Zeroing for 200 yards with only 100 yards range to use.

[newcastle]

Morning Gents. Our range is holding a 200 yard military bolt gun match soon and the 200 range is ONLY open for competitions so I don't get the opportunity to actually zero at that range in advance. I can only use the 100 range to prepare. On a No.4 Rear sight, if I zero at 100 yards with 174gr 303, is there a set number of clicks upwards to hit 200 yards? I'm using a 6 inch black at 100 and it would be a 12 inch black at 200 so how does the 3 inch above point of aim become 6 inches? I do not have good enough eyes to use a center hold so I have use a 'dot the I' sight picture. is there any magic formula here? One additional question. I was shooting a no.4 at 50 yards this weekend and the rear sight was set at 400 yards or so. Is there a known distance of intersection for standard 174gr .303 through an Enfield ? (like using an AR where a .223 zero for 50yards also hits thereabout at 200yards) .

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[Robert303]

Come on chaps let's have some replies. I'm in the same position and so could do with as much help as possible. I'm an ex pistol shooter who'se never really been taught to shoot rifle. I really must learn how to use Parker Hale 5s on my SMLE and No 4.

[Patrick Chadwick]

Come on chaps let's have some replies.

Don't be so impatient everybody! I've only just seen these posts.

First point: If you are using the 6 'o'clock hold on a 6" target at 100 and then on a 12" target at 200, then the angle between the line of sight - POA - and the line to the target center - the hoped-for POI - is the same in both cases, so no correction is required for target size.

Secondly, unless you are using some very odd ammo, then the muzzle velocity will be in the range 2300-2600 fps for a 174gn .311 bullet fired by a reasonable charge. At this point, we who have no ballistics software turn to the Sierra exterior ballistics tables. The drop at 200 yards for a 174gn MatchKing is given as 11.23" (2600 fps) to 14.44" (2300 fps). Relative to the bore centreline, of course. If you were to draw a straight line from muzzle to POI, this looks like half as much at 100, i.e. 5.6" to 7.2" (there really is no point in calculating to .01").

But the drop at 100 is in the range 2.66" to 3.41". So you need to elevate the muzzle to put the aiming line about 3" to 3.6" higher at 100 yards. Since the sight radius on a No. 4 is about 28", the peep hole need to be raised in proportion. I.e. 3 to 3.6 divided by 100 times 28/36.
In other words, about 0.023" to 0.028". On a standard No. 4 backsight that means 3 to 4 clicks.

Ideally, one should correct for the fact that the line of sight is actually about 1" above the barrel. For the greater precision expected with a scope, and the fact that a scope is mounted much higher, it is indeed necessary to take this into account. But for iron sights - forget it.

There is no point in making involved calculations to the micron - no software can take into account the fact that your sight picture for the 6 o'clock hold will not be quite the same at 200 yards as for 100 yards, because the blade/target contrast is different, so your eyesight and the light conditions also come into the equation. Just raise the backsight 4 clicks and get going!

I know this is a rough method, and make no claim that it would work going from, say 100 to 1000 yards, but for 100 to 200 it will provide a good first approximation. I do this sort of thing frequently, in BP competitions at 100, 200 and 300 meters, with "best ten out of 13" scoring, so there isn't much to play with. Your first shot may not be a 10X, but it should be well enough in the black.

[Peter Laidler]

You will not get an answer because the rear sight calibrations and foresight adjustment is/are calibrated for bog standard, issue, 303" NATO Mk7 ball ammo. We don't know what you are using so we cannot possibly answer the question. And there is no magic formula for the unknown - as yet! It's like asking '..........my Ford will only do 76 miles/hour how can I make it go faster'

[newcastle]

Sorry wasn't clear enough, if I am using Greek HXP Milsurp Mk7 ball ammo how many clicks UP would it take on no.4 Micrometer rear sight to move from 100 yards to 200 yards with 6 and 12 inch black respectively using a dot the i sight picture on both (so at 100yds I have a 3inch POI above point of aim and at 200yards I will need a 6 inch impact above point of aim).

[muffett.2008]

Can't help with 200 on a service sight Newcastle, but this may help Robert303 with his target sight.
Attachment 43274

I would think the rise would be minimal, in service comps at that distance I adjust off my sighters.

[Parashooter]

Zero 6" above point-of-aim at 100 yards, and impact will be very near to 6" above POA at 200 yards. Or, if zeroed for 3" above POA at 100 yards, elevate 3 MOA for 6" high POI at 200. (IIRC that would be about 3 clicks on the Mk1 leaf.) Table calculated for 180 Sierra @2470 fps. MkVII should not vary significantly. Note "Path" column, which gives deviation from line of sight.

┌──────────────────────────────────────────────────────────────────────────────
│ Bullet : Sierra Spitzer                 Zero        : +  6.0 ins at  200.0 yd
│ Weight :    180 grs                     Altitude    :      0 ft
│ V0     :   2470 ft/sec                  Temperature :     68 °F
│ BC     :  0.411                         Crosswind   :   10.0 mph from 90°
│ L.O.S. :    0.8 ins above bore axis     One click = 1.00ins at 100yds
├──────────────────────────────────────────────────────────────────────────────
│Range   Velocity  Energy   Time     Drop   MaxH    Path   Drift  Up     Side
│[yds]   [ft/s]    [ft.lbs] [s]      [ins]  [ins]   [ins]  [ins]  [  clicks ]
│
│     0   2470     2438     0.000     0.0   -0.8     -0.8    0.0    0.0    0.0
│    50   2368     2241     0.062     0.7   -0.1      3.4    0.2   -6.8    0.4
│   100   2269     2056     0.127     3.0    0.5      6.0    0.9   -6.0    0.9
│   150   2171     1884     0.195     7.0    1.5      6.9    2.2   -4.6    1.5
│   200   2077     1723     0.265    12.8    3.1      6.0    3.9   -3.0    2.0

Attachment 43275

[newcastle]

Wow. Thank you parashooter. That makes it significantly easier than I anticipated. Do you have any more of those graphs that would show trajectory for 3" above POA at 100 yards for the same ammo. Even better would be interactive so you could drag the trajectory to allow for your 100 yard Zero. just to check, but is there ANY reason the same would not work for a No.1 Mk 3 if I used on of those instead?

[Parashooter]

Do you have any more of those graphs that would show trajectory for 3" above POA at 100 yards for the same ammo. Even better would be interactive so you could drag the trajectory to allow for your 100 yard Zero. just to check, but is there ANY reason the same would not work for a No.1 Mk 3 if I used on of those instead?

The figures and graph supplied are all you need for the problem initially posted. Just zero to put center group 6" above POA at 100 yards and it will also be very close to 6" above POA at 200 (with standard MkVII ammunition). If you want to do more ballistic calculations, see any of several online ballistic calculators - such as JBM's at http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

In most discussions I've seen, the G1 ballistic coefficient for the .303 MkVII projectile is usually pegged somewhere between .420 and .470. At the short ranges involved in this exercise, there is minimal difference in results with either figure.

[Bruce_in_Oz]

According to the Canadians, in C71-111-000/MM-000, paragraphs 14, 15 and 16:

“14. Test dispersion and accuracy as follows:

a. Mount the weapon in a bench rest or other suitable support;.
b. Fire two warming rounds;
c. Set the rear sight to the 200 yard range setting; and.
d. Fire 5 shots at a single point of aim.

15. The barrel dispersion shall be considered acceptable if the 5 shots all fall within or cut the edges of a rectangle with sides measuring 2.54 centimetres (1 inch) horizontally and 3.81 centimetres (1 ½ inches) vertically at 22.86 metres (25 yards).

16. The sights shall be considered accurately aligned if the MPI of an acceptable group falls on a vertical line drawn through the point of aim within 6.35 millimetres to 3.18 centimetres (1/4 inch to 1 ¼ inches) above that point of aim. No horizontal displacement from this centre is allowable.”

End of extract.

Make sure you have fresh Mk7 ball on hand………..Oh, wait…….

Anyone have the British version?