Medicineman
While it is true that I don't live in 2075, I'd thank you not to make assumptions about what I am and am not familiar with.
The concept of shock absorbing stocks is hardly unique to Shadowrun tech; in fact, my service weapon in the military was a Sako TRG-42 chambered for .338, and it had a kick like a mule even with stock-mounted shock absorbers. I dare say that hitting someone with the flat of your stock (which very likely isn't made out of rubber even if the shoulder pad is) is probably going to sting...
In any case, you'll note that I also offered an alternative explanation that doesn't require the entire stock to be made of rubber (which I find to be highly unlikely, even in 2075), or for the attacker to suddenly decide to attack with the rubber shock pad on his perfectly good wooden stock.
In fact, there are several reasons for why we can safely assume that rifle stocks are NOT made out of rubber, chief of which is descriptions like this:
Shock pad: A shock-absorbing pad is situated on the rigid stock of a rifle, shotgun, or heavy weapon
You'll note that nearly every description of stocks in the rifle categories mentions that the stock is "rigid", like in the above quote for the shock pad itself. While it's not explicitly spelled out that a stock is generally made of something firmer than rubber, this can easily be assumed by looking at the illustrations used, as well as deduced with just a basic knowledge of firearms. A "rigid" stock is desirable as it means the stock won't break from misuse (such as hitting someone with it), and it actually helps manage recoil better because the kinetic energy is sent along a directed path instead of along undesired directions that could potentially compromise the structural integrity of the weapon. The shock pad, then, is designed to absorb some of the kinetic energy being transferred from the rigid stock of the rifle to the shoulder of the person firing it. It makes little to no sense for someone to hit someone else with the same part of the rifle designed to lessen the impact of kinetic energy upon something, and it makes far more sense, at least as far as I'm concerned, for someone to simply hit with the broad side of a rifle stock as this is not only an easier maneuver to accomplish but also more likely to inflict actual damage.
While Xenon's explanation might be sufficient for you, it wasn't for me, so I chose to present an alternative. Take it or leave it, but as previously mentioned I'd appreciate it if you'd not assume things about me that you have little to no way of knowing, nor disregard my argument simply "because I don't live in Shadowrun land". As I've clearly shown, there are reasonable assumptions that can be made, so next time, how about just asking why I made the comments I did and then reading the rest of my post that, at least in my opinion, clearly puts the first part of the post into context?
With that, I'll repeat my last point so it doesn't get lost in this:
I will say that I think the applied force is more concentrated in the case of attacking someone in close combat with a pistol grip (small surface area with defined, if not sharp, edges) vs a rifle stock (large surface area), and there's also likely going to be a big difference in terms of how that force is delivered (sharp jabbing motion with a pistol grip vs more of a two-handed shove). Of course, this is assuming that one is attacking with the weapon from as close to a firing position as possible, and not, say, grabbing the rifle by the barrel and using it like a bat.
Either way, this is another one of those areas where there are very clearly defined rules for it (at least in Run & Gun), and I have yet to have had it come up in a game so I'm not willing to waste a lot of thought on it and will just accept what the book tells me. Changing these kinds of details are way down on my list of priorities, even if I wanted more "realism" in my games.
Cheers,
Martin
