Home Forums Hunting & Shooting Long Range Hunting Smaller dispersion at longer range than at close range.

No, bullets do NOT start out traveling in a corkscrew, then settle down to fly in a straight line. Instead, the NOSE--and base--of the bullet wobble in a corkscrew as it comes out of the muzzle, but the center of the bullet travels in a straight line.

Charts of the nose wobble have given some people the impression that the entire bullet is somehow circling around a centerline, but that is most definitely not the case. Instead, for a little while it wobbles like a poorly-thrown football. That's it, not a spiral path like a kudu horn through the air.

Sorry, can't agree with that for two reasons:
1. If the nose and base weren't aligned, the holes in the target wouldn't be round (but they are).
2. If the nose was always centred, then this dispersion discrepancy would not exist in the first place - instead we would have consistent dispersion except with oblong holes in the target at closer ranges.

A spinning top is not an entirely good analogy but it does demonstrate where the corkscrew effect would come from - except the tops spinning axis is not perpendicular to the surface it is spinning on.

Sorry, but the nose wobble is very small, and settles down very quickly. You won't be able to see any evidence from the holes in most targets, except perhaps slightly at close range, but it has been proven many times. It's a basic fact of rifle ballistics. So once again, no, bullets do NOT travel in a spiral path.

So far nobody has proven any "dispersion discrepancy" with groups from the SAME shots at different ranges, and Bryan Litz has not been able to reproduce that in any of his tests. This is why he's offering to pay the travel expenses for anybody and their rifle that does this. He's trying to find out if there's some reason for it other than scope parallax.

Once liberated from the confines of the barrel, a bullet spins around its center of mass. Sometimes that doesn't lie on the bullet's geometric center. When this is the case, the bullet moves laterally as soon as it exits the barrel (lateral throw off), and then spins around its center of mass for the duration of is flight. This, I think, is where the idea of a bullet corkscrewing comes from. A bullet such as this does indeed 'corkscrew' as it flies. However, it is only a very, very tiny amount because even the most horribly imbalanced bullet cannot have a center of mass that lies outside itself.

Bryan, I hope you are able to find a some folks who experience the phenomenon of decreasing angular dispersion, that will come to your lab, so you can investigate the observation further.

Well I have certainly seen it when using open sights (peep sights actually) - full bore event out to 1000m using both 303 and 308. I've only noticed it at shorter ranges (up to 300m) because wind starts having more noticeable affects at ranges beyond this, where I used to shoot.

I've spoken with a few full bore shooters from earlier days (before I ever started shooting) and it was commonly accepted to be a real phenomena - they used to shoot 174gn boattails (long boattail) out of their 303s using peep sights.

I know a bullet travelling in a spiral seems ludicrous, but a wobble in one plane would turn into a circular wobble with a spinning bullet which results in a corkscrew as it travels downrange. There's really no other way to explain it.

So I've seen SMLEs do it with 174gn boattails, M14s do it with 144gn boattails and my Remington 700 will do it with 155gn boattails (PALMA projectile). My M14 used to shoot 2" groups at 100yds, 2.5" groups at 200yds and 3" groups at 300yds fairly consistently (if I did my part) with the peep sight. My Remington is a bit different and will be MOA out to 200yds then sub-MOA (0.85MOA) at 300 yards.

How exactly did you see this?

If you can spare the time, I'll cover the expense of your travel to MI to demonstrate this. My shoot thru target is 100-300 yards, and will show if the bullets actually fly that way or not.

No disrespect, and I'm not questioning your observation. I've just been unable to observe this happening with everything I've tried (and I've tried a lot).

-Bryan

A top that is "corkscrewing" is simply rolling along on it's tip while leaning

Bullets do not do it at all

They CAN tip over coming out of the muzzle, and then straighten themselves in a short distance, but that has not effect on long range group sizes.

Here are some pictures showing just how much pitch and yaw there can be on leaving the muzzle.

Look at the last picture in the first post

http://thefiringline.com/forums/showthread.php?t=529137&highlight=high+speed+photography


A top that is "corkscrewing" is simply rolling along on it's tip while leaning

Bullets do not do it at all

They CAN tip over coming out of the muzzle, and then straighten themselves in a short distance, but that has not effect on long range group sizes.

Here are some pictures showing just how much pitch and yaw there can be on leaving the muzzle.

Look at the last picture in the first post

http://thefiringline.com/forums/showthread.php?t=529137&highlight=high+speed+photography

http://kuulapaa.com/home/highspeed.html

WOW!!!

No offence taken - I'm keen to see the issue examined too.

The only rifle I have now of the ones I've mentioned above is my Remington.

I would love to take you up on your offer but I live in Australia.

Many of the older full bore shooters (100-1000yards, 303SMLEs, open sights - peep) over are familiar with the effect, although none know the explanation (who does?).

I think the style of the boattail makes a big difference to the effect. The 174gn 303 projectile had a rather long boattail. I have one lying around here somewhere and will try and find it and take a photo. I believe the boattail is the critical factor and does not depend too much on the rifle.

You probably have tried many boattail projectiles?

Edit - Found an image of the older style 174gn projectile:

http://www.google.com.au/imgres?imgurl=http%3A%2F%2Fwww.milsurps.com%2Fattachment.php%253Fattachmentid%253D18299%2526d%253D1292974451&imgrefurl=http%3A%2F%2Fwww.milsurps.com%2Fshowthread.php%3Ft%3D40884&h=1060&w=2731&tbnid=AjDQ_jY6e-eeEM%3A&zoom=1&docid=nuqZ1fsPplpbaM&ei=HYKiVIxVlYLyBeCkgpAG&tbm=isch&ved=0CB8QMygCMAI&iact=rc&uact=3&dur=720&page=1&start=0&ndsp=40

Also found an article that claims velocity variations cause the effect (?):

http://www.targetsportsmagazine.com/features/view/10157/303-british-compensation-claims/

Looks like a Sierra.

Found some interesting info. I haven't gone through it all and just wanted to link so others can peruse:

http://www.ar15.com/forums/t_1_5/15..._at_600yd_but_not_100yd_.html&page=6

http://yarchive.net/gun/ammo/bullet_helical_path.html

That first link is full of the same "Corkscrew bullet" fantasies that were brought up here.

Until someone does the testing, it's all just more hearsay

I think so. A lot of scopes out there have terrible parallax at close range.

Most of those making the claims are shooting AO scopes so parallax shouldn't be an issue

Has STICK chimed in yet?

Here are the NBRSA records as of 2014. There may be some still pending. If you go to the 5x5 aggregates note that, in all weight divisions, the 100 and 200 yard records are not remotely lineal.
I've always wondered about this. http://nbrsa.org/sites/default/files/World%20Records%20as%20of%2012-30-2014.pdf

Those records don't tell you much since they are different shooters, and different guns.

I notice none of the groups are smaller at longer distances, but it still really doesn't address the claims here about a particular gun being "more accurate" at long range than at shorter range.

Someone who owns one of these magic rifles needs to do the test to prove the phenomenon

OK, just recalled a small factor at least with the M700 as it lives in AK (the BOSS M70 lives in KS).

Since the 700 is zeroed at 300 yards...I have a test target, 3 @300 3200 3100 and just one at 50 yards so that my hold under data are more factual not what some table says...anyway the 50 yard hole is about a half inch right, the 100 still a fuzz right but kind of superimposed 4-5" high over the 200 yard...but the 100 is surly, just a fuzz, right.(125 gr. ballistic tips)

I shoot the BOSS gun even less as I have a limited supply of cartridges in the cupboard in the 'Shack. The earlier mentioned 2014 11/8" 3 shot @ 300 yard zero check. In the 2013 Fall (in the BOSS gun,) I shot one @300, 1200 and 150. If I connected the holes with a marker, it would be a curved line. (150 gr. Xs)

I really think it is parallax and by golly, I surprise myself every now and again shooting out there a ways. I can live with that.

Snyper, I agree regarding same gun, same load, same shooter. The fact still remains that the 5x5 aggregates at 100, 200, and 300yds. are not even remotely lineal. I have no background in BR but this obviously raises questions. The numbers are statistically more significant in many ways. As a general statement, "the further a bullet travels and the longer the time it spends in the air, the more it will be affected by environmentals" is a generally accepted premise. So what produces the trend in the groups? It's easier to shoot at longer yardage? Probably not. As the yardage gets longer the shooters get luckier. I don't think so. It's easier to misadjust parallax at Shorter yardage. Maybe but I don't think so.

You see my dilemma.