I would suspect the 25-300WSM would give 25-06 velocities wouldn't you? Either the "American Rifleman" or "Rifle" magazine (they both arrived in the mail yesterday) has an article on the WSM and the 300 RSUM concerning all the "stuff" folks are doing with them. No loading data or specifics.
We're thinking similar thoughts, although I went the other way looking at the 35-300 WSM to rechamber my M336 .35Rem. I'm sure there are folks out there doing these very things, and sooner or later, the results of their efforts will come our way!
I just logged on to the forum for the first time yesterday and was glad to find someone else interested in the .25-300wsm. I've gone as far as having the gun built, and I'm waiting, not so patiently, for RCBS to finish my custom dies. RCBS estimated one more week. I started out with a Ruger No. 1B that was chambered for a .257 Arnold Mag. (7mm Rem. Mag. necked down to .257) I enjoyed this round so much it only took a few years to shoot the barrell out. I was going to have Arnold Arms Rebarrell it again, but as near as I can tell they went out of business. I was calling around trying to decide what to do next when I found out that the folks at Montana Rifleman (Kalispell, MT) had a chamber reamer for the .25-300WSM. I kind of departed from the norm. as far as the WSM's go by using a single shot action. The reason I did this is because I'm left handed and I'm limited to short action bolt guns. The other thing I did different is I don't mind long barrells and I like the added velocity. As a result I ended up with a Ruger No. 1 with a 28" stainless steel tube that is almost exactly the same length as my Ruger M77 Mark II with a 24" tube (No bolt, shorter action). I suspect velocity to be compairable or slightly less than what I got from the .257 Arnold. This is no 25-06 it will be more in the .257 Weatherby range if I'm correct on the velocity guess. I will check back with you when I get some loads developed. If any one else has information on loads I would be happy to have it.
Mat: I like the idea of that long tube on a #1. What twist did you specify or did the smith recommend something in particular? I've been considering the same form of rifle and in particular I would want it throated for some of those long 115-120 grain bullets seated out so the bullet does not go into the case beyond the base of the neck. I think you are going to have a winner there and it should be very comparable to a 257 Wby. (without the extra action length). Will be looking for your shooting reports with this one. besto.
I went with the 1 in 10 twist which is the same rate I had in the 257 Arnold mentioned above it worked great for the 100 to 120 grainers. I did try loading some 75 grain Hornady V-max bullets for Montana ground squirrels. In the Arnold they were clocking over 4000fps and were flying all over the place. Some of them I couldn't even see hit. I suspect they were coming apart in the air. I think with the 25-300wsm I'll try the 87 grain Nosler Ballistic Tips if I load any varmint type bullets.
I like your idea on the long throat. I'm not sure what the throat length is like on my new barrel, hopefully it will be somewhat adiquate.
If your thinking about building a rifle in 25-300wsm, and you find a place that allready has the chamber reamer be sure to order your loading dies well in advance. It took six or seven weeks to get the rifle back on my door step with the new barrel. It's taken over four months and counting to get the dies. If your like me it drives you nuts to have a newly rebuilt rifle setting in your rack that you can't shoot.
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