In the MPF chart, certain irons have #5 or #6 next to them. Does this mean only the 5 or 6 iron was tested?
#5 irons and #6 irons are the irons that are tested. We have only done the #6 irons for at least the last 5 years. Ralph started the database when #5 irons were considered “mid irons” and eventually went to #6 irons. Impossible to do entire sets, but in his book Ralph did test entire sets of many popular models at the time to see what variations there could be within a set. The paragraph that explains this is as follows:
“It can be seen that the Playability category will generally remain the same throughout the set. Generally, but not always, the only irons that tend to change to lower categories are the #8 and #9 irons. This occurs in some cases because the loft angle of the short irons coupled with the higher basic Vertical Center of Gravity and the Rearward Center of Gravity location can sometimes cause the Actual Vertical Center of Gravity to be in front of the face plane and not behind it, which is usually the normal case. When the Actual Vertical Center of Gravity is located in front of the face plane the column marked VCOG(Adjt) adds a calculate amount to the Basic Vertical Center of Gravity (balance point on the face) instead of subtracting an amount if the Actual Vertical Center of Gravity was behind the face. This in turn causes the Actual Vertical Center of Gravity to be a bit higher than the other irons in the set. Note that the Playability category can also go up on the short irons vs the other irons, if the iron is a lower center of gravity design. The reason for this is that the Actual Vertical Center of Gravity remains behind the face.” The Maltby Playability Factor – Understanding Golf Club Dynamics 2004 (page 91).