Rifles Made

For Total Control

Each point of contact

is fully independently adjustable

for a PERFECT fit to the shooter










Foresight extension tube

Uses an offset cylinder/collar for clamping, to ensure minimum interference with the sight line, and that the clamping screws threads cannot be stripped. The clamping collar and tube are removed as a unit from the end of the barrel, to ensure easy access to the crown (end of the barrel). The crown should be cleaned after each shoot, some ammunition can leave a residue which will corrode the crown.


A foresight is shown in the picture but is not supplied. The collar and tube are removed from the barrel as a unit and use a fixed screw in the barrel to exactly relocate it each time. This location screw fits in the rearmost hole for the original foresight dovetail mounting block (this block has to be removed). A pair of screws at the rear of the collar are used to clamp it to the barrel. A further pair of screws at the front of the collar enable the tube itself to rotate relative to the barrel. This enables the tube to be set up so that with your chosen cant the rear sights windage adjustment can be set centrally (when there is no wind blowing!). A scale is provided on the tube, however very slight movements have a large effect: rotation of the tube by 0.25mm (1/7 of a division on the scale) will typically shift the shot on the target from the bull to the six ring.


There are four clamping screws in the collar, the rear pair of screws (leftmost in the picture above) are used to clamp the extension tube to the end of the barrel. When the collar and tube are removed the crown of the barrel is readily available for cleaning (and it needs it, some ammunition may leave a residue which will corrode the crown). The front pair of screws are used in the setting up of the tube.

The recommended set up procedure is:

  1. Enlist the help of a spotter to see where your shots are going.

  2. Zero the windage adjustment on your sights, this will ensure you have the maximum possible adjustment to allow for any wind direction once the tube is set up.

  3. Clamp the extension tube to the rifle.

  4. Fit your foresight at the desired length on the tube.

  5. Fire an aimed shot at a visible mark (where a target would be) into the sand butts behind the targets.

  6. If the shot is to the left of the mark (ie left of where it was aimed), then slacken the tube clamping screws (the front pair) and rotate the tube anticlockwise (to the left, as viewed through the sights) and retighten the screws. As a guide; one division on the supplied scale will roughly equate to 500mm sideways movement at 100yards.

  7. With the tube set to hit the mark (the elevation on the sights may also need adjusting), some final refinement may be done on a proper target.

Why use a sight extension tube?

  1. Theoretically you will be able to more accurately aim the rifle, in practice the full benefit will only be achieved if all the other factors are optimised (to enable a good hold and release as well).

  2. Use of a circular tube with a double clamping action (once to the barrel and once to the tube), enables the rearsight to be optimised for a full range of windage adjustment in either direction regardless of how much cant you shoot with.

True or False?

  1. As your eyes age their close focus moves further away, some say that the standard rifle sight base (typically 750mm) is beyond this point. Yet most people will start to use reading glasses when their arms are too short to hold the paper/book far enough away, and fully extended arms are some 750mm!

  2. A bullet exiting a barrel into still air is less disturbed by the wind.

  3. Use of an extension tube will increase your group size, maybe by less than the improvement achieved through a better aim.

Two test results achieved at Eley (see the ammunition testing page for the procedure), shot on the same day in the same vice with the same rifle and the same batch of ammunition - without and with a 250mm extension tube.

Without Sight Extension Tube

With Sight Extension Tube

Consolidated Score



40 shot group size (mm)



average for 4 groups (each 10 shots)



Further Information

Mob: +44 (0) 7973 217 650

Tel: +44 (0) 1256 817 280

E-mail: richard@RMFTC.EU

© RMFTC Ltd. 2006