SD and extreme spread?

[74honker]

Just curious whether the brass was new or already fireformed? I've had similar spreads and good groups, retested the FF brass and it all came together inline. Like others have said, retest and see if it's repeatable. If so I'd take that any day!

 

[Longtine88]

What Lance said above

 

[ncfireman83]

I recently built a 280ai and noticed with both a 140 AB load and a 160 AB my best "groups" so far out to 300 yards (holds .5 MOA all day long, are not my best ES and SD numbers. I still have found close to .5 MOA with single digit ES and SD loads but at the end of the day it's a hunting rifle…. An animal doesn't care or notice what your ES and SD's were that you hit them with. In saying this, I plan to take those same loads out to 500 this coming week, time and weather permitting and shoot more than 3 shot groups to get better data. In working my load developments I'm trying to conserve components and running to a range close to my part time job after work. Blue targets were initial tests at 100 yards and cardboard was at 300. The 300 yard tests were only the 3rd time shooting at that distance for me and we had more wind that day down range than we wanted for working with load development but sometimes you gotta do what ya gotta do when you can do it.

 

[Tiny Tim]

Alot of your groups seem to have 2 close together and one that opens up the group. Is this "flier" the same bullet in each shot sequence? Try letting the barrel cool longer between shots, and shoot a 5 shot group. I think your close to havinga great load, just need more data.. A 1.5" group at 300 yards for the first time is spectacular.

At 300 yds, your group is still .5 moa. That's darn fine if you can do it day in and day out, especially in less than ideal conditions.

 

[FireFlyFishing]

 

[bangstick]

Just curious whether the brass was new or already fireformed? I've had similar spreads and good groups, retested the FF brass and it all came together inline. Like others have said, retest and see if it's repeatable. If so I'd take that any day!

It is lapua brass. Fired 4 times. I FL resize. BR2 primers, V 565.
I appreciate all the help. I will load again test.

 

[bangstick]

I recently built a 280ai and noticed with both a 140 AB load and a 160 AB my best "groups" so far out to 300 yards (holds .5 MOA all day long, are not my best ES and SD numbers. I still have found close to .5 MOA with single digit ES and SD loads but at the end of the day it's a hunting rifle…. An animal doesn't care or notice what your ES and SD's were that you hit them with. In saying this, I plan to take those same loads out to 500 this coming week, time and weather permitting and shoot more than 3 shot groups to get better data. In working my load developments I'm trying to conserve components and running to a range close to my part time job after work. Blue targets were initial tests at 100 yards and cardboard was at 300. The 300 yard tests were only the 3rd time shooting at that distance for me and we had more wind that day down range than we wanted for working with load development but sometimes you gotta do what ya gotta do when you can do it.

Iv always struggled with distance of my tests. Everybody said 100 yards but i have hhad
Loads that barley shoot moa at 100 and and at 300 +, 1/2". I will definitely go further out and like you, increase groups to 5. This is a hunting rig like yours. As long as it hits to 600, I'm good.

 

[ncfireman83]

Alot of your groups seem to have 2 close together and one that opens up the group. Is this "flier" the same bullet in each shot sequence? Try letting the barrel cool longer between shots, and shoot a 5 shot group. I think your close to havinga great load, just need more data.. A 1.5" group at 300 yards for the first time is spectacular.

At 300 yds, your group is still .5 moa. That's darn fine if you can do it day in and day out, especially in less than ideal conditions.

Those fliers were actually first shot on each. Can't figure it out for the life of me, very well could be me though. Before I start down the road of seating depths I'm going to try Winchester LRP to see if that makes a difference.

 

[ncfireman83]

Iv always struggled with distance of my tests. Everybody said 100 yards but i have hhad
Loads that barley shoot moa at 100 and and at 300 +, 1/2". I will definitely go further out and like you, increase groups to 5. This is a hunting rig like yours. As long as it hits to 600, I'm good.

I have a great friend whom I actually met on this forum that has helped via FaceTime and voice calls on numerous occasions as I start reloading 2 years ago. One of the best bits of advice he told me was this, don't settle on a load that's in or near the same hole at 100 nor the one that is 1 1/2 to 2" at hundred with good numbers…. That great 100 yard group may turn to crap past 200 and that 1 1/2" to 2" group may tighten up to 1/2" at 300 and beyond. I'm anxious to shoot these at 500 to see what they do! I also have some Hammers in 152 HHT and 163 HHT that I'm going to shoot for groups. I've loaded Hammer hunters in my .308 and they are hands down some of the easiest to load for and the most accurate bullet I've ever shot. Both weights in the HHT have shown very promising outcomes. So much so I ordered some 182's in the HHT to try in my 300 WSM. Good luck with the load development and keep us posted! I will do the same here on my end

 

[Dentite]

Iv always struggled with distance of my tests. Everybody said 100 yards but i have hhad
Loads that barley shoot moa at 100 and and at 300 +, 1/2". I will definitely go further out and like you, increase groups to 5. This is a hunting rig like yours. As long as it hits to 600, I'm good.

I've heard guys talking about this on the forum and it makes no sense to me. Can you provide a scientific explanation as to why/how a 1 MOA group at 100 would be a 1/2 MOA group at 300?

I'm not saying it's impossible. It could certainly happen. But for it to consistently happen? I just don't see how it's possible.

 

[ncfireman83]

I wish I could explain it! I personally haven't shot enough at distance or been in the reloading game enough to see it first hand but I do trust the seasoned guys if that helps

 

[bonie]

move your seating depth in and out (preferred) buy .001 steps and see if it tightens up. if so run your chrony tests with a larger test # of rounds. see what ES and SD looks like then but believe the target!

 

[Okanogan]

If you have access to Bryan Litz's Modern Advancements in Long Range Shooting he has a good explanation of trade offs between velocity consistency, ammo/ rifle precision and some of the other factors affecting long range shooting from a statistical sense at varying ranges. (He calls it WEZ modeling for weapon effect zone) The book would say SD/ES in the original post aren't great but they shouldn't be much of a factor out to 600 yds +/-.

I agree with the earlier posts that suggests more data to ensure repeatability. If it were my load development effort, I'd be concerned if there was a big different in group size as the distance from the lands increases by only 0.015. This link might provide a little more consolidated bullet jump information than the video's linked earlier in the thread. https://precisionrifleblog.com/2020/04/28/bullet-jump-research-and-load-development-tips/

 

[Doom2]

It often seems to be overlooked that trying to compare 100yd group dispersion with chronograph data including SD and ES is not practical. The flight time to 100yds of most centerfire cartridges is so short that vertical dispersion is minimal. In the case of a 69gr SMK it requires about a 100 fps to move the vertical POI by about 0.2" or one bullet diameter. In the case of a 168 SMK (308) its about 130 fps to move the POI by about 0.3" or one bullet diameter. This essentially means that the dispersion in groups at 100 yds is a function of factors outside of velocity and incremental charge weight and is predominately a function of barrel harmonics and chamber/cartridge/barrel interface.

As for groups improving at distance that is observed but to the best of my knowledge is more related to shooter and small sample sizes. The trajectory of the bullets require some external force to change the path.