7remmag latter test.

[zr600]

Ok I want to do a latter test for my 7mag. My range only has out to 200 yards. I have a magneto speed so I was just going to use the numbers work up 1 at each powder charge and look for flatlines in velocity. Since I will have the chrono graph on the barrel do I even pay attention to the holes on paper or just use the numbers? I have shot up to 70g of returning with no pressure yet. I'm using 180vldh Berger's retumbo I have over 9lbs of it, and fed215m primers. Also is .5 g to much of a jump in powder charge? My buddy says he would only do .2 but that seems like a tiny jump for this large case. In my smaller cases like 308,243 I do .2 jumps. Any advice would be great.

 

[Blackhawk]

Ok I want to do a latter test for my 7mag. My range only has out to 200 yards. I have a magneto speed so I was just going to use the numbers work up 1 at each powder charge and look for flatlines in velocity. Since I will have the chrono graph on the barrel do I even pay attention to the holes on paper or just use the numbers? I have shot up to 70g of returning with no pressure yet. I'm using 180vldh Berger's retumbo I have over 9lbs of it, and fed215m primers. Also is .5 g to much of a jump in powder charge? My buddy says he would only do .2 but that seems like a tiny jump for this large case. In my smaller cases like 308,243 I do .2 jumps. Any advice would be great.

By paying attention during your ladder testing and while line graphing out you will notice that your nodes will even out once you find the optimum ES & SD numbers. You will also exhibit tighter numbers when that node has been reached.
Now by carefully monitoring your powder in 2/10th grain increments once you find that node it will become clear where it begins and where it ends.
Now it will take a little longer this way but once you have found and documented it on your graph (everything else being the same) there will be absolutely no doubts in your mind as to your optimum recipe.
I believe that this is called establishing load development, and I would take a little longer to determine my optimum settings now rather than get the dreaded "what if I only did this, or changed that later".
As the saying goes "If your gonna do it, remove all doubt and do it correctly the first time."
Just my 2 cents worth !

 

[zr600]

Where in the world do you find a powder dispenser that's is accurate to .0002? Or was that a typo and you meant .2?

 

[Jud96]

He most likely meant 0.2gr increments. When looking for velocity nodes with the Magnetospeed, I ignore accuracy. On sporter barrels I get erratic results with groups, so I just ignore it for the most part.

 

[Blackhawk]

Where in the world do you find a powder dispenser that's is accurate to .0002? Or was that a typo and you meant .2?

1 grain is = .0022 ounces & 1/10 grain will = .02 ounce
Unless I am incorrect almost every quality reloading digital scale will provide for a + - 1/10 grain accuracy.
However, Thank You for your response !

 

[zr600]

Well I use a Rcbs 1500 scale and dispenser it's accuracy is .1, .0002 I can even type into the dispenser to charge.

 

[TRG65]

Even with the large case I would still do .2 grain steps. I when I was loading 7, my loads were in the 66-68 grains range with retumbo. I think. I was only shooting 2950 from a 26" barrel with the 180, but it was accurate. If you do one set, and you think you can get more velocity, then just bump it up, or do a really large test. 66-70 in .2 increments.

I've started to really like the 6.5 guys spreadsheet. When I do velocity tests, I load 3 at each charge and use that spreadsheet.

 

[dok7mm]

May I suggest instead of shooting a ladder at your range's 200 yd limit, just shoot 3 shot groups at 100 yds with .3 gr increments. You won't have to deal with conditions at 200.

You can still get your velocities, SD & ES and you should see some targets that are good enough to work around.

 

[chev4x4s1975]

Zr600 ritch does .3 with his cartridges