Finding the lands...amazing

[balderclev]

I've been reloading for many years but just used the col printed in reloading manuals. I was getting MOA +/- .5 accuracy in my 308, 223, 22-250, 6.5 Creedmoor, and 220 Swift after working up loads.

I recently purchased a Hornady OAL gauge and bullet comparator. I was amazed at the difference in accuracy and the length I was moving the bullet out.

I'm getting .5-.8 MOA now in all these rifles using the same loads as before. I started at .020 from the lands but had to move it to between .030 and .045 in order to fit in the magazine. Even at that, the Creedmoor for example was more than .18 inches longer. All cartridges ended up being the maximum length that would fit in the magazines.

I wish I had done this years ago. I've got quite a few rounds to disassemble now!

 

[taliv]

Now you understand why defiance built their xm action....

 

[Howland]

I tried using the OAL gauge on my RPR .338LM and found it impossible to get consistent results. Measurements were 0.070" apart. Even if the shortest is correct, OAL still won't fit the mags, so mag length is going to be the limiting factor.

With the same tool, my brother got very repeatable results with his .338LM. I'm guessing it has something to do with how the lands are cut.

 

[forty_caliber]

I tried using the OAL gauge on my RPR .338LM and found it impossible to get consistent results. Measurements were 0.070" apart. Even if the shortest is correct, OAL still won't fit the mags, so mag length is going to be the limiting factor.

With the same tool, my brother got very repeatable results with his .338LM. I'm guessing it has something to do with how the lands are cut.

Interesting. Could be lots of things here. Are the rifles the same manufacturer? Are you using the same bullets as your brother? Have you tried a different bullet with a different ogive profile? If you use your modified case and gauge in your brother's rifle does the problem follow?

.40

 

[sparkyv]

Minimizing the bullet jump often improves performance. Some competitors even jam it into the lands!

 

[Grumulkin]

I have never used the Hornady OAL gauge. My practice has been to get bullets as close to the lands as possible while still functioning from a magazine. For single shot firearms, I chamber a round several times and seat the bullet a little deeper each time until it just fits. You can see the marks from the lands on the bullet even if you don't blacken it with candle soot.

For some guns, getting a bullet close to the lands doesn't seem to matter a lot. I think it has to do with how precisely the chamber, throat and barrel are aligned. Getting a bullet close to the lands, makes up for imprecission in those alignments.

 

[crestoncowboy]

I wouldn't pull every bullet for every gun. Ive found that some guns or loads don't change at all. Kind of like neck sizing rather than FL. Some times it makes a difference. Others it hasn't

 

[otisrush]

Someone (I believe on this board) summarized it so well a year or two ago that it really stuck in my head: For tight groups, powder charge is the "big knob". OAL/jump is the "fine tune knob".

As others have stated, if a magazine is in the picture that can be the limiter on OAL. But if it's single shot then there are lots of options.

 

[Allen One1]

I tried using the OAL gauge on my RPR .338LM and found it impossible to get consistent results. Measurements were 0.070" apart. Even if the shortest is correct, OAL still won't fit the mags, so mag length is going to be the limiting factor.

With the same tool, my brother got very repeatable results with his .338LM. I'm guessing it has something to do with how the lands are cut.

It could be as simple as using a different bullet. I was having a similar issue with 6.5 Creedmoor after switching to the ELD-M bullet I got very consistent measurements.

 

[lordpaxman]

I've got quite a few rounds to disassemble now!

Use those for your cold bore shot!

I've found every one of my guns to be a bit different on what they like. I've settle on working up the powder charge first, and then the land's second. I found this article to be interesting!

http://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

 

[30Cal]

I have never used the Hornady OAL gauge. My practice has been to get bullets as close to the lands as possible while still functioning from a magazine. For single shot firearms, I chamber a round several times and seat the bullet a little deeper each time until it just fits. You can see the marks from the lands on the bullet even if you don't blacken it with candle soot.

For some guns, getting a bullet close to the lands doesn't seem to matter a lot. I think it has to do with how precisely the chamber, throat and barrel are aligned. Getting a bullet close to the lands, makes up for imprecission in those alignments.

I do the same thing, but don't bother looking for marks on the bullets. And I start long and go a little shorter each time. Stick the round into the chamber with your thumb. When it falls out on it's own when you tip the muzzle up, it's no longer touching.

 

[GTS Dean]

I found that one of my rifles is EXTREMELY sensitive to consistent ogive-to-land jump. After I had already laddered powder charge to find an accuracy node, I laddered 4-shot groups moving the seating depth out by approximately .003" increments. There was no appreciable difference in the first 4 groups, and then.....WOW!

 

[Howland]

Interesting. Could be lots of things here. Are the rifles the same manufacturer? Are you using the same bullets as your brother? Have you tried a different bullet with a different ogive profile? If you use your modified case and gauge in your brother's rifle does the problem follow?

.40

It could be as simple as using a different bullet. I was having a similar issue with 6.5 Creedmoor after switching to the ELD-M bullet I got very consistent measurements.

The same OAL guage was used, his. Both of us used the 285gr. ELD-M. I haven't tried a different bullet. If I don't find a good load with this one, I'll choose another to work up a load with and try measuring with that. If I do find a good load, I'll still know optimum CBTO, but knowing actual jump would be nice. His is an FN Ballista, mine a Ruger Precision Rifle. He measured his, I measured mine.

 

[jmorris]

I was getting MOA +/- .5 accuracy in my 308, 223, 22-250, 6.5 Creedmoor, and 220 Swift...

I'm getting .5-.8 MOA now in all these rifles using the same loads as before.

What am I missing, seems you are the same or lost .3 MOA.

 

[Allen One1]

What am I missing, seems you are the same or lost .3 MOA.

MOA = 1" +or- .5" So from .5-1.5"
I had to read that a couple of times the first pass as well.

 

[balderclev]

MOA = 1" +or- .5" So from .5-1.5"
I had to read that a couple of times the first pass as well.

Correct...sorry, I should have made that more clear.