Update:

I'm going to send the rifle in to Ruger to have it inspected with a note explaining the short-stroking "symptoms" for each load of ammo I fired through it, if applicable; main reason is I don't want to give them a reason to void the warranty. In a "concerns" section on this document, I relied on your diagnostic list, NoMercy---so in case someone is interested in doing a half-a** job over there minutes before lunch break, there's at least one psychological obstacle.

We'll see what happens then.

On a separate note, I'm fairly stoked about using this as a stalking rifle (when I'm hunting deer in states where legal to use a .22 cal). There is no comparison in overall weight and trigger pull between it and my Remington 673 (still has the old trigger; haven't mustered the will to send it in for recall).

I've read some killer reviews for the Barnes VOR-TX higher-grain offerings. Aside from user reviews on game, there's two reasons I feel comfortable committing to these:
1) The 55-grain TSX's in .223 Remington shoot well out of my rifle, already.
2) The 62-grain and 70-grain offerings are actually 5.56, not .223. Since my MPR's got a 5.56 chamber and a 1/8" rate of twist, I cannot imagine either of these bullets performing worse than the .223 55-grains have.

I'm just not sure if I want to order the 70-grain or the 62-grain. Reviewers have said the 70gr. fits in an AR mag fine (despite the fact all-copper bullets take up more space than lead), so that's not an issue. But I am wondering if the seating depth of the 70gr. load might imperil accuracy in some way (I have no idea what it is).

Here's a link to Barnes' ballistics table (from 2016) for all their VOR-TX loads, for reference:
https://www.barnesbullets.com/files/...cs-for-web.pdf

Cabela's website differs from this by saying that the 5.56 loads are actually TTSX bullets, not TSX. Either that's a typo, or Barnes has changed the bullet used over the past year. That the 5.56 loads, unlike the rest of the VOR-TX lineup on Cabela's website, ship directly from the manufacturer---not from Cabela's---is consistent with the possibility that Barnes has changed things up.

Either way, what do y'all think, 62gr. or 70gr.?