A math question

[oremike]

If my dies are 14 threads to the inch then 1/4 turn is .0178 inches of movement, correct? My thought that I've done in the past is to start at whatever fits in the magazine and see if it chambers then push the bullet into contact with the lands and then turn the die down the 1/4 from there. Now that I've shot my benchmark load I'm wanting to make the load correct for this rifle with this bullet so feel that getting the OAL right is the next step before changing powders and charges. This is for my Savage 25-06 with the Lehigh 102gr Controled Chaos bullets. My Benchmark load was a mid-range powder charge seated to the factory OAL and shot a 3/4" group.

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[WillametteWill]

My math comes up with the same number as you.

 

[NobullSKS]

I'd say so

 

[BigGame]

I agree with the math, but a question on the method. If I understand right, you'll jam the bullet into the lands and then back off 1/4 turn (0.0178"). Keep in mind there is a difference between the "jam" point in the lands vs. the "touch" point. You can smash a bullet past the initial touch point to the point where it will no longer advance under pressure from the bolt.

Erik Cortina recommends this method to find your lands touch point, which he estimates is 0.020" shorter than the jam point. But one then measures jump from the touch point, not the jam point.

If I understand your method correctly, by backing off 0.0178" you're only getting back to the touch point (essentially touching the lands with no jump). That can cause pressure spikes and I would recommend caution, or backing off a bit more.

 

[oremike]

I agree with the math, but a question on the method. If I understand right, you'll jam the bullet into the lands and then back off 1/4 turn (0.0178"). Keep in mind there is a difference between the "jam" point in the lands vs. the "touch" point. You can smash a bullet past the initial touch point to the point where it will no longer advance under pressure from the bolt.

Erik Cortina recommends this method to find your lands touch point, which he estimates is 0.020" shorter than the jam point. But one then measures jump from the touch point, not the jam point.

If I understand your method correctly, by backing off 0.0178" you're only getting back to the touch point (essentially touching the lands with no jump). That can cause pressure spikes and I would recommend caution, or backing off a bit more.

I guess I should have been more clear I don't jam the bullet, I touch the bullet the to lands and move the bullet by seating deeper on the press.

 

[Hemlock]

Changing the die? Wouldn't you be changing the bullet seating stem?

 

[po18guy]

If you have the components, try several seating depths. Every rifle has a sweet spot. Some with land contact, some just short and some set back based on magazine and other considerations. However, if what you are using has that level of accuracy and no signs of pressure, SHOOT IT!

 

[thorborg]

For the nats azz to be fully recognized, you must embrace unavoidable tolerances, otherwise, .02 will do :
more play allowed the bolt than the nut.
And don't even get me started on creep, stress relaxation and embedding of the threads

 

[Mikej]

For the nats azz to be fully recognized, you must embrace unavoidable tolerances, otherwise, .02 will do :
View attachment 1771273more play allowed the bolt than the nut.
And don't even get me started on creep, stress relaxation and embedding of the threads

Ooof! Sounds like SEX talk to me!

Good thing there were pictures is all I can say!

 

[dangerranger60]

Is this a load for your rifle or one for use in any rifle? I have gotten good results with 20 thousands off the rifling with lead core/ copper jacketed bullets. But when I had to go to solid copper I got poor accuracy until I moved that bullet back to closer to 80 thousands.
This was 10 years ago, Have the bullets changed to make them shoot better up close to the rifling? Or have they learned to make a better bullet? DR

 

[oremike]

Changing the die? Wouldn't you be changing the bullet seating stem?

Good catch, you are correct I'm not adjusting the die. I'm using the Lee dead length seater so adjusting the knob on top. I wonder what those threads are. I was trying to avoid the adjust and measure, wash rinse and repeat method to get close.

 

[Mark W.]

Set up a EMPTY case with a slightly loose neck so you can easily push a bullet into it with your thumb. Then seat the bullet long so that as you slowly load the chamber the contact with the lands will push the bullet back into the case. Then when you extract the round you should have the OAL adjust to that for your loads. You can use a second dummy round to double check the bullet is no longer touching the lands.

 

[toast]

You're essentially making a poor man's non-precision micrometer. You'll get (slightly) different measurements when moving the threads tighter vs. looser. Always back the thread off and then tighten back up to produce better repeatability. This will eliminate one of the tolerance/play issues by forcing the bearing surface to always be on the same side of the thread.

It works on a Bridgeport mill, and it works on a 20 cent bolt from Lowes.

Else, buy the proper micrometer from Starrett.

 

[oremike]

Is this a load for your rifle or one for use in any rifle? I have gotten good results with 20 thousands off the rifling with lead core/ copper jacketed bullets. But when I had to go to solid copper I got poor accuracy until I moved that bullet back to closer to 80 thousands.
This was 10 years ago, Have the bullets changed to make them shoot better up close to the rifling? Or have they learned to make a better bullet? DR

This is for my rifle only and my first run at using these bullets. So I'm trying it figure it out as I go. I've already made my benchmark load with a middle of the data powder charge seated to Lehigh specs and will use that as a reference point for comparisons.

 

[jbett98]

All this math makes my head hurt.

 

[Stomper]

NERDS!!

 

[Flopsweat]

All this math makes my head hurt.

 

[dangerranger60]

This is for my rifle only and my first run at using these bullets. So I'm trying it figure it out as I go. I've already made my benchmark load with a middle of the data powder charge seated to Lehigh specs and will use that as a reference point for comparisons.

When CA went lead free, I went through this. Barnes was the only bullet to be had. I got very erratic results until I read that they needed more jump to get the harder copper bullets started down the bore. My extreme spread kept dropping until I got about 70 thousands off the rifling.
I'm still using the same bullet and load. But a call to Lehigh might help, DR

 

[gmerkt]

When CA went lead free, I went through this. Barnes was the only bullet to be had. I got very erratic results until I read that they needed more jump to get the harder copper bullets started down the bore. My extreme spread kept dropping until I got about 70 thousands off the rifling.

Thanks for the tip. I've been experimenting with lead-free bullets here for several years. I'm getting ready for the inevitable. But mostly with handgun bullets so far. Your information re. bullet jump needed for copper solids may save me some valuable bullets in experimentation.

In the rifle category, I've done more experimentation with frangible bullets in .223. Various types.

Last weekend, I fired some experimental loads that utilized a LeHigh Extreme Defense bullet in 9mm Luger. I don't ordinary notice much difference in pistol load accuracy, but the copper solids were markedly more accurate.