Bullet Stability Questions

[RockChucker]

I recently finished chambering a Lothar Walther 1-8" twist barrel in 22/250 AI.
Haven't had a chance to test beyond 100mtrs for accuracy. Chronograph not dependable @ -25C so I haven't checked velocities yet.
What is the maximum bullet weight that will stabilize @ 100mtrs out to 1000yds?
Found Lapua Scenar 77gr. , Sierra HPMK 80gr. to work well in the accuracy department. Berger 90gr VLD are another story, first three loads shot well under an inch @ 100mtrs but all bullets went into the paper tipped to almost full side on. The last load tested {not max charge yet} all bullets went point on, grouping just under .300". I'm sure I can up the powder charge a couple of more grains to gain more velocity. Just curious as to if this bullet will remain stable out to the 1000yds.
Obvious that once I get my chronograph working {when it warms up} and get a velocity reading I should be able to determine downrange velocities.
I haven't seen any test results {loading data} for the 90 VLD bullets in the AI version so I had to start in the basement and work my way up. I'm sure the 77 -80 gr bullets will easily top out @ 3300 fps out of a 26" barrel.
Any real world results and information would be appreciated.

RC

 

[ajax]

i think you will find that a 1-8 twist is about the boundries of a 80gr pill, but when you add a cold temp into the equation you might need a faster twist rate.

 

[Mystic Precision]

I shot the 90gr VLDs in my Shilen 223 at just under 2700fps and it made it no problem to 1200yds which was the furthest I was shooting at the time. This was done to check stability.

With your extra speed, you should be able to get them to work out ok. But then there are 8 twists and then 8 twists.

According to the calcs, the 8 twist is right on the borderline of stability.

The 80's will go no problem and definitely 3300fps is within the realms of possibilities - already been shot by other varminters in the US. Not sure how the Bergers will do at that speed though.

I will be putting together a 22/250 with a 7 twist. The 90's will have no issue with this twist.

Jerry

 

[rnbra-shooter]

If a bullet is stable at 100 yards, it'll be stable out to 1000 yards and beyond (except for some pretty unusual special cases). Bullets get more stable as they go.

Sounds like you have been able to get your 90 VLDs to stabilize; good!

Denser air makes it more difficult to stabilize a bullet. (Even if you couldn't get your 90 VLDs to stabilize at 100 yards, it would be worth trying again in warmer (less dense) air.)

 

[Mystic Precision]

If a bullet is stable at 100 yards, it'll be stable out to 1000 yards and beyond (except for some pretty unusual special cases). Bullets get more stable as they go.

Sounds like you have been able to get your 90 VLDs to stabilize; good!

Denser air makes it more difficult to stabilize a bullet. (Even if you couldn't get your 90 VLDs to stabilize at 100 yards, it would be worth trying again in warmer (less dense) air.)

How true? a tumbling object doesn't get straighter further downrange

I found the 90gr Bergers to be very easy to dial in. I was expecting a PITA bullet given all the comments. But it loaded up and shot great with simple loading tuning.

I even had them set to mag length feeding so certainly away from the lands. Shot great.

Quite a number of shooters are finding success with 7 twist which would be my SAFE recommendation. I think shoooters were going with too fast a twist rate at 6 and 6.5.

If I had an 8 twist, I would also send some downrange to see what would happen. May just surprise you.

Another local shooter has been testing these bullets and getting 1/3 min accuracy 10rds at 300m. Set up for both F classes. His 223 loads are right aroung 2800fps so we have a competitive set up for F TR.

Look forward to getting my barrels and sending more downrange.

Jerry

 

[gunrunner8]

The faster the bullet spins, the better for its stability. Acording to old Greenhill formula bulets that are 2700fps or more can use #170 constant and up to #190. Lenght of bullet-L=170xdia square /8" (your twist). With that numbers You will stabilise bullets up to 1,o66" in lenght. Your rifle being 22-250AI and speeds of bulets up to 3300fps and #190 constant I would even experiment with bullets up to 1,191" in lenght. I hope this will be of some use to You.

 

[Suputin]

How true? a tumbling object doesn't get straighter further downrange

There are degrees of instability which can range from a slight wobble to spinning completely sideways. A bullet that is totally unstable is not going to regain stability with distance. However a bullet that displays only minor instability should gain stability with distance because its forward velocity drops quicker than its rotational velocity.