I've come across a problem(mostly personal) that I may have an answer for, finally.
I have a .257 Roberts in an M722. It's a factory gun, or has been until now. I really like .25s, and have several. This Bob stands out in my mind, eventhough I have more powerful .25s, and more accurate rifles...I just like this gun. But... I have thought about unscrewing the barrel and puting it in an M721 actioned rifle.
I have decided I'm going to put a new stock onto the M722, but I haven't decided on the cartridge, yet.
The main problem for me is the leade in this barrel. If I put the bullet where I want it in relation to the throat, it is too long for the magazine. Something that has been discussed since the rifle came out. So...my options are to back the bullets to match the magazine, cut a thread off the barrel, and rechamber with less leade, and rebarrel. I got to running this through my little pea-brain and went on a tangent. What's the possibility of a .25/284 in THIS barrel, after backing it up a bit?
I would buy a reamer without a throat, then get a throating reamer so I can get it done MY way. I don't care if the bullet protrudes into the powder-room a little, my concern is the bullet-rifling relationship. A .25WSSM came to mind, and if I were using a Mauser, I'd do that. Since this is a Remington action, I'd sooner not work the bolt-face over. I know I'd have to rework the frame-rails, and I'd only have a 2-round magazine, but that's OK. The barrel is 24", and the gun would be for hunting.
Any thoughts on the conversion?
Thank you,
Gene

Remove the barrel from the 722 and rechamber it to .25-06 and install it to the 721 action.

Get a new barrel and chamber it to .25-284 or .25-08....your choice for the 722.

Get them throated the way you want them!

Vapodog-
Good suggestion. The problem I have at THIS point...I haven't found an M721 action, yet.
Maybe you can tell me how much difficulty I'd have working the magazine over for the .284 case.
I have a 98 Mauser in a wildcat I call the .25X2. It's a .243 necked up and trimmed to 2". It has a long neck and a 40* shoulder.
Is there any particular reason you suggest a new barrel for the .284? Maybe...the shoulder is too near the taper so it may cause a thin spot?
Just wonderin'.
Thank you.
Gene

An additional problem, inletting wise, with the 721/722 barrels is the "boss" for the rear sight dovetail on the earlier rifles. It is unlikely that a 722 take-off barrel installed and headspaced on a 721 action would have the "boss" on the barrel line up with the inletting for the 721 barrel on the original 721 stock.

1 solution to getting a longer OAL in your 722 is to install a longer Wyatt magazine box.

www.wyattsoutdoor.com

I have a couple 25-284s on Remington 7, 700, and 722 actions with the factory magazine boxes and don't have any trouble getting good hunting grade accuracy with bullets in the 75 grain VMax to 110 grain AB range.

I can't see that there is a whole lot of difference, performance wise, between the 257 Roberts, 257AI, and 25-284. A little more possible speed from the AI and 25-284, but enough to make a "practical" difference in a hunting rifle? The 722s in 257 Roberts that I have owned have not had particularly long throats, unlike most 6.5x55 and 7x57 barrels, and have been, on average, about as accurate as any other standard grade factory installed barrel.

Jeff

260remguy- Absolutely perfect.
I didn't know about Wyatts, but I do now. The mag box is exactly the answer to my problem. I like the way my rifle shoots, but none of the bullets allow the ammo to be loaded into the magazine.
When I planned to put the barrel on the M721, I was going to turn the "boss" down and continue the taper. I was also going to turn the front sight-ramp off.
This will work well, because I'm putting a new stock on as well.
Thank you,
Gene