Seating depths What difference does it make ?

[Worker]

Ok we all know how critical seating depths can be with various bullets ,small changes can make tremendous difference in accuracy. My question is why ? If you could fire a rifle and freeze the bullet as it exits the muzzle what distinction will be noticeable on the jacket ? If its jammed into refiling will the jacket be visibly distorted or if its seated as to jump into rifling will it be scar less ? Isn't the bullet swagged to new dimensions during its journey down the bore ? How does the bullet know how deep it was seated ? How does it affect accuracy ? I guess what I'm asking is
What the HELL " ?

 

[Dusty Stevens]

More jump without resistance creates different pressures

 

[mwezell]

More jump without resistance creates different pressures

..and thus, different harmonics, and exit times.

 

[Wilbur]

Nobody actually knows but a rifle will shoot a little better if you experiment with the seating depth. What I'm trying to say here is knowing why doesn't matter in the slightest.....you'll always need to find the best seating depth.

Yes, I know, I know...but give what I wrote some thought and apply it to other items as well. Life's too short to ponder things that you can't change.

 

[shootsteady]

"A Rifle"

Nobody actually knows but a rifle will shoot a little better if you experiment with the seating depth. What I'm trying to say here is knowing why doesn't matter in the slightest.....you'll always need to find the best seating depth.

Yes, I know, I know...but give what I wrote some thought and apply it to other items as well. Life's too short to ponder things that you can't change.

a rifle

Not just any rifle.... but a custom built, target rifle, or a high quality factory rifle. It's a complete waste of time on a standard lowend factory rifle. Considering this a bench rest site, would mean that guys here have high end well built rifles correct?

Weatherby Mark V's shoot extremely well with set factory ammunition COAL...

 

[Wilbur]

I was under the assumption that we were talking reloads....and, that seating depth plays a small part of any reload. I would say that if a rifle is shooting an inch at 100yds with the best and a bit over an inch with the worst....then it really doesn't matter. If the rifle is shooting an inch and goes to an inch and a half, then seating depth might keep you on that coke can with the wind blowing.

That out of the way, a hundred years ago, I said to my friend - "Bring that 270 over and we'll find a load for it". Turns out that it would shoot factory rounds (don't remember which) into a much smaller group than anything I could load. I had a lot of stuff and couldn't even come close. I was embarrassed at the time but the lesson stuck hard.

Then, there was that young fellow shooting smaller three shot groups with a Savage .308 than I was with my new benchrest barrel......but y'all get the picture....

 

[Bob Blaine]

Mike has it nailed. One of the best ways to relate as to why we adjust bullet seating depth for our rifles is to think of your barrel as a big tuning fork, and the bullet is the moving weight. When we move the bullet seating depth we are actually tuning for the barrel vibration the same way that you move the weight on the tuning fork to change the tone. You also need to keep in mind that the muzzle is not only vibrating up and down but radially when the round is fired. This will set up a star pattern at the muzzle and our goal is to get the bullet to exit the barrel at one of these "points" the same way every time. The barrel is not to concerned which one that we work with as long as we are consistent with one of the points for when the bullet will exit the muzzle. This means that you could have several potential jump points available to you with your barrel and the only way that you will find any of them is by jump testing your bullets with your barrel.

We have a bullet jump testing article that Eric Stecker has written primarily for use with our line of VLD bullets, but it is just as applicable for any other bullet design. You might want to change the seating depth jumps for a B/R rifle, but always keep in mind that the principles of the physics involved are always the same for the goal of improving accuracy for your rifle. If you would like a copy of Eric's article you can e-mail me directly at bob.blaine@bergerbullets.com and I will happy to forward a copy of it to you.

Bob Blaine

 

[muley]

Mr. Blaine nails it

Mike has it nailed. One of the best ways to relate as to why we adjust bullet seating depth for our rifles is to think of your barrel as a big tuning fork, and the bullet is the moving weight. When we move the bullet seating depth we are actually tuning for the barrel vibration the same way that you move the weight on the tuning fork to change the tone. You also need to keep in mind that the muzzle is not only vibrating up and down but radially when the round is fired. This will set up a star pattern at the muzzle and our goal is to get the bullet to exit the barrel at one of these "points" the same way every time. The barrel is not to concerned which one that we work with as long as we are consistent with one of the points for when the bullet will exit the muzzle. This means that you could have several potential jump points available to you with your barrel and the only way that you will find any of them is by jump testing your bullets with your barrel.

We have a bullet jump testing article that Eric Stecker has written primarily for use with our line of VLD bullets, but it is just as applicable for any other bullet design. You might want to change the seating depth jumps for a B/R rifle, but always keep in mind that the principles of the physics involved are always the same for the goal of improving accuracy for your rifle. If you would like a copy of Eric's article you can e-mail me directly at bob.blaine@bergerbullets.com and I will happy to forward a copy of it to you.

Bob Blaine

Haven't posted in a while, so it's nice being back. I think Mr. Blaine has summed it up. It all has to do with timing bbl harmonics. For ppl who don't shoot non-magazine BR guns, there is one limiting factor re OCL and that is magazine length, assuming you aren't just single loading rounds, so regardless of how close to the lands your sweet spot is, if he OCL is longer than the mag length then its pretty much all for naught.