Kuhnhausen says(I KNEW that book would come in handy) that factory Min/Max trigger weight is 3 1/2-6 1/2 lbs. Both of my "Serious" 870s have pulls under 4 lbs, and my TB has a 3 3/4 lb pull. All pulls are clean, w/o overtravel and little creep.
BTW, a quick fix for overtravel is a piece of pencil eraser superglued to the guard behind the trigger. Cut to fit after mounting.
Never had Frank's trigger measured, but it's about the same. The 20 ga Youth Express runs under 5.That's the newest in the battery, about 95 or so.BTW, slug groups with the RS, fixed IC choke slug bbl run 3" at 50 yards with the Rottweil Brennekes,tho recoil is,uh,stout. I'd use that one more for deer but my old eyes do not so well with those sights.
Can't say about the Mossies, but I'd be surprised if any come from the factory with weights this good.The 835 I shot once recently had a heavier but controllable trigger.Practically ALL modern US made shotguns have decent slap triggers, tho a rifle style trigger is best for max effectiveness.
As for steel, I didn't see much difference in times pre and post trigger work. However, we're talking about a trigger job that removed at most 1- 1 1/2 lbs. Slug groups did improve.
I note that trap guns all have good triggers. That's a short time frame game that demands consistency, tho not short lock time. Some trap legends have pulls down to 1 lb, but I sure do not recommend going that light on a gamer gun and NEVER on a field or "Serious" gun.