes the case, i.e., lengthening it creating a chambering problem.
4. While a shoulder set back of .002" is a sort of standard rule of thumb, it may be too much for your rifle and brand of cases. By starting with a zero bump and assessing chamber adequacy, you can determine the degree of bump, if any, that is needed. Check chambering with the firing pin assembly removed which will give you a significantly better feel and ability to assess chambering adequacy.
1. Cases must be dedicated to a specific rifle. Do not interchange with another rifle or use cases fired in another rifle.
2. Because neck sizing only sizes the neck, not the body of the case, it usually does not work very well with magnum cartridges because this creates chambering issues because of the radial dimension expansion that occurs which is magnified at the pressures generated encounter in magnum cartridges. The FL die even with zero bump, will size the radial dimension of the case which is often enough to allow issue free chamber.
3. Trying to neck size with FL die, as another has said, is not an effective approach. This invariably extrudes the case, i.e., lengthening it creating a chambering problem.
4. While a shoulder set back of .002" is a sort of standard rule of thumb, it may be too much for your rifle and brand of cases. By starting with a zero bump and assessing chamber adequacy, you can determine the degree of bump, if any, that is needed. Check chambering with the firing pin assembly removed which will give you a significantly better feel and ability to assess chambering adequacy.
jepp2
Gold $$ Contributor
I can share my experience if that helps. Both of my 7 Mags were Remingtons.
The first firing of new belted mag brass with a modest load will blow the shoulder forward around 0.016" for the case head to datum measurement. But they were still short of bolt contact. In all my bottleneck rifle cartridges (included belted mags), I want to know 3 measurements:
- what my case head to datum length is coming out of the rifle
- what my case head to datum length is where I encounter bolt contact on a stripped bolt
- what my case head to datum length is that I want to size my cartridge to (normally 0.001 - 0.002" short of bolt contact)
I prefer on most cartridges to use a body die then a neck die. I set the shoulder bump with the body die, then deal with the case neck. After the first firing, I set the body die high enough so there is no shoulder contact. The will result in the case head to datum getting LONGER. Sometimes this is enough to obtain bolt contact, but usually not until the 2'nd firing. On my belted mags, it took at least 2 firings. Then I do my normal sizing of 1-2 thousandths less than contact.
If you are getting a complete case head separation after the 3'rd firing, you should be able to detect the stretch inside the case with a bent paper clip. It also could be visible on the outside. Without knowing more about how much your case grew during the first firing, and if your 0.002" shoulder movement was indeed back from the after fired length, just difficult to analyze in words. And I'm not challenging you, just like to see before I believe.
For folks that believe the belted mag case does indeed headspace off the belt and use that when sizing, complete failures after the 2'nd or 3'rd firing is common.
What I use to check for incipient case head separations inside the case body.
When I originally purchased this gun I also purchased 10 different boxes of ammo to try out different loads to see what my gun liked best. 139gr all the way up to 175gr. The gun liked Hornady Precision Hunter 162gr ELD-X. So all of the brass that I am using is factory Hornady ammo that has been fired once in my gun. The two subsequent firings were hand loads done by myself with a .002 shoulder bump. I have hand loaded about 120 rounds that have been put through the gun. All were either 2nd firing, or 3rd firing. Virtually every 3rd firing has resulted in case head separation. I know I am getting pretty consistently about .018 growth from never fired brass (still new in box measurement) to once fired. I removed the projectile on the box ammo and got 2.1045 for the measurement using the Hornady headspace comparator. After being fired I get 2.1225 pretty consistently giving me .018 growth. And this once fired brass slips right into the chamber just as easily as an unfired round or a sized piece of brass. I have an appointment with the gunsmith tomorrow to look at the gun to see if everything is in spec. I am throwing away all of my brass except for the 20 pieces of once fired brass I have from two days ago. That said, if anyone knows where I can get some Peterson 7mm mag brass at I sure would appreciate it. Thank you all for your input. I am very new to this, started about a year ago, but it took me 6 months just to find projectiles, powder, and primers so I could get started. I'm loading for my Remington Model 7 predator in 22-250, and my Sako 7mm mag. It's going really well in the 22-250. Just shot my best group ever at .5in w/ an SD of 4.2 at 100yrds with 40gr Hornady Vmax, Staball match powder, and BR-2 primers. Now I just need to replicate that. Now I'm so disappointed that I ever bought a gun w/ a 1/14 twist, but I didn't know better back then. I have fell in love with this world of hand loading, I find it so fascinating. I'm looking forward to building a 6.5x47 in the near future, and will start loading 223 as soon as I can find a small base die set. I'm not sure what I would do without all of you sharing your hard earned knowledge on here.
No one mentioned the trick of seating the bullets long enough to engage the lands to keep the case head on the bolt face during fire so the brass would stretch from the shoulder area instead of in front of the belt. Take a couple of factory rounds and bull the bullets and reseat them so they are jambed in the lands. Shoot them a couple times and see if they go more than 3 firings. Either use your not hot load or back off the factory load 2-3 full grains for this.
Frank
Frank
I just went through this on my rifle. I completely went through everything and here is what i found among other thins
1-headspace was incorrect from when it was built - the rifle would easily close on the field gauge.
2- as @jepp2 mentions the cases will grow 016 or more. that combined with point 1 above made it even worse. that metal comes from somewhere - the head
As @Walt Krafft mentions the fix, in your case, is new brass. Take a look at Peterson brass belted mag long version. next problem is where to find it. That is a different story. it is made in 7mm and 300 mag versions.
Until the brass is in stock i have come to realize life will be limited and i need to be extra vigilant in looking for signs of separation. But higher quality brass will get you further.
Good luck
1-headspace was incorrect from when it was built - the rifle would easily close on the field gauge.
2- as @jepp2 mentions the cases will grow 016 or more. that combined with point 1 above made it even worse. that metal comes from somewhere - the head
As @Walt Krafft mentions the fix, in your case, is new brass. Take a look at Peterson brass belted mag long version. next problem is where to find it. That is a different story. it is made in 7mm and 300 mag versions.
Until the brass is in stock i have come to realize life will be limited and i need to be extra vigilant in looking for signs of separation. But higher quality brass will get you further.
Good luck
You should not be getting case head separation at all if you size the brass correctly.
Use your chamber to tell you the condition of the brass. Remove the firing pin from the bolt, and chamber the brass between incremental sizings in a full length die. When you get resistance in the last half inch of bolt travel, your brass is sized right.
If the bolt drops freely, you've bumped the should back too far, and you will get case head separation, no matter what headstamp your brass is.
You mention that you are bumping the should a particular amount, but you're not saying what your chamber thinks about your shoulder bump.
Right now, based on your description, if you chamber your sized brass with no firing pin in the bolt, it will drop closed with no resistance at all.
Make sure your trim length is within spec after sizing.
Use your chamber to tell you the condition of the brass. Remove the firing pin from the bolt, and chamber the brass between incremental sizings in a full length die. When you get resistance in the last half inch of bolt travel, your brass is sized right.
If the bolt drops freely, you've bumped the should back too far, and you will get case head separation, no matter what headstamp your brass is.
You mention that you are bumping the should a particular amount, but you're not saying what your chamber thinks about your shoulder bump.
Right now, based on your description, if you chamber your sized brass with no firing pin in the bolt, it will drop closed with no resistance at all.
Make sure your trim length is within spec after sizing.
46and2
Silver $$ Contributor
Yep.
This is a Hornady issue, not a general belted magnum issue.
I have Winchester 300wm brass with 7 firings. This brass grew .015 on first firing and has been bumped .002" each firing.
Now ADG is making 7mm RM brass. I'd suggest the OP get some of this top tier ADG brass .
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Peterson Brass 7mm Remington Mag Long Unprimed Box of 50 - Graf & Sons
All 50 count listings of Peterson Cartridge casings come in one of their plastic ammo boxes. Made in the U.S.A. Peterson Cartridge Co is committed to producing Match-Grade Brass that enables our customers to get more reloads per casing than industry average. Warning: Only use Peterson...
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This is the "long" brass
Just to add a further 2c ...
There is an opinion that because the case is belted, it headspaces on the belt. That is true.
After proper resizing, a belted case headspaces on the shoulder. If the shoulder is too far back, you get the same result as with any non-belted rifle case.
Addendum : assuming the case has a shoulder. Some belted magnums are straight.
There is an opinion that because the case is belted, it headspaces on the belt. That is true.
After proper resizing, a belted case headspaces on the shoulder. If the shoulder is too far back, you get the same result as with any non-belted rifle case.
Addendum : assuming the case has a shoulder. Some belted magnums are straight.
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Edd
Gold $$ Contributor
Selling: New Norma 300 WSM brass and Norma 7mm Rem Brass
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