key hole with custom tube.

[SierraCJ5]

This is an interesting problem. I have a 14 twist 22-250 that shoots the 55g V-Max into tiny groups. I once ran the stability numbers with Applied Ballistics software and it wasn't even close to being stable, but my experience differs. I'll try to get a picture of a typical group posted tonight. ???

 

[Hatchet_Jack]

As has been pointed out, its not necessarily weight, its length and shape. I had a 22-250 and started testing with 50 and 55 grain bullets. All shot poorly BUT all were boattail bullets. I was about to give up but tried 55 grain flat base bullets and it shot 5 into one hole. The powder didn't matter either. It just wouldn't shoot a boattail for some reason but was incredibly accurate with several different flat basers.

 

[AlNyhus]

I am caught up in this stability business. I ran the numbers on typical 30 BR BR bullets and they come up in the red....I ran a typical 6 ppc match bullet and it comes up yellow. For all practical purposes, these bullets shoot hundreds of sub 0.250 aggs every match season @ 100 and 200 yd events.

What did you use to calculate the stability? -Al

 

[LHSmith]

Al--- 0.243/66/0.810/3200/14..........0.308/118/1.000/2975/18

 

[AlNyhus]

I meant which program was used to calculate the Sg? -Al

 

[LHSmith]

The simpler formula, the second one you referenced in the above post.......I don't have the bullet geometry info do input in the first formula.

 

[AlNyhus]

You'll find that if you run the parameters through the McCoy Drag/Twist formula, the results will be significantly different.

As an aside, the McCoy program played a key part in the development of the so called 'slow twist. .30 cal. efforts in BR. Randy Robinett has chronicled this extensively both online and in the Precision Shooting Magazine article 'Confessions of a Ballistic Idiot'.

For anyone that wants to truly understand rifle precision, a thorough understanding of bullet stability is a must.

Good shootin'. -Al

 

[LHSmith]

Al- I know Robinett is "THE" guru when it comes to the 30 BR and that he often advises on stability issues on these forums....I did not know how he calculated stability.
However, the short simplistic version of the stability formula seems to be of little value, since the calculated values between the two formulas are so far apart.