Pressure signs in a 7mm magnum

Those primers look too flat for my comfort. I don't think your rifle likes RL22. I use IMR7828 for magnum rifles, and have not experienced pressure signs.

Also, are you trimming with a Lee trimmer? They are cheap and a good way to trim your brass back to minimum. Cause if your necks are too long they can bind in the throat and drastically increase pressure.

Jimro
 
Having trouble extracting is a sign of excessive pressure. I shot 50 rnds of Milsurp and had troubles extracting the cases (had to pound them out),after getting them out most of them had blown primers and this was in a 7mm Mauser. I use IMR 4350 with 58gr. behind Speer 145gr.SPBT bullets, this gives me a very accurate load for deer with no extraction or cratering issues.:) (this is what I load for my 7mm Rem Mag)
 
RTB, not trying to preach, just astonished that you've loaded that long without the understanding of case head measurement as a sign of pressure. With Magnum cartridges, it's common for some primer flattening. Measuring the 7mm RM case head (just above the belt) showing .0005 greater than factory spec is maximum. The factory measurement for the rim is .532 and the head is .512, so .5125 is the limit. Add 9 and 10 to your list. 9 is a Franklin Arsenal Electronic Caliper for a $22 at Midway. 10 would be a Nosler Reloading Manual.
 
I began reloading for 7mag in1975 and have reloaded for several other mags since then. I learned way back then that the 7mag stretches brass worse than anything else that I have loaded for.

If you are not measuring and trimming brass to the right length, the brass, especiallly on a hot load, can intrude into the chamber raising pressures considerably.

Because someone else has safely used loads five gr higher doesn't mean that it will be safe in your rifle. MDL 70's are very strong design and should handle higher pressures, but the components may not. There can be considerable variance from a chamber in one rifle and a chamber in another.

A good caliper and trim die or good trimmer are essential for anyone that reloads. Also, how well are you crimping? There are many details that can effect pressures, that you need to be aware of. Someone mentioned a Nosler manual earlier, I recommend that, or Speer manual, or Hornaday reloading manuals all give great info on these subjects. All of them say sternly" always look for signs of excessive pressure" 61gr RL 22 may be all your rifle will allow..
 
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OP,I just reread your post.I had assumed your black soot was at the primer pocket.Now I wonder if perhaps you have a partial case head separation.That would be very likely at some point in the late life of 7mm mag brass.It is potentially dangerous ,as an intact brass is what keeps the gas out of your face,even at safe pressures.I highly recommend you take one of those cases,split it lengthwise with a hacksaw,exacto knife the burrs off,and study the wall thickness just forward the belt.I suspect you will find an internal stretch ring,pronounced,where the brass is very thin.Tell us what you find,and we can talk about it.Once again,this is common,and can be dangerous
 
but how does a laymen without gauges measure headspace and how do you measure COL?
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Without a micrometer you can't measure headspace, but your rifle will tell you what it likes.

For example, I have one .30-06 rifle, a Savage, that likes a 150 grain bullet and RL19 powder. However the load it likes best acts like it's toying with high pressure, but in the charts it's a mid-range load. Great velocity, magnificent accuracy, but the bolt starts to get a little sticky and the primers are flattened. So, in my rifle that's as high as I'm going with that particular combination.

Every reloader needs a caliper. They're fairly inexpensive for a digital and even an inexpensive one will help you tremendously.

COL is fairly easy to find in a particular rifle. Using your rifle, your brass and your bullet, take a hacksaw and cut a slit down the neck. Seat a bullet long in that empty cartridge, color that bullet liberally with a felt-tip marker and chamber it. Then extract it gently, taking care to not leave the bullet in the throat. You should see marks where the bullet touched the rifling or throat of the barrel. That's the "jammed" length. Seat the bullet 0.010 shorter than that.

Different bullets have different ogive profiles, so if you change bullets you'll need to repeat the process, but the process above will give you a starting point and show how long you should load your ammo.
 
I'm set to try some shooting with my 7mm magnum this weekend. using only 60 gr RL22 and an OAL of 3.31 (previously 3.60) All cases were trimmed back to 2.5" (most were substantially longer!) I'm betting some of my severe pressure signs diminish. Thanks everybody for the instruction. I have been reloading a long time but apparently, not correctly. In the times acomin' we might have to reload to get our ammo.
 
I tried getting close to the lands with the bullet vs. normal length listed in the data sheets. I ran a long test comparing different loads and powders. No improvement in accuracy by getting the bullet closer to the lands. The bullet used was critical and the right powder. Seat them to the book and you'll be better off pressure wise.

I can't remember the rule of thumb but you only trim the case so many times before pitching the brass. I think I only trimmed it twice and dumped it. And I kept the brass in marked locations so I knew how many times I trimmed it.
 
did some shooting today. no problems, no pressure signs, no extraction difficulties. You guys are a digital seminar. Problem was case length too long and improper seating. As far as I am concerned it's a closed case. Great rifle, great round, and now its off to another project.
 
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