Need help adjusting front and rear sights for zero on No4 MK1/2

[logandiana]

This is my first post here so bear with me.
I have a 42 Shirley that became a '53 FTR No4 Mk 1/2. The rifle has the +.075 front blade in it and a MK1 rear ladder sight. I took the rifle to the range for the first time and was able to shoot a 1 inch group with 3 shots at 50 yards. Since this was the first time I had shot the rifle I didn't bring any tools or replacement blades. It wasn't my intention to zero the rifle on the first time out. I didn't shoot on the 25 yard range because it doubles as a long pistol range and is standing supported only. I also didn't shoot on the 100 yard range after my shots on the 50 yard range.
So my 3 shot group was 4.5 inches low (and a little left) at 50 yards.
I have the full set of replacement blades, but i'd like an idea of a good starting point. I think it did the math right onhttps://www.milsurps.com/enfield.php?pg=ti12.htm calculating front sight height for zero, but I may have got it wrong. I came up with 28.5 x 4.5 = 128.25 / 1800 = .07125 My front blade is .075 - .07125 = .00375 so my closest blade is the 0.00 blade. So am I right that this would be a good start at acheiving a 200 yard zero on a 50 yard target? I have read that this is for surplus 174 grain ammo. Wihat difference will it make that I am using 150 grain soft point boat tail ammo?
Second question- I read on a different website that with the MK1 rear sight that each click will move your shot up or down 1/2" at 100 yards. I can line up the marks on my rear sight so it's set for 200 yards... but it's not bottomed out. I don't know if all sights were like this or if I have something special or maybe mine is out of spec. Mine will drop an additional 3 clicks below the 200 yard line on the sight. So does this mean that if I zero the rifle at 200 yards (with the sight exactly on the 200 yard mark) my shots at 100 yards should be an a couple inches high right? So then if I bottom out my sight those extra 3 clicks at 100 yards then I should pretty much have POA = POI... Is that correct?

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[Peter Laidler]

There's no adjustment for the rear sight Loggy. All we need to know is this. What ammo are you using because all the formula are calculated on zeroing with .303" Mk7 NATO ball.

There are a couple of good recent threads on this very subject and I hope that someone who is comuter literate will bring them up. It'll save going into the whole palava again

[logandiana]

read that this is for surplus 174 grain ammo. Wihat difference will it make that I am using 150 grain soft point boat tail ammo?

As I said above I am using 150 grain soft point boat tail ammo. Prvi partisan to be exact.

I know there's no 'adjustment' for the rear sight, but theoretically dropping the rear sight below the 200 mark on the sight 3 clicks must do something to the POI. My question is what.
Maybe I didn't explain myself clearly enough, it was my first post...
The MK1 sight has markings from 200 yards to 1300 yards. If I line up the lines on the sight with the 2 mark for 200 hundred yards and establish my zero there at 200 yards then what happens to my POI if I then lower the sight 3 clicks below the 2 mark on the sight?

I know there are other threads on this already, but it all of them I could find are asking about how to adjust their 200 yard zero on a 100 yard target or a 25 yard target. I was just just asking about the math for a 50 yard target.

[Brian Dick]

To answer your question, it's going to lower the point of impact. 150 grain projectiles will shoot low compared to the 174 grain projectiles. To make life simple since I'm no mathematician, just set your rear sight on 200 and change the front sight blade to a lower one until you get pinpoint hits on a 1" paster at 25 yards. Do this with whatever ammo you plan to use. Then fine tune at 100 yards and further as necessary. Don't expect to get perfect hits using the graduations on the sight leaf because you aren't shooting the ammo for which it was designed. Learn and record the clicks for each range you desire to shoot and write it down so you don't forget. When I was shooting competition, we learned to put the number of clicks for 200-300 and 600 on a nice sticker and attached it to the buttstock for ready reference. Then all we had to really deal with was wind variation.

[Parashooter]

Since you're not using Mk7 ball with an NCO calling out yardages to a platoon of approaching hostiles, you can simply ignore the graduations and record your zeroes in terms of clicks up from bottomed-out. Clicks are close to 1 MOA - or 1" per 100 yards.



Nobody can give you reasonable come-up figures without knowing your sight picture (6:00 or center?) and aiming black size. If, for instance, you were holding at 6:00 on a 6" bull at 50 yards and hitting 4.5" below center bull, your POI is actually 1.5" below your aiming point. You have to come up about 5" (10 MOA/clicks) to put the POI at 3.5" above POA at 50 and ~6" above at 200 yards for a 6:00 hold on a 12" bull. If you use a different hold, target, or load, you'll use different numbers.



See Zeroing for 200 yards with only 100 yards range to use for more detail. Also no.5 micro sight on a no.4?

[Peter Laidler]

On the other hand, until I got out into the real world where I learned the simple formulas like 'foresight into the error, backsight out of the error and the mantra 'where there's a will, there's a simple way' and 'KISS' I learned the catch all zeroing formula:

x = h and x = rh
r R+h R+r

where X= change in height of foresight blade
r = sight radius
R = range
h = change in MPI

Now you can see why when it comes to zeroing the many weapons we were charged with looking after, I keep it simple

[logandiana]

On the other hand, until I got out into the real world where I learned the simple formulas like 'foresight into the error, backsight out of the error and the mantra 'where there's a will, there's a simple way' and 'KISS' I learned the catch all zeroing formula:

x = h and x = rh
r R+h R+r

where X= change in height of foresight blade
r = sight radius
R = range
h = change in MPI

Now you can see why when it comes to zeroing the many weapons we were charged with looking after, I keep it simple

I think this is the formula that I was using in my original post. I printed up some one inch targets to take to the range next week. I am going to try to start out on the 25 yard range with the 0.0 blade and go from there. Then I'll move to 100 yards. Once I have established what I believe is a good 200 yard zero at 100 yards (2-3 inches high) then I'll drop the rear sight those last 3 clicks to see what happens. Hopefully that will put me right on at 100 yards. I won't be able to test out an actual 200 yard range until I travel this fall to New Mexico.

[Peter Laidler]

Er........ surely if your group is 4.5" low, then you've got to RAISE the backsight - if you're using the backsight as the zeroing medium. And on the VERY rough ready reckoner method that 1 click equates to 1" at 100 yards (it doesn't but it's sort of close in a sort of average sort of way.....) then to raise the group you've got to RAISE the backsight by 2 or 3 clicks. No?

[logandiana]

Er........ surely if your group is 4.5" low, then you've got to RAISE the backsight - if you're using the backsight as the zeroing medium. And on the VERY rough ready reckoner method that 1 click equates to 1" at 100 yards (it doesn't but it's sort of close in a sort of average sort of way.....) then to raise the group you've got to RAISE the backsight by 2 or 3 clicks. No?

Either I am not explaining myself correctly or you are just not understanding what I am trying to do. I'll try again to make this as simple as I can.
I am not using the backsight as a zeroing medium. I am using the front sight. From my original post and using the same formula you suggested it looks like my starting point for selecting a new front blade should be the 0.00 blade.
So I'll go to the 25 yard line, install the 0.00 blade, and set the rear sight for 200 yards. At this point depending on how close I am I can change the front blade again until I am about .75 high, correct.
Then if I change nothing and move to the 100 yard line then I should be about 2-3 inches high, correct?
Then if I were to change nothing and move to the 200 yard line then I should be right on, correct?
So at this point I'll have the correct front sight blade and I'll be zeroed at 200 yards (with the rear sight set to 200 yards).
At this point if I move back to the 100 yard line (I haven't moved my rear sight, it's still set to 200), my shots should still be 2-3 inches high right?
Okay now that we have that established...
I am now at the 100 yard line and I lower my rear sight from 200 to 3 clicks below the 200 yard line on the sight. Where are my shots going to hit?
If 1 click equals approximately 1" at 100 yards then it seems to me that lowering my rear sight 3 clicks would lower my POI at 100 yards approximately 3 inches. Which would put me where at 100 yards?

[Patrick Chadwick]

I am not using the backsight as a zeroing medium. I am using the front sight.

Please do not take this as a personal comment, but as practical observations based on experience with long guns from a Napoleonic vintage musket through to a modern 6mm BR shooting machine, and a lot of what came between. That means everything from a howitzer-like trajectory to a very flat one indeed, and I have given up trying to make precision calculations for range changes, being happy if the correction puts the bullet in the black at the altered range. I realize that I am also partly repeating what has already been put quite precisely and in detail, so I shall put it quite straight and simply.

Be CAREFUL to compare like with like. If you are using a 6 o'clock hold, then you are applying a vertical offset of half the diameter of the target black between your actual POA and the intended POI.

If, for instance, you shoot with a 6 o'clock hold at 50 and then move the same size target out to 100, then the black now subtends half the angle in your sights compared with 50, so you are raising the POA by an amount equivalent to half the difference between the bottom of the black and the center at 50. That is quite a lot - in fact half of the apparent size of the black if you double the range - and this effect alone often means that a rifle that is in the black at 50 will also be in the black at 100 without any further adjustment. The POI may be higher or lower, depending on the height of the sights and the trajectory of the bullet. The same effect applies if you go from 100 to 200 with the same size of target black. Even if you use proportionally scaled targets to produce the same apparent size at all ranges, there is still the following effect:

CONTRAST CHANGES WITH DISTANCE*. Your judgement of the correct aim for a 6 o'clock hold is affected by the contrast between the blade, target white and target black. So shooting one-hole groups at 25 yards will still not enable a perfectly calculated correction for 200. And if you are using a center hold (generally not advisable with a blade foresight) then the contrast effect is even stronger.

Use 100 if you can, 50 if you must, but forget 25, where the "uphill shooting" deviation caused by the sight line being above the barrel center line is quite extreme.

Be GLAD that you have a +.075 foresight blade. I wish I had a couple myself. The vast majority of old service rifles were zeroed for a longer range and/or have foresights so worn down that you can hardly get on target at 100. As has been pointed out, the higher foresight gives you room for adjustment if/when you try out different loads. DO NOT SNOOKER YOURSELF BY REDUCING THE BLADE HEIGHT TO SUIT ONE LOAD AT ONE RANGE. You have a height adjustable backsight. Use it.


*And lighting conditions!