Spin drift question

[Distant Thunder]

Arnie,

It would be an easy matter to calculate a shim thickness to put under the typical .500 wide base of an otherwise plumed tang sight to achieve the angle if I knew what that angle was, but as of yet I have not seen a confirmed angle posted here. A lot of numbers but no angles. I can guess that it is somewhere between 1 and 1 1/2 degree.

[Distant Thunder]

Ok,

Sifting through Dan T's post I think I finally found the answer as well at how he set up his rifles for long range.

We lost a valuable resource when we lost Dan. I know he, like all of us, had some hard edges but he could explain things so I could follow along and I miss talking with him. Rest easy, Dan.

[John Bly]

I measured the angle that the slide on the Buffington sight is to the upright staff. I measured the change in the width of the slide groove to the edge and divided by the length of the sight. This gives the sine of the angle. The angle turns out to be 1.56 degrees that the slide moves to the left as it is raised.
I hope this helps. The twist on the trapdoor is one turn in 22" if I remember correctly if this makes any difference.

[XTR]

Stumbled onto this thread and am pretty amazed at the drift at 2 to 3 moa drift at 1000,

In my F class shooting it’s just one of those things that you know for your rifle and adjust to compensate. In the case of a 308 shooting a 200 grain bullet at 1000 yards in a 1:10 it’s 5/8 to 3/4 moa.

[XTR]

I know a couple of Palma shooters who cant their front site so they don’t have to adjust for Spindrift when we shoot fullbore matches, On those days we shoot 300, 500, 600, and 1000 in the same day

[Distant Thunder]

Well, this isn't F Class that's for sure! I'll bet they don't very often have 10+ minutes of windage cranked in either. I've had 22 minutes or so a few times. It's a different world in the transonic zone!

[Don McDowell]

Pffft at the midrange match in Cheyenne last sommer it was taking about 26 minutes to hold paper at 600

[bruce m]

2 things that affect spindrift are yaw of repose of the spinnng bullet, and time of flight.
so the longer the bullet takes to get there, the more spindrift.
the yaw of repose is the angle relative to line of flight that the spinning bullet adopts when it goes to sleep.
this is what does the steering.(to the right in a r.h. twist barrel.)
the faster the twist the more the spindrift, because faster spinning bullets that are stable have a greater yaw of repose than a slower spinning (shorter)
bullet of equal stability.
given a 40 cal which requires a 13" twist and a 45 cal with an 18" twist at roughly the same speed and stability, the 40 cal will have a bit more spindrift.
with all the current hype around long range (non)hunting, those guys need to realize that 0.6 moa spindrift equals 6" at 1000 yds.
bruce.

[Distant Thunder]

Don,

It was probably a little difficult to hold the X-ring at 600 with that breeze a blowin'!

[Don McDowell]

Jim just a touch. The wind flags down range looked like they were cut from 1/2 inch ply wood.

[Distant Thunder]

I've watched F-Class being shot at 600 yards. I could predict where the shot would come up in the X-ring by watching the flags. It must be a real challenge for those guys. I have absolutely NO interest. I don't think any of the shooters knew there were flags or what they were for if they did.

[gunlaker]

One of the more interesting aspects of shooting these rifles is vertical variation based on air density changes. I'm familiar with ballistics simulations and had run the numbers before hand but there is nothing like seeing the effects in real life. The first time I experienced, and properly understood it, at long range was the second time I'd been to Phoenix. The elevation settings used on the first relay in the early morning would put you completely over the target if you re-used them after returning from the pits for your next relay.

I imagine those air density variations don't affect the f-class guys nearly so much at 1000 yards.

Chris.

[jackrabbit]

I've watched F-Class being shot at 600 yards. I could predict where the shot would come up in the X-ring by watching the flags. It must be a real challenge for those guys. I have absolutely NO interest. I don't think any of the shooters knew there were flags or what they were for if they did.

BWAAAHAHAHAHAHAHAHAAAAAA!!!!

I agree!

[beltfed]

Actually, F class shooters are largely Hi Power shooters who do indeed watch flags--and trees --and grass,etc
as well as mirage. Mirage can be read in their Large rifle scopes as well as thru spotting scopes..
Been there done that
beltfed/arnie

[Kurt]

What do you do when flags go left to right at the 1026yd line at the Big hill at Baker Mt. and like 1/2" plywood like a board like Don said and at the target at 900 or the 800 buffalo where the flag follows the pole straight up in the air like I have seen them at the Big Hill at Baker Mt.
I just about sold my rifle that day.