Bullet seating depth

Ucsdryder

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Jan 24, 2015
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Almost all of the info regarding seating depth refers to seating in relation to the lands. Assuming you can adjust the lands to fit your seating depth, where would you seat the bullet? Is the “optimal” position to seat the bullet (where the boat tail drops off) right where the neck meets the shoulder? Assuming you’ll want to fine tune seating depth from there, that allows you to seat a little deeper into the case without taking up too much powder space, or seat shallower into the neck to get a little extra COAL. Does that make sense? I’m sending the bullet along with the gun to have it throated off the oal of the dummy round I’m sending in. It’ll be throated .020” off the lands.
 

peterk123

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You probably know everything I am about to say. Seating deeper increases pressure, so better know what you are doing. Going in the opposite direction has the opposite effect; to a point. Jamming a bullet into the lands could have ill effect I think, meaning pressure issues. Then there is bullet jump. I forget which bullet manufacturer tested for this but do a search and you will find it. Having some gap so the bullet can "jump" can have a positive affect. Then there are the limitations of your magazine. My tikka 308, will not allow me to put a cartridge in there that will touch the lands. It's trial and error as far as I am concerned. Go to the range and play around. Just be safe. That is the great thing about reloading.
 
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Ucsdryder

Ucsdryder

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You probably know everything I am about to say. Seating deeper increases pressure, so better know what you are doing. Going in the opposite direction has the opposite effect; to a point. Jamming a bullet into the lands could have ill effect I think, meaning pressure issues. Then there is bullet jump. I forget which bullet manufacturer tested for this but do a search and you will find it. Having some gap so the bullet can "jump" can have a positive affect. Then there are the limitations of your magazine. My tikka 308, will not allow me to put a cartridge in there that will touch the lands. It's trial and error as far as I am concerned. Go to the range and play around. Just be safe. That is the great thing about reloading.

mag length shouldn’t be an issue. 7saum in a long action. I agree with playing around, but I need to send in a dummy round to have it throated . I guess what I’m asking is what’s the “middle” ground where I’ll have the most ability to fine tune depending on where the bullet likes to be in relation to the lands, and what bullet I am using based on bearing surface.
 

Rob5589

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Generally, you want the bearing surface above the neck/shoulder junction. I would send my dummy round in with the bullet slightly above that so I would have a little play each direction, as rec'd by my gunsmith. Your smith should have some rec's as well.
 

Harvey_NW

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Awesome article with input from some of the highest accredited shooters and data collectors. Also kind of defies a lot of precision reloading theories, at least in terms of hunters wanting to develop very accurate, consistent, and forgiving load.

 
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I built my 6.5 PRC in a long action and had the chamber built to my dummy round to take advantage of the long action. I am shooting 156gr Bergers and have .280 thou of bearing surface in the neck of the case and then had the lands set 0.015 off of this dummy round.
 
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I hunt exclusively with monolithic bullets, which typically shoot best with a relatively big jump.
Barnes recommends seating .050" - .150" jump. With my rifles 0.40"-0.80" is best for monolithic bullets.
 
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Ucsdryder

Ucsdryder

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Thanks for the replies. I called Berger and they confirmed that the “optimal” seating depth would be where the shoulder/neck meet. Putting the start of the boat tail here gives room to move the bullet deeper or shallower. Thanks everyone.
 
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