Just wondering if you should go off the book for seating depth even if the jump is further than 40 thousands
Bullet seating depth
- Thread starter Tbrown3998
- Start date
Only if you dont know what youre doing.
Measure the lands via one of the many ways described all over this forum (cough wheeler method) and you can then disregard the book as youll actually know what youre working with rather than having to make it work universally like the book is for.
If that length is longer than your mag allows then go back to max mag length and start testing from there.
Measure the lands via one of the many ways described all over this forum (cough wheeler method) and you can then disregard the book as youll actually know what youre working with rather than having to make it work universally like the book is for.
If that length is longer than your mag allows then go back to max mag length and start testing from there.
Typically "book loads" are as generic as can be, a one-size-fits-all product.
If you're going to go through the trouble to load your own ammo, then you might as well figure out where your lands are and then start your "recipe" from there.
FWIW, the legacy thinking on bullet-seating depth doesn't apply so much these days, jam to 20 thou off isn't the only way to do it.
Many guys including myself who shoot PRS-style matches run a jump from 50 to 120 thou off the lands (which coincidentally usually puts one's case necks completely within a chosen bullet's bearing-surface) while getting groups ~.5" or under at 100, and staying .5 MOA or under out past 1000.
I like/recommend this for finding one's lands:
If you're going to go through the trouble to load your own ammo, then you might as well figure out where your lands are and then start your "recipe" from there.
FWIW, the legacy thinking on bullet-seating depth doesn't apply so much these days, jam to 20 thou off isn't the only way to do it.
Many guys including myself who shoot PRS-style matches run a jump from 50 to 120 thou off the lands (which coincidentally usually puts one's case necks completely within a chosen bullet's bearing-surface) while getting groups ~.5" or under at 100, and staying .5 MOA or under out past 1000.
I like/recommend this for finding one's lands:
Book length is listed to a SAAMI spec standard so your ammo fits in a factory rifle. You are free to go outside the spec so long as it’s safe. For example, if your chamber allows you to seat the bullet to 2.900” coal but SAAMI spec is 2.800” you can absolutely load to 2.900”. It might not fit in your mag. It might not leave enough bullet in the neck to stand up to cycling through the firearm. It might not produce optimum accuracy. But then again it might.
Don’t get stuck on having to be .020” off the lands or whatever people say it should be. Try different coals. Find the coal that works well for you.
Don’t get stuck on having to be .020” off the lands or whatever people say it should be. Try different coals. Find the coal that works well for you.
Your results will strongly depend on the context of the rifle and the bullet.
Some combinations have a strong response to seating depth, while others do not. The context really matters.
For example, hundreds of threads go into a swirl over how big/small each step in the search should be as well as where to start and where to stop. Often both sides of that argument are right, but because they fail to mention the context it turns into confusion.
The confusion is real because some combinations of bullets and guns are so forgiving to the point where one could say seating depth doesn't matter, while other context means it makes a big difference. Both results are real as are ones in between.
With a zero background, it can be hard to know how to get started and what to expect.
You can get better advice if you describe your context (bullet, chambering, rifle, etc.).
Here is a little nightstand reading. Check the links to the other posts too, not to mention several of the books and manuals.
https://precisionrifleblog.com/2020/04/05/bullet-jump-load-development-data/
I often put in a plug for a rookie to get a mentor. A search at the clubs or ranges that host competition is a good place to start.
You will make much faster, cheaper, safer progress with a mentor than doing this on your own. YMMV
Good Luck and play it safe.
Some combinations have a strong response to seating depth, while others do not. The context really matters.
For example, hundreds of threads go into a swirl over how big/small each step in the search should be as well as where to start and where to stop. Often both sides of that argument are right, but because they fail to mention the context it turns into confusion.
The confusion is real because some combinations of bullets and guns are so forgiving to the point where one could say seating depth doesn't matter, while other context means it makes a big difference. Both results are real as are ones in between.
With a zero background, it can be hard to know how to get started and what to expect.
You can get better advice if you describe your context (bullet, chambering, rifle, etc.).
Here is a little nightstand reading. Check the links to the other posts too, not to mention several of the books and manuals.
https://precisionrifleblog.com/2020/04/05/bullet-jump-load-development-data/
I often put in a plug for a rookie to get a mentor. A search at the clubs or ranges that host competition is a good place to start.
You will make much faster, cheaper, safer progress with a mentor than doing this on your own. YMMV
Good Luck and play it safe.
Last edited:
This^^^.
You can always go with the book length as that is what the load data is based on. For a beginner working with seating depth approaching the lands requires some understanding of cartridge overall length, cartridge base to ogive and having the tools and technique to accurately determine the CBTO ogive dimension. Also some commercial chambers will not allow seating depths approaching the lands. Remington 700 308 chambers are a case in point.
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