Seating depth variation

[VenatusDominus]

I'm gonna watch the videos and read the outdoor life article but more data does make sense.

It reminded me of an article on finding the cold bore zero for a given rifle and load I read years back. I believe it was Carlos Hathcock's method…. it was a single shot at the same target on different days and in different conditions or elevations. The shooter takes notes and keeps the targets to overlay one another and continues to add to the data. It is different but similar in that your plotting the cone of fire and learning the predictability of your system in "all" conditions and circumstances for first shot hits.

It seams that for the studies they were trying to keep the outside variables, wind, temp, pressure and humidity the same for a given group so they could get a best case scenario for cone of dispersion. You can then normalize those values to standard atmospheric conditions and use ballistic calculator to make adjustments for different environmental conditions. It was amazing and inspiring what Carlos Hathcock was able to achieve without lazar range finders, modern optics, and ballistic computers.

 

[Phil Rizzo]

It's interesting that Berger recommends doing a seating depth test when from what I have read here it really doesn't matter.
I have been using the Berger method with most bullets nowadays and I have seen the results and I believe results.
As far as science goes, I have a hard time believing MOST so called scientists. Most seem to be pushing a agenda instead of actual science. JMO

Bergers also tend to repeat somewhat, at .030 increments.
In my experience the farther back away from lands I get from that first sweet spot the less precise my groups print.
But supposedly, and it makes sense, the more stable performance occurs when there is more jump, in those increments. I value powder space and don't have short chambers, so I don't use any deeper depths than needed.

 

[Idaho Lefty]

I only use, Three shot group's when, just Starting to, "Work Up" Loads for, a Rifle. That, tells me that, I'm, "getting Close" to, a good load.
Then, I shoot, a couple of 5 shot, Group's ( Hopefully around, the 1/2 MOA size ) with, a Sub, 8 Pound,.."Hunting Rifle".
Then, I Do, a 10 Shot, 200 Yard group for, the FINAL Testing and, Zeroing of, my Rifle. ( running it as Cool as Possible, takes, TIME )
I shoot, 600 Yards after that, for Matching the arc of, my Bullet,. to my, Data,. Done !
Shooting 10 shot Group's at, 200 or, 300 Yards, tells Me, the "True Accuracy capability" of My Rifle and, the Reloads, It likes, Best.
WARNING,. You may or, may NOT Have,. a TRUE, 1/2 MOA, Rifle ! ( this 200 / 300 Yard testing, can be, a Humbling Experience ! )

 

[VenatusDominus]

I only use, Three shot group's when, just Starting to, "Work Up" Loads for, a Rifle. That, tells me that, I'm, "getting Close" to, a good load.
Then, I shoot, a couple of 5 shot, Group's ( Hopefully around, the 1/2 MOA size ) with, a Sub, 8 Pound,.."Hunting Rifle".
Then, I Do, a 10 Shot, 200 Yard group for, the FINAL Testing and, Zeroing of, my Rifle. ( running it as Cool as Possible, takes, TIME )
I shoot, 600 Yards after that, for Matching the arc of, my Bullet,. to my, Data,. Done !
Shooting 10 shot Group's at, 200 or, 300 Yards, tells Me, the "True Accuracy capability" of My Rifle and, the Reloads, It likes, Best.
WARNING,. You may or, may NOT Have,. a TRUE, 1/2 MOA, Rifle !

I think many have a 1/2 or 1/4 MOA rifle with 3 -5 shot groups, but once you compile a group set of 30, not so much. I used to get my load to shot sub 1/4 MOA for 3 shots and then when a shot missed that mark, it was blamed on being a "flier", the wind or me pulling it. Now I know that the sub 1/4 MOA group was just 3 shots close together in the cone of dispersion. I now focus on mean group size and not total group size. Mean group size takes into account every shot in the group and not just the two that are furthest apart and is a much better predictor of your probability to hit a target.

 

[Willys]

If you don't tune a load to optimum jump you will get random results and some shots will be close to each other and some won't - ie "cone of dispersion". If you rely on this data to decide tuning for optimum jump doesn't work you may be mistaken. This study admittedly never found an optimum load. Hmmmmm

 

[Idaho Lefty]

I think many have a 1/2 or 1/4 MOA rifle with 3 -5 shot groups, but once you compile a group set of 30, not so much. I used to get my load to shot sub 1/4 MOA for 3 shots and then when a shot missed that mark, it was blamed on being a "flier", the wind or me pulling it. Now I know that the sub 1/4 MOA group was just 3 shots close together in the cone of dispersion. I now focus on mean group size and not total group size. Mean group size takes into account every shot in the group and not just the two that are furthest apart.

****,.. You sound like, My Son ! ( He's Bought into, the Hornady, chit,. LOL )
He's finally gotten me to Shoot, the 10 Shot, 200 Yard Groups and that's,.. Humbling, enough !
Sometimes, I Will shoot a second, 10 Shot group, just to PROVE to Him that,.. My Rifle / Load,.. "Can Do, It" !
Thirty Rounds,. NO Way,. LOL,. I don't want to, wear My Barrel, Out !
A 1 to 1 1/2 inch, 200 yard, 10 shot Group, Now,.. "Looks", pretty Good !

 

[VenatusDominus]

If you don't tune a load to optimum jump you will get random results and some shots will be close to each other and some won't - ie "cone of dispersion". If you rely on this data to decide tuning for optimum jump doesn't work you may be mistaken. This study admittedly never found an optimum load. Hmmmmm

Agreed, but statistically speaking the only way to arrive at an optimal load is shoot a large enough sample size. If you shoot your optimal load in 3-5 shot groups and plot the data over a total of 30 shots, believe you will find it will not shoot a statistically different group size than another compiled 30 round group with same powder/bullet and a "sub optimal" seating depth. I am hoping to test this, but have not had the time at the range yet.

 

[Idaho Lefty]

I Try to Tune my Bullets for,"Optimal, AVERAGE Jump" then IF, within .005 +- I don't "Worry", as the Throat is MOVING forward about, .005 to .008 EVERY, 100 Shots, in a fairly Hot, Hunting Rifle, Cartridge,.. anyway !
IF my group's Do "Open Up", later, I May have to, "Re-Tune".

 

[Phil Rizzo]

I have gotten in the groove of taking a mid-range powder charge and working on seating, starting 10-15 thou off the lands and moving the bullet deeper in until the shrinking trend is broken. Then I back up, of course. And hopefully the node is wider than .003

The I raise powder until it gets good, and if it doesn't I change powder. If I like it, it has to repeat. Again that day and usually on a couple more attempts. May be tomorrow, may be next week or whenever I can.
Just my habit. Not saying it's best or the only way by any means. But it has served me, for hunting and play. I have no competition experience.
I'll play with neck tension a tad too, usually a thou on either side of .004
The above is using Berger Hybtids.
Nosler BT-AB are not treated the same, by me.
I'm going to play with some mono's at some point.

 

[Idaho Lefty]

I move My Bullets "Jump" .020 to .030 per Time when, Load Testing, I Can't shoot good enough to see,.. a .003 Bullet,. "Move".
We've Had,. terrific, repeatable, group's and Kill's on Game with, Berger Hunting VLD's / Classic's and Hornady ELD-X / M, Bullets.
I Try to Find, Max / Safe, Powder charge at, .020 to .025 Off the Lands,. THEN "Move" the Bullet,. in / Out.
In my 6 XC, I back off about, a 1/2 a grain of Powder, from Max chg when Lightly "Jamming" the Bullet into, the Lands as, the 107 grain SMK's shoot BEST,. "Jammed" for, Me.

 

[birddog 68]

have gotten in the groove of taking a mid-range powder charge and working on seating, starting 10-15 thou off the lands and moving the bullet deeper in until the shrinking trend is broken

This is how I have been doing it.
If I don't get to my expected velocity I just change powder but keep the seating depth that was preferred with original powder.
This has worked well for me.

 

[RichCoyle]

I think many have a 1/2 or 1/4 MOA rifle with 3 -5 shot groups, but once you compile a group set of 30, not so much. I used to get my load to shot sub 1/4 MOA for 3 shots and then when a shot missed that mark, it was blamed on being a "flier", the wind or me pulling it. Now I know that the sub 1/4 MOA group was just 3 shots close together in the cone of dispersion. I now focus on mean group size and not total group size. Mean group size takes into account every shot in the group and not just the two that are furthest apart and is a much better predictor of your probability to hit a target.

With my .223 I fired a ten shot group at 100 that was 7/16". Then I did it at 200 yards and the group was 7/8". If I fired twenty more at 100 and 200 respectively, would the groups get bigger?

 

[Phil Rizzo]

More importantly, would it help you hit more targets if you dump another 40 rounds?
Would you seek a better load if the groups increased 50%?
If it's not a comp gun I'm betting I know the answer.