Joe, I ran some numbers through the JBM stability calculator !!!

From what I'm seeing the 9 twist should work. Depending on your actual velocity I could see where you could start having an issue when the temps drop below 20.

Joe, you didn't say what powder you are using. You could have a double wammy of cold day needing more bullet stability due to the denser air and cold day reducing your velocity provided by your powder. I'm using the 62gr Barnes TSX in my 1:9 twist 16 inch with Varget about .5gr under max load. I've had good groups at 100 yards. Varget is supposed to be pretty consistent with varying temperatures. Regardless, the 55gr TSX should give you higher velocity and stability

heres a thought Joe. maybe try to take the offside shoulder out. that way you get your good lung\blood vessel distruction and maybe not so much mobility after the shot. the 223 may not enuf oomph to give a exit wound but your photos show you have energy to spare. just a thought.

I checked the stability factor for the two different bullets. The velocities are an estimate based off Barnes data for Varget powder and reducing for our 16" barrel. I assumed about 30 fps loss per inch. The stability of the 62gr is marginal. I estimated bullet length for the 55gr based off their 53gr TSX. Muzzle velocity changes has little impact. Drop the temp 30 degrees to 20 F and you loose almost a .1 of stability. Looks like the 53 to 55gr TSX would work better in our shorter barrels.

Caliber _ 0.224 Inches
Weight _ 62 Grains
Length _ 0.942 Inches
Twist _ 9 Inches/turn
muzzle vel _ 2700 fps
Temp _ 50 degrees Fahrenheit (59 is standard)
Pressure _ 29.92 inches of mercury (29.92 is standard)

Sg = 1.28


Caliber _ 0.224 Inches
Weight _ 55 Grains
Length _ 0.8 Inches
Twist _ 9 Inches/turn
muzzle vel _ 2900 fps
Temp _ 50 degrees Fahrenheit (59 is standard)
Pressure _ 29.92 inches of mercury (29.92 is standard)

Sg = 1.84


Sg shouldn't be less than 1.4. If Sg is greater than about 2.0, you may gain some accuracy by going to a slower twist barrel.

slimjim wrote:

I checked the stability factor for the two different bullets. The velocities are an estimate based off Barnes data for Varget powder and reducing for our 16" barrel. I assumed about 30 fps loss per inch. The stability of the 62gr is marginal. I estimated bullet length for the 55gr based off their 53gr TSX. Muzzle velocity changes has little impact. Drop the temp 30 degrees to 20 F and you loose almost a .1 of stability. Looks like the 53 to 55gr TSX would work better in our shorter barrels. Caliber _ 0.224 Inches Weight _ 62 Grains Length _ 0.942 Inches Twist _ 9 Inches/turn muzzle vel _ 2700 fps Temp _ 50 degrees Fahrenheit (59 is standard) Pressure _ 29.92 inches of mercury (29.92 is standard) Sg = 1.28 Caliber _ 0.224 Inches Weight _ 55 Grains Length _ 0.8 Inches Twist _ 9 Inches/turn muzzle vel _ 2900 fps Temp _ 50 degrees Fahrenheit (59 is standard) Pressure _ 29.92 inches of mercury (29.92 is standard) Sg = 1.84 Sg shouldn't be less than 1.4. If Sg is greater than about 2.0, you may gain some accuracy by going to a slower twist barrel.

Im using 25 grains of Varget. Im gonna try the 55 grain TSX and see what happens. My buddys Bushmaster is shooting the 62's ok at 100yds I guess mine dosean't like them. Thanks for the Info. Do you have a program on your computer to figure that factor out ?
Joe

JBM stability calculator

www.jbmballistics.com/...ab-5.0.cgi

chambered221 wrote:

JBM stability calculator www.jbmballistics.com/...ab-5.0.cgi

Thanks Buddy

Here is another source. They provide some explainations and an excel spreadsheet you can save to your computer to use at anytime.

Calculating Bullet RPM — Spin Rates and Stability

slimjim wrote:

Here is another source. They provide some explainations and an excel spreadsheet you can save to your computer to use at anytime. Calculating Bullet RPM — Spin Rates and Stability

Cool Thanks.

Joe