Second opinion on seating depth

[SHAGGY101]

So I just started loading some 190gr Berger VLDs for my rem 700 in 06. Instead of just selecting a middle of the road seating depth and shooting a couple of ladders I decided to try seating depth first. I heard that VLDs with the secant ogive could be a little unforgiving with seating depth and it might be best to find a depth that works ok before shooting a ladder. I did the test accoroding to what's on bergers website. I used hornady brass, sorted for weight, pockets uniformed and fh debuted, all trimmed to 2.5", bumped .002 from chamber size, .001 press on bullet, wlr primers, no crimp, and 54.3gr IMR4350 from an RCBS Chargemaster.

I found my lands at 2.814 o-b for the VLDs. This leaves me with .183" of shank in the neck. I then followed bergers test using .010", .050", .090", and .130" off the lands. Concentricity was measured with Sinclair tool at intersection of ogive and shank to +-.003 to +-.001 for the longer seated bullets and shorter ones respectively.

Rifle was cleaned of copper and carbon between strings with five fouling shots before shooting test loads. 54.3 of IMR 4350 was used for a light, safe load for this new load. After shooting the test (started raining so I only got a few velocities) I expected to see a clear victor but was a little confused. What I saw were consistency issues. I think this may be due to concentricity issues with just having so little shank seated. .010 was by far the best group. But not consistently. However, .090 showed excellent consistency just not the best group. My gut tells me to use .090 from the lands to start with but I really like the other group.

Thoughts?

.010" from lands



.050" from lands



.090" from lands



.130" from lands

 

[Bart B]

I don't think you are shooting enough shots per test group for any to represent the accuracy a load will give that can be counted on 90% of the time.

Read the following thread:

http://www.longrangehunting.com/forums/f28/measuring-lands-159898/

 

[SHAGGY101]

Bart, thanks for the input and copy all the statistical variations. This was is what stemmed my original question of should I go with known consistency or the best group. I absolutely wish I had a bigger sample size... But I don't, that is time and money I don't have.

Here are some numbers. Obviously the .090" distance to lands was consistent with my 2 3 shot groups, producing just under MOA groups. If you look at the numbers a little closer, you will realize that the group center has not shifted much at all. I wish I would have done this test and 200yds as well.

So which one would you guys choose?

.010" from lands





.090" from lands

 

[Bart B]

Any one load may well be the most accurate. The ones you show are, in my opinion, too close to the same size.

I don't think single 3-shot groups are very credible for what 20 to 30, or even 10 or 15 shots may show.

 

[FearNoWind]

If you're testing seating depth trying to find both group accuracy and consistent grouping you're matching apples and oranges. Your experience is why I usually start with a finding the best group with a series of powder charges and then work with seating depth (sometimes with the Berger ladder test) to refine the results. I sometimes eventually need to tweek the powder charge a bit more but adjustments at that point are minimal.
I your case I'd take the most consistent group and work at that seating depth to find a powder charge that brings it all together.

 

[Mikecr]

Why did you chose 54.3gr IMR4350?
Is that middle of the road, low, or high?

I ask because if powder has you on an edge of a node, then seating can take you into/out of it. This, causing two big changes at once.
Later Berger testing procedures have you back way off from any node/higher pressure charge for the testing.

 

[SHAGGY101]

That is on the low end, velocity was about 2450 fps. Since it was my first time seating/ shooting VLDs I wanted to make sure they wouldn't do anything squirly if I changed the seating depth.

I'll be starting out .090" from the land to do my ladder and then adjust seating depth from there.

 

[rcoody]

I did the berger jump test on my .308 deer rifle. Shooting 168 gr berger hunting vld's over 44 grains of varget.

I found my jump 0.117 off the lands. I then did a little fine tuning the target below I seated the bullets 0.01 deeper. You can plainly see that the starting load is not in the seating depth node and the last group shows it going away. That seat depth node is obviously about 0.03 wide.

 

[Sully2]

How can you beat that group thats .010 from the lands? Starting off...I seat mine slugs( various calibers) at .010 to .015 regardless as long as the OAL of the loaded round will still feed from the magazine. I prefer at least "1 caliber" in the neck (.25 for a 1/4" round....28 for my 280 rifle....etc)...thats AT LEAST.

I shoot for groups and then for speed ( velocity)

 

[Bart B]

Do all you folks seating bullets for a new barrel to .XXX" off the lands seat them .001" further out of the case to compensate for throat erosion wear for every dozen or so shots so bullet jump distance stays inside a .001" spread? .308 Win chamber throats lengthen .001" for every 30 to 40 rounds fired.

If you're using bottleneck cases head spacing off their shoulders, case headspace spread across a batch of them will easily be .003" The bullet's jump to the rifling will have at least that much spread. Their cases will also have that much spread in head clearance to the bolt face when fired.

 

[rcoody]

Do all you folks seating bullets for a new barrel to .XXX" off the lands seat them .001" further out of the case to compensate for throat erosion wear for every dozen or so shots so bullet jump distance stays inside a .001" spread? .308 Win chamber throats lengthen .001" for every 30 to 40 rounds fired.

If you're using bottleneck cases head spacing off their shoulders, case headspace spread across a batch of them will easily be .003" The bullet's jump to the rifling will have at least that much spread. Their cases will also have that much spread in head clearance to the bolt face when fired.

the reason I was looking for the jump was to get to mag length for hunting. For targets I jam VLD's 0.01 into the lands. O.01 off the lands would not get me to mag length.

I use my stoney point periodically to check the throat erosion and adjust my col especially if accuracy starts to go away. Don't shoot my hunting rifles that much anyway.

As far as headspace. I neck size. When the case starts to get sticky I full length resize but I have my sizing die adjusted for a 0.0015 shoulder bump on bolt guns. On my AR's I full length resize and have the die set for a .004 shoulder bump.

 

[rcoody]

Do all you folks seating bullets for a new barrel to .XXX" off the lands seat them .001" further out of the case to compensate for throat erosion wear for every dozen or so shots so bullet jump distance stays inside a .001" spread? .308 Win chamber throats lengthen .001" for every 30 to 40 rounds fired.

If you're using bottleneck cases head spacing off their shoulders, case headspace spread across a batch of them will easily be .003" The bullet's jump to the rifling will have at least that much spread. Their cases will also have that much spread in head clearance to the bolt face when fired.

If you notice the target I posted above the seating depth node is 0.030 wide. That be 30 thousands. Should not have to worry about throat erosion for a while.

 

[Bart B]

As far as headspace. I neck size. When the case starts to get sticky I full length resize but I have my sizing die adjusted for a 0.0015 shoulder bump on bolt guns.

Have you ever tried full length sizing all your bolt gun cases setting their shoulders back .001" to .002"?

That's the popular trend these days in benchrest disciplines.

 

[rcoody]

Have you ever tried full length sizing all your bolt gun cases setting their shoulders back .001" to .002"?

That's the popular trend these days in benchrest disciplines.

B did you read my post?