i have been working on some loads for my 7mm mag. I am pushing 150 gr eld-x bullets. I had my loads narrowed down to two powders by group and had a previous test with one powder on the cronograph. My powders where Vihtavuori n-160 and it 4350. My previous test was with 63 gr of one 4350 hornady neck sized cases and federal primers. I got a 3020 FPS average. I was visiting with a trusted friend and he suggested ditching the hornady brass and using nosler custom grade brass. So bought a box and loaded them up. One set of five with the 63 gr 4350 and 64 gr of the n-160. I wanted to compare the two velocities to choose my load. I got 2910 FPS average with the 4350 this time. And about the same with the n-160. Can not figure out why my velocities dropped so much after already being less than the book. The only thing I can think of is the nosler brass and it is full length resized from factory. Is this why? Does anyone else have any ideas? By the way my rifle is a 1in 9.5 twist and it measures 24.5 ". Like the book uses
Velocity troubles with 7mm mag
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eshorebwhntr
Well-Known Member
New brass forming to your chamber absorbs, for lack of a better word, some of the energy. So you went from the extremes in neck sized to new brass. The intermediate step there would have been full length sizing. New brass is actually 'smaller' than full length resized.
If you now only neck size that nosler I bet they'll jump back up. Still may be different from the Hornady so you'll have to check.
As a general rule of thumb you should always work up your load in whatever brass you intend to use. Taking load data developed from one brass manufacturer and simply applying it to another manufacturer can cause issues. The least of which would be bad accuracy. The worst would be over pressuring with a top end load and damaging your brass or something else. I also recommend FL resizing on everything. I know some will say not to bc of the belt on the 7RM but I've got one lot of Winchester brass that I've reloaded 16 times and never had a case head separate.
Don't feel bad...i learned this same lesson the hard way when I started reloading.
If you now only neck size that nosler I bet they'll jump back up. Still may be different from the Hornady so you'll have to check.
As a general rule of thumb you should always work up your load in whatever brass you intend to use. Taking load data developed from one brass manufacturer and simply applying it to another manufacturer can cause issues. The least of which would be bad accuracy. The worst would be over pressuring with a top end load and damaging your brass or something else. I also recommend FL resizing on everything. I know some will say not to bc of the belt on the 7RM but I've got one lot of Winchester brass that I've reloaded 16 times and never had a case head separate.
Don't feel bad...i learned this same lesson the hard way when I started reloading.
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Thanks for the input. I was assuming the difference had a volume issue but never gave thought to the stretching issue makes sense. I was planning on using the hornady brass because it's what I had only switched by suggestion to try to close the difference in feet per second from one load to the next.
thatguyshm
Well-Known Member
I've never heard the brass absorbing that much energy that new brass has significantly lower velocity. In my personal experience, I've had new brass provide higher velocities due to a smaller combustion chamber, then have to had a few tenths of a grain of powder to get back to my velocity window.
That being said, I've changed brass manufactorers before and had significantly different velocities due to the same thing. Some brass is thicker less internal capacity, higher pressures which mean higher velocity. I'd take the two cases in question, sized however they will be for firing and put a spent primer in them. Then weigh and fill with water until flush with the mouth of the case, weigh again, and it will give you your case capacity in water. I wouldn't be surprised to find your new Nosler cases to have more case capacity, so it will take a bit more powder to get the pressures back up.
That's why it's important to always start load development over when you change components. Imagine if you had started with the Nosler and gotten a good load, then went to the Hornady with the same load. It could have been dangerously over pressure.
Most of my 7mm RM cases from Nosler weigh in around 234gr over all weight. I don't have my notes in front of me right now so I can't tell you H2O measurements but they are more than WW brass I have laying around. The WW stuff weighs in anywhere between 213-240gr, so that stuff gets weight sorted to 10gr groups for close range hunting stuff I may lose. For precision, it's all Nosler brass, berger 180 HVLD.
That being said, I've changed brass manufactorers before and had significantly different velocities due to the same thing. Some brass is thicker less internal capacity, higher pressures which mean higher velocity. I'd take the two cases in question, sized however they will be for firing and put a spent primer in them. Then weigh and fill with water until flush with the mouth of the case, weigh again, and it will give you your case capacity in water. I wouldn't be surprised to find your new Nosler cases to have more case capacity, so it will take a bit more powder to get the pressures back up.
That's why it's important to always start load development over when you change components. Imagine if you had started with the Nosler and gotten a good load, then went to the Hornady with the same load. It could have been dangerously over pressure.
Most of my 7mm RM cases from Nosler weigh in around 234gr over all weight. I don't have my notes in front of me right now so I can't tell you H2O measurements but they are more than WW brass I have laying around. The WW stuff weighs in anywhere between 213-240gr, so that stuff gets weight sorted to 10gr groups for close range hunting stuff I may lose. For precision, it's all Nosler brass, berger 180 HVLD.
thatguyshm
Well-Known Member
When you use a 380 load in a 9mm, it's a mouse fart load. Pressures go way down. Same kind of thing. Same amount of fuel goes into a larger combustion chamber the pressures will lower.
That example is exaggerated to make it easier to understand the difference.
That example is exaggerated to make it easier to understand the difference.
eshorebwhntr
Well-Known Member
That's odd. Whenever I develop a load with new brass I typically have to back down a few tenths to get it right with 1x fired.
eshorebwhntr
Well-Known Member
Did a little reading. Seems like broz saw the same thing new vs 1x...after fire formed velocity jumped significantly with same charge.
https://www.longrangehunting.com/threads/accuracy-loss-in-fired-brass-30-nosler.185945/
https://www.longrangehunting.com/threads/accuracy-loss-in-fired-brass-30-nosler.185945/
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I'm going to throw one of each in the once fired brass and try on the chrono I will post my resaults tonight. Also going to water weigh each shot and neck sized case for comparison will also post that. Will get some further input after I am sure, And look forward to, for this a learning experience for me.
eshorebwhntr
Well-Known Member
You're on the right track now...collecting your data, taking notes, learning. That's the name of the game my friend.
Let us know what you find.
Let us know what you find.
Ok so here is my test I only did one she'll of each. Wish I had done more to see an average. But any way
63 gr into 4350 federal 215 primer 150 gr elf-x
New nosler custom brass never fired. Water weight of 83.4 gr. And a velocity of 2993 FPS
Nosler 1x fired neck sized water weight 85.8 gr and a velocity of 3060 FPS
Hornady 2x neck sized water weight of 84.2 gr and a velocity of 3055.
All of my velocities where a bit on high side compared to my first chrono test with hornady brass running 3030 FPS.
Still not sure why the speed was so far off the other day but I am more satisfied today. I guess I need to load up five more of my n160 and 4350 and give it another try.
I like the idea of logging all this about the load. Had not wrote every detail down that maticulasly. After this experience I don't see how anyone can reload and not use a chronograph
63 gr into 4350 federal 215 primer 150 gr elf-x
New nosler custom brass never fired. Water weight of 83.4 gr. And a velocity of 2993 FPS
Nosler 1x fired neck sized water weight 85.8 gr and a velocity of 3060 FPS
Hornady 2x neck sized water weight of 84.2 gr and a velocity of 3055.
All of my velocities where a bit on high side compared to my first chrono test with hornady brass running 3030 FPS.
Still not sure why the speed was so far off the other day but I am more satisfied today. I guess I need to load up five more of my n160 and 4350 and give it another try.
I like the idea of logging all this about the load. Had not wrote every detail down that maticulasly. After this experience I don't see how anyone can reload and not use a chronograph
eshorebwhntr
Well-Known Member
There you go. Good job.
Consider FL sizing every time in my opinion. Nosler is good stuff quality wise. I've seen its not all that tough so don't push it hard and it should last you a few firings.
Consider FL sizing every time in my opinion. Nosler is good stuff quality wise. I've seen its not all that tough so don't push it hard and it should last you a few firings.
eshorebwhntr
Well-Known Member
There you go. Good job.
Consider FL sizing every time in my opinion. Nosler is good stuff quality wise. I've seen its not all that tough so don't push it hard and it should last you a few firings.
Consider FL sizing every time in my opinion. Nosler is good stuff quality wise. I've seen its not all that tough so don't push it hard and it should last you a few firings.
