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Foresight Zeroing No1 MkIII*

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ajjkhan View Drop Down
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    Posted: May 16 2017 at 4:30am
Hi Everyone

I have been trying to zero my recently purchased No1 MkIII* Enfield. Its a BSA and dated 1917.
I'm shooting at 600 yards, but to hit the target I have to set the rear sight to 725 yards!
The foresight has letters and numbers stamped on it - "PH" and "030". Having read some of the zeroing posts, I think maybe this foresight is too low? And I'm not sure what the "PH" is about. Is the "030" in thou of an inch?
Could one of the armourers here give me a suggestion as to which number foresight i should be searching ebay for and how do I remove the old one and fix the replacement?

Kind regards
Aja
Many Thanks AJJ
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Zed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: May 16 2017 at 12:12pm
I believe the fore sight would be too high if you are having to set the sights to 725 yards.
A shorter front blade will raise the muzzle. 
However the ammunition may also play a part at that distance. I would suggest zeroing it at 200 yards initially; but before doing that I would settle on the type of ammo or most accurate load (if reloading) before zeroing the sight blade. 
Most of the factory ammo such as PPU are boat tail design and have different aerodynamics than the original flat base bullets.
There is a basic calculation for finding out the necessary change in height. 
Working in inches for example: length of sight radius (distance between front and rear sights) multiplied by the error between point of aim and point of impact divided by the distance from muzzle to target.

So lets say 20" sight radius x 12" error divided by 7200" (200 yards in inches) =0,033"
Thats to say a 33 thou change will have an effect of 12" at 200 yards if the sight radius is 20".

I hope that makes sense!
Alternatively, you could measure the difference between the height of the rear sight at 600 and 725 and change the front blade by the same amount (shorter).
It's nice to be important, but it's more important to be nice!
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ajjkhan View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ajjkhan Quote  Post ReplyReply Direct Link To This Post Posted: May 16 2017 at 12:47pm
Thanks for your reply, it does make sense!

I went to the zero range today at my club. Its 30 yards long. I fired a group of three and got a MPI 2"
below the aiming mark. So using your formula, I need to lower the foresight blade by 20 x 2 /1080 - 0.037 which means i'm looking for a 000 stamped on a replacement blade?

So if I've got this right I need a lower foresight - by an amount that can be measured by the distance in height of the backsight at 600 and 725 so I can check the calculation - very cool
Many Thanks AJJ
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: May 16 2017 at 1:48pm
I found this, which you might find helpful

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Zed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: May 17 2017 at 9:46am
If you want to zero at 25 yards using a special target that shows the normal expected impact height different sight settings. i.e for 200-400 and 600 yards. Aim is taken at the lower part of the target and there are graduations for the different settings. 200 yards being about 0,75" above point of aim at 25 yards, as per Shamu's list.
Also please measure your sight radius; I could not remember the exact measurement for the No1 rifle so used 20" as an example for the calculation. 
If your in the UK you can get the sight blades from Valmont Firearms; I got a set from them a few years ago. Very helpful and fast service (at least that was my experience!)
It's nice to be important, but it's more important to be nice!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ajjkhan Quote  Post ReplyReply Direct Link To This Post Posted: May 17 2017 at 11:29am
The sight radius on my No1 is actually 19 1/2" putting that into the formula with an error of 2" and the correct range distance yield 0.045. As the current blade is 030 i think I need a -015.

Once I get one fitted I'll take it back to the zero range.

I was zeroing at one of the graduated targets as you describe - the rifle was shooting low and I had to push the rearsight forward from 600 to 725 to get it to group at the 600 line
Thanks Zed and Shamu
Many Thanks AJJ
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: May 17 2017 at 1:29pm
OK, you have the ladder target. That's good.
Should anyone else need one this is it with dimensions so you can make your own if you need one.


You can just copy/paste/print on 8 1/2X 11 paper.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ajjkhan Quote  Post ReplyReply Direct Link To This Post Posted: May 19 2017 at 3:13am
Thanks for all your help!

Here's a treat for you both. There is an excellent film on Netflix called Siege of Jadotville, involving a bunch of Irish UN peacekeepers who get attacked by French mercenaries in the Congo during the Katanga crisis in the 1960's

Lots of No4's being used, a Bren and the star of the show was a sniper using a No4T - though without the 1907 sling....

I wont spoil the ending but its worth it!
Many Thanks AJJ
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Post Options Post Options   Thanks (0) Thanks(0)   Quote musketjon Quote  Post ReplyReply Direct Link To This Post Posted: May 25 2017 at 9:30pm
ajjkhan,
Since the rifle is shooting low, why not just file the front sight down a bit? No need to replace it if it can be fixed by a little hand work.
Jon
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