Enfield foresight adjustment

#1
Sure I could work this out but cannot be arrsed.

How much movement of the foresight produces a lateral point of impact shift of 1 minute for a:

SMLE

No4?
 
#2
No.4: 0.008" per inch off the top of my head. No.1 will be something around the order of half that.
 

ugly

LE
Moderator
#3
I have a table which is stuck to the inside of my range book, when I get home and if I am sober I will look it up!
Mind you the fore sights both require a cramp device and in the No1 it needs the nose cap removing to adjust the foresight!
I have one each for the No1 and the No3 rifles and I no longer use them, Ex_Stab has first call on them!
 
#4
ugly said:
I have a table which is stuck to the inside of my range book, when I get home and if I am sober I will look it up!
Mind you the fore sights both require a cramp device and in the No1 it needs the nose cap removing to adjust the foresight!
I have one each for the No1 and the No3 rifles and I no longer use them, Ex_Stab has first call on them!
Kind of you, I have one for the No.4 ........


For any firearm with iron sights the formula is easily calculated as follows:

(Correction at Target X Sight Radius)/Range = Correction on Sights.

Unit must all be common, eg, if you uses inches for hte sight radius then the range must be in inches.

For a No.4
Correction @ Target =1"
Sight Radius = 28 1/2"
Range = 100yds = 3600"

Correction on sights = (1x28.5)/3600

Correction on sights = 0.007916667"

Which if we round it up is 0.008 or 8 thousandths of an inch.

In metric:
Correction @ Target =25mm
Sight Radius = 28 1/2" = 724mm
Range = 100m = 100,000mm

Correction on sights = (25x724)/100,000

Correction on sights = 0.181mm

Which might reasonably be rounded up to 0.2mm


It wouldn't be hard to come up with a formula to give results in MoA or Mils but there's not really a lot of point as far as I can see, you can work out your correction on target easily enough separetely and in practice, for zeroing, you'll just measure on the target.



Hope this helps.
 
#5
Ugly, if he has the earlier/later clamp-type foresight block with the number 4 he doesn't need the funny business of the adjustment tool, just a dial caliper and a home-made tool to loosen the clamp.

I've even done it on a plain foresight block with a hammer and a drift before, but that is a real fag and takes ages to get right.
 
#6
Its not worth buying (expensive: £50-70 on eBay) No1 and No4 adjustment tools, if you only have a couple of rifles. A small hammer & punch is fine to make most adjustments. The later screw-clamp No4 foresight block is very weak, so its easy to drift the blade without slackening the screw.

One standard foresight blade width equals 2" at 25 yds, or 7-8" at 100yds.
 

ugly

LE
Moderator
#7
Maybe I should flog mine on flea bay then?
 

ugly

LE
Moderator
#9
What I have is some notes from an old club sec gleaned from his old manuals;
 
#10
No1 and No4 both have sights calibrated to be zeroed with bayonet fitted up to 300 yds, and then true range increments over 300 without the bayonet fitted.

All rifle/bayonet combinations are unique, but broadly speaking, a No1 bayonet throws the shots about 18" high at 200 (and up to 6" L or R, depending which way the blade hangs), whilst a No4 spike throws them about 6" low.
 

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