Tech note from Berger on seating depth

[mdesign]

The text below is from the Berger website on how they recommend finding the correct seating depth for their bullets.

Anyone here tried it this way? Seems like the general line of thought is that Bergers need to be into the rifling to shoot well.

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The following has been verified by numerous shooters in many rifles using bullets of different calibers and weights. It is consistent for all VLD bullets. What has been discovered is that VLD bullets shoot best when loaded to a COAL that puts the bullet in a “sweet spot”. This sweet spot is a band .030 to .040 wide and is located anywhere between jamming the bullets into the lands and .150 jump off the lands.

Note: When discussing jam and jump I am referring to the distance from the area of the bearing surface that engages the rifling and the rifling itself. There are many products that allow you to measure these critical dimensions. Some are better than others. I won’t be going into the methods of measuring jam and jump. If you are not familiar with this aspect of reloading it is critically important that you understand this concept before you attempt this test.

Many reloaders feel (and I tend to agree) that meaningful COAL adjustments are .002 to .005. Every once in a while I might adjust the COAL by .010 but this seems like I am moving the bullet the length of a football field. The only way a shooter will be able to benefit from this situation is to let go of this opinion that more than .010 change is too much (me included).

Trying to find the COAL that puts you in the sweet spot by moving .002 to .010 will take so long the barrel may be worn out by the time you sort it out if you don’t give up first. Since the sweet spot is .030 to .040 wide we recommend that you conduct the following test to find your rifles VLD sweet spot.

Load 24 rounds at the following COAL if you are a target competition shooter who does not worry about jamming a bullet:
1. .010 into (touching) the lands (jam) 6 rounds
2. .040 off the lands (jump) 6 rounds
3. .080 off the lands (jump) 6 rounds
4. .120 off the lands (jump) 6 rounds

Load 24 rounds at the following COAL 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 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL +/- .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).
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Here is a link

Berger Bulletin

 

[Bacarrat]

Re: Tech note from Berger on seating depth

FWIW, I jump my 180gr Bergers .140 (magazine fit) and they seem to shoot fine.

 

[bohem]

Re: Tech note from Berger on seating depth

I did this test using JLK bullets and Berger's instructions. My dies are standard RCBS seating dies so I only got a .045 jump instead of the .04 they mentioned, I called that close enough.

The "touch", 10 jump 45 jump 80 jump and 115 jump showed what I needed, and that is 3/4" 5 shot groups at 200y with an 045 jump.

 

[ReaperDriver]

Re: Tech note from Berger on seating depth

Is this method unique to Berger VLDs or will it work for any other match style bullet like SMKs or AMAXs?

 

[hombre]

Re: Tech note from Berger on seating depth

I just finished the second round of this method and ended up .022 off the lands. I think this method will work for any bullet manf. I only used half a box to find great groups. First I started w/ .o1,,.05,.09,.13 jump and then took the best group was .01 off the lands and then went every .003 farther off the lands. Out of a CDNN FN PBR XP 300wsm 190gr vld,win. brass, cci mag prim. hybrid 100V, 64.6gr at 2915fps bedded in a Manners GAT I shot four groups, 3 shot groups that measure in the low to mid .4s. Now that I have a great load, I'm going to load up the next 50 and run them out to 1250 yds tommorow and I'll let ya'll know how they do down range. I will shoot a 300 and 600 5 shot group to see how well they do.

 

[Clark]

Re: Tech note from Berger on seating depth

90% of my rifles shoot best with the bullet jammed into the lands.

The amount jammed into the lands is important.

Too much and pulling the round unfired will leave the bullet in the lands and powder spilled in the action.

Every bullet and every chamber and the co-efficient of friction between bullets to necks varies.
So one must take data on the threshold of sticking and back off.


I like to measure the length of lands engagement with a microscope, looking at the lands marks on a bullet chambered but not fired.

Typically .010" marks on the bullet are not involved with sticking.

Typically, the bullet jams, and then pushes deeper into the case.
The length of the mark on the bullet is the threshold of stuck.
That may be at .040" or .120".

My hunting loads, if they fit in the magazine, are half way between stuck and just touching the lands.


I know someone who worked up an accurate load jammed all the way.
At the end of a day of elk hunting, the powder spilled into the action and a bullet was stuck. No one had a cleaning rod. But with pliers, they pulled a bullet and powder from the cartridge of another rifle. They put the two rifles muzzle to muzzle and the primer of one blasted out the bullet stuck in the lands of the other. That guy now carries an Aluminum sectioned cleaning rod when hunting AND has reduced his over all length from seating depth.

 

[JRWALLSIII]

Re: Tech note from Berger on seating depth

I use to think that a Bergers need to be in the lands.

That is not even close to the truth.

I have shot several rifles with VLDs.

Follow the seating reccomendations.

In my experience. I have shot rifles that junp .020 to .145 with one ragged hole accuracy at 100 yards with 5 shot groups. It just depends on what the rifle likes.

Now if you are ever planning on hunting or shooting a tactical match. You absolutly do not want to seat the bullet in the lands.

Murphy is always close buy. Ask me how I know!!!

 

[Clark]

Re: Tech note from Berger on seating depth

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: .257</div><div class="ubbcode-body">

In my experience. I have shot rifles that junp .020 to .145 with one ragged hole accuracy at 100 yards with 5 shot groups. It just depends on what the rifle likes.

Now if you are ever planning on hunting or shooting a tactical match. You absolutly do not want to seat the bullet in the lands.

Murphy is always close buy. Ask me how I know!!! </div></div>

The reason that a rifle likes it up the lands is because the bullet would not otherwise be lined up.

So it is not just the rifle, it is the ammo too.
Shoving up the lands may not do much for a $4k bench rifle.
But it does allot for a $50 surplus rifle.

 

[citabria]

Re: Tech note from Berger on seating depth

I use to think they needed to be seated into the lands but have strayed away from that for two reasons first is experience has taught me otherwise and second with most all guns if your are using your magazine you cant and i like to use my mag.