Bullet Jump vs Charge Weight

[Idaho Hunter1]

Thanks in advance for the help.

I'm new to this and have been reading how people run ladder tests for charge weights to find a "node" and pressure signs. I've also seen people talking about playing with jump. That's 2 variables in the equations so one has to remain constant I would think. So I'm having a hard time figuring how (or more accurately "when") do you play with jump?

I've done a series of ladder tests with a couple of rifles I have and have found places where my velocities level off for a bit and then start to climb again. I believe this is a node? My OAL has been set to either the bullet load data recommended distance or to a replication of factory ammo that shot well in my rifles.

The problem is my accuracy is not great at any place within the ladder. I'm seeing about 1-1.25 MOA with usually 1 shot that throws an otherwise excellent group out the window.

Components and rifle are very high quality and the rifles shoot sub .5MOA with Nosler Partition and Hornady ELDM and ELDX factory ammo.

Can someone please point me in the right direction for how to crack this problem?

Calibers are common, 7RM and 300 Win Mag.

 

[snox801]

Ok first yes those should be node you are seeing.
Second I usually find the charge weight first then take the best of those and start messing with depth. The other way would be to find a general consensus of what the bullet you wanna shoot should like for jump and try that. Or simply do a ladder test with different depths starting at 10 thou off the lands and working out.
Third option would be to load with hammer bullets and not have to worry about jump much.
You could also help trouble shoot your issues by seeing what you es and sd are on your loads.
If you are hoping to stretch it out for long range say over 500 yards where bc is king. Then look more for those numbers than what it doing on paper at 100 within reason.
Also I've had this happen a lot. Make sure when shooting you are giving ample time to cool the barrel between shots. I've run into that many times where I would get that random shot ruining the group. Happens most on thinner barrels but I even have one heavy barrel shotgun that cold bore mapping with print clover leafs, but back to back shots make a 3" group.

 

[Idaho Hunter1]

Ok first yes those should be node you are seeing.
Second I usually find the charge weight first then take the best of those and start messing with depth. The other way would be to find a general consensus of what the bullet you wanna shoot should like for jump and try that. Or simply do a ladder test with different depths starting at 10 thou off the lands and working out.
Third option would be to load with hammer bullets and not have to worry about jump much.
You could also help trouble shoot your issues by seeing what you es and sd are on your loads.
If you are hoping to stretch it out for long range say over 500 yards where bc is king. Then look more for those numbers than what it doing on paper at 100 within reason.
Also I've had this happen a lot. Make sure when shooting you are giving ample time to cool the barrel between shots. I've run into that many times where I would get that random shot ruining the group. Happens most on thinner barrels but I even have one heavy barrel shotgun that cold bore mapping with print clover leafs, but back to back shots make a 3" group.

Ok, so if I see a group of small SD/ES (Low teens or single digits) then is that the charge I want to try and play with the jump on? Is that the reason people try different powders? To reduce those FPS deviation

I'm game to try hammer bullets as well but wanted to understand the process not just fix it.

Thanks

 

[Wedgy]

This is one way of wading thru it, addressing the VLD characteristics, the hybrids aren't as sensitive to seating depth. From Berger;

Load 24 rounds at the following CBTO if you are a hunter (pulling a bullet out of the case with your rifling while in the field can be a hunt ending event which must be avoided) or a competition shooter who worries about pulling a bullet during a match:

1. .010 off the lands (jump) 6 rounds
2. .050 off the lands (jump) 6 rounds
3. .090 off the lands (jump) 6 rounds
4. .130 off the lands (jump) 6 rounds

Shoot 2 (separate) 3 shot groups in fair conditions to see how they group. The remarkable reality of this test is that one of these 4 CBTOs will outperform the other three by a considerable margin. Once you know which one of these 4 CBTO shoots best then you can tweak the CBTO +/- .002 or .005. Taking the time to set this test up will pay off when you find that your rifle is capable of shooting the VLD bullets very well (even at 100 yards).

VLD - Making it Shoot

VLD bullets are designed with a secant ogive. Berger VLD bullets are consistently and exceptionally capable of putting game down quickly

bergerbullets.com

 

[Deputy819]

You'll get varying opinions on the subject of "Which Comes First.....Seating Depth or Powder Charge". Search this site and you'll see that it gets discussed quite often.
I've always performed seating depth test FIRST as a 'rough adjustment' using an arbitrary (minimum) powder charge. Then I'll carefully and methodically take the rifle to pressure (loading in .5gr increments and using a chronograph) with the components I'm using to see where the 'ceiling' is. Then I'll do a ladder test (in .2 increments of powder) and look for those nodes. When I find a node I'll load in the middle of it and use slight powder adjustments on either side as a 'finer adjustment'.
I won't say that doing it any other way is wrong, but this is what has worked well for me.

OAL or OCW first?

I've always used OCW with varying charge weights with a constant OAL (usually the longer of SAAMI max or .020" off the lands), but I was listening to the Modern Day Sniper podcast and their guest (can't remember his name) made an effective argument for using a constant (safe) charge weight with...

www.longrangehunting.com

 

[Shane Lindsey]

It sounds like you are close already with your low ES. As mentioned, try seating depth test. I used the Alex Wheeler method on a recent one and it really opened my eyes to what I thought was the lands, to actually how to find them.


If you are getting a flyer, possibly change your primer. This may bring the flyers into the group.

You could also try this. If you have a chrono and know the velocity of the factory ammo you have had good results with, you can try to match the velocity (or close) with another similar type powder. I say this, because your barrel is favoring the same velocity of the factory stuff. Take the given charge weights and velocities from the reloading data. Do the math on what each grain produces in FPS. Then this will give you an approximate charge weight.

 

[Alex Wheeler]

If you do not already have past experience with this bullet/cartridge combo, just pick a powder charge that looks decent and figure out your seating depth. Personally I would go .010" at a time to rough it in. Then fine tune it from there. Dont worry about single small groups you want it be repeatable. Then go back to tuning powder charge.

 

[Kmccord]

When I discussed this with Phil at Berger bullets, he mentioned to use the lowest powder charge for the bullet you are shooting and run the seating depth chart listed on there website. It works for me, I found the 7mm Rem Mag liked them at .050 off the lands, and it was repeatable. Then I started on my powder charge until I found what was repeatable as well.

 

[L.Sherm]

I'm with Alex on the .010 at a time and then fine tune.

 

[ShtrRdy]

If you do not already have past experience with this bullet/cartridge combo, just pick a powder charge that looks decent and figure out your seating depth. Personally I would go .010" at a time to rough it in. Then fine tune it from there. Dont worry about single small groups you want it be repeatable. Then go back to tuning powder charge.

How many 0.010" steps do you like to do? From touching lands to ???

 

[Alex Wheeler]

You will find multiple spots that shoot. In most cases I end up within .020 of the lands. But if you keep going you will find other spots even farther off. If it was a new to me setup, I would bring the seating press to the range and seat bullets there and go as far as you need to.

 

[L.Sherm]

You will find multiple spots that shoot. In most cases I end up within .020 of the lands. But if you keep going you will find other spots even farther off. If it was a new to me setup, I would bring the seating press to the range and seat bullets there and go as far as you need to.

This is exactly why I have went to an inline press and making seating dies from my chamber reamers.

 

[Alex Wheeler]

Yep, 90% of my customers have as well. I could never go back to seating on my threaded press.

 

[Calvin45]

Ok, so if I see a group of small SD/ES (Low teens or single digits) then is that the charge I want to try and play with the jump on? Is that the reason people try different powders? To reduce those FPS deviation

I'm game to try hammer bullets as well but wanted to understand the process not just fix it.

Thanks

that curiosity should serve you well in all this, not wanting to mitigate problems before understanding them.

some bullet types are indeed less "finicky" (as are some cartridges, powders, barrels, etc...). No experience with hammers (or most monos) but can indeed attest that flat base bullets are much less sensitive to jump than boat tails and are often more "easily accurate" within 3-400 yards as well.

hexagonal boron nitride treatment of bullets and the bore has also, in my recent and limited experience, made loads a lot less finicky regarding jump and less prone to pressure spiking when loading close to or on the lands.