Vertical dispersion at 600 yds to 1000 yds

[GSells]

A relevant old thread . Just don’t take any notice of that Plumbd bloke lol!

[GSells]

Ok last one ! I just want to say a disclaimer! With the up coming Nats which will be my first in open ! I realise that by putting up my testing and experiences has made me little bit of a target ( pardon the pun) truth is I'll be pooping myself on the 300 yd line in a couple of weeks ! So don't read much into my abilities as there are sooooooooo many world class shots ! I just need to take that pressure of myself or I'll know I'll crash and burn !

With that out the way ! This one is at Belmont again at 600 yds , 168 load which at 300 for 4 shots went through the same hole ! I blamed my rest and some is shooter error !

What caused that ?? I won't keep u in suspense!
My rectile was out of focus! Redid it and it grouped again ! All be it with 180 load but yep was all over the shop!

The 168 Gr load in the above post with 3 shots side by side ( hardly a scientific sample but shows promise) is the same load !

look great threads that for me started at development squad and training sessions ! I think we have all benefited and had some real input from world class shots ! I will be reading over and over again a few time to get it to sink in! Kind regards Graham Sells Dalby/ Tara rc

Well 3 odd years later , my words came back to haunt me , I cannot stress how important it is to have your graticule focused properly . Especially with my astigmatism which is in the vertical! The difference was my x count went through the roof and the groups were reliable!!
This was a great thread and reviewing it shows how much enthusiasm I had and how green I was too!
Look these days I will only comment to help others and newbies .

[GSells]

Ok , deep breath! Gyroscopic torque precession vertical! This is a theory only and from a dumb Plumber at that ! But it seems to explain the phenomenon that I've been experiencing over the past few years and most notably at Squad and practice over the past 10 months. In the past Mr Litz has said ( and I think a lot of Mr Litz!) that head and tail wins don't amount to much vertical! About 2" at 900 yds !

One of the wonderful things with a really accurate Rilfe is there is a good chance of patterns developing . Yes some of my vertical is me , and in the earlier days when I use too bag my Teamie Ecomeat about his OCD reloading practices ! My loads May and I'm sure they weren't good as they should've , as the x ring just seemed elusive even at the best of times ! So some can be blamed on reloading and sd or a poor compensating tune !

However there has been a pattern developing of heads winds drop rounds low and tail winds lift rounds high in relation to the strength and direction of the wind !
So Mr Litz says heads and tail winds vertical are nothing to worry about ! But experience and head scratching says something else !
Leads to the Question " What the fire truck is going on!)

Let's examine ( from a plumbers view) the forces at play!
Magnus is a minor effect ( rh wind ) and to some effect in a right wind right twist barrel goes against aerodynamic jump as it creates downward lift . As aerodynamic jump is more powerful and wins out and creates lift from a right wind .
Remember the pill is doing about 300 000 rpm and is creating lift !

Ok if aroedynamic jump was what was causing a 2-8 clock slide it would be creating the most lift from a full value right wind and would likely to producing groups in an upside down v .
But it's a linear 2-8 slide ! Left wind from 8 - 10 clock produces a 10-4 slide was and is explained by aerodynamic jump!


But what's happening the other direction!???
First up let's look at the below YouTube video and see the force in plain action !
http://youtu.be/GeyDf4ooPdo
Your bullet is doing the same thing and is pointing slightly nose high and a little right as the metplate is chasing the tourque . If it were possible to insert a shaft into the base at 300 000 rpm into 180 Gr vld pill the metplate would want to chase the torque I the direction it's spun . This is part of the force of spindrift and Magnus does the rest . Which is worth in the Southern Hemisphere with coralis effect helping us , at 1000 yds Brisbane Lat about 1/2 Moa from a 100 yds zero 180 Gr 7 mm pill 1:9 twist.

Back to Rh winds and head winds ! When the winds come from 12 clock the pill is induced under load and lifts the nose slightly higher and causing or changing the BC lower and drag higher . Thus causing the round to go low .
Is the effect linear ? Yes , to a point until the gyroscope loads up enough and says no more yaw ! So from light to moderate winds the effect is most noticeable! Length of the pill and the leverage that can loaded up too can have an effect to a point . But our 7 mm pills are quite efficient compared to a 155 .308 and time of flight is shorter so it's not as noticeable ! A good argument for a Saum !


The opposite happens when the wind is behind and makes the round go high with a slightly more nose down attitude and more aroedynamic flight !

Wind from 2 clock tends to drop rounds at 8 clock and rounds that are shot in a 4 clock wind tend to drop rounds up in the 2 clock area . The effect seems to be more unpredictable from a right wind with aroedynamic jump fighting against the wind and torque .
Left winds seems to be a little calmer but similar effect !

Like I said theory from a plumber so most likely rubbish.

Lastly I've shot the ton that much this year if I said 30 times or more I think that would be about right thanks to squad and has pushed me to hopefully be a better shot and person ! Getting off topic !
There seems to a speed , twist relationship to dynamic stability at 1000 yds . Meaning even if you have a perfect load , sd etc at ranges even up to 900 yds . At 1000 yds it's just crap!
Basically stay above that area of dead speed zone ! and it can even be a fair way above the transonic region !
Look I really loves this topic and I love this sport because of the physics!
This is a theory so take it as Mills and Boone type reading !
Better than watching Neighbors! Hehe!

Struth , did I actually write this ? This basically explains head and tail winds . Still some conjecture whether right winds or left winds are better . Willaidia told me once ( my Sensai !!) a right hand twist
Is crashing into a rh wind causing problems. Personally I haven’t really noticed.
Good revision !!