If a bullet groups well at a 100yds, does this mean it would be properly stabalized at 500yds?
Or may it not be accurae to say if it shoots well at only 100yds. My range yardage is to limited to test this.

I don't know about 500 yards but will soon. The wind will effect the bullet the longer it stays in the air and the lighter the bullet the worse unless it is blistering along. I have had snipers (military) tell me that a scratch on a bullet will not effect the path sometimes until it reaches 200 yards or so. As the bullet slows down in flight so does the turning speed and can effect the accuracy. I also am limited to range but will soon move to a big cotton field and go for 2,3,5 and 1000 yards. I have shot good .375 yard 20, 50 and 100 yard groups in the same shooting but don't know from there on. I have shot the 180 grain bullet in a 20 mph cross wind at 100 yards and didn't make any differance. The 150 slipped just abit. Don't know but some long distance shooters will know for sure.

Rambo
A good group at 100 does NOT mean good groups at longer ranges, nor does a "bad" group at 100 mean bad groups at longer distances. While the 2 normaly track, they don't always (isn't this fun?) If you have the ability to do your load development at 2-300 yards, than your longer distance results will track more closly. All this is a result of stability in flight (marginal on the "under stabilized" side will look good at 100 but fall apart past that, while marginal on the "over stabilized" side will do better at longer distances but look bad in close)
Blob
Wind drift and stability are 2 different things.

Don't know, but someone told me that if a bullet is stable from the muzzle, it will stay stable at long range also, as the velosity will
decrease much more quickly than the spin rate.?
My experences at up to 900 yards suggest that in general a good group at 100 will extrapolate out until the bullet starts to keyhole.
And a bad group at 100 will inverably only get worse ?? one would think.
John L.

quote:
Don't know, but someone told me that if a bullet is stable from the muzzle, it will stay stable at long range also, as the velosity will
decrease much more quickly than the spin rate.?

Some stuff I have seen written by professional ballisticians like McCoy, Pejsa, and McDonald seem to support this contention. If the forward velocity of the bullet decreases considerably, but the rotational velocity decreases very little (the usual situation) then the so-called 'stability factor' INCREASES.

I sometimes wonder if people occasioonally see slightly oval shaped holes in their targets at long range because the bullets have been in the 'trans-sonic wobbles' stage as they have gone through. Then they mistakenly attribute these funny shaped holes to lack of gyroscopic stability ...

Just a thought.

[QUOTE]Originally posted by Rambo:
If a bullet groups well at a 100yds, does this mean it would be properly stabalized at 500yds? Probably, BUT NOT NECESSARILY! For example, a .38 Special full wadcutter shoots accurately to 50 yards, but not much beyond that distance, as it begins to keyhole. If it were spun faster, it would shoot accurately to a greater distance. The same applies to rifle bullets as well, IF THEY ARE ONLY MARGINALLY STABLE TO BEGIN WITH! Most rifle bullets are being spun fast enough to shoot accurately at all ranges at which you are likely to use them, however.
Or may it not be accurae to say if it shoots well at only 100yds. My range yardage is to limited to test this. You can use the GREENHILL FORMULA to predict how your bullets are likely to perform at long ranges. If the twist of rifling you have is adequate for the bullet you are using per this formula, then your bullets should be properly stabilized at any range you choose to shoot them!

The Greenill formula - "Length of required twist IN CALIBERS = 150/length of the projectile IN CALIBERS."

If you want to understand external ballistics, here is one of the best sites that I have found --- Link

As you will find, bullet stabilization only occurs within a moderate range of velocity and spin. Push to either side of this margin and bullets do not fly well.

If you're key hole’ing a target at 100 yards, you’ve got problems. However, most of the concerns about stabilization occur when shooting long range target. Then things can get very interesting...

Although it EXTREMELY rare,a projectile can be marginally stabil and loose stability when the speed of flight and rotation drop. If a bullet is just barely stable out of the muzzle,it may become totally unstable as the rotation speed slows.The same as a weebling top that is spinning fast.It doesnt become terminal until it starts to slow.So like I said in the start,extremely improbable,but I have seen it.

For long range target work, marginally stabilized bullets can lose stability during transonic flight. In addition, as velocity drops bullet ballistic coefficients also change causing once stable bullets to become less so. Changes in temperature (air density) can also alter BC. You can solve these problems in several ways - change barrel twist (the most expensive), bullet length, bullet BC, and/or velocity.

Over stabilizing (over spun) bullets can also cause problems at long range. Over spun bullets do not nose over during the ballistic arc. This can cause key hole’ing at long range.

Shoot a lot of long range and you will find an occurrence of improper stabilization. Can happen a lot if you are not aware.

Didn't say wind drift was the same as stablization. But wind can cause a bullet to be come unstable in that it can cause the bullet not only to drift but to osolate upon it 's length. But what do I know, these were old Vet snipers telling me all this who made kills at 1500-1800 yards in all kinds of weather, day and night.

quote:

Originally posted by redrover:
quote:

I sometimes wonder if people occasioonally see slightly oval shaped holes in their targets at long range because the bullets have been in the 'trans-sonic wobbles' stage .

Maybe! Don't forget, however, that a bullet striking a target perpendicular to the earth is not in any way hitting that target head on at 500 yards or beyond . The holes are not round.

Rambo; In his "Rifle Accuracy Facts" Vaughn shows a method to measure the actual stability of a bullet. Basically it involves shooting in varying wind conditions and measuring the angle of the bullet spread. If you are interested in
the technical side of guns this is a great book.
Good luck!