Help with rate of twist

Anees

Anees

Member
Rating - 99.7%
393   1   1
Location
Nova Scotia
Hi Gents

Using Load from a disk, I would like to load 7mm-08 using a 162Gr Hornady which the program states that it will need a rate of twist of 9. Yet the barrel has a rate of twist of 9.5,,
Would that still stabilize the 162Gr.


Any intelligent input would be very appreciated.

Thanks in advance

Anees
 
You will have to try them, some barrels like yours could be closer to 10 twist or could be closer to a 9 twist
 
Twist rates stabilize a broad range of bullet weights, (actually bullet lengths), even if the mathematical formula seems to suggest a specific bullet weight for a given twist or a specific twist for a given bullet weight. Consider that in the .30/06 a 1:10 twist will stabilize bullets from 110 grs to 240 grs. When you get into a bullet weight that is marginal and shows a tendency towards instability, a round nosed flat based bullet is as short as is possible for a bullet bullet of that weight and therefore has the best chance of stabilizing. I see no reason why a 1:9.5 twist would not stabilize bullets up to 175 grs in the 7-08.

Just so there is no misunderstanding, while accuracy is dependent on stability in flight, stability in flight does not ensure accuracy. If bullet X groups into 3" that is not a sign of instability. But, if the bullet holes in the target are elongated or key-holed, that is an indication that the bullet has not stabilized.
 
Last edited:
I came up w/ a load for my 7mm-08. H-414/ 162 Hornady btsp/ Rem brass. The bullet stabilized just fine out of my m70 classic featherweight, but I can't be sure what it's got for a twist rate. I wouldn't expect you to have any trouble getting the bullat to stabilize, but you will have to try them for yourself to be sure. If they don't work, go get some 120-140 TSX and never look back.
 
Measure the bullet length and apply Greenhiil'S formula :
Twist = 150 x diameter squared / Bullet length.
That should be a good indication. Then you need to try it in your rifle.
Grouch
 
Boomer said:
When you get into a bullet weight that is marginal and shows a tendency towards instability, a round nosed flat based bullet is as short as is possible for a bullet bullet of that weight and therefore has the best chance of stabilizing.
Click to expand...

X2 for me. I have found over the years that VLD bullets are the most sensitive to instability due to twist in my rifles. fred
 
One thing to keep in mind is that if it turns out that you are on the very edge of stability, air density will make a difference. Thus, you could work up your loads on a sunny July day and everything will be gravy, but take them out on a crisp November morning and they won't shoot worth a poop.
 
You must log in or register to reply here.
Back
Top Bottom