Why do some boolits like jump and others dont?

High Binder

Resident Tribologist
Full Member
Minuteman
Jun 18, 2008
502
19
Occupied Colorado
I have a 168gr Nosler Custom Competition load that loves a .010" jump but the 168 Noslers ballistic tips hate small jumps, favoring about .200" jump. Why is it that of the 5 different bullets I have loads for, that the jump matters so much?

-Confused in Colorado
 

Rovieairto

Sergeant
Full Member
Minuteman
Oct 4, 2007
633
0
47
Minneapolis MN.
Re: Why do some boolits like jump and others dont?

Well I've noticed that tangent ogive bullets seem far more tolerant of a jump than secant profiles.
With that being said, some things have so many variables that they defy a single, easy to follow explanation.
 

Unsichtbar

Online Training Member
Full Member
Minuteman
May 19, 2008
610
1
Texas
Re: Why do some boolits like jump and others dont?

http://www.the-long-family.com/OBT_paper.htm

This might be of interest to you optimum barrel time link above, different bullets might have different barrel times. Due to different jacket materials, bearing surface etc. Ajusting bullet changes internal volume/preasure, which effects bullets exit times.
 

High Binder

Resident Tribologist
Full Member
Minuteman
Jun 18, 2008
502
19
Occupied Colorado
Re: Why do some boolits like jump and others dont?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Unsichtbar</div><div class="ubbcode-body">http://www.the-long-family.com/OBT_paper.htm
</div></div>

Wow, good read. That is very interesting. I've heard some talk about that for quite a while now but that page really lays it out well. Thanks for the link Unsichtbar!
 

bowslngr

Sergeant
Full Member
Minuteman
Dec 29, 2009
311
1
56
North Carolina
Re: Why do some boolits like jump and others dont?

I have been wondering if bullet hardness/jacket thickness might be a key variable dictating whether or not a particular kind of bullet prefers to be jammed into the lands or prefers a bit of a jump. Based on my limited observations I am getting the impression that softer bullets with thinner jackets like to be up close, while harder bullets (copper solids, for example) like to be backed off a ways.
 

Unsichtbar

Online Training Member
Full Member
Minuteman
May 19, 2008
610
1
Texas
Re: Why do some boolits like jump and others dont?

You can drive yourself nuts trying to guess, best to go shoot them and ajust the seating depth. If you use a method like OCW you will achive your results with a lot less fustration. Like VLD bullets need to be seated close to the lands, well maybe or maybe not.
 

High Binder

Resident Tribologist
Full Member
Minuteman
Jun 18, 2008
502
19
Occupied Colorado
Re: Why do some boolits like jump and others dont?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bowslngr</div><div class="ubbcode-body">I have been wondering if bullet hardness/jacket thickness might be a key variable dictating whether or not a particular kind of bullet prefers to be jammed into the lands or prefers a bit of a jump. Based on my limited observations I am getting the impression that softer bullets with thinner jackets like to be up close, while harder bullets (copper solids, for example) like to be backed off a ways. </div></div>

That would make sense in my situation. My hunting rounds, GMX and the like, live a long jump and the match rounds like a short jump. Interesting.
 

High Binder

Resident Tribologist
Full Member
Minuteman
Jun 18, 2008
502
19
Occupied Colorado
Re: Why do some boolits like jump and others dont?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body">TAG </div></div>

Mech, is that an acronym for something, or a method?
 

The Mechanic

Gunny Sergeant
Full Member
Minuteman
Sep 9, 2006
1,927
8
San Diego County Ca.
Re: Why do some boolits like jump and others dont?

Not an acronym, it is just a way to mark the thread for use later. You can go to your My Stuff and then the my posts and it will show up like a bookmark. You will see it often in "good" threads that has good info, often during the day when people are at work and want to download or view stuff when they get home.
 

High Binder

Resident Tribologist
Full Member
Minuteman
Jun 18, 2008
502
19
Occupied Colorado
Re: Why do some boolits like jump and others dont?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body">Not an acronym, it is just a way to mark the thread for use later. You can go to your My Stuff and then the my posts and it will show up like a bookmark. You will see it often in "good" threads that has good info, often during the day when people are at work and want to download or view stuff when they get home. </div></div>

Oh, cool! I didn't know you could do that, thanks for the heads up.
 

High Binder

Resident Tribologist
Full Member
Minuteman
Jun 18, 2008
502
19
Occupied Colorado
Re: Why do some boolits like jump and others dont?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Unsichtbar</div><div class="ubbcode-body">You can drive yourself nuts trying to guess, best to go shoot them and ajust the seating depth. If you use a method like OCW you will achive your results with a lot less fustration. Like VLD bullets need to be seated close to the lands, well maybe or maybe not. </div></div>

Well, I liked what the website said and can dig it as I have degree in mechanical engineering. However, and he mentioned this, I would like to keep my velocity pretty high regardless of OCW because I routinely shoot 1200yds, the website seemed to be mostly aimed at the 300yrd range and more of a bench rest idea. So I'm forced to work within the realm of seating changes to achieve good groups.

On a side note, I have a buddy with an adjustable "break" in which he can adjust the length that the break protrudes from the crown, to tune his barrel to some mystical harmonic state of equilibrium but outside of a 1000 years of endless load development to ever achieve the level of accuracy promised by such a break I don't see the point in practical/tactical shooting.

Thoughts?
 

Unsichtbar

Online Training Member
Full Member
Minuteman
May 19, 2008
610
1
Texas
Re: Why do some boolits like jump and others dont?

I don't know were you are getting the idea that OCW is geared for 300 or benchrest. The loads after OCW ( there are several nodes) are just confirmed at 300 yds. The method does not have any restriction on velocity. You can pick the velocity range you want to work with, if you high node do so, high nodes are usually over 100% fill. After you find the OCW for the high node, ajusting the seating depth just tunes the load even more.
Please go back and read the articals on this web site.

http://optimalchargeweight.embarqspace.com/#/ocw-instructions/4529817134

 

mavrick10_2000

Private
Full Member
Minuteman
Jan 8, 2009
360
2,649
Oklahoma
Re: Why do some boolits like jump and others dont?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Shot In The Dark</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body">Not an acronym, it is just a way to mark the thread for use later. You can go to your My Stuff and then the my posts and it will show up like a bookmark. You will see it often in "good" threads that has good info, often during the day when people are at work and want to download or view stuff when they get home. </div></div>

Oh, cool! I didn't know you could do that, thanks for the heads up. </div></div>

TAG is old school before forums had a "subscribe to thread" or "Add to watched topics" option.

Look at the top of the thread, select Topic Options, then click on add topic to watched topics. Nearly all forums have one of the above mentioned methods rather than using "tag".
 

Breeze260

Sergeant
Full Member
Minuteman
Aug 10, 2009
980
0
Ohio
Re: Why do some boolits like jump and others dont?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body">Kind of frowned upon if you are a newbie but OK for you being an 800+ poster </div></div>

So because your new your not aloud to bookmark good info...