Rear sight offset

[Smellysniper]

Hi. I have a Martini Enfield in .303 ,with a rear sight cap offset .060" to the left and the whole sight bed appears to be also offset. I was told that Martini`s had sights offset to allow for heavy bullet drift! Is this so? The bullet strike at 100 yards is left and high. Are there Martini sights about that are set central, so I can just fit them and get on target,or will I have to make my own.? Can anyone give any info? Thanks.

Information

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[Patrick Chadwick]

British .303 rifles normally had a left-hand twist. This causes a long-range drift to the left. (And right-hand to the right, natch!) Some types of rifle therefore had the foresight (not the backsight block!) set over to the left to compensate. In the case of the Lee-Metford, for instance, the offset was 0.023".

An offset of 0.060" to the left on the backsight is therefore a) far too large and b) in the wrong direction! No wonder that the POI is way over to the left.
I would take a very close look to see whether the backsight block shows signs of being detached at some time and incompetently refitted to the rifle - or whether the barrel is bent! Or the wood badly warped.

Whatever the reason, something is wrong! Since the backsight block is fitted onto a round barrel, shifting it to the left will simultaneously rotate the whole block. Put the ladder up to the vertical position and see whether it is tilted to the left. If so, get the block refitted before testing the POI again.

[Smellysniper]

Patrick. Good call! I have just looked at the rifle again. The bore appears to be straight and is indeed left hand twist and the wood is not warped. I think it is all down to poor rear sight bed fitting, although I cannot understand the offset ,machined "V" being present, which obviously makes things worse. With the ladder up it leans to the left.! So we have a cap with an offset "V",and the whole sight bed and ladder leans to the left ! It is a wonder that it actually hits the target at all. It`s a complete mess and now you have told me that it should all be straight I can do something about it. I should really remove the sight bed and correct the whole thing. Luckily I can do that sort of work,but I may take an easier path and just offset the cap to compensate. That would be OK for short range work. .I suspect that the sight bed will be soldered and screwed on. That will be fun to get off! Thanks for the info. I did not want to start sorting it until I knew what it should be like.

[Smellysniper]

Further to this problem,I have just read in Temple and Skennerton`s "Treatise on the British Military Martini", in the List of Changes ,that the R.111 Model had a lengthened sight bed fitted "in such a position that when the leaf is raised it is inclined at an angle of 1 degree 6 minutes' to the centreline of the bore. This inclination is to correct the permanent deflection due to the rifling" So there we have it.My sight bed does just that.It doesn`t explain why the sight cap is offset but it does mean that it was done for a purpose ,probably on a larger bore rifle. What it is doing on my .303" I don`t know! I give up! Too difficult! I`ll just fit another sight cap

[Patrick Chadwick]

I suspect that the sight bed will be soldered and screwed on. That will be fun to get off!

If you want to unsolder the backsight block, do not just go straight at it with a blowtorch, as this could locally overheat the barrel and may cause distortion. Heat up the barrel fairly evenly with a hot-air gun, rotating it if you can, and then apply localised heat as well to the sight bed. At no stage should anything be visibly glowing!!! The principle is to avoid sharp temperature gradients that stress the barrel.

How about a photo of the dubious backsight?

[Smellysniper]

I will try to send a photo but I really doubt whether i have the skill to take it so that it shows the detail required or send it. I`ll have a go,but don`t hold your breath. I don`t think I will attempt to unsolder the bed.I think the risk outweighs the result. I have just read that when the manufacturers soldered them on originally ,they put solder on both sides of the barrel to avoid distortion and removed it when cold! If they went to all that trouble, I think I will pass! Many thanks for your advice.