And the moral is: Don't believe everything you read...

I had the joy of spending at the range today - actually, quite a long time at the range. Almost 7 hours. It was a good day.

I normally shoot at a 100 yard target and a 200 yard gong. They didn't have the gong up though and I wanted to shoot at a 200 yard target today.

So after checking my Zero on my rifles I moved out to 200 yards. I was sighted about 1.5" high at 100 yards - should have been about a 200 yard zero.

Nope. More like 4" high at 200! I fired over 15 rounds. Every single one of them high. About 4" high.

I was absolutely stunned. I was truly expecting to see the rounds impact dead center and not 4" high.

Just goes to show: if you want to know what your gun does at 200, gotta shoot it at 200.

Peace!

rnovi
what are you shootin'?
What load what cartridge?
Were you out shootin' that .257 Bob again?

quote:

Originally posted by Snellstrom:
rnovi
what are you shootin'?
What load what cartridge?
Were you out shootin' that .257 Bob again?

.257 Roberts. 44.0gr. H4350. 117 SGK. Velocity: 2800

Heh, yeppers! Shootin the bob. I also shot up a bit of .350 RMag (LOL! don't ask how I did there! I was "Minute of Moose" for the most part.)

The AR15 was shooting 1.5" 10-shot groups at 200 yards. But that rifle is just stupid accurate and at around 12# I think it's cheating a bit.

The Bob was a stunner. I had one group of three that ran a horizontal string around 3/4". I'm calling it luck. I'm sure the rifle's capable but I can't say I am! For the most part the Bob shot a 2-3" group if I did my part.

It was my first day shooting groups at 200 yards so I call it a Success!

rnovi, might I ask what the wind conditions were? I had something like that happen with my hornet - it was due to wind and the fact that the wind was being channelled into a blind gorge and being forced up at the cliff face. What is your scope hight?

An important but sometimes underestimated parameter is the distance between scope and barrel axle. Published data usually are caöculated on the very low side.

I experienced this when shooting a over&under combination in 30/06 where this distance is with about 7 cm much higher than normal. It shoots 4 cm high at 100 meters and about 8 cm high at 200 meters!

Lie said here, only a trial under real condition - shooting at paper, not at animals! -gives reliable results.

quote:

Originally posted by rnovi:
...Just goes to show: if you want to know what your gun does at 200, gotta shoot it at 200.

Yes indeed.

DUK has hit on it! When you look at the ballistic tables they ALWAYS ask for the height of the scope above the bore. Also, the 257R has different ballistics than the 223 or 308 which as I recollect were the calibers quoted in the (responses to) the original thread.
Peter.

I'd also ask if you have actually chronographed your load or are just using the load manuals stated velocity....

also doing a little jerking on the trigger, can make your shot higher the further out you go...
( speaking of personal experiences....)

the same as actually using a chronograph to determine velocity, I have also learned to personally test and find out what my point of impact is at 200 and 300 yds...

it is not infrequent to have low velocity loads to shooter flatter than published to 200 meters..

and to have high velocity loads not shoot quite as flat as represented in manuals either...

trigger pull can have a lot of input on the trajectory at further distances...

when that happens, I move my trigger contact from finger tip to the second knuckle on my shooting finger...you can't jerk the trigger as much at that point as compared to with your finger tip...

quote:

DUK has hit on it! When you look at the ballistic tables they ALWAYS ask for the height of the scope above the bore.

You mean like this?
http://i388.photobucket.com/al.../303Guy/MVC-496F.jpg

All my scopes are mounted high so I am quite familiar with the effect. It does increas the point blank range by about 10yds or so. It annot explain a rising bullet. A tail wind has to rise over the berm and will therefor lift the bullet but not that much. A rizing head wind maybe? I did some JBM calculations with different scope hights and wind directions.

quote:

.257 Roberts. 44.0gr. H4350. 117 SGK. Velocity: 2800

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -1.5 *** 0.0 *** 2800.0 2.508 2036.4 0.000 0.0 ***
100 1.5 1.4 0.9 0.8 2563.1 2.296 1706.4 0.112 19.7 18.8
200 -0.8 -0.4 3.6 1.7 2336.2 2.092 1417.6 0.235 41.3 19.7

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -2.0 *** 0.0 *** 2800.0 2.508 2036.4 0.000 0.0 ***
100 1.5 1.4 0.9 0.8 2563.1 2.296 1706.4 0.112 19.7 18.8
200 -0.3 -0.1 3.6 1.7 2336.2 2.092 1417.6 0.235 41.3 19.7

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -2.0 *** 0.0 *** 2800.0 2.508 2036.4 0.000 0.0 ***
100 1.5 1.4 0.0 0.0 2561.1 2.294 1703.7 0.112 19.7 18.8
200 -0.3 -0.1 0.0 0.0 2332.3 2.089 1413.0 0.235 41.3 19.7

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -2.0 *** 0.0 *** 2800.0 2.508 2036.4 0.000 0.0 ***
100 1.5 1.4 0.0 0.0 2573.6 2.305 1720.4 0.112 19.7 18.8
200 -0.3 -0.1 0.0 0.0 2355.9 2.110 1441.6 0.234 41.1 19.6

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -3.0 *** 0.0 *** 2800.0 2.508 2036.4 0.000 0.0 ***
100 1.5 1.4 0.0 0.0 2573.6 2.305 1720.4 0.112 19.7 18.8
200 +0.7 0.4 0.0 0.0 2355.9 2.110 1441.6 0.234 41.1 19.6

The bold numbers are the changes. The first bold number of 1.5 is the scope hight. I raised that to two, changed the wind direction, bullet type then raised the scope to 3 inches, keeping the 100yd 1.5 inch setting.

Something else has to be happening!

As I don't own a Bob can't comment if this is normal but would think it's Not !.

Remember ANY DAY at the range or Hunting Fishing is better than ANY OTHER DAY ,save maybe for I got

LUCKY DAY !.

Try a different loading with same bullet and see what happens . Practice Practice Practice

until you can't do it wrong !!!!.

quote:

I'd also ask if you have actually chronographed your load or are just using the load manuals stated velocity....

Even raising the velocity considerably doesn't answer the Q. rnovi did say "about 1.5 inches high at 100yds".

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -2.0 *** 0.0 *** 3200.0 2.866 2659.8 0.000 0.0 ***
100 2.0 1.9 0.0 0.0 2952.3 2.644 2264.0 0.098 17.2 16.4
200 2.0 1.0 0.0 0.0 2718.1 2.435 1919.0 0.204 35.8 17.1

Was group shot at 100yds the same day to extablish the actual 100yd setting? Has the scope changed somehow?

Well, when they open the 200 yard range (next week) I will have to check this out with my 257R. This has me interested. Thanks for all your work 303!
Peter.

quote:

Just goes to show: if you want to know what your gun does at 200, gotta shoot it at 200.

Yes. And the same applies in spades to distances beyond 200 yards.

Beyond 200yds is where I start getting into trouble. I just have not practiced enough!

The 200 yard range I shoot on has 3 berms before the 200 yard berm. If the wind is behind us it is not uncommon to have as much as 6 inches of "lift" working on our POI. This from the wid being directed upward off the berms.

I wonder how many times I have blamed myself for crap shooting when it was actually the wind?!
Thanks for providing the answer rickt300 and thanks for raising the question rnovi.

LOL! I had to go out of town for a week and missed out on all your answers!

I blame nothing on the wind - yes, there was a little bit of wind - minor stuff though. 5-10mph - which could make some of the difference. But it wouldn't explain WHY I was shooting so consistently about 4" over where I thought my point of impact "should" be.

I can live with a 5" group as long as it's statistically consistent. It was my first time shooting groups at 200 yards so my expectations were fairly modest. I figured that my groups should be pretty much a wide statistical triangle.

Anyway, I'm not exactly trying to figure out what I did right or did wrong. I think the obvious starting point is to take about 6 clicks out of the elevation!

You did say it was 'an observation'! Nevertheless, it was an interesting thread!

Still, it would be intereting to hear what caused your apparent POI shift. I have also experienced apparently inexplicable POI shifts!

At my range 200-300 yards doesn’t prove much except how far the wind can push bullets out of a group while testing loads. I keep my testing at 100 yards. Once I’ve developed a load at 100 yards, then I shot it at 200-300. It’s more of a test of myself (judging wind drift) than the load at that point.

Something does not compute here. In the absence of strange air movements lifting the bullet, there's simply no way to explain such a result, unless the scope was mounted so high that the 1.5" above POA at 100 yards was the first time the bullet crossed the line-of-sight.

quote:

Originally posted by Jefffive:
Something does not compute here. In the absence of strange air movements lifting the bullet, there's simply no way to explain such a result, unless the scope was mounted so high that the 1.5" above POA at 100 yards was the first time the bullet crossed the line-of-sight.

What are you shooting?
Jefffive is right. Even if that was the first time the bullet crossed the scope at 100 yards it would have to GAIN 2.5 more inches before reaching 200 yards.
I ran several trajectory comparisons through my software and I can't duplicate those numbers...

There is simply not enough room between 100 and 200 yards for the bullet to change path so dramatically.
That is 2.5" of differential in 100 yards.

No offense, but if you are 1.5 inches high at a hundred yards you can bet your left testicle its the FIRST time it crossed your line of sight. I dont understand all the confusion. Depending on scope height 4 inches would not be uncommon. I have seen worse. (imo) Wind had nothing to do with it.

quote:

Originally posted by Henry Hoover:
No offense, but if you are 1.5 inches high at a hundred yards you can bet your left testicle its the FIRST time it crossed your line of sight. I dont understand all the confusion. Depending on scope height 4 inches would not be uncommon. I have seen worse. (imo) Wind had nothing to do with it.

Not so, with normal sighting-in the bullet first crosses the line-of-sight (LOS) at around 37 yards (depending on caliber) on an upward trajectory (relative to LOS) (this is the "point blank" range), with the bullet then falling back to coincide with the LOS at the point of zero (with impact 1.5" high at 100 yards most rifles will be "zeroed" at 160 or so).

Since a bullet must start falling relative to the line-of-bore immediately upon leaving the muzzle (Law of Physics apply) I don't personally know of any way to achieve a trajectory that would be 1.5" above LOS at 100 yards and 4" above at 200, with any cartridge.

quote:

Originally posted by Henry Hoover:
...Depending on scope height 4 inches would not be uncommon. I have seen worse. (imo) Wind had nothing to do with it.

quote:

Originally posted by Jefffive:
Something does not compute here. In the absence of strange air movements lifting the bullet, there's simply no way to explain such a result, unless the scope was mounted so high that the 1.5" above POA at 100 yards was the first time the bullet crossed the line-of-sight.

quote:

Originally posted by Jefffive:
Since a bullet must start falling relative to the line-of-bore immediately upon leaving the muzzle (Law of Physics apply) I don't personally know of any way to achieve a trajectory that would be 1.5" above LOS at 100 yards and 4" above at 200, with any cartridge.

With the info he provided, the only way I could duplicate his scenario (1.5" high at 100--4" high at 200) on level ground, was to have his scope 6" above the bore, with a 300 yard zero.

Anything else I could come up with would not duplicate these numbers.

quote:

Originally posted by Flippy:

quote:

Originally posted by Henry Hoover:
...Depending on scope height 4 inches would not be uncommon. I have seen worse. (imo) Wind had nothing to do with it.

quote:

Originally posted by Jefffive:
Something does not compute here. In the absence of strange air movements lifting the bullet, there's simply no way to explain such a result, unless the scope was mounted so high that the 1.5" above POA at 100 yards was the first time the bullet crossed the line-of-sight.

quote:

Originally posted by Jefffive:
Since a bullet must start falling relative to the line-of-bore immediately upon leaving the muzzle (Law of Physics apply) I don't personally know of any way to achieve a trajectory that would be 1.5" above LOS at 100 yards and 4" above at 200, with any cartridge.

With the info he provided, the only way I could duplicate his scenario (1.5" high at 100--4" high at 200) on level ground, was to have his scope 6" above the bore, with a 300 yard zero.

Anything else I could come up with would not duplicate these numbers.

A rifle only a gerenuk could shoot...

A little more info:

Yes, these are chronographed loads. I get 2750-2800fps consistently.

The bullet is the 117gr. SGK: BC data as follows:

.410 @ 2500 fps and above
.403 between 2500 and 1800 fps
.370 @ 1800 fps and below

The center of the scope is 2" above the bore. This is a leupold VXiii 2.5-8x, mounted in medium height leupold quick detach rings.

Per the ballistics calculator, i see the following info:

0 yards: 2800 fps.
100 Yards: 2,573 fps, + 1.64",
200 yards: 2,363 fps, + 0"
300 yards: 2,164 fps, -7.91"

Ok, so I zero'ed my rifle at 2" high at 100 yards. Theoretically by the numbers, I'd be just a hair over 0" high at 200.

As to the wind, could wind cause bullet to rise? Maybe, but I'd be much more inclined to believe that it was shooter error more than anything else.

So, I think I'm going to try this a bit differently. I'm going to head back to the range in a week and refire the groups, setting the rifle with a true 200 yard zero. Then I'll move the target back to 100 yards and see where the rifle impacts at 100. That will give me a much better idea of what's going on.

Peace!

quote:

Originally posted by rnovi:
A little more info:

Yes, these are chronographed loads. I get 2750-2800fps consistently.

The bullet is the 117gr. SGK: BC data as follows:

.410 @ 2500 fps and above
.403 between 2500 and 1800 fps
.370 @ 1800 fps and below

The center of the scope is 2" above the bore. This is a leupold VXiii 2.5-8x, mounted in medium height leupold quick detach rings.

Per the ballistics calculator, i see the following info:

0 yards: 2800 fps.
100 Yards: 2,573 fps, + 1.64",
200 yards: 2,363 fps, + 0"
300 yards: 2,164 fps, -7.91"

Ok, so I zero'ed my rifle at 2" high at 100 yards. Theoretically by the numbers, I'd be just a hair over 0" high at 200.

As to the wind, could wind cause bullet to rise? Maybe, but I'd be much more inclined to believe that it was shooter error more than anything else.

So, I think I'm going to try this a bit differently. I'm going to head back to the range in a week and refire the groups, setting the rifle with a true 200 yard zero. Then I'll move the target back to 100 yards and see where the rifle impacts at 100. That will give me a much better idea of what's going on.

Peace!

If the facilities were available, I would fire a group at 50, 100, 150 and 200, holding dead on at each range, with a cooling period between groups, and see what I had.

quote:

Originally posted by rnovi:
So, I think I'm going to try this a bit differently. I'm going to head back to the range in a week and refire the groups, setting the rifle with a true 200 yard zero. Then I'll move the target back to 100 yards and see where the rifle impacts at 100. That will give me a much better idea of what's going on.

Peace!

Good idea!

If your scope was wacko, your group size would not be very good, something like 6-8" not 2-3".
When scopes go they usually are way off, not just off vertically. The pattern looks like a shotgun.
Same thing for parallax.

I will be interested to see what happens and what you conclude.

I'll also be interested in the outcome!

quote:

Originally posted by Jefffive:
Since a bullet must start falling relative to the line-of-bore immediately upon leaving the muzzle (Law of Physics apply) I don't personally know of any way to achieve a trajectory that would be 1.5" above LOS at 100 yards and 4" above at 200, with any cartridge.

Oh, that is not so difficult and in fact only a matter of geometry or, in other words, the distance between scope axle and bore axle.

With the bolt action rifles you generally use over there, this distance varies little. Do not forget that in Central Europe we use quite a lot of comnbination rifles with a shotgun barrel between scope and rifle barrel.

Besides, also our scopes are usually larger because we hunt at night. 56 mm is not uncommon.

I simulated that once with Quickload or rather, Quicktarget, there is a big leverage for the above mentioned parameter which directly translates into a changing POI at 200 yards.

Jefffive,if your bullet is high at ANY distance it has only crossed your line of sight ONCE.
I have zeroed rifles for idiots who have see-thru mounts so high I had my cheek COMPLETELY off the stock. They were a pain in the mule to zero until I realized the problem.(many years ago)When scopes are mounted very high over the bore it is hard to be 1.5 inches high at 100 yds and not be high at 200, especially with a fairly flat shooting cartridge. All we are doing is speculating. Its still not that big a problem.

I do not know if you had any head wind during your shoot, but I know that I have had between a 10 to 15mph head wind along with the mirage off a heated barrel, move my impact points up as much as two to three inches at 200 yards.

quote:

Originally posted by Rae59:
I do not know if you had any head wind during your shoot, but I know that I have had between a 10 to 15mph head wind along with the mirage off a heated barrel, move my impact points up as much as two to three inches at 200 yards.

Yup, been there, seen that. 10 to 15 mph? I don’t think many people really realize how strong that kind of wind is. Or even know what it feels like. But than again, most people don’t own an anemometer.

quote:

I have zeroed rifles for idiots who have see-thru mounts so high I had my cheek COMPLETELY off the stock.

I had no choice with my MkI Lee Enfield. I had no problem sighting it in nor with face support on the stock. It must be the shape of my face and length of my neck and so on. I mount all my scopes high - I find I shoot better that way. My 22LR gives me a wonderfully long point blank range with sub-sonics. But realistically, one only gains 5 to 10 yds of point blank range with very little difference in the 100yd POI - less than the group size.

quote:

Originally posted by Doc224/375:
Remember ANY DAY at the range or Hunting Fishing is better than ANY OTHER DAY ,save maybe for I got

LUCKY DAY !.

I gotta disagree with you on that last one. I gotta go to the range to get away, rest, and replenish the bodily fluids.

Finally - what, 4 weeks later I finally got a chance to return to the range to revisit the .257 Roberts.

The goal this time was to start at 200 yards, site to Zero at 200, and then move the target into 100 yards.

The first group went low but I was more than happy with the group size - 1.38"!



I moved up a few clicks, refired. Second group looked good. 1.385".

Third group went a tad high, pulled the second shot a bit. Gotta love two shots near touching though! Backed off a click, and fired for effect.



Three more shots, decided that was "good enough". I figured that's close enough to a 200 yard zero as I'm likely going to shoot. Definitely pulled the second shot (someone fired at the exact same time - and I knew I pulled the moment the sear broke).

Anyway, 2-shots dropped into .808"...3-shots grew the group to 2.15". Good enough.

Moved the target to 100 yards and refired.

The Target came back darn near exactly 2" high on the money. IMO, that group is tight enough to qualify as being centered.

**********

To cap it all off, I decided to see how the AR was doing at 200 yards.



Not bad for a DPMS upper, huh?

Yes indeed, nice shooting with both rifles.