I'm rather partial to the .257Roberts.
I've owned one for a third of a century, and own two at present. I know a little about the chambering.
1. It can, has, and is able to be built on the short action format. I have a Remington Mod7 (actually 2), but the 7mm08 is the one in question. It will handle a loaded round of up to 2.830" oal in the magazine. Most all bullets seated to this length will either be contacting the rifling, or near it. This is due to the short throat in the chamber. The Remington custom shop will build you a .257Robts on the M7 action.
SAAMI max oal for the 257Roberts is 2.775". Hence, it will EASILY fit a short action. I have cycled .257 loaded ammo through it that was intended for my short chambered Ruger M77. Of course it wouldn't completely close in the 7mm08 chamber, it would feed and extract. No problem !! A Sierra bullet(87-117gr PtSpt) seated to 2.83" will touch the rifling in my Ruger M77 .257Robt. but it's a Long action....but dosen't need to be.
2. There are two basic chamber dimensions/designs for the Roberts. The short one was orginally used by Remington in the model 722 and 760 rifles. The 722 being a short action, Remington chose a short throat and estabilished a max of 2.775"oal. All modern factory ammo complies with this standard. My custom M98 uses the longer so called "3in" chamber. It will take cartridges up to and slightly longer than 3.000". A Berger 115gr VLD must be 3.115" to touch the rifling. However, accuracy is only slightly reduced by seating bullets such as the 100gr Hornady, Sierra, or Speer bullets to 2.775" One of the most accurate loads for this rifle is 46.0gr of H380 under a Hornady 75gr HP for 3,550fps. About like a good .22-250 and a 55gr bullet. Only, the "whap" you get when it hits a deer at 350yds is significantly louder than that from a .22-250, or even the .243 and an 80gr bullet at 3,350fps which is "supposed" to out perform the "Bob", only it dosen't..................A co-worker shot 11 deer one night doing population control work. He shot 5, I shot 6. he took 7rds. I took 6........ Even the inmates at the prison that took the deer commented on the difference in exit wounds on those that had similar shot placement. The 75gr .257 left a 50% larger exit wound......Yes, all 5 exited with shoulder/spine, and head shots (the closer range ones...)
3. Most .257Robt shooters handload. Those who own a chronograph will tell you that it usually exceeds the velocities given in the manuals. I ususally "easily" get 3,100fps and occasionally with an "lucky" combination of components (particular mixture of different lot#'s) see 3,200fps. Or, about like what I get from the .25/06.
My best friend is usually driven to a conniption when he see's my "Bob"s get better velocity with a shorter barrel and lighter powder charges.......... (Think barrel quality). His is a MkX Viscount with factory barrel, mine has an E.R. Shaw #2 taper barrel at 22" and is veryyyyyyy smooth. The other a Ruger M77 has the "short" throat, and is even more efficient. It gets the same velocities with 1-3gr less powder........ In reality, the difference, if you hand load, is the .257 and the .25/06 compare like the .308wcf and the .30/06. Not enough to get excited about. Actually, they're closer than that. About like the 7mm08 and .280Rem in equal lenght barrels. FWIW, my 7mm08 gets faster velocities from a 20"bbl than an aquaintances .280Rem. Same powder(different charges-mine are lower...), bullets, primers, and make of case..... Go figure! (It's the barrels...... not the cases......).
4. There is a noticeable difference between the .243's and the .257 in the field. It has to do mostly with bullet construction. John Barsness addressed this in an article on bullet construction several years ago in "Handloader" magazine. It has to do with surface area contact between the jacket and core. To get a .243 bullet to "perform" as intended and "mimic" the .25's, it takes a thicker jacket leaving a smaller quantity, and longer sliver of lead in the core. There is less surface area in the jacket to grip the lead core. Result is at close range, the bullets will "blowup" due to seperation and rupture, and "fail to expand" at longer distances. My brother who has much more .24 experience noticed this about 5yrs ago when we did some deer control work on a lease. 4 of us took 21 deer in a weekend. Three were lost, all with the .243. I took three with a .223, and 3 with the .257. None lost. I've taken over 100deer with the .25's to include the .257wbymag. It is definitely superior to the 24's, and not much different than any other "light medium" between 25 and .33". I do see a little difference between the .25's vs. .30's; about like the difference between the .30/06 and the .338/06. Not really enough to get excited over. Hence, I haven't taken but one deer with the .30/06 in 12yrs. I haven't even taken the .338/06 out this year, and only once last year. (I hunt about 50days a year, sometimes more than 75).
No the .257Roberts isn't "magical", it just rides the boundry between small bore (under .17, .17's, .22's, and 24's) and the "light mediums", .25-.30's. It just happens to be "closer" to the .30's in performance than the .24's to be noticeable.
No, I don't "hate" the .24's. I just see them as too close to the .22's in performance to get excited about.
What is fascinating is that I see less penetration, and fewer "bang-flops" with my .257Wbymag than I do with the "bob". Same bullets (same box!), but with 300-500fps more velocity.
Those who can't get excited about the .257 share my opinion of the factory ammo in this cartridge. Except for the Hornady "light magnum" loads, and the Federal Premium 117 Sierra's and 120gr Nosler Partitions which fairly closely match the handloads..........
Just my 1/3 of a century with the "bob".... and "opinion"........Your results may differ......