This rifle has a 1:12 rifle twist, so does it stabilise 300gr SMK bullet for extra long range shooting ?

-- mike (mike@ipod.com), March 13, 2003

Answers

The weight of the bullet is not, directly, the critical determining factor; rather, it is the length. While a heavier bullet in a given bore diameter generally involves a longer bullet, even a significantly lighter bullet with a more streamlined ogive (>10 caliber secant), a small, rounded meplat and a longer boat tail calculated not to cause loss of laminar flow and hence minimal aft turbulance will generally be longer than a poorly designed, large meplat, short ogive flat-base bullet.

The widely but incorrectly assumed belief that driven an overly slowly spun bullet will correct for the asininely slow twist in nearly all rifles due to the 1879 formula derived by Sir Alfred George Greenhill does not remotely apply to sharply pointed, boattail bullets, especially those which have a "rho" (specific gravity) below 10.9 (pure lead is about 11.45 grams per cc or 11.45 times heavier than water at its most dense point of 4 degrees Celcius for the exact same volume, which is the definition of specific gravity). Pure copper or copper:zinc alloys (much, much less prone to causing severe barrel fouling) are below a specific gravity of 10.

In "the olden days" (which were not so long ago), many bullets had voids in them, making them dynamically unstable for precisely revolving about the center of form, but instead revolved about their randomly offset center of gravity. The rifle and pistol manufactures therefore used the very slowest possible twist rate in order not to exacerbate the common problem of serious bullet defects, as quality control was so poor, and hunters were generally so appallingly ignorant or worse.

With the current vastly increased competition, many of the higher quality bullets manufactured are now void free, allowing the gun buyer to demand that the manufacturer greatly increase the rifling twist or the intelligent rifleman does not purchase that brand of rifle.

Despite old wives tales and near religious zealotry fanaticism about using the slowest twist possible, with high quality bullets, there is NO -- I repeat: NO -- downside to an overly fast twist, within a sane limit of course. As Mr. Tubbs, the greatest rifleman of our time, and winner of too many highest level matches to count, has said and keeps saying: "If in any doubt, always go to a faster twist."

Those people without benefit of an education in physics and mathematics combined with pragmatic field experience, neverthe less still insist on following the long, long ago proven grossly incorrect "Greenhill Formula", primarily because it is so simple, even though known to be wrong.

For a 300 grain highly streamlined bullet for the .338 Lapua or other .338's, a twist of one turn in nine (9) inches is the MINIMUM twist to stabilize the bullet over long distances. If you plan to use copper or bronze bullets, the twist rate will have to be faster still, at least one turn in eight (8) inches.

In ordinary hunting, a much faster twist than currently offered will allow the bullet to continue on course, retaining its original orientation.

In short, there is everything to be gained and nothing to be lost by increasing the twist rate considerably faster than what is now the standard. For all of the longer, sharper, streamlined and hence higher ballistically efficient bullets, the current overly slow twist barrels will not adequately stabilize the bullets, starting from the enormously disruptive influence of the blast effect suffered by the bullet upon exiting the barrel to the effects of the enormously powerful and cumulative pressures on the nose of the bullets attempting to tumble the bullet.

If the amount of energy required to spin the bullet at these faster rates concerns you, keep in mind that the formula for angular kinetic energy is E = I(omega)^2, where "I" is the moment of angular inertia and Omega squared is the angular velocity in radians per second. All of this is less than or approximately equal to 0.5% (one-half of one percent), which is so insignificant as to be safely ignored because there are so many other variables that overwhelm this tiny factor.

If in doubt, demand a faster twist. Do not settle for less. If you cannot get what you want, then go to Krieger for a new barrel at the twist rate you know is correct (8 or 9 twist, as per your needs, again, the faster twist hurts nothing). Lost River Bullets has a web site that is supremely knowledgeable -- quite opposite to nearly all other supposedly "expert" websites and writers who discuss this subject, even benchrest experts. That is a shameful statement but true.

I hope that this helps. There are various elementary books on the subject that are simple enough that a person without any education beyond the most basic algebra can effortlessly understand. If anyone has any questions, I shall be happy to help as my time and location permits.

My real name is "Gary(space)Gerlach", but I must do all I can to prevent web bots from grabbing my address. Still, the provided email address will also get through to me if I am in America.

-- Strasse, G. (gstrasse@oriongroup.com), December 29, 2003.

In the shooting time mag issue oct 2003 there is a gun review on the sake trg 42 vwery interesting. The test he did showed that the 300 grain sierra did not stabalize after 500 yards the 250 grain shot around 5 inch groups and the 300 grain shot 8 inch groups. He thinks it needs a faster twist to stablize the 300 grains

-- Dan Phillips (daboel@triton.net), September 30, 2003.

If you look at the berger bullets website it will give you the minumum twist needed to shoot their bullet. I think you are OK from 1/13 twist and tighter. Steven Shaw

-- Steve shaw (Stevenshaw@cox.net), June 03, 2003.