Q on ISSF rule for butt plate

[TargetTerror]

I was reading through the ISSF rules and have a question regarding rule 7.4.3.1 (this deals with butt plate adjustments for 300m standard rifle and 10m air rifle). The rule reads:

The butt plate may be adjustable up or down. The lowest point of the stock or toe of the butt plate, with the butt plate in its maximum downward position must not exceed 220 mm from the center line of the barrel. It may be offset parallel to the center line of the normal end of the butt plate left or right a maximum 15 mm OR the complete butt plate (not part) may be turned on the vertical axis. Turning the butt plate on the horizontal axis is not permitted.

I am a bit confused by exactly what they mean. How are they defining horizontal and verticle axis of rotation? If you imagine the shooter holding the rifle in firing position, I understand that:

-the butt plate can move up or down (towards your head or feet)
-the butt plate can move perpendicular to the axis of the barrel (toward or away from your shoulder)
-the but plate can rotate in a plane perpendicular to the floor (eg, if you connected the butt plate by 1 screw and spun it, adjustments in that axis would be legal)
-the butt plate CANNOT rotate on the plane parallel to the floor

Do all of these stipulations seem correct? I'm a bit annoyed with the last stipulation, as I would like to be able to rotate the butt plate towards my shoulder - I feel it would make a better fit. I ordered some of the Anschutz angle spacer to accomplish this, so would they be illegal in ISSF AR competition?

[Jose Rossy]

The vertical and horizontal axis of rotation are defined in conventional terms, with respect to a reference plane. In the case of rifle shooting the horizontal plane of reference is the floor (and all planes parallel to it). IOW, the horizontal axis of rotation for the buttplate is parallel to the bore axis and the vertical axis is normal (perpendicular) to the bore axis.

[JeroenH]

There's 3 perpendicular axes about which the plate can be rotated.
In my picture (see attachment):
x is horizontal, parallel to the bore.
z is vertical.
y is horizontal, perpendicular to x and z.

So both x and y are in the horizontal plane. The rule saying "Turning the butt plate on the horizontal axis is not permitted" does not have a definition explaining what is meant with 'the horizontal axis'.

In my understanding, the rule does not allow rotating around x.
Rotating around z is allowed for sure (as in Jose Rossy's picture).
And rotating around y is OK as well.
Some air rifles (FWB, Hammerli, and probably others too) allow you to rotate around the y axis, although the physical axis of rotation is further forward than in my picture.

[Jose Rossy]

Jeroen, you are of course right. The X and Y axis are both in the horizontal plane. The ISSF would be better off renaming its "horizontal" axis as "the axis parallel to the bore line" or simply the rifle's longitudinal axis.