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Normal Topic Bullet jump for load development (Read 1047 times)
ted6.5
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Bullet jump for load development
Aug 9th, 2019 at 7:02am
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Hi All

I am about to start testing projectiles for a 280AI (Sierra Tgk 165, Eld-x 162, Berger VLD 168) and have measured case length to land by neck sizing a case enough to grip the projectile but allow it to move when chambered. Did lots of test per projectile to get an average.

My reading on the www indicates that this average in fact represents 20 thou into the lands. I understand that he type of projectiles I am using prefer a jump. So I am considering pulling them back 40 thou which should give a jump of aprox 20 thou. Does this sound about right?

My aim is to settle on a reliably accurate load for hunting to ranges of 500m.

Cheers

Ted
  

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ChrisHB
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Re: Bullet jump for load development
Reply #1 - Aug 9th, 2019 at 7:13am
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It largely depends on the bullet profile. VLDs on -average- seem to like jam or at least minimal jump but only your load/rifle combo will confirm that. I personally would be starting short and working back only if needed.

The other issue is the risk of leaving a jammed projectile behind when unloading a live chambered round. Last thing you need while hunting..
  
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JaSa
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Re: Bullet jump for load development
Reply #2 - Aug 9th, 2019 at 5:26pm
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Depends on rifle, projectile and load.
For my 223 loads I have jumps from 0.050 to 0.125 and everything in between. For the 6.5CM with the 143gr ELD-X I have a 0.054 jump.
Don't see the point of jamming a bullet into the lands for a hunting rifle for reason mentioned by ChrisHB.

Personally I would start with a jump of 0.050 and find a good load first. After that you can play with seating depth to fine tune things.

Another thing to consider is how long can you load so bullets will still fit your magazine?
  
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10-Ring
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Re: Bullet jump for load development
Reply #3 - Aug 10th, 2019 at 9:45am
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If your bullet is .020 into the lands using the method you're using to determine base to ogive length then it's more than likely you've sized the neck portion too much. Every rifle is different and some rifle lands will grip the bullet more than another rifle and pull out the bullet out slightly when extracting the test case. I've never found that method to work very well. A split in the neck works better I.M.O.

The best system I've found is the Hornady Lock-N-Load® O.A.L. Gauge using a modified case fired in your rifle. It's a hassle to make the modified case to fit the gauge though. Still the generic cases you can buy for the gauge work reasonable well depending on the headspace of your rifle.

There are also other methods that you can use.

You could try this method which is similar to what you're using.

https://www.rodandrifle.co.nz/bullet-seating-depth.html

  

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Re: Bullet jump for load development
Reply #4 - Aug 11th, 2019 at 7:03am
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Thanks for the replies guys.
  

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