180gr Sierra, Scope Off; NO, Gyroscopic (spin) Drift

When I adjusted my scope 4" to the right, I remembered when I last adjusted the left/right adjustment; when I started using the 220gr bullets again. It doesn't make sense to me, but I think those bullets fly differently than the others. Maybe someone will be along that can explain it.

But, tomorrow I think I'll be on target again!
...
Hopefully...
:)


(About 4 hours after I wrote the above.)
I figured it out!

I couldn't sleep thinking about why there is an at least a 4 inch difference at 400 yards. There had to be a reason, and I had to know that reason!

Barrel twist!

That is what it is! Barrel twist!

[deleted incorrect content]

I always knew about the twist making the bullets trajectory head in a lateral direction, but I never seen any numbers on the subject or a detailed explanation; so I thought it was a negligible amount. It seems as if I was in error!

[EDIT] As I am uploading the video, I am searching for info on bullet drift and twist rate. If I find some info I'll post a link to it.
Found one! http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1257843
(Example: A .308 Win shooting a 175 Sierra MK in a 1:12 barrel will experience about 8" spin drift in 1000 yards; the same bullet will drift 12" (a 50% increase) in a 1:10 barrel.)
It doesn't say which direction but I think I must be correct.
http://www.appliedballisticsllc.com/index_files/SpinandCoriolisDrift.htm
"Bullets fired from right twist barrels drift to the right,"
I am correct but for the wrong reason. It makes better sense now. Much more drop, much more drift.

I love missing targets! I learn so much!

Guess what?

All my 600 yard shots were all right about the same amount, (around 6 to 8 inches from center.) I was kicking myself in the ass for not calculating the wind drift right. Now I suspect it may have been a little wind and a lot due to twist!

I would have never came up with this epiphany if it weren't for me deciding to be more precise in my shooting at these shorter distances to get better at longer distances. 4 inches difference at 400 yards, most people wouldn't have thought anything of it.

I'm going to hit that paper plate at 600 yards next time, you just watch!

Category:

Education

Tags:

• shooting
• Howa
• 30-06
• Sierra
• Nikko Stirling
• gun
• rifle
• weapon
• scope
• 400 yards
• bullet

[barsmars]

Very interesting. I got more out of what you wrote than from your vid. I don't agree with all of your reasoning - but I really do agree with your direction of thinking.