How does .8" at 100 yds become 2.5" at 200 yds?

Wind?

Hard to say. There are tons of variables. Wind is always a big factor. From the front , back, sides can all change poi. We’re you getting consistent. .8 groups at 100 yards.? If not you have no data to compare your 200 yard groups to.

The 200 yard group you are showing is just a bit over 1.25 moa. That’s pretty good shooting. Too better it you would have to do all your testing at 200 yards so your results could be compared.

Two different days, could be a lot of things, wind is just one of them. Ambient temperature is another, along with you. Some days we don't shoot as well. Could be the amount of coffee, or what we are wearing. Target picture can make a difference to our eyes/mind.

.......still pretty good shooting.

Picked up a comment the other day......believed it was Scott Satterlee of Saterlee load development fame. Crux of it was a load with wide variation in velocity won't show up at close range........100 yards.......but will at distance due to the velocity related drop. As noted, wind also a factor.

Was the open group at distance vertical, horizontal or random?

This may or may not be the case here, but this is a good explanation of extreme velocity spread and its effect. The further out you shoot, the more impact it has (if I understand correctly)

200 yards is more than 2x difficult that 100 yards. Many of the factors that impact accuracy have more than a 2x impact when you 2x the range.

Crosshairs and target size plays a bigger role at distance. If your crosshairs cover “X” of the bullseye at 100, than they cover “X x2” at 200 yards harder to make sure you are punching the same spot each time when the crosshairs cover more.

A good thing to do is sight in a rifle for bullseye and then when shooting groups move the crosshairs mechanically with your turrets over a few inches so the bullseye stays clean and consistent from shot to shot without bullet holes causing issues with your crosshairs and sighting.

Distance magnifies every error. The further you go out the worse it gets. Beyond 600 is where the men and boys are separated.

Lee Q. Loader said:

I posted the target above.

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Ooops. My bad. Both of those look like vertical stringing to me, which would be the case if velocity is variable. That video explains it better than I can.

Lee Q. Loader said:

I guess I just assumed that if my load was sub MOA at 100 yards, it would be sub MOA at all distances.

Can someone please help me understand what happened?

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Sometimes it helps to see things if we take them to absurd levels. How about we apply that to a spring piston air rifle.?

That would make a daisy read rider with the barrel in a vice (so it’s sub MOA a few inches from the muzzle) sub MOA out to 190 yards and we all know that’s not going to happen, why? Because all of the other variables involved in it traveling that distance and the time they have to cause error in the BB’s flight, that’s in a perfect world where they would all exit at the identical speeds.

Lee Q. Loader said:

View attachment 1114707
Here's the 100 yard group from a few days ago

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"The" 100 yard group? As in one group? If you only fired one group at 100 yds., then that may be your problem. Fire several groups at 100 yds., average their sizes, then set your expectations for 200 yds.

35W

Rate of rifling
Bullet design
Stability

All you can do is shoot and see.

I had a 7 mag 150gr Nosler shot 4" @100 yards. 4" @200 yards, 4" @300 yards and 5" @400 yards.

It just took a bit to stabilize. Most shots from my stand were 300 - 400 yards. I was sighted in at 350. Was very surprised when I shot 200 and 100.

You are slightly less than MOA at 100 yds and slightly over MOA at 200 yds. Human error will expand your groups the longer the distance. Besides, slightly under and over MOA at the two distances seems pretty good to me.

Howa 9700 said:

Howa 9700 said:

Was the open group at distance vertical, horizontal or random?

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Both of those look like vertical stringing to me, which would be the case if velocity is variable.

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Yes. Vertical stringing = Velocity variance + bullet drop + barrel whip + trigger/grip input

A minor scope misalignment or slightly off level can cause groups like your 200 yd group. I suspect your scope might be a tiny bit canted left.

Think about it. You shot .8 MOA at 100 yards and 1.25 MOA at 200 yards. That's roughly 1/2 MOA worse. From that perspective it doesn't seem all that bad. Everyone wants to do better, but in the real world your 200 yard groups are in the ballpark.

If you want a real head scratcher wait until you get a gun that shoots 1" (1MOA) at 100 yards and shoots 1.5"(.75MOA) at 200 yards. I don't have anything in my safe at the moment that does that. But I've had at least one rifle in the past that did. Others have observed this too and there is no clear-cut explanation.

Many possibles. Mirage comes to mind. I would consider that very normal. My 50 bmg will consistantly make better goups @ 200 yd then 100 yd.

jmr40 said:

Think about it. You shot .8 MOA at 100 yards and 1.25 MOA at 200 yards. That's roughly 1/2 MOA worse. From that perspective it doesn't seem all that bad. Everyone wants to do better, but in the real world your 200 yard groups are in the ballpark.

If you want a real head scratcher wait until you get a gun that shoots 1" (1MOA) at 100 yards and shoots 1.5"(.75MOA) at 200 yards. I don't have anything in my safe at the moment that does that. But I've had at least one rifle in the past that did. Others have observed this too and there is no clear-cut explanation.

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Was explained to me (by the late Skip Talbot) as a very heavy bullet needs more distace to stabilize out of the bore. The way he explained it, heavy bullets need more time to "wake up". That guy donated his time with a call service to answer questions just like this.

Lee Q. Loader said:

I guess I just assumed that if my load was sub MOA at 100 yards, it would be sub MOA at all distances.

Can someone please help me understand what happened?

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Pretty straight forward - that assumption doesn’t hold water.

Lots of things here:

Did you shoot ONE 0.8” group at 100yrds and ONE 2.5” group at 200? What is the repeatable standard result for these two distances?

0.8” at 100 is 1.6” at 200, so you slipped an extra inch. 0.76moa slipped to 1.19moa… not super surprising.

Did you double your target size at 200yrds? Did you double your magnification? If not, your reticle picture on target changed dramatically. When you lose reference dimension at range, your wobble zone inevitably increases and you’re not able to hold consistent POA.

Vertical stringing as a symptom of velocity variability is REALLY rarely significant at 200yrds. It takes a LOT of velocity variation to present on target at these SHORT ranges. I reshared math this week outlining the influence of 50fps ES which only yields slightly over 4” group size at 1,000yrds - just one click in a riflescope. Punching 50fps ES at 200yds, the group size only increases 0.1moa at MAX theoretical limit, whereas the actual statistical influence would be something around 0.02moa… whereas you’re getting 0.4moa growth…

So my money is on a floating mechanical error - you’re simply breaking the shots more broadly, just driving the rifle differently.

Lee Q. Loader said:

View attachment 1114705
Picture of target for reference.
There was a breeze. Guessing variable between 4 and 5 mph, right to left.

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A right to left will blow your rounds high left and that’s not what we see here, rather split groups. Repeat your test with more attention to gun handling.
One addition note- when shooting groups try to maintain a smooth steady pace, don’t take extra time to cool the barrel look around etc. just return to battery with the sights on target and watch the round all the way to the bullseye. If you worry about heating shoot less rounds like three instead of five.