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Bubble level for rifle

#29
03-04-2004, 09:44 PM
 Silver Member Join Date: Dec 2002 Posts: 374
Re: Bubble level for rifle

JB.

Don't thank me now! I just saved you a bunch of money!
__________________
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!
#30
03-04-2004, 10:01 PM
 Silver Member Join Date: Dec 2002 Posts: 374
Re: Bubble level for rifle

Oh,

I will specifically ask Dave King, (because I will trust he can do the math accurately) or anyone else who thinks they can answer this correctly. I am "Asking" if my thinking is correct here. To calculate the true error, would you not take 1/2 the total drop figure (Apex of verticle travel), times the SIN() of the angle or error to compute the total cant error?

IF this is correct and I think it is, we are talking about something so small, that there are probably only a handfull, perhaps NO guns on the planet that shoot well enough to demonstrate this without exaggerating the angle to something noone would ever do. Just exactly the way was done in the product literature by saying 6 degrees is a lot without showing an example like I just posted.

And you guys say that "I" try to make figures lie.
__________________
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!
#31
03-04-2004, 11:10 PM
 Platinum Member Join Date: May 2001 Location: Lock Haven P.A. Posts: 1,071
Re: Bubble level for rifle

[img]images/icons/grin.gif[/img]
__________________
Boyd Heaton...
#32
03-04-2004, 11:22 PM
 Platinum Member Join Date: Jun 2001 Location: Palmer, Alaska Posts: 2,539
Re: Bubble level for rifle

Phil,
Hold up there...

I think either my ballistic program is way off, which I think Jim Ristow would argue that, or you're figures are not correct. I will say this, "I do not know which", as I have not tested it myself.

1-3 degrees cant is what I would expect to see in the field, maybe more in the mountains with no flat land or good reference. 6 degrees was only a referance most can understand, as it is 1 minute on a clock. It is a lot however, and one minute doesn't sound like barely a smidge, but as you point out, it is quite a lot and not something you should be worried about on fairly easy to judge terrain, not by a long shot if you pay attention too it. The point is, PAY attention to it, it can have an effect.

I'l run some number for the 300 Ultra at 500 and 1000 yards when I get back for us to look over and scrutinize. I can enter any degree of cant into the RSI LAB program and see the deflection in MOA or inches.

My Dad's having problems getting his online cable router working so I've got to go hang on the line with tech support and help the computer elliterate. [img]images/icons/grin.gif[/img]

Those pix are great!

Run this. 210gr Berger, BC .640, MV 3100 fps, BP 29.53, Temp 59 deg F. 500 and 1000 yard deflection. 2 deg, 4 deg, and 6 deg cant.
__________________
Brent Moffitt
#33
03-05-2004, 12:26 AM
 Silver Member Join Date: Dec 2002 Posts: 374
Re: Bubble level for rifle

Sorry Brent,

I don't have RSI's software except that for my chronograph.

I would be more than happy to run the ballistics, but my pc is dead and I have no program at home for that at this time. I worked late today and will again tomorow. I won't get time to deal with the pc till the weekend at the earliest. I'm typing on my server right now and I'm afraid it's RedHat Linux Version 9, not windoze which my ballistics programs run on. I do have a dos version of Baltec from sierra, but not on the Linux box. I could emulate it but I'd just as soon go to work and run it. By then, someone else will certainly have the figures.
__________________
If you have something that you disassemble and reassemble enough times, sooner or later, you'll have two!
#34
03-05-2004, 05:44 AM
 Platinum Member Join Date: May 2001 Posts: 2,369
Re: Bubble level for rifle

Cant Error:

http://www.longrangehunting.com/cgi-...c&f=3&t=001300

Cant is often an unseen problem. The shooter is on a side hill, shooting across or onto other non-uniform terrain. I can easily imagine cant erros of several degrees and values of the stated six (6) degrees don't seem unlikely.

As I understand it, Cant induced error, unlike inclined fire error is more significant in the smaller (initial) angles. A six (6) degree inclined fire deviation factor (cosine) would be .005 while the cant deviation factor would be .104.

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). 12 MOA of elevation required for a 500 yard shot. Add this to the elevation required to get to to 100 yard zero, ~ 3 MOA and we get a total of 15 MOA elevation, this amount to 15*5*1.044 and we get 78 inches of total drop.

Now, shoot on a 6 degree incline and get use 78 * .005 = .39 inches of POA to POI error.

Cant the rifle over 6 degrees (assume we're shooting in a no-wind condition so no windage on the scope) and we'll get 78 * .104 = 8.1 inches of POA to POI error.

<UL TYPE=SQUARE>POA to POI error for 78 inches of elevation
and the indicated angle.

Error in inches
Columns are

Canted

Inclined

Angle

Cant Incl Angle in degrees
1.36 0.01 1
2.72 0.04 2
4.08 0.10 3
5.44 0.19 4
6.79 0.29 5
8.15 0.42 6
9.50 0.58 7
10.8 0.75 8
12.2 0.96 9
13.5 1.18 10
14.8 1.43 11
16.2 1.70 12
17.5 1.99 13
18.8 2.31 14
20.1 2.65 15
21.4 3.02 16
22.8 3.40 17
24.1 3.81 18
25.3 4.24 19
26.6 4.70 20
27.9 5.18 21
29.2 5.67 22
30.4 6.20 23
31.7 6.74 24
32.9 7.30 25
34.1 7.89 26
35.4 8.50 27
36.6 9.13 28
37.8 9.77 29
39.0 10.4 30
40.1 11.1 31
41.3 11.8 32
42.4 12.5 33
43.6 13.3 34
44.7 14.1 35
45.8 14.8 36
46.9 15.7 37
48.0 16.5 38
49.0 17.3 39
50.1 18.2 40
51.1 19.1 41
52.1 20.0 42
53.1 20.9 43
54.1 21.8 44
55.1 22.8 45
56.1 23.8 46
57.0 24.8 47
57.9 25.8 48
58.8 26.8 49
59.7 27.8 50
60.6 28.9 51
61.4 29.9 52
62.2 31.0 53
63.1 32.1 54
63.8 33.2 55
64.6 34.3 56
65.4 35.5 57
66.1 36.6 58
66.8 37.8 59
67.5 39.0 60
68.2 40.1 61
68.8 41.3 62
69.4 42.5 63
70.1 43.8 64
70.6 45.0 65
71.2 46.2 66
71.7 47.5 67
72.3 48.7 68
72.8 50.0 69
73.2 51.3 70
73.7 52.6 71
74.1 53.8 72
74.5 55.1 73
74.9 56.5 74
75.3 57.8 75
75.6 59.1 76
76.0 60.4 77
76.2 61.7 78
76.5 63.1 79
76.8 64.4 80
77.0 65.7 81
77.2 67.1 82
77.4 68.4 83
77.5 69.8 84
77.7 71.2 85
77.8 72.5 86
77.8 73.9 87
77.9 75.2 88
77.9 76.6 89
78.0 78.0 90
[/list]
My out: This is as I understand these issues, it may or may not be the truth. I choose to believe this is the manner in which this happens based on several tests at 100 yards.

Maybe we can get one of our real ballistic guru's to add on here. I'm only posting based on what I've seen and tried and then tried to qualify and quantify. JBM, Warren Jensen, anyone... will a real ballistics guy please stand up

[ 03-11-2004: Message edited by: Dave King ]
#35
03-05-2004, 07:03 AM
 *WyoWhisper* Posts: n/a
Re: Bubble level for rifle

Dave,

You are welcome! Reguardless of the opinions I feel those are a "priceless item" to anyone into longrange hunting...

Hey 4 mesh....

OK so 6 degrees/minutes is alot but totally possible especially out here as there is very little flat land in the hills to reference from... I have seen seasoned shooters cant their rifle A LOT due to the terrain and the tricks your mind plays on you with what is level...
Not only will the cant get you and according to you the cant will or cannot be that much by any God fearing, rifle toting man that has the priviledge of owning one that has any intellegence.... but now.. factor in a little wind with the cant... most guys here, I think will do what Dave K. does .. they figure in 2 MOA error in most situations.. now add a bit of cant to that and see what your error could be? at 500 yards maybe not so much.. but take it to 1000...

I havn't run the numbers but I bet it is the differnce between a hit or a miss or worse a kill and just a wound...

Ever see the any othe the LR hunters take 6,7,8 shots... I bet I know why they just couldn't seem to hit their target from a rifle they know is capable of it... I rarely see anyone think about or check the cant...

In my opinion and for the record ( God knows this will be held against me) it is just my opinion.. you see guys go out and shoot a screamer group.. then a fews days later or whatever.. the same rifle same load.. the group is not near the size of the screamer group... could it be the shooter, sure ( lost the groove ) but ever think that the cant had something to do with it?

coffee anyone....

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