Is 'jump' the same as freebore?

[Axle2010]

Hey guys as you know I'm just starting to reload, I'm watching Erik Cortinas videos on chasing the lands and he's calling his 3 versions of seating depth "jump, in the lands, and jam". So if jump is not touching the lands isn't that the same as freebore or am I not understanding freebore?

 

[Papa72]

I have heard the terms used interchangeably. My benchrest friends seem to prefer jump while this long time handloader says freebore.

 

[Joker12]

Yes, they are the same.

 

[Hogpatrol]

Freebore is the straight cylindrical part of the chamber after the end of the neck and before the lands/lead angle start.
For the .223 & 5.56

 

[Axle2010]

OK thanks guys I was getting confused as they sounded like the same thing. So next confusion, if distance from the lands don't matter then why does seating depth matter? Isn't the point of changing your seating depth all about changing the distance from the lands to the ogive?

 

[Hogpatrol]

To answer your question, yes, seating depth is just one variable in reloading that can affect accuracy. Having said that, I'm curious, do you have a reloading book? Some of the bullet manufacturers like Berger, Hornady, Sierra and Nosler publish them in print with extensive information on reloading techniques and their ramifications. Lyman is a good one for beginners. Sierra has a good phone app with most of it's print info included.

 

[BourbonTrail]

Freebore (chamber to rifling start) & bullet jump (ogive to the lands) matters in accuracy and pressure curve (i.e. Weatherby rifles have large freebore to reduce the max pressure and increase velocity).

This is a good demonstration of the benefits of tuning freebore:

More Bullet Jump Research!

This is the 4th article in a series on some new research on bullet jumps. Here is a recap of the pr...

precisionrifleblog.com

Good explanation of terms:

Bullet Jump & Seating Depth: Best Practices & Conventional Wisdom

With so many events canceled and stores closed, what a great time to do some reloading! Over the pa...

precisionrifleblog.com

 

[JimP]

When you first start loading on your own, follow the manuals advise. Just about every bullet and powder manufacture out there publishes a book on loads for their components. I have around a dozen manuals sitting on my book shelf. In these manuals they will walk you through the loading process to the point that you can load safe loads and ones that will go bang every time that you pull the trigger.

Don't get caught up on freebore or bullet jump yet. Just follow the practice of putting together safe ammo. Then after you feel confident in your loads you can start changing things around.

Just as a example I have some loads that will shoot sub 1/2 moa at 200 yards. If I change the seating depth of the load it can either go up or down. With my best load for that round you can pull the bullet out of the loaded case with your fingers and it comes as close to touching the rifling of the rifle as it can without actually getting stuck in them when I remove the loaded round. It is totally impractical to load this one sine you can't even place the loaded round into a box without the bullet coming loose.

 

[Axle2010]

To answer your question, yes, seating depth is just one variable in reloading that can affect accuracy. Having said that, I'm curious, do you have a reloading book? Some of the bullet manufacturers like Berger, Hornady, Sierra and Nosler publish them in print with extensive information on reloading techniques and their ramifications. Lyman is a good one for beginners. Sierra has a good phone app with most of it's print info included.

I have the Nosler Lyman and Hornady books and one specifically for AR's. I ask questions to hear from experienced reloaders that have "been there done that".

 

[Firebird]

Think of freebore as a noun and jump as a verb. Freebore is the place a bullet must jump through. Wether that is .2 thousandths of an inch or .25 matters BUT not when you are just beginning. They are hard to measure and there are much more important variables to tinker with and become proficient when using.
Longer bullets especially those built for shooting long range tend to need more jump. I don’t know the exact science but I suspect they need to fill all that open bore to build pressure and become consistently accurate.
Working within the load data limits set by the manufacturers will keep you safe and improve your skills-there’s good on the internet but also a lot of guys that just want to be popular

 

[Hogpatrol]

I have the Nosler Lyman and Hornady books and one specifically for AR's. I ask questions to hear from experienced reloaders that have "been there done that".

Starting out, good practice to go with bullet manufacturer's book loads and book COAL.