Watched the video. I'll save everyone else trying to diagnose issues with his revolver the time, the video isn't helpful in the least.

First off, there is no such issue as excessive headspace in a cylinder. Revolvers chambered for rimmed cartridges like the .44mag headspace on the rim. Frame stretch is a real concern, but often gives itself away, but I won't go into details here.

Secondly, you don't give any information as to what types of groups you are getting. "Not hitting a 10"x10" page at 10yrds doesn't mean anything if it's putting 6 shots in a 1" circle 3" off of the page (i.e. you may just need to sight in your weapon).

The question I'd have after watching your shooting technique(s):

Do you have experience with other handguns in which you CAN hit a 10"x10" page at 10yrds? Has another proven pistol shooter handled the revolver to try out groups? I have taken in many revolvers in the last decade that the owners said were terribly inaccurate, but in my hands, would put up fantastic accuracy. I have a Taurus 85 on my bench right now that the owner was trying to sell because they didn't think it could hit the broadside of a barn. 15yrd 5 shot groups that fit under a quarter with FN FMJ's in my wife's hands last week convinced him it wasn't the revolver.

After watching the video, I can think of one specific test I'd like to do with you shooting this revolver that involves me loading the gun and you shooting it, but I can't tell you, otherwise it'd ruin the test Here's a hint - Looks to me like you flinch like crazy.

Have you shot it from a suitable rest, rather than offhanded?

Diagnosing revolvers is actually very straight forward, but if you're not familiar with it, I'd highly recommend you take it to a qualified pistolsmith (not all gunsmiths are qualified to work on, or experienced with handguns). If you insist on diagnosing yourself, I can give you some pointers, but for what it's worth, if there's an issue, you won't be able to fix it anyway, so you might as well take it in. There's nothing that doctors love more than patients self-diagnosing their diseases.

As far as Ruger warranty work goes, at least it's a Ruger. Ruger has one of, if not THE best reputations for customer service and acceptance of warranty work in the business. However, accuracy is a hard pill to swallow. You may very well send it to them then get a piece of paper back saying that they shot it and the accuracy is within their guarantees. Don't be telling Ruger that you know the previous owner was shooting heavy reloads though, as that will void your warranty. I'm not sure what the revolver accuracy specification for Ruger is, but the rifle "guarantee" is around 1.5", so don't expect them to turn it into a match pistol for you.

First thing they will ask, however, is "what ammo have you shot in it?". If all you have fired is cheap bulk stuff, then they won't be inclined to fix it until you've put some proper ammo through it.

More than happy to help diagnose revolver troubles, one of my favorite joys in life in fact, so if you want the help, I'd offer it. BUT, in this case, taking it to a qualified smith is likely your best option.