mo bill have you run a straight edge down your rib?
If your POI is very high at all you would be amazed at the amount you can raise the rear of your comb and still remain parallel to your line of sight(so exact forward/back head position is not as critical). The same holds true if you have cast off in your stock.
I have often wondered about this well-supported tecnique for reducing felt recoil. I am no expert on stockfitting, but I have two issues with this technique. First, if your comb is not parallel with the bore, note I did not say rib, then there is one and only one spot on the comb where you can place your cheek and have the precise POI that you desire. Mounting forward or back of that point will result in a variation in the POI. I understand this would be nearly negligible, depending upon how much tip you put in the comb, but if you visualize this to an extreme, I think you can understand my theory. Phil Kiner feels a spacer as thin as 1/32 can make a difference when fine-tuning your gun, so tipping the comb, I believe, can make a difference as well.
Secondly, if the front of your comb is down relative to the back, when you fire the gun, I agree that the initial recoil would, in theory, take the comb down away from your cheek as the gun moves rearward. But I wonder if the gun doesn't within a microsecond move back up and "slap" your cheek due to muzzle jump. If this were the case, then theoretically the recoil to your cheek could be more instead of less, just opposite of what this long held theory postulates. I wonder if anyone has ever done any research on this, such as time-lapse photos showing how the comb moves just following discharge, and comparing a perfectly parallel comb with one that is tipped down in front.
As I said, I don't know the answer to this and am no expert, so I could be totally off here, but would welcome some discussion from those who perhaps have studied this and can shed some light on it.
As an aside, even if the theory of a tipped-down comb is true, that is, it reduces recoil to the cheek, I wouldn't want to put it in my doubles gun as I don't want to have to "recheek" my gun after the first shot. I would want the comb to be parallel so my POI is the same no matter where on the comb I mount, and to help me stay in the gun in preparation for the second shot.
Recoil has two phases. The first involves the gun's rotating around its center of gravity. The muzzle rises and the butt declines. That first phase ends when the butt makes solid compressive contact with the shoulder and the second phase begins. At that instant, the barrel continues to rise while the butt remains stationary.
The second phase occurs because the heel of the stock (the portion where the the maximum force of rearward movement should be concentrated) is below the axis of the bore. This is why the bottom barrel of O/U guns is fired first and is also the primary advantage of unsingle styled guns. The bottom barrel is nearer the axis of the bore than is the top barrel and barrel rise is reduced.
The above fact explains why pitch can become involved in cheek slap. If the pitch is inadequate and the toe of the recoil pad sticks out too far, the pivot point of the gun during the second phase of recoil, is the toe rather than the heel. Since the toe is farther below the axis of the bore than is the heel, muzzle rise increases significantly and can result in cheek slap.
The pitch on a stock is correct if, when mounting the gun, the entire pad, heel to toe, makes simultaneous contact with the shoulder. When the gun moves to the rear during recoil, the shoulder structure behind the heel is more robust than that behind the toe. The gun therefore pivots upward on the heel, which is nearer the axis of the bore and minimizes barrel-rise.
Other things that can cause cheek slap are an incorrect angle of the cheek on the comb, to much or too little pressure applied by the cheek to the comb and raising the cheek from the comb during swings.
As to variable angles of the comb relative either to the bore or the rib and their affect on cheek slap, the effects are minimal. With the barrel often rising more than an inch during recoil, the comb would have to slant downward beyond an acceptable limit to have a significant effect. The same is true with the outward angling of combs. This concept is why combs are narrower in front. They are designed that way to make sure there is not a wider portion of the comb to be driven into the cheek of the shooter as the gun moves to the rear during recoil as is the case with field stocks with their rising combs.
Turning or rotating the front of the comb outward with an adjustable comb serves no useful purpose and eliminates one of the benefits of a level and parallel comb. The cheek's placement on the comb can vary and that will change the eye's alignment with the rib (and bore axis, to save argument), which will alter the gun's POI.
The "recoil has two phases--" got me to wondering Rollin?
If you hold the gun loosely when firing is it possible to ->feel<- the two distinct phases?
I've noticed when I fire my Ruger unsingle this spring that sometimes I feel two distinct recoil impulses. Never noticed that before, I've been thinking it might be caused by the delayed reaction of the 4" Edwards reducer in the stock? Maybe instead I'm holding the gun looser than normal and feeling the two distinct recoil phases? Or maybe I'm lighter on the comb than usual and feeling the recoil to the shoulder and then to the cheek with a perceptable interval between?
Move that recoil pad up on the stock. That is what someone on this site recomended to me, and it worked. But, when I did I had to adjust the comb also to get my figure eight once again. I don't know why, it just worked out that way.