Good groups @100yds.

[Hohn]

I really like that term "cone of dispersion". I think it can help people understand what happens at longer distances with various bullet's. It seems to me that generally, lower BC bullets have a larger cone if dispersion than higher BC bullet's. Therefore, to shoot well at long range, lower BC bullets must shoot smaller short range groups that higher BC bullets.

It is a good term, although most oscillatory modes of a barrel aren't round. So the "cone" you observe with a lot of rounds in a single group is rarely round. It's usually oblong in some way.

I think if you asked the BR guys you'd find that low BC bullets often have a LOWER "cone of dispersion" because they are so much less jump sensitive. That's why the short range BR folks run low BC bullets with slow twists.

Thus, it's a shift from mechanical accuracy at short range to robustness to wind at long range. At short range with short times of flight, the wind is less important than jump sensitivity and mechanical accuracy. And that's reversed at long range where BC and wind resistance become dominant.

 

[Erik Cortina]

I remember hearing that some long bullets made for long range do not stabilize until around 200 yds. When I first started using .22 75 gr Amax bullets my groups were better at 200 yds then 100 yds just like when the author tested his

I remember hearing about Santa Clause as well, but that doesn’t mean it’s true.

 

[INTJ]

BC has nothing to do with the “cone”. In identical wind conditions, they would all fly the same path.

I agree, but wind conditions are rarely if ever identical or consistent. That is why in LR BR it's very seldom a picker will group as well as a runner.

Given all the wind variations over 1000 yds, even if each bullet left with the muzzle in the exact same position, each bullet would still have a slightly different path so it makes sense that a higher BC bullet that is less affected by the wind would have a tighter cone. This assumes both loads are well tuned.

I would be interesting to see how bullets behave in a 1000 yd indoor range. There would still be varying air currents across that distance but it should be much less than outside.

 

[BartsBullets]

How many guns shoot repeatedly .1 or less (.0s) groups? Or is this just hypothetically to make the point?

Mine do, Pretty sure Jim’s do to! My long range guns group like a good 6PPC.

Bart

 

[Dusty Stevens]

I remember hearing that some long bullets made for long range do not stabilize until around 200 yds. When I first started using .22 75 gr Amax bullets my groups were better at 200 yds then 100 yds just like when the author tested his

Thats the old “going to sleep” wives tale. No such thing.

 

[INTJ]

It is a good term, although most oscillatory modes of a barrel aren't round. So the "cone" you observe with a lot of rounds in a single group is rarely round. It's usually oblong in some way.

I think if you asked the BR guys you'd find that low BC bullets often have a LOWER "cone of dispersion" because they are so much less jump sensitive. That's why the short range BR folks run low BC bullets with slow twists.

Thus, it's a shift from mechanical accuracy at short range to robustness to wind at long range. At short range with short times of flight, the wind is less important than jump sensitivity and mechanical accuracy. And that's reversed at long range where BC and wind resistance become dominant.

I shoot LR BR and what is I have seen is lower BC bullets will (must) shoot tighter at short range than higher BC bullets, but long range groups will be similar in average conditions. In good conditions the lower BC bullets usually shoot smaller than higher BC bullets at distance. In average conditions there isn't much difference, and in poor conditions then higher BC bullets have an advantage.

I should be even more specific. I am comparing a 300 WSM with 220 SMKs and 215 Berger's with a 6mm BRA/Dasher with 105-108 grain bullets of varying makes. Currently my 6BRA is for good to average conditions and my 300 WSM is for average to poor conditions.

Now the respective advantages of the 300 vs 6mm are slight and are overwhelmed by conditions and how well each rifle is tuned. BC is way down on the list, and we are talking BC differences between .5 and .7.

Anyway, I am using variations in the cone of dispersion to try and understand WHY I am seeing what I am seeing. I am not sure of the exact reason, but I do know that the 300 shooting .3 MOA at 200 yds is competitive at distance while the 6mm needs to be .175 MOA or better at 200 to be competitive at distance.

Jump sensitivity varies with a lot of things, but a consistent factor seems to be the farther away from zero jump, the less sensitive the bullet is to small changes in seating depth.

 

[KY_Windage]

I agree, but wind conditions are rarely if ever identical or consistent. That is why in LR BR it's very seldom a picker will group as well as a runner.

Given all the wind variations over 1000 yds, even if each bullet left with the muzzle in the exact same position, each bullet would still have a slightly different path so it makes sense that a higher BC bullet that is less affected by the wind would have a tighter cone. This assumes both loads are well tuned.

I would be interesting to see how bullets behave in a 1000 yd indoor range. There would still be varying air currents across that distance but it should be much less than outside.

I'm not sure what I have learned shooting F-Class but I have learned a hell of lot scoring F-Class, and one thing I learned very quickly was that if I set up directly in line with the shooter's bore-to-target line (or very close) on a dead-air day I could usually tell where the bullet was going to hit when it was no more than half-way to the target. Other than the very predictable effect of gravity, the bullets fly in very straight lines that are apparently determined by the time the bullet has left the barrel, or very shortly thereafter. It is trickier to predict vertical impact because I have to see where the bullet peaks and try to remember if that is the right spot for that person, but I can clearly see whether a bullet is going to hit left, right or center, and with a pretty good idea of how much, very soon in its trajectory. That told me to not worry too much about BC and "stabilization" and focus on getting every bullet to leave the barrel on the correct line, and then to learn wind.

The other interesting thing is that on a windy day the vast majority of the wind-effect occurs at the end of the bullet's flight. The bullet flies pretty straight for most of the trip and then curves over dramatically to the POI near the end. Of course, I knew they did that from spotting over thousands of rounds shooting p-dogs, where the very light bullets exacerbate the effect, but it happens with the bigger bullets, too.

 

[INTJ]

Thats the old “going to sleep” wives tale. No such thing.

I too thought that was an old wives tale until I talked a tech at Berger last week, and now I wonder. He described shooting on a day with high humidity where they could see the bullet trace. Bullets do not follow a clean straight line to the target.

He said the higher BC bullets would be be somewhat erratic at short range and then settle down and fly straight. He attributed that to bullet yaw until it went to sleep.

A highly experienced BR shooter (both long and shot range) who is constantly developing and testing new stuff told me something similar.

Than again, maybe the bullet trace as seen in humidity isn't a reliable way to draw any conclusions.

 

[INTJ]

BTW, I think this has been a very interesting and informative thread. Either that or else I am just stir crazy from not being able to shoot........

 

[johara1]

How many guns shoot repeatedly .1 or less (.0s) groups? Or is this just hypothetically to make the point?

You want to bet on that one, it kind of obvious you need better equipment.... jim

 

[johara1]

I agree, but wind conditions are rarely if ever identical or consistent. That is why in LR BR it's very seldom a picker will group as well as a runner.

Given all the wind variations over 1000 yds, even if each bullet left with the muzzle in the exact same position, each bullet would still have a slightly different path so it makes sense that a higher BC bullet that is less affected by the wind would have a tighter cone. This assumes both loads are well tuned.

I would be interesting to see how bullets behave in a 1000 yd indoor range. There would still be varying air currents across that distance but it should be much less than outside.

This is where barrel quality comes in to play, a hummer will shoot through conditions an average barrel won't.... jim

 

[M14AMU]

This rifle is just plumb damn boring!!

800 yards by Sharps Man, on Flickr

Five shots 800 yards out of Jon Beanland 6.5x47 Lapua using 38.2 grains H4350 and Berger 140 gr. Hybrid Target Bullet! A 50 cent piece would touch/cover all five.

 

[johara1]

BTW, I think this has been a very interesting and informative thread. Either that or else I am just stir crazy from not being able to shoot........

Doesn't look good here, the schools will remain closed the rest of this year. Maybe they know something we don't. I never knew how lucky I was to go out the door and shoot in the back yard..... jim

 

[JEFFPPC]

How many guns shoot repeatedly .1 or less (.0s) groups? Or is this just hypothetically to make the point?

I have 2, both BRXs shoot much like my PPC. The barrels that don't go away. When I can shoot back to back groups 2 days in a row in the zero or 1s, I have a load. After that I only use a tuner for adjustment.

 

[Drop Port]

I remember hearing about Santa Clause as well, but that doesn’t mean it’s true.

There you go, you had to bring up Santa, once you stop believing shits never the same, it's all down hill from there. Everyone's first lesson on reality.

 

[Ccrider]

You want to bet on that one, it kind of obvious you need better equipment.... jim

Or to learn how to dance?

So, you are saying that these guns agg in .1s and zeros for five shot groups at 100. That is intriguing since the best short range BR shooters don’t agg 0s on their best days from what I have read.

 

[Northridge]

"cone" of dispersion, wind drift, BC consistency , exterior Ballistics all factor into the end result of that I think most would agree. But what I have found is there is a cut off on reliable BC considering any caliber. when I document what means the most from a "cone" of dispersion stand point I have to consider "all" sent shots in the cone of dispersion not 95% but 100% of shots on a given string cuzz that is what is scored or Measured.
often as BC go's up I will find as many have said, wind drift less, vertical dispersion less, but my random spit shot count will increase making my Total "cone" of dispersion Larger. so even though my bullets that have less BC and a larger MOA at 100 yard will in fact have a smaller total cone of dispersion at say 1000 yards because of a smaller kick out percentage being the winner. In my group of "clowns" out in the North West we refer to it as "tractability" as BC go's up a bullet becomes more slippery if you will, it has a harder time picking a line. like the difference between steering a truck in the mud vs dry ground. Even score shooting falls into this equation as guys are shooting smaller there with higher BC bullets a popped shot into the 9 ring that slipped in the mud will be false info for the next shot. those can be things that reduce success while tuning at a shorter distance because resolution is so small, can it be done yes for sure but there are lots of factors to consider regardless of distance quality of bullet or barrel some things statistically just do a cleaner job..

Shawn Williams

 

[johara1]

No I'm not shooting a match but I like to see repeatability, and I did say a .1 or less. After I settle in on a load I want it to repeat 4 times with single digit ES. Plain and simple nice round small groups that repeat. Now if you can read the conditions and put 10 down range in the same condition you will see how good your equipment is.... jim

 

[bcarico]

Mine do, Pretty sure Jim’s do to! My long range guns group like a good 6PPC.

Bart

Mine do too. If it won’t group at 100 it dang sure ain’t going to group at 1000.

 

[INTJ]

"cone" of dispersion, wind drift, BC consistency , exterior Ballistics all factor into the end result of that I think most would agree. But what I have found is there is a cut off on reliable BC considering any caliber. when I document what means the most from a "cone" of dispersion stand point I have to consider "all" sent shots in the cone of dispersion not 95% but 100% of shots on a given string cuzz that is what is scored or Measured.
often as BC go's up I will find as many have said, wind drift less, vertical dispersion less, but my random spit shot count will increase making my Total "cone" of dispersion Larger. so even though my bullets that have less BC and a larger MOA at 100 yard will in fact have a smaller total cone of dispersion at say 1000 yards because of a smaller kick out percentage being the winner. In my group of "clowns" out in the North West we refer to it as "tractability" as BC go's up a bullet becomes more slippery if you will, it has a harder time picking a line. like the difference between steering a truck in the mud vs dry ground. Even score shooting falls into this equation as guys are shooting smaller there with higher BC bullets a popped shot into the 9 ring that slipped in the mud will be false info for the next shot. those can be things that reduce success while tuning at a shorter distance because resolution is so small, can it be done yes for sure but there are lots of factors to consider regardless of distance quality of bullet or barrel some things statistically just do a cleaner job..

Shawn Williams

So you are finding the opposite of what I have found. For me, the lesser BC bullets have to shoot smaller at 200 yds than the higher BC bullets to be competitive at long range. Then again I am comparing two dramatically different cartridges and that must give different results than higher vs lower BC in the same cartridge.