I found a picture (I know, you're happy for me [img]images/icons/wink.gif[/img]).
I'll post two pictures (It's getting worse huh!) and you all tell me how much angle is in the picture and which is the original (un altered)
Pict # 1
Pict # 2
Should be easy... remember I'm trying to trick you.
I'll post the entire original picture later
I found a site that has a rather interesting article about cant induced error. Good reading I thought. (At first glance the results the author obtained were in agreement with that I've taken as the magnitude of the problem.) http://www.microlevel.biz/cant_errors.html
Dave, thanks for the math. If I am reading you correctly, you are including 100% of teh drop in the calc, not 50% as I suggested with the apex of verticle. Still, an absolutely insignificant error to me. Time will show everyone that this is true.
Yes, it would appear that pic 2 is rotated left, about 5 or 6 degrees. If it's the other way around, so be it.
Now, are you trying to trick me, yes. And that's fine.
WHERE ARE THE CROSSHAIRS? What you are telling me is that IF my scope has NO crosshairs in it, then I may hold the gun on an angle when I'm on uneven ground, and have no other point of reference. What everyone is missing, is that there is a point of reference. It's called Gravity. Your body and brain, and inner ear hardware, are pretty damn accurate. Your point of reference is, your memory. Lets say you are 40 years old. Well, for the last 40 years, you have spend most every waking second of that time looking at references which are plumb, square, and level. Laying in bed at night you look out the window and the image you see even reaffirms this for you when you're laying down.
I WILL give you that I can think of a time when this is a significant device. A person who shoots switch, right handed one shot, then left handed the next, will definitely be "more prone" to having error than the person who shoots right or left all the time.
Don't forget, all this error is based upon CHANGE FROM NORMAL. If you hold the gun at a 2 degree angle normally, for whatever reason that I cannot possibly understand, then it is only when you hold it otherwise that this ever comes into play.
And not by SIX degrees will it ever happen. NO DEAL.
I will again point to the picture I provided above WITH crosshairs in it and ask again, who out there thinks they could ever hold that far off. Anyone raising thier hand, please stay away from guns.
I have a better test for everyone. Since everybody is gonna waste thier hard earned money on these things anyhow. Please, anyone who has one of these, go again and put that picture somewhere so you can see it in your scope. Now, cant the gun till the crosshairs line up with the photo, on whichever side is most compfortable to you (since everyone holds to one side I guess). Now, look at the bubble. Tell me you ever saw that condition without your gun standing in the gun rack.
I will say again. DIFFERENCE FROM SHOT TO SHOT. If everyone claims to have a great zero on thier guns for hunting, then they certainly should be able to see this phenomenon as ranges increase. This of course if they ever practice. Though I think most people will find that they have mounted thier scope off level to the round bottom gun, or that thier optics have internal problems. IF your gun shoots at all, you should be able to see this and should have corrected the problem LONG before you shot at anything at a range where it matters. Even refering back to the original thread, Brent gives some pretty BIG numbers in my mind. I think some of them are from a program and assuming 6 degrees is possible and that's fine for the sake of arguement. My point here is, HE SAW IT. Then fixed it (i'm sure by rotating the scope, or doing something else mechanical. The reason he saw it is because the gun GROUPed differently at longer ranges. NOT because he was holding the gun out of level. Even if it was his hold, his hold was consistant enough to see this phenomenon and correct for it, never to see it again. It's not like he's gonna shoot at game at 2000 yards from a different bench than he practices. At 500, if you guys still believe you change 12Deg included from one day to the next, then I suggest you practice more on holding the gun.
You know, I think if I took my crosshairs out of my scope, then in a dense fog, handed it to Stevie Wonder, he could see it was out of level before it hit 6 degrees. I do not care if you are sitting, laying, standing offhand, you WILL NOT convince me that you could in only one lifetime, hold 6 degrees left one time and 6 degrees right the next. Not half of that. Not a quarter of that. You would absolutely have to have your eyes closed to miss it.
I also do not understand the table you posted. You seem to go a little beyond even the angles that you guys think are attainable. Does anyone hold the gun at 90 degrees? OK! I think we all can agree that that person should be taken out behind the barn and shot. The numbers seem astronomical. I'm just gonna wait for Brent to run them in RSI to see what his findings are there.
Put a crosshair in the photo's at 1 degree of rotation and I'll tell you which is which.
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!
The chart shows angles to 90 degrees... Tactical shooters shoot at all types of induced cant angles. Shoot through a slightly opened window, from under a car or truck, through a loop-hole where a piece of siding has been pried loose. 90 degrees of cant is not an uncommon encounter at a sniper match.
All the "drop" belongs in the chart as I see it. When shooting with Zero -0- cant and 78 inches of up elevation the max ordinate will probably be (this is a SWAG and not calculated data) 2/3rd's that value or about 50 inches. What I believe you're trying to say is that's the most can't error or "lost" drop we can consider. I disagree and here's why. The elevation we place on the scope (or any sighting device) is to overcome gravity. We need 78 inches of up to overcome 78 inches of down "fall" the bullet (projectile) will experience over the TOF required to get to 500 yards.
The max ordinate is of little consequence except for figuring wind if you're shooting where the projectile will rise above surrounding structures and the possible need to thread the bullet under or over an intermediate obstruction (bridge, house, tree, etc.).
If I place enough elevation on the sighting system to compensate for the 78inches of drop and then rotate the weapon 90 degrees I get two (2) projectile deviations from my POA. The projectile will "fall" vertically 78 inches for the already determined TOF and it will be displaced 78 inches to the side(horizontal) by the "old" elevation set into the sighting system. Your bullet will strike 78 inches low and 78 inches to the side for a 90 degree cant.
Gotta go... I'll be back!
Here's another look at those pictures.
How are you going to "square-up" the crosshairs on this elk before you shoot?
Pict 1 then Pict 2
P.S. Found my Seekonk torque wrench...UPS had it and kindly left it at my door. My wife might believe this for a while, until the credit card bill comes ($112.00 or so, it's expensive for overnight shipment!) Now... where's that other stuff [img]images/icons/confused.gif[/img] )
I knew we trusted you to spend out tax money for a reason.. what that reason is I don't know but.. I'm glad you are as intellegent as you are cause inmy mind that's what I wanted to say I just didn't know it...
so if you "square" your cross hairs on that rag horn elk are you really canting them?
I'm at work also and I can't get a picture posted back to ya now. It may even be a day or so. I took the 2 photos after looking at them and telling my brother and Boyd here, they are dead level in both shots. So, I opened both photos in Paint Shop Pro and did image arithmetic adding the two photos together. The Crosshairs are DEAD THE SAME in both photos. There is no adjustment to make, thank you very much. So, then I actually rotated ONE photo ONE degree and it was painfully obvious that you had not rotated either photo. Now, they are different sizes so in order to make this simple, it would be easier for others to see if the images were the same size. No problem here though.
Now. Not only are we not talking about Sniper competitions. I don't need the table out to 90 degrees. I don't need the table to 1 degree. AND EVEN IF I DID, your level WILL NOT FUNCTION for ANYTHING BUT LEVEL. Please tell me how you expect to use this thing when your gun is held on a 45, or a 90. I don't shoot at game from behind a hole in the siding!
I am loosing faith in your reasoning ability which I actually gave a lot of credit to. You are using exaggerated numbers to an incomprehensible degree to sell an item which IS USELESS. All your numbers are for a 6 degree CHANGE FROM SHOT TO SHOT which is impossible under any circumstances while hunting. This is total BS. I liken it to Precision Shooting Ragazine publishes an article where "respected shooters" say that the piloted tap from Pacific tool will "TRUE" a Remington 700 action with a hand tap wrench and a reamer.
I will get my system running again and post these. I will also get a nicer photo so someone can actually see. Rerun all your numbes for + or - one degree and I'll buy it. You will find this INSIGNIFICANT. IMMEASURABLE on paper. Certainly IMMEASUREABLE on game. If you didn't order the other 2 yet, do yourself a favor and save your money.
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!
Notice the elk are walking down an slope. The elk I have circled is the one in the smaller picture.
Pict #1 is the uncanted picture and the crosshairs are level to the original picture (horizon).
Pict #2 IS canted 6 degrees (according to the software I used to adjust the image). The crosshairs are leveled in reference to the elk in pict #2 so they have a 6 degree cant too. This is how a shooter can induce cant without knowing it, as the point of reference becomes the target on a confusing background. *WyoWhisper* picked up on the problem right away.
You asked about the table.. "I also do not understand the table you posted. You seem to go a little beyond even the angles that you guys think are attainable. Does anyone hold the gun at 90 degrees? OK! I think we all can agree that that person should be taken out behind the barn and shot. The numbers seem astronomical. I'm just gonna wait for Brent to run them in RSI to see what his findings are there."
And the explanation is that it's useful, maybe not for your limited application but you don't set the bounds other shoot to.
Another answer for you. "Now. Not only are we not talking about Sniper competitions. I don't need the table out to 90 degrees. I don't need the table to 1 degree. AND EVEN IF I DID, your level WILL NOT FUNCTION for ANYTHING BUT LEVEL. Please tell me how you expect to use this thing when your gun is held on a 45, or a 90. I don't shoot at game from behind a hole in the siding! "
For long range shooting the rifle should be level, hence the level. For short(er) range we can use cant and the numbers are good to know. If I shoot at a 4 x 4 inch tile at 100 yards and need to cant the rifle I know the max error is going to be ~3 inches low and ~3 inches horizontal deviation. If the sniper shoot states it'll have a 250 yard precision shot with a canted rifle I use the chart to figure the max and expected error. The chart as shown here offers what error is possible when shooting with a cant (known or unknown).
I'm not using exagerated number, in fact I believe I said it wouldn't make any difference what numbers I used as someone would blow up over them. "500 yards... I'll just pick number for elevation (doesn't matter the number I pick, someone will make something of it other than offered anyway). "
That chart shows cant changes by 1 degree values. Isn't that what you want? The distance is for 500 yards, a number stated somewhere earlier in this thread I believe.
Once you come to your senses and re-read what's there and what being said/offered you may change your mind.
I'll run the numbers, but Dave is I believe running the numbers for 90 deg to exagerate an example as well. How much cant you have in the rifle is not relivant unless you'd just like to know the impact it would have on a shot had you NOT kept it level, and you were sighted in LEVEL.
I will disagree with you on one point you made here.
Don't forget, all this error is based upon CHANGE FROM NORMAL. If you hold the gun at a 2 degree angle normally, for whatever reason that I cannot possibly understand, then it is only when you hold it otherwise that this ever comes into play
Holding at 2 deg cant normally, and zeroed at 100 yards, as soon as you crank in 18 MOA for a farther zero at say 800 yds, what just happened to your zero out farther? It's now off, is it not?
Point is, you're at the range, turrets leveled to the action, crosshairs level, bubble level clamped on scope and level too, everythings great, good frame of referance and you're ready to fire. The bubble you notice is off just before the shot. How much? Don't matter at all how much, you straighten it up and fire. You go out to 800 yards, do the same thing. You know the rifle and turrets you're dialing with are level. The main issue is that the center of your crosshair tracks the plumb line from the crosshair to the bore line perfectly, and this intersecting line is kept plumb and not canted. Matching POI with POA is all I'm concerned with, and it being repeatable.
We are dealing with angles, and anything that changes them or causes ANY error that CAN BE eliminated is first on my list, anything that can be compensated for is next, but still takes a back seat to those things that can be ELIMINATED.
Back with the RSI Lab cant numbers here shortly...