Bullet Weight and Barrel Rate of Twist

NorthernCX

NorthernCX

CGN Regular
Rating - 100%
30   0   0
Location
In My House
Question for everybody:

One of the gunsmithing books I have has a chart of appropriate rates-of-twist for different calibers and bullet weights. It mentions 1-in-14 for all bullet weights in .458 caliber.

The current Marlin levers have a 1-in-20 rate; what should I be looking for for a bullet weight/length/speed that will reliably stabilize in that barrel?

Is there a formula or other, more complete chart that maybe I could use?

Thanks all.
 
I wouldn't worry about it too much if you are getting good accuracy and nice round holes in your target with the bullet you have chosen to shoot. In order for the Marlin to feed properly, you can't have too long an OAL so it is unlikely you would choose a bullet with a long nose section and apparently even a 500 gr bullet with a short flat nose section is short enough to feed and to stabilize in standard Marlin barrels.

Google the Greenhill formula. It can be used to determine the optimum length of a bullet that will stabilize in a barrel with a given rate of twist, or suggest the optimum rate of twist for a bullet of a given length. The formula is useful to a degree, but answers only the ideal rate of twist for a bullet of a given weight, construction, length and velocity. Change any one of those parameters in the equation and the answer changes as well, which disregards the fact that most bullets shoot very well in a broad range of twists, and that any given twist will provide good accuracy with a broad range of bullet weights and styles. Consider the ubiquitous 1:10 twist found in .30 caliber barrels. These barrels produce good accuracy and stability from bullet weights as light as 110 grs to as heavy a 240 gr round nose bullets (Sierra's 240 gr MK requires a faster twist). Thus you only need to be concerned about the rate of twist if you intend to shoot very heavy for caliber bullets, or if you wish to optimize the rate of penetration of a long bullet through the target by choosing a faster twist which reduces the effect of precession (yaw) from impact with the target.
 
You must log in or register to reply here.
Back
Top Bottom