Seating depth tuning- need suggestion

[Koda_]

I only fired 3 shot groups, which isn't a great sampling, however, over the course of 6- 3 shot groups, which was 1.2 grains of delta from high to low, there was only 45 FPS delta from highest to lowest, so I feel that at 100 yds, these delta don't produce 3/4" differences in elevation, so I deemed the data relevant.

So you shot 18rds over different charge weights to determine your ES?

 

[Bang4theBuck]

No. As I said in my initial post, I shot multiple 3 shot groups. ALL of the groups had individual ESs of sub 10 ft per second. The ES over 6 groups of varying charges was only 55 fps. If three shot of almost the exact same speed impact at different elevations, the number of speed captures in the sampling is not relevant.

The issue is something to do with :
* Harmonics (seating depth, bedding, etc)
* Shooting technique (initially rules this out as I produced multiple .300" groups with another rifle just minutes before shooting these groups)
* Other (neck tension, etc)

*velocity consistency is not the issus, the chronograph doesn't lie.

 

[MagnumManiac]

I will help you out here, your ES is excellent, however, your vertical is from the powder charge not being in tune with your seating depth and barrel time. Bullets are leaving the barrel in a node that is either in the middle of barrel whip or at the bottom and top.
Seating depth should change this in your favour if you start at .020" off and increase in .010" increments away from the lands.
This is why, I, and what I recommend, is to do seating depth testing first. Great ES/SD numbers are not the be all, end all if the harmonics it produces are wrong. Any load can have bad harmonics out of the barrel time node.
Fine tune seating depth in +/- .005" increments once found to see if it tightens.

Cheers.

 

[Huntnful]

You absolutely don't need .284" of bullet engagement in that case neck. That's just some random crap someone came up with lol. Get that bullet up closer to the lands and see how it shoots. Try .010 off and .020 off.

 

[Bang4theBuck]

I will help you out here, your ES is excellent, however, your vertical is from the powder charge not being in tune with your seating depth and barrel time. Bullets are leaving the barrel in a node that is either in the middle of barrel whip or at the bottom and top.
Seating depth should change this in your favour if you start at .020" off and increase in .010" increments away from the lands.
This is why, I, and what I recommend, is to do seating depth testing first. Great ES/SD numbers are not the be all, end all if the harmonics it produces are wrong. Any load can have bad harmonics out of the barrel time node.
Fine tune seating depth in +/- .005" increments once found to see if it tightens.

Cheers.

Thanks for the feedback. This aligns with what I thought.

 

[Bang4theBuck]

You absolutely don't need .284" of bullet engagement in that case neck. That's just some random crap someone came up with lol. Get that bullet up closer to the lands and see how it shoots. Try .010 off and .020 off.

Thanks for the feedback. I've got my next round of load development loaded, but I've got a few rounds left that I can use to try closer to the lands. .010" off the lands would give me .212" engagement. I'll try that and work back from there with the rounds I have. I'll let you know how it goes.

 

[Pdyson]

I like to start just under magazine length unless I have a short throat. I've heard people say they like to jump Bergers… not me. I've always found good nodes longer and it allows me to avoid seating bullets into the donut. Since you have good velocity, ES & SD you are almost there you can shoot a bunch of groups at different seating depths or you can try what I started doing 2 years ago. I call it the EZ button. Just load near mag length and screw on an EC Tuner brake. If you can't tune a group with Erik's brake. You've probably got a bedding or scope mount issue.

 

[AussieWriter]

With sporter weight rifle barrels, I seat .003" - .006" increments. Different bullet bearing surfaces need accomodating. A Hornady BT will usualky require smaller.movements than tbe same weight Partition.
With light profile barrels, I found shorter movement recordable at around .002" - .004".
With heavier barrel profiles, I would seat .005' - .006" and walk them in.
Sometimes caliber makes a difference too, which is why you get varying opinions.

 

[southpa]

I dont understand the ".080" of an inch, and that gives me one cartridge diameter of bullet engagement into the case (my self-imposed minimum)."
I would let the barrel/chamber/bullet tell you what it likes. I'm not sure a self imposed limit on seating depth allows for full potential of any barrel. Personally, I start at .010 or .020 and usually find what I need to find in increments of .010. If I need to get more precise I can test .005s but rarely do I need to do that because .010 inrements get me there. Unless you find a real picky one.

 

[bfarms]

I mostly do .005- .010. Depending on rifle and what I feel it's capable of. I have went as low as .002 at a time. But I feel you need to bump up the powder some or lower it some. I think that's where you are getting vertical. Barrel whip will do that. I agree with others. Start closer to the lands if mag length allows.

 

[Bang4theBuck]

I promised feedback from the seating depth testing, and here it is. Suffice to say, I found the range of depth that the rifle likes. Here are the targets. The target with more dots represents my original starting point at 2.350" Base or Ogive. This represents. 082" jump. As I pushed the bullet back into.the case, the tune definately changed, and generally got worse as I approached the extreme end of the spectrum (.141" jump).

I then switched to the rounds I loaded after advice from you guys on not letting the .284" bullet engagement into the case be a minimum. The first load with an increased overall length was significantly better. And the final load touched all the bases. It ended up at 2.385" Base to Ogive which was a .047" Jump, and .266" of bullet engagement in the case. The group was well under 1/2" with two in the same hole.

Also, the ES for thos load was 5 fps, traveling at an average of 2880 fps. This rifle is going to be a long range hammer.

Thanks for the nuggets of information.

 

[Huntnful]

Thanks for the update! Glad you kept an open mind and were willing to break your self imposed rule on bullet engagement. Looks like it paid off. I'll shoot out to minimum of .150 or so of bullet engagement if need be. Never had an issue.

 

[Dean2]

Good update and good progress. Less jump gave you smaller groups and less bullet engagement gave you less vertical, though you still have some. I still think neck tension is affecting your groups. I would lightly turn the necks and anneal them. My bet is, all the bullets end up in the same hole after that.

 

[AussieWriter]

The .47" could be seated a little more to bring that third bullet into the group. I'd suggest .004-.005" and shoot a couple or three groups to see if there is a tightening.

This is why some handloaders seat to max OAL so there is only one direction to go and simplify the process, also remembering that seating deeper lowers pressure.