Better Groups At Distance

[jensenj71]

I have been searching for a rational reason that bullets wouldn't maintain a constant angular deviation between POA and POI as they travel down range. In other words, how could groups at say 600yds be smaller MOA than groups at 100yds?

Initial, it doesn't make sense that a bullet could improve the MOA over distance. It starts at the muzzle and passes through the hole in the target 1MOA off of POA at 100yds. It has to stay on that line and be 1MOA or more at 600yds!

Yet, many folks state that is exactly what happens and I believe that is what they are seeing. They say their 600yd group is better than their 100yd group. They see 1 MOA at 100yds and 0.5MOA at 600yds. I have seen it explained as it simply takes time for the bullet to "stabilize".

Aerodynamic jump seems to explain this if we assume the jump or slide is caused any time the bullet axis isn't aligned with the air. A cross wind causes the bullet to turn very slightly into the wind any the gyro effect causes the bullet to slide up or down as long as the cross wind is present. A constant wind results in a constant slide that shows up as a constant MOA angle.

If a bullet gets tilted for some other reason then there would be a slide as long as there was a tilt. The bullet could engage the rifling and travel down the barrel slightly tilted. The bullet could be knock silly as it exists the barrel and gas escapes around it. Eventually, the bullet would align and the slide would stop or the bullet would "stabilize". In other words, once the force that caused the tilt is removed the bullet wants to stabilize and stop sliding and just travel along the line in which it was launched.

This seems to explain how groups could get smaller. Each bullet follows a path that is somewhat colinear, however the lines are slightly offset because of the slide. The slide is a finite change in POI that does not continue to increase after the bullet stabilizes because the slide stops. If the slide is 3/8" at 100yd it might still be 3/8" at 600yds.

Layered on top of that we have the whip of the barrel which changes the POI and causes small changes in angle that would be constant for each bullet after it leaves the barrel. 1 MOA at 100yds would remain 1 MOA at 600yds. The observed performance at 600yds would be primarily driven by changes in angle at the time the bullet leaves the muzzle.

It seems like we are tuning loads to minimize both effects. We want to get the bullet out of the barrel while it is pointed in the same direction for the longest period of time. Then we want to minimize the time it takes the bullet to stabilize and stop sliding. If you get the timing right the changes in exit timing will have a minimal impact. Perhaps adjusting seating depth minimizes the tilt and time needed for the bullet to stabilize?

 

[jensenj71]

This seems to follow the observation that a rifle that shoots bad at distance doesn't ever shoot better at 100yds, but a rifle that shoots okay at 100yds might shoot better than expected at distance.

 

[PBramble]

So what you are describing is impossible from a physics standpoint. The bullet never pulls itself back into the line of sight once it deviates. I've heard this described as the bullet is going to sleep or some such nonsense. Windage could explain only but half of the group as bullets shot further to the other side would be pushed out of the group the same amount. What I believe explains it is that at 100 yards, the shooter focuses too much on the small center of the target. That's why you see larger deviations. When the target is at distance, the shooter has a much less detailed target to focus on and is less likely to try to make last minute adjustments in rifle movement before pulling the trigger. Given my anecdotal experience with it, I'd say this explanation is more likely.

 

[Elk Fire]

I have shot better groups at distance than I ever have at 100! MOA wise. With some guns that is. I have never thought that my gun shot better at distance than at100. I have however thought that I sometimes do shoot " better " at further range.
I also think I can get more likely get lucky at long range due to unknown or unaccounted for factors than at 100.

 

[Koda_]

I dont think Im qualified to answer this question but my guess is maybe many people aim differently at distance than they do at close range. When a target appears smaller people focus more on the reticle and not all the errors in movement. At close range people zoom way in more than needed and focus on the target spot and pull when they think the crosshair is centered but its already moving offline.

 

[RegionRat]

We now have e-targets that can replace the closer paper target on the shoot-through target so there can be no excuse like the closer paper upset the bullet before it got to distance.

A close e-target will just be the microphones on the open frame with no paper and the shooter can just aim at the distant target. This can eliminate all those excuses about distant aim being different or better than close aim too.

 

[Tiny Tim]

I hear of this phenomenon enough. I believe it is akin to urban legend. While I've witnessed anecdotal evidence, empirical evidence has been lacking. Myself, I recognize that I have to intentionally focus more at 100 yds that longer ranges because I get lazy, subconsciously thinking it's a chip shot. 40 years ago we were shooting 1 moa groups at 100 yards with 1.5-3 x scopes. Likely old mentor used to say, " I'm from Missouri, show me."

 

[milo-2]

This seems to follow the observation that a rifle that shoots bad at distance doesn't ever shoot better at 100yds, but a rifle that shoots okay at 100yds might shoot better than expected at distance.

I don't really want to enter this conversation, but if you develop a load at 600 yards and it is tight, you bring it back to 100 you will have some wallet groups as fudds call them.
I'm with PBramble, a bullet exiting its flight path at 100 cannot recover and shoot better at distance.
I myself would rather group my rifles at 500 over 100 yards, not because they shoot better at distance, it is because I set up for the shots up better. I pick prime conditions, anchor my rifle better, and I match my dot size to the dot in the reticle, or crosshair size. Being I shoot mostly floating dot reticles, shooting a bullet hole on paper will be the closest thing to a match at 100 yards, shooting 1" orange dots does little for me.
This may sound better, at 100, I expect great things, at distance, I am more relaxed and willing to see what unfolds, no pressure.

 

[chav0_12]

There's a really long thread in here about it. There's a video or blog post from Brian Litz about it too.

Basically, you're not. You might have a smaller POA at 600 yards so you try harder or something but, you're not shooting groups that would be bigger at 100 and smaller at 600, they dispersed equally.

 

[lancetkenyon]

Concentration.

 

[26Reload]

Concentration definitely helps...of which I lack at 100yds....but back at 400yd I'm less than moa..sometimes 1/2moa...
Depends on bullets and speed too I believe.....as some say above 2950fps can blow tips off of noslers LRABs...
..can't be positive..but I've never recovered a LRAB with a tip on it...........

 

[ElkValleyHunter]

Nah. It's statistically possible to get a smaller group at at a longer distance if you have a small sample group. It will happen from time to time.

Increase your sample size, and the likeliness will be reduce significantly. Shoot 30 or more rounds at 100 yards, then 30 or more at 600 yards, and your 600 yds. group will be larger, possibly wider. Rarely smaller.

 

[milo-2]

Nah. It's statistically possible to get a smaller group at at a longer distance if you have a small sample group. It will happen from time to time.

Increase your sample size, and the likeliness will be reduce significantly. Shoot 30 or more rounds at 100 yards, then 30 or more at 600 yards, and your 600 yds. group will be larger, possibly wider. Rarely smaller.

I get what you are saying, but in reality, not a fair comparison. Most cartridges favored on this forum aren't going to have much outside influence when shot at 100.
Parameters change dramatically at 600 yards. If 600 yard BR guys were shooting 30 shot groups, your argument would have merit, but.

 

[chav0_12]

I get what you are saying, but in reality, not a fair comparison. Most cartridges favored on this forum aren't going to have much outside influence when shot at 100.
Parameters change dramatically at 600 yards. If 600 yard BR guys were shooting 30 shot groups, your argument would have merit, but.

What he's saying is that you could shoot a group that falls into the statistical range of a rifles grouping ability that is smaller at 600 than one that was just shot, that also falls into that range, at 100.

So like a real true average 1/2" rifle's statistical range is like 3/4" to 1/4". Possibly higher. So, if you shoot a 3/4" group at 100 then shoot the 1/4" group at 600, they're within the average group size that is to be expected.