Group size at various distance

[jre4192]

I've been debating with a co worker and want to get some other opinions. The question is if all things are equal can a round group better at say 300 yds vs 100 yds. I say no, he says yes. Remember all things equal except for the distance.

 

[Coyotejunki]

Re: Group size at various distance

I guess anything is possible, but I would bet not very common, or likely. I'm sure someone has done it though.

 

[MitchAlsup]

Re: Group size at various distance

Consistently and reliably, no.
Occasionally, yes.

 

[BuzzBoss915]

Re: Group size at various distance

Well, there seems to be quite a bit of empirical evidence that says some bullets settle down and group better at 200 than at 100. I don't know about that, but with the same rifle I have shot just as good groups at 200 as at 100.
BB

 

[armorpl8chikn]

Re: Group size at various distance

Are you sure you understand what he is asserting?
For example I have seen my rifle shoot .75 MOA at 100 and then shoot .46 MOA at 300, then .416 mOA at 600, then .5 MOA at 1000.
So if you look at the numbers some might assume that my load shoots better at 300 than it does at 100, which indeed it does but the group itself is actually bigger in inches than the 100yd group. Technically speaking it is shooting better at 300 than at 100. With some rifles and loads it is quite common. If you are testing loads for eventual use at 1000 yds then you better test them at greater distance than 100yds. I have had loads that shot bugholes at 100 and then moved to 300 and they were way over MOA. I have also tested loads at 100 that grouped only so-so that tightened up considerably at 300. It has a great deal to do with bullet choice and powder choice too. None of the loads I have mentioned showed anything but stellar SD's and ES's.

 

[jre4192]

Re: Group size at various distance

I guess I'm looking at this from a physics point of view. The projectile leaves the barrel in a defined path once it deviates from that path its going to get further from it. Meaning the further it travels the further it deviates from that path. I cant think of a force that would put it back onto that path. So if its left the original path before 100 yds, at 300yds in theory it should be further off the path.

 

[eracer]

Re: Group size at various distance

Smaller groups (less dispersion?) Or better accuracy relative to angular separation?

I've heard the "Some bullets have smaller MOA groups at 200 than at 100 yards."

But I've never heard - and can't imagine it being physically possible) that measured group size could be smaller at longer distances from the muzzle. (Assuming all other test parameters are equal.)

 

[Greg Langelius *]

Re: Group size at various distance

Competitive shooters I've spoken with all seem to expect group size MOA to increase as distance gets well out there. Many seem to accept a rule of thumb that a rifle that shoots 1/2 MOA at 100yd is still doing pretty well shooting 2 MOA at 1000yd.

I think they (we) are acknowledging that what I call uncertainty factors (small random and unpredictable environmental and equipment deviations) accumulate along the trajectory, and open up the expectations as distances get significantly large. I think the growth probably follows some sort of parabolic numeric curve, probably similar in nature to the deviations caused by gravity or a constant crosswind.

I'm not an expert at this stuff, just commenting in a general way on observed trends

Greg

 

[Guest]

Re: Group size at various distance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jesse Engle</div><div class="ubbcode-body">I've been debating with a co worker and want to get some other opinions. The question is if all things are equal can a round group better at say 300 yds vs 100 yds. I say no, he says yes. Remember all things equal except for the distance. </div></div>

The answer is yes.
Shooter removed, it's do to the interaction of the rifles crown not being 100% correct an using certain boat-tail bullets. A improper crown will induce very slight yaw on some boat-tails at the muzzle, that will be removed by spin at X distance based on Y amount of muzzle yaw.
A flat base bullet is not near as prone to this, an also why most BR guys use FB bullets.

 

[armorpl8chikn]

Re: Group size at various distance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jesse Engle</div><div class="ubbcode-body">I guess I'm looking at this from a physics point of view. The projectile leaves the barrel in a defined path once it deviates from that path its going to get further from it. Meaning the further it travels the further it deviates from that path. I cant think of a force that would put it back onto that path. So if its left the original path before 100 yds, at 300yds in theory it should be further off the path.
</div></div>

Aha so you told your coworker, in a sense, that if a rifle and load are capable of 1MOA at 100yds, then that same load can be no better than MOA as it moves out into never never land. Did you suggest that the load would be no better than 2" at 200, then no better than 3" at 300, and follow a linear progression to worlds end? If you did, you would be wrong, get ready to eat crow.
This is why I tell people to go shoot instead of talking about shooting. Lots of gunstore hangouts think 1" at 100 means 10" at 1000, it can, but I have seen evidence to the contrary too many ties to call a fluke.

 

[MALLARD]

Re: Group size at various distance

i think i remmeber somewhere in the bryan litz book he talked about parralax issues , and what i got from it suggested that the parralax issues effects group size at close range more so then long range.

i remmeber my buddies EDM 50 would shoot 1 inch groups all the way out to 500y. That solidified the parralax issue in my mind because his 100y groups looked the same as his 500y groups.

 

[BuzzBoss915]

Re: Group size at various distance

For those that wonder about measured groups, say half inch @100 and assuming this is a straight line. You need to consider the actual bullet path and it is never a straight line so that the divergence increases linearly. At least that's the way I understand it and why (one explanation) groups can "improve" with distance. Maybe?
BB

 

[psinclair]

Re: Group size at various distance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MALLARD</div><div class="ubbcode-body">i think i remmeber somewhere in the bryan litz book he talked about parralax issues , and what i got from it suggested that the parralax issues effects group size at close range more so then long range.

i remmeber my buddies EDM 50 would shoot 1 inch groups all the way out to 500y. That solidified the parralax issue in my mind because his 100y groups looked the same as his 500y groups. </div></div>

Exactly spot on.....

 

[Bob 964]

Re: Group size at various distance

I know some bullets take longer to stabilize than others. Perhaps that would explain why a bullet might group tighter at 200-300 yds than at 100 yds.

 

[BuzzBoss915]

Re: Group size at various distance

I probably didn't explain it clearly. I have seen plotting (I think in American Rifleman) where they plot out bullets at various points in their travel. They spiral around kind of a parabola best I can describe, like a screw pattern. What I don't know is if (or don't remember) is if every bullet follows the exact same pattern, or every bullet plows it's own path through the air?

Anyway, if you ask me, this could easily explain why a bullet forms a better group at 1000 yards than 100/200. If you think of it as rattling down a pipe, it's going to the same general place but who can predict where each bullet will touch the sides of the pipe? Assuming this "pipe" is curved exactly following your trajectory. BB

 

[shamrockcattleco]

Re: Group size at various distance

Well... I think you guys just saved a novice some headache. I am able to group very well at 100 around 1 MOA but at 600 I"m getting 18 inch groups, I was sure it was my Parallax, Because if its 1 @ 100 it will shoot 2 @ 200 and so on. I also ran across a video describing Pitch and Yaw on You-Tube and thought that if my bullet was stable for shooting at 100 it would be stable for shooting any distance past that until it went transonic.

Back to the range I go.......

 

[Fuzzball]

Re: Group size at various distance

<span style="font-style: italic">"I know some bullets take longer to stabilize than others. Perhaps that would explain why a bullet might group tighter at 200-300 yds than at 100 yds."</span>

That's true in terms of MOA if not actual group size; it appears some get confused about that. And it's much more common for the angle of dispersion to increse at greater distances than to decrease. Serious BR matches usually include shooting at both 100 AND 200 yards. It's common for the winners to use slightly different loads at each range but those matches are often won (and lost) by a few thousanths of average group size, not what many of us would ever even notice.

Scope parallax can cause sighting error at all distances except for where it's been set and the displacement increases directly with the range (meaning it will be exactly three times more if the shooting range is trippled passed the corrected range). However, that's a 'worse case' scenerio, it's not as much of a problem as it may be thought; there is no parallax error at all if the shooter is careful to sight through the middle of that big circle of light coming outta the rear lens of his scope!

 

[gstaylorg]

Re: Group size at various distance

The potential for parallax error is much greater at close distance than far. Ask any .22 rimfire competition shooter. Also, one other thing to think about is how group sizes and precision have been determined whenever you come across someone reporting that their rifle shoots tighter groups at 300 yd than 100 yd (for example). Unless they shot through two pieces of target paper in line at the two distances so that group size could be measured at both distances for the same projectiles, it doesn't mean all that much. The closer you are to the target, even tiny changes in head position and/or cheekweld become more significant and can generate parallax issues causing the closer group to become larger in terms of angular dispersion.

If on the other hand, someone shows you two targets that were correctly aligned, so that the projectile hit both targets at near/far distance, where the closer group was larger in terms of angular dispersion than the farther, then it is unlikely that parallax was the culprit. However, it is extremely rare that you will ever see this type of proof for the phenomenon being discussed. First, because it takes more effort to set up and correctly align targets to effectively do this kind of experiment. Second, and more importantly, because truly observing and documenting a larger group spread at closer distance than farther is pretty uncommon and usually the individual claiming to have observed that effect has been misled by other sources of error and by the manner in which the groups were actually shot and compared.

Edit: link to Bryan Litz' discussion of projectile "yaw" upon leaving the muzzle:

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=918725

 

[Paladin2147]

Re: Group size at various distance

Some bullet designs take time to "settle down" or "go to sleep" as some may refer. There is a reason that most benchrest shooters shoot flat based bullets at short distances. Think of it this way, if a bullet is unstable at 100yds then between 100 at 200yds becomes stable, where will the best groups be? Additionally, a unstable bullet is more affected by wind etc.., once it settles down and goes more pointy end forward - better groups.

 

[TexIndian]

Re: Group size at various distance

It is confusing for sure. I've heard too many shooters with more knowledge and experience than me talk about bullets that 'settle down' at greater distances. OTOH, it's hard for me intuitively to understand how a bullet that is 'off path' at 100 can get back 'on path' at 300.

 

[Tripwire]

Re: Group size at various distance

I only shoot a LOT, and have never only read about shooting, so I may not be qualified to add to this discussion......

I've never personally SEEN anything but "groups" open slightly, and progressively, as the distance increases....some rifles are better at it than others.

With good equipment, with a correct bullet/twist match, for distance; with a good node; with attention to the RIGHT details at the loading bench; with attention to the RIGHT details when sending the bullet; with a GOOD shooter pulling the trigger....a rifle will shoot well from near to far.

That said...90% of the "shooters" out there can't read conditions well enough, or pull triggers good enough, to actually see/know the difference.

Which is why they can only speculate about what they've read somewhere.........

 

[MMAJunkie]

Re: Group size at various distance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eracer</div><div class="ubbcode-body">Smaller groups (less dispersion?) Or better accuracy relative to angular separation?

I've heard the "Some bullets have smaller MOA groups at 200 than at 100 yards."

But I've never heard - and can't imagine it being physically possible) that measured group size could be smaller at longer distances from the muzzle. (Assuming all other test parameters are equal.) </div></div>

Not to even mention that it will be harder to see and target accurately as distance increases meaning harder to hold a bullseye perfectly centered with a scope

 

[1lnbrdg]

Re: Group size at various distance

I have an old 2-groove 1903 Springfield "sporterized" that shoots the 173gr FMJBT bullet 1.25" @ 100yds & 1.5" @ 200yds, 300yds is 2.5".

That's the only rifle that I've shot that liked that bullet.

I've done this repeatedly, 10-shot groups.

I've heard elsewhere it was a scope paralax issue but I can't find proof of that. I've played with the paralax and didn't improve anything up close.

I used to shoot it with the local PD snipers in their practice, blew their minds that an old "deer rifle" would shoot with them at distance although they would out-shoot me group-size up close.

 

[ChadTRG42]

Re: Group size at various distance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kolkio</div><div class="ubbcode-body">Some bullet designs take time to "settle down" or "go to sleep" as some may refer. There is a reason that most benchrest shooters shoot flat based bullets at short distances. Think of it this way, if a bullet is unstable at 100yds then between 100 at 200yds becomes stable, where will the best groups be? Additionally, a unstable bullet is more affected by wind etc.., once it settles down and goes more pointy end forward - better groups. </div></div>

^^^This is why. The longer the bullet in a given twist, the longer it takes to fully stabilize. You see this in a 243 Win shooting a 115 DTAC, 7mm shooting a 180 VLD, 308 Win shooting a 208 A-max. It doesn't have to do with the crown, and other reasons. The bullet comes out of the barrel with a little bit of yaw, and needs 200-300 yards to "settle down". This is why long range bullets need to be tested at distances further than 100 or 200 yards. I test ALL competition rifles at 300 yards or further for this reason. I've seen my personal 300 WM shooting a 208 A-amx group .5" at 100 (1/2 moa), and shoot less than an inch at 300 yards (less than 1/3 moa). So, in comparison, the 300 yard groups tighter or more consistant at 300 than it does at 100. I have also seen a .2" group at 100 yards and 3 inches at 300 with the same load.

Remember, it's not how much the bullet weighs for stability, it's how long it is. The longer the bullet, the more twist needed to stabilize it. Longer bullets are naturally heavier. But the weight is not used to calculate the stability of the bullet. Flat base bullets are easier to stabilize. The boat tail on a bullet increases the length, and does induce some variation on the base of the bullet, which makes it inherantly less accurate than a flat base. But flat base bullets have a much lower BC for longer range shooting. So boat tail bullets are used.

 

[Paladin2147]

Re: Group size at various distance

Nice addition Chad - thank you.

 

[Guest]

Re: Group size at various distance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">You see this in a 243 Win shooting a 115 DTAC, 7mm shooting a 180 VLD, 308 Win shooting a 208 A-max. It doesn't have to do with the crown, and other reasons. The bullet comes out of the barrel with a little bit of yaw, and needs 200-300 yards to "settle down". </div></div>

No bullet gains speed or spin past the barrel. What induces the yaw in the first place, bad ammo, bad barrel?

The longer the bullet the less crown to boat-tail base issue it takes. Why would one weapon do it an not another with the same loading, of same lot of components.

Uncle spent a lot of money testing the T-44 and it's food. At one time they were trying to match the 7.62X54R's explosive tip with "American Accuracy an Punch" which required a very long bullet (1.375 long if memory serves) Some weapons would not stabilize said close, but did farther. Long short, random samples of ammo was chosen an shot, it came down to the crowns. They retouched the crowns on those that were giving issue an the problem went away. Crowns being so touchy with long bullets an that bullets spin rate, stopped that project in it's tracks. Everything was fired from machine rests to prevent human interference.

The longer the boat-tail bullet, the less off set gas pressure release, it takes. Most flat base do not have that issue, until the crown is really hosed up.

 

[avidflyer]

Re: Group size at various distance

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