R9 barrel pic

[R9SCarry]

Out of interest - taking some pics today .. tried to get a shot of R9 barrel . to show rifling.  Not easy in fact ..... depth of field and lighting logistics!

Got this one and so .. thought it might be of interest to some .... and shows the RH twist (1:18 Eric??  Shucks - I forget and haven't worked it out!).

The specular background is a rather dusty mirror - used to get a light source reflected!!!  Could be better.

[MurrayNevada]

Can someone explain the rationale for different "barrel twists?"  Why does a manufacturer choose right over left?  What does the different ratios ( i.e. 1:18 ) accomplish compared to other ratios?

[shooterjb]

Hi Murray,

Not to give the short answer, but the twist in the barrel serves to stabilize the bullet in flight so that your bullets don't squirt out of the barrel and keyhole into the target. The rate of twist is calculated to stabilize the bullet for the caliber of bullet and the normal velocity range that it will be fired at. 1:18 means that the rifling in the barrel will spin the bullet one complete revolution in 18 inches. The lower the second number is the faster the rifling is considered and the higher the second number is the slower the rifling or spin on the bullet is considered. Volumes have been written on the subject but the short answer is that the rifling in the barrel imparts stability and accuracy to the bullet. I hope that this has been of some help.

Frank

[Richard S]

Frank:

That is about as fine and concise an explanation of the subject as I have seen lately.

RS

[RJ HEDLEY]

R9SCarry
That is a great job you,and camera, did on the barrel shot...

[R9SCarry]

Just quick addition to Frank (#2)'s excellent twist synopsis.

Mike ... the choice of RH or LH is in some ways perhaps arbitrary, tho right is the more common.  I fancy the torque effect from right twist (gun rotates left - counter -clock) are better and more naturally absorbed by right hand shooters.  may be wrong tho too!  

A very broad generalization - twist rates tend to be on low side for lower velocities .. handguns ..... and rise with high velocity rifles.  1:7 is my Mini-14 twist, which is meant to be able to stabilize a 69 grain or even heavier bullet .... as long as they don't fly apart!

Almost any axial spin is good ... but not much point in trying to ''over spin'' a low velocity bullet .. it is probably used at short ranges ... and the effort required to impart high spin rate is, IMO, going to be quite significant.

[shelb]

This page has some pretty nice descriptions, as well as some mathematical relationships between bullet geometry, velocity, and twist.  Its a very intersting read.

http://www.aeroballisticsonline.com/ballistics/riflings.html

[R9SCarry]

Handy link Shelby .... quite a lot of info all in one place.

Pity about the annoying javscript mouse follower script!

[Texas_Bob]

  I'm "surprised", that with all the knowledgeable people on this BB, NO ONE caught the fact the picture captures a good image of the "freeboring" of about .02(guessing) that shows the "little" extra care that goes into an R9.

[R9SCarry]

Bob .. you'll have to believe me here .. I very nearly did point out just that - but as it was so apparent thought I'd be just insulting others by mentioning it!

Indeed ..... more Rohrbaugh finesse.

[Texas_Bob]

  I guessed freebore of .02, wrong, from the owners manuel, bbl freebored 0.250 inches.