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What yardage for load testing?

 
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  #1  
Old 07-01-2012, 08:57 PM
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What yardage for load testing?

At what yardage do you guys test new loads for long range shooting? I have always tested at 100 yards but after get a .308 to go out farther, I started testing at 200 for thought that the 175 SMk may need more range to stablize to get a better veiw of what's going on out there. I read recently that temp., barometeric pressure, and wind can mess with your results at 200. I can see the wind maybe with a lighter bullet.

So what do you do?

Jason
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  #2  
Old 07-01-2012, 09:23 PM
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Re: What yardage for load testing?

I do the initial load testing at 100 and try to get the smallest groups I can then I move out and see how the loads go at longer ranges .
I just find that it's too hard to see slight accuracy changes at long range that can only be atributed to the load tweaking and not sudden wind changes .
It is quite practical to have some wind flags up all the way to 100 but not very practical to have wind flags all the way to 300 or 500 .
With good scopes you could do initial testing at 200 no problem if you wanted .
Wether the 175 SMK is more stable at 200 compared to 100 I can't really say , you would have to test your setup and see.
I think you may save ammo by starting at 100 first and when you get a nice tight group going then test at 200 and tweak some more if need be .
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Old 07-02-2012, 06:49 AM
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Re: What yardage for load testing?

Bullet Bumper,
Thank you for the reply. I do know that I have had some really tight groups at 100 yards but opened up when I go out further.

Jason
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Old 07-02-2012, 08:13 AM
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Re: What yardage for load testing?

Quote:
Originally Posted by cornchuck View Post
Bullet Bumper,
Thank you for the reply. I do know that I have had some really tight groups at 100 yards but opened up when I go out further.

Jason
Hi, Jason I am pretty new to the LR shooting but I have just recently started down the same road that you are going down. I was told by some experienced shooters from this very site , to start at 200 yards as the bullet will start showing you what it will do on out further . I have developed at 100 yards for several years and to be honest I thought "thats the crazyiest thing ive ever heard !" but it is true or at least when I started doing this my group at 300 was very small and then I shot at 752 yards and it was around 2 1/2 " center to center for three shots. I figure not to bad for a newbe... To break it down a little more my 200 yard 3 shot group you could barely cover with a dime. Then at 333 yards the 3 shot group measured .613 then I tried my first ever 752 yard 3 shot group and it was really just a hair under 2 1/2 " .

Hope this helps and good luck shooting.

P.s Broz knows his stuff and is very nice and polite . I would read all of his info that I could . It has definatly helped me.
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  #5  
Old 07-02-2012, 02:38 PM
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Re: What yardage for load testing?

Until someone proves that bullets at the outer edges of their combined trajectory paths know both where they are compared to all other bullets fired at some short range point and what direction to change to so they head back towards the point of aim at some long range, I think it's best to know that groups open up about 10% for each 100 yards down range after the first one hundered yards for front locking bolt action rifles. Positive compensation from vertical barrel whip (such as what happens with the British SMLE's) excepted. There's three things that cause that; muzzle velocity spread, a tiny spread in BC (all bullets ain't perfectly balanced) and subtle air currents.

Groups with only 3 shots are not significant enough to represent where all the shots fired will go. Good way to tell if you're shooting enough shots per test group for them to be meaningful at a given range is when all of several groups are within 10% of the same size.

All bullets are pretty well stabilized by they time they reach 100 yards. Shoot 20-shot test groups. Do it in calm conditions so the results will be meaningful. Temperature and barometric pressure don't effect accuracy as both are typically constant for a string of shots.

Note that a .308 Win. with a 50 fps muzzle velocity spread may have only 1/10th inch of vertical shot stringing at 100 yards due to velocity differences. At 1000 yards, that much velocity spread will cause a 20 inch vertical spread in bullet impact.
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Old 07-02-2012, 07:30 PM
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Re: What yardage for load testing?

Quote:
Originally Posted by cornchuck View Post
Bullet Bumper,
Thank you for the reply. I do know that I have had some really tight groups at 100 yards but opened up when I go out further.

Jason
I know what you are saying but how do you know what is making the groups open at 200 as compared to 100 ? Is it extra wind you can't read or shooter error etc.
All long range loads need to be proven at the ranges they will be used at and some that shoot well at 100 or 200 may be no good at some longer range sometimes due to lost velocity and going subsonic .
100 is just the starting point and I find I can see and aim better and wind variables are reduced at the closer range as I have flags out to 100 . I try for the best 100 yard groups with enough velocity to stay super sonic at the range I want or as far as I can get .
I just find it is way more convenient to start work at 100 when a chronograph is also being used .
You also want a low velocity spread as Bart B has mentioined I get the best group I can at the best velocity with the least velocity spread.
There is no rules and no right or wrong as far as what range you develop a load at , it is a personal choice .
Another thing I found was that at 200 walking back and fourth up a hill every time I wanted to retrieve targets and measure groups after a few times fatigue was becoming another accuracy issue that opened groups. If you are young an fit then it may not matter but at my age with my war injury it does. It's a personal choice .
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  #7  
Old 07-02-2012, 07:48 PM
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Join Date: Sep 2009
Location: Northwest Ohio
Posts: 223
Re: What yardage for load testing?

Thanks for all information given. After thinking more about, I will stick with the 200 yard mark when trying new loads. It may help me get better prepared for shooting at longer ranges.

Keep the advice coming.

Jason

P.s. I have always enjoyed reading what Broz has to say.
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