DanDeMan wrote:................Below is a link to some pics of the Swiss Rifle Club. Click on Gallery to see the pics. You can see the HP rams way up on the side of the mountain from the firing line. Their Mother's Day and Father's Day HP silhouette matches are awesome. There is a huge feast that goes on after the match with several hundred members and friends in attendance. And, for you gambles they have dice and card games going on as well as an open bar.

http://www.theswissrifleclub.com/

Dan, We'll have to see if Al can post some pictures of the Consolidated Sportsmens club in PA. The rams there are up on the mountain as well.

Yeah, agreed... shock wave. I had it right at my finger tips but forgot about it. The aging mind thing, ya know.

Dan, I had a feeling you would know!
It's fairly common to see the glint of the bullets at CRC, when the angle of the sun is right for it they can be seen for most of the flight to rams. Funny thing is that most of time they don't appear to be on the correct path looking like they will fall short or go over the top on what turns out to be a good hit.

Pop Quiz.....how many complete revolutions did that 150 gr. Match King make before striking the turkey? From the case mouth.

Bob Mc Alice wrote:Pop Quiz.....how many complete revolutions did that 150 gr. Match King make before striking the turkey? From the case mouth.

I'd guesstimate something like 2,131.

WRONG...but thanks for playing.

I did 547yds x 3 = 1641ft

1641ft+2ft (barrel) = 1643ft

1643 x 12in = 19,716 inches

1 in 9.25 twist rate

19,716 / 9.25 = 2,131.5 rotations. This of course doesn't take into account changes during time of flight.

Bob Mc Alice wrote:Pop Quiz.....how many complete revolutions did that 150 gr. Match King make before striking the turkey? From the case mouth.

Bob,

Since I believe your rifle's ROT is 9.25" per rev, the math is easy. Turkeys are 385 meters. The conversion factor is 2.54 cm per inch so:

38,500 cm / 2.54 cm per inch = 15, 157" Now divide that by 9.25"per rev and we get 1,638 revolutions to turkeys.

OH. I was calculating to Rams.

Duh.

Oh, and based off the 208,000 RPM I'd be somewhere in the 2773 rotations area to Rams.

To Turkeys I get 1641 based on twist rate, and 1733.3 based on RPM of 208,000.

Dan, you forgot the 2 feet of barrel length.

Trent wrote:Dan, you forgot the 2 feet of barrel length.

Trent,

I figured the muzzle was at the firing-line. And, since the forward motion of the bullet is retarding faster than its spin-rate, the actual number of revs will be greater than what I posted. That is, one rev of the bullet happens in shorter and shorter distances as the bullet flies down range. At the muzzle 9.25" of travel is required for one rev of the bullet. At the turkey is will be less. I can't think of how to calculate that decrease over the time-of-flight. But, we can estimate the number of revs using the bullet's time-of-flight. Be back soon.

You are both very close, my twist rate is NINE per. We have winners! I will instruct Mordecai to mail you each the latest edition of the Steelchickens.com sticker.

Time of flight based on that days weather conditions and bullet technical data is .52 seconds.

OK, back...

If we assume Bob's Big Boy was going 2,600 fps out of the muzzle, given his barrel's 9.25" ROT the bullet was spinning at 3,373 revs per second at the muzzle. Estimated time-of-flight to turkeys for the 0.435 BC bullet is 0.581 seconds. So, 3,373 rev per sec X 0.581 sec = 1,959 revs to turkeys. But, the actual number of revs will be lower due to the spin-rate decreasing with range caused by what's called "skin drag." We see that the estimate I made using distance and ROT was too low while the estimate using time-of-flight and RPS is too high. So, the actual number of revs is somewhere between those two estimates.

I read somewhere years ago that the rpm's increased once the bullet left the barrel for a short distance then slowing down due to the friction of the rifleing grooves on the surface of the jacket, not so? They used a childs toy top as an analogy as I recall.


BTW Bob, that reloading manual you have is highly sought after by book museums, I hope you have bought a new one in the last 35 years!!!
My first rockchucker kit came with one of those, #10 or #11, that was a while ago.