Can the age of a primer affect rate of powder burn and slug velocity? I have new pellets but primers are several years old. It seems like recoil is greatly reduced even though slugs are going downrange.

Bear Charge, in theory I would guess a primer that is not igniting the powder sufficiently could impact the rate at which the powder starts to burn efficiently, (but I think powder is supposed to burn at a specific rate once ignited), but I have used old primers (for sighting and inconsequential shots) and have never noticed any difference. But, I always try to use new primers (and powder) on a hunt just in case such a problem could occur. I have used old primers for all sorts of reloading and have never had a situation develop where a lot of old primers was causing a problem. But, different primers do have different ignition characteristics (whether old or new), so different primers can have an impact on the overall discharge. I would try to dial in before the hunt with new primers and powder and use the older stuff for practice.