My personal experience with factory Remington rifles is that the best groups I can get consistently is about 1-1.5" and that's it.
I guess I'm brainwashed but I really don't want to put effort into loading for factory rifles anymore. And if I did, it would have to be a rifle that has a known better barrel from the factory, like a Savage, Sako, or Weatherby that comes with a Criterion bbl.
Bedding is so very critical in my opinion. In my experience it made all the difference in the world with my old factory Ruger MK II M77. I had 2 things done to that rifle in 1989: trigger pull reduced to 3 pounds and "glass bedded." Nothing else. That alone changed things for the better.
I later had a Hart barrel put on it and had the smith accurize the action. More difference!
I've been told by competition shooters that the powder charge doesn't make quite as much difference as brass quality and concentricity and bullet seating depth. Even Tubb says in his video he made for Sierra years ago that as much as a 1 grain powder difference doesn't make a lot of change out to (600 yards) I think.
I'm still quite anal though. I sort brass by weight with strict tolerance. I weigh EVERY powder charge, and I seat bullets one at a time with measuring overall length in an RCBS precision mic.
I don't sort bullets using a comparator/bearing surface check. I just make sure that each one is loaded exactly the same distance off the lands and this has served me well. It required me lengthening the seater by about .07 each time and it is time consuming but it works.
I have to say that my Sendero barrel is pretty good. It's not a Hart but it doesn't foul and with the right load its better than the .308 TAC that I have. The .223 TAC is better than the Sendero at 100. FWIW- 0.1 gr made the difference between 1/2 moa and hole in a hole with the .223.
I have 4 rifles that I shoot "for accuracy".
.223 Remington TAC. I installed a Jewell trigger @1.5 ounces. It has a Nightforce NXS, 20 minute NF base, DE cheek piece and that's about it. Basically it's set it up as close as I could to my DE Canyon rifle
.308 Remington TAC. It's set up the same as the .223 and I have almost no time on the trigger
7mm Remington Magnum Sendero SFII. Same drill as the first two except that I had a muzzle break put on. It was my first attempt at owning a long range rifle. It's pretty decent but needs work. Like bedding. and accurizing. If I do that then I'll switch to a Hart barrel
.338-300 Defensive Edge Canyon rifle. This was my first custom and it's a dream to shoot. I let a friend of mines son shoot it a few weeks ago. He's a small kid (8th grade) and he shot it at a barrel that was 725 yards away. We had a cold front blow in the night before so the wind was gusty and unforgiving from about my 200°. The ground was wet so we couldn't spot any hits. It was an exercise in wasting bullets but the grin on the kids face when he shot it was priceless. I hit the drum on the first shot in a 10mph steady xwind the day before. It's a lot easier to dial the wind in when it's steady an predictable and a drum (barrel, whatever) is a pretty easy target.
So all in all I agree with you about factory barrels. The Sendero is decent... but the custom is orders of magnitude better. With the custom I know where the bullet is going to go if I do my part. No so much with the Sendero and definitely not with the TAC's The other two... I was really surprised at how rough the barrels were and how long it took to clean the .223 up. I resorted to Tubb's "sandpaper" bullets for both of them. I haven't played with the .308 enough to know where it stands. The .223 is a good hog gun and at 100 it's accurate. But for a rifle that Remington calls "Tactical"... they ain't much.
Oh... one of the biggest *** that Remington sells is their "triangle barreled" VTR. I have one in .308. I know that I put over 500 rounds through that thing just to get it to settle down to a minute or better at 100. It fouled like crazy before it finally got broken in. I changed the *** factory stock, retriggered it, etc... I've heard some people that like theirs but I'm not one of them. Shot #1 is usually pretty good but after that they start walking "northeast".