"Off the lands"

[garandman]

Are there any universal truths about how far your bullet can be "off the lands"?

Both my 338 Norma and 6.5CM shoot very well about 0.015 off the lands. Faster boolits would be nicer, but getting them to a proper seating depth would mean being 0.060 off the lands...or more.

Any wisdom / comments to help me? Thanx.

 

[Rhyno]

What does faster bullets and jump have to do with each other.

 

[MJY65]

I don't think there is any universal truth. Some bullets like SMK don't seem to mind the jump. I'd bet a factory loaded FGGM has a jump of at least .060 in most rifles.

 

[garandman]

What does faster bullets and jump have to do with each other.

In a causative respect, nothing.

But lighter bullets are generally shorter bullets, which typically have to "jump" further when pressed to the correct seating depth.

 

[roggom]

to MJ's point, its about the ogive. The SMK, Nosler CC, Amax use more of a tangent ogive which allows more latitude with seating depth. Is those pointy little Secant bullets that must be "kissing the lands" or fractions thereof (Berger VLD, and Hornady BTHP can be similar although not exactly secant)

You can google some Bryan Litz articles he goes pretty in depth into this stuff.

 

[garandman]

"Ogive" is admittedly something I've had difficulty understanding.

 

[siscoe308]

Tag for knowledge

 

[roggom]

Tangent, Secant, Hybrid Ogive Bullets within AccurateShooter.com


I like to load to magazine length, so for the most part I use Tangent Ogive bullets. You can get away with a "hybrid" bullet. It will not have the same BC but a little easier to seat.

Another bullet to keep an eye on is the Nosler Accubond Long Range. The BC is a little over estimated, but they are nice long bullet.

Here is a 168 ABLR I load for 7 mag

 

[garandman]

Is those pointy little Secant bullets that must be "kissing the lands" or fractions thereof (Berger VLD, and Hornady BTHP can be similar although not exactly secant)

.

I've become a fan of Berger OTM's in both my fave calibers.

 

[djskit]

On my 6.5 rifles, I always load .015" "off the lands" and have never encountered a compelling reason to change that.

For my 308 with 175 SMK's - I loaded to 2.8 OAL for starters and never changed. I don't even know how far off the lands this is - because in this case, it doesn't matter. The rifle shoots tight enough.

Answer: No universal truth.

 

[djskit]

"Ogive" is admittedly something I've had difficulty understanding.

The ogive is the curved part of the bullet and starts at the point where the diameter of the bullet moves below the caliber. in other words, where the sides of the bullet are no longer parallel.

A lot of guys (myself included) use the term ogive somewhat lazily. When I say .015 off the lands, I'll also put in my notes - cartridge length 2.35" from ogive. That is, measured from the base of the case to where the START of ogive using a caliber specific comparator insert for the calipers.

For example, this 6.5 Creedmore round measures 2.270" from the base of the cartridge to the start of the ogive. And the start of the ogive is .015" off the lands.

 

[wrangler5]

You can take a look at this article Berger Bullets Seating Method for VLD Bullets - A "Sweet Spot" with a Long Bullet Jump will give the best accuracy. originally written by somebody at Berger Bullets. My own best accuracy, using the process laid out in the article, is 0.065 off the lands for my Berger 70g VLD bullets in a 223 Marlin X7. (I modified the test loads a bit as I couldn't get 0.080 setback without having to seriously crunch the powder charge - 0.065 is just starting to compress things.) The article is written for Berger VLD bullets, but I tried it with Sierra SMKs too and found my 69 grainers also group very well using the same seater die setting as for the Bergers, which makes things very convenient.

Using individually weighed charges (Varget) and well prepared cases, I rarely have a 5-shot group over 1MOA (bipod or front rest, rear sandbag) and usually it's 0.4 to 0.6 MOA at 200 yards (I don't shoot at 100yds any more since I have a spotting scope that can see those little holes at 200.) Groups open up a bit at 300 yards if there's any wind, and 600 yard groups are entirely wind-dependent - I'm just beginning to learn how to read the wind on our 600 yard range, where it's common to see the wind flags going opposite directions between the firing line and 600 yard targets. Your mileage will almost certainly vary, of course, which is the point of the testing process outlined in the article.

 

[garandman]

DJSKIT -

I got one of those chamber slugs from my rifle builder with my custom 338 Norma. How do you measure to the ogive when the bullet is chambered in the rifle?

This has plagued me for MONTHS.

Or.....what is that red and aluminum thing in the pic, and how can you measure to the ogive in the rifle chamber?

 

[MitchK]

Gman

Hornady Lock-N-Load Bullet Comparator Basic Set 6 Inserts

 

[supercorndogs]

yes there is. all guns and bullets are different

 

[Thebelly]

Tag

 

[STI_1911_Guy]

In a causative respect, nothing.

But lighter bullets are generally shorter bullets, which typically have to "jump" further when pressed to the correct seating depth.

^^^^^
Perfectly said. You cant keep enough bullet in the case to reach the lands on SOME instances.

 

[djskit]

DJSKIT -

I got one of those chamber slugs from my rifle builder with my custom 338 Norma. How do you measure to the ogive when the bullet is chambered in the rifle?

This has plagued me for MONTHS.

Or.....what is that red and aluminum thing in the pic, and how can you measure to the ogive in the rifle chamber?

I use the Hornady modified case thingy and measure that with the comparator, then subtract .015" for the die set up.

Hornady Lock-N-Load Overall Length Gage Bolt Action

Hornady Lock-N-Load Overall Length Gage Modified Case 308 Winchester

There may be better ways to do this, but this set up has served me well for the last 5 years.

AND Hornady will modify any wildcat cases for a small fee.

Here is the first hit I got on YouTube when I searched it up. Looks like this guy seems to be getting it right.

https://www.youtube.com/watch?v=llvsEsaK8-M