I have a 7 Mag in a stainless Ruger MK2 that I want to change into a medium bore screamer for deer and antelope. I was thinking that it would be easiest to rebarrel to 257 Weatherby Magnum because of the similiar case head and body dimensions.
Is there any conventional/factory round that makes the 257 Roy look slow?

If it is it would really eat up barrels. The 257 wby has the same case capacity as the 7mm mag. I think I'm running 100 grainers out of my 257wby at just under 3700 fps. Mines been real accurate too and it seems most everyone reports good accuracy with this cartridge. I'm glad you asked the question--I was planning on taking my 300 wby to Alaska this fall for a carribou hunt and now you have me thinking about my 257 wby....hmmm.

I did the same thing....rebarrelled a LH 700 to 257WM. installed a Mcmillan stock and a 3.5-10 Leupold. I shoot 85 gr. Nosler BT's at 3850 at Oklahoma deer. Kills instantly with shots in the chest.

Fjold ----- You will find the .257 Wby is hard to beat. I have an Accumark that is deadly with a 115 or 120 grain Nosler Partition at 3500 fps. ------ Kraky be careful with the .257 Wby in Alaska hunting Caribou. On my last trip for Wolfe and Caribou I counted 69 Brown Bear in 6 days of hunting. Consider where you are hunting and be prepared. Good shooting.

Thanks Pat--point taken. I've been there 3 times and not come near (as far as I know) a bear encounter. We usually wind up in real open territory but this year we are hunting with a "friend of a friend" and it's going to be a river area hunt and you got me imagining about rivers, fish, brush, and bear. Darn you anyhow---back to the 300 wby.

Your 7mm RM will shoot a 120 gr bullet faster than the 257 Mangelum will shoot a 115 gr according to Nosler 5. Comparing the coefficients of those two bullets there is not a lot of difference.

So the easy way out is to use the rifle you have. Of course you know that and you want something new just like the rest of us.

The 264 WM here will shoot 120 gr Ballistic Tips easily at 3350 fps. I use that for long range stuff that's not tough.

My favorite rifle in that catagory, at the moment , is the 270 WSM. It shoots 110 Vmaxs quite fast for coyotes and 140's start at over 3200 fps.

Thanks guys, I have a couple of holes to fill and one is a screamer and one is a light deer gun. The 7 Mag is going to become a 257 Weatherby and I think one of my old 308s is going to become a 7-08.

quote:

Originally posted by Fjold:
Thanks guys, I have a couple of holes to fill and one is a screamer and one is a light deer gun. The 7 Mag is going to become a 257 Weatherby and I think one of my old 308s is going to become a 7-08.

I like the 7mm-08 for a very light deer rifle. I got a 260 also and I wonder why? The 7mm just seems better for just a deer rifle.

Have you thought of a WildCat?

I've seen some interesting data on the 257 STW but, I can imagine it would be a real barrel burner and pressures have to be out of sight.

What about a .264 WM necked down to .257? You could easily make your brass from 264 WM brass and cost would be much cheaper than the .257 Wby brass. A nice custom tube w/ a set of custom dies and you'd be set. Of course, that wouldn't scream past the 257 wby but it would be cheaper to load for and probably wouldn't be that tough on barrels.

The Problem w/ the Roy is the Freebore. If you get a custom tube chambered for the Roy that doesn't have Freebore, you wouldn't be able to shoot any factory Wby loads (Safely That is).

Good Luck!

Reloader

I keep jumping back and forth between the 257 WBY and 264 Win. Both are small bore screamers and they both are at their best in 26 inch barrels.

Just something else to consider.

Fjold,

If you want speed, check out the Lazzeroni calibers.

The 7mm STW is also an option. Or take the 375 RUM and neck it down to .257. But be sure to use 100 grain Sierras only.

Hey Frank, How about the .257 WSM???

I have a drawing and have been thinking of this one myself, and I already have a .257 Bob and a .25-06. Brass would be easy to make from the .270 WSM and with no belt it would be easy to avoid feeding problems. A standard length action would also allow more room to seat the heavier bullets out to make room but still fit the mag box.
Nate

I have a hole at 25 caliber and have a 6.5x284 being built right now so I don't want to go with another 264. I was thinking about just necking the 7 mag down to 257 which would be basically be a 257 Roy without the double radius shoulder or the freebore.

Nate, I saw the article on Winchester deciding on the 25 in the WSSM case instead of the WSM because of the poor expansion ratio with the big case necked down to 25 caliber. I actually think Remington could create a really successful round by necking down their SAUM to 25 as it's just a little smaller than the WSM case.

quote:

Originally posted by Fjold:
...I was thinking about just necking the 7 mag down to 257 which would be basically be a 257 Roy without the double radius shoulder or the freebore. ...

About 5-6 years ago I met a fellow at the Range who had one made just like that on a Savage action. I'm sure it was McGowan(sp?) who did the chambering and installed the barrel for him. His initial Loads were in the 7s-10s and we both figured he could get it into the 5s with little development effort.

Nice low-recoil rifle that had great potential for our bean and cotton fields.

I guess I don't understand expansion ratio science well enough. It would seem the WSM case and the Weatherby case would be close in expanion ratio's given volume and bore.??? Nate

Nate, No, you're right. Both the WSSM and the Roy are overbore using the old definition. I was just expanding upon Winchester's reasoning behind picking the WSSM case for their 25 instead of using the WSM.

If was going to hotrod a short action in 25 caliber I would use the SAUM case because of this. I think that a factory load using the 25 in the SAUM case would be the big winner.

What is case capacity difference between a SAUM and the WSM?

The .257 Wby has also been a little of a curiocity with me but it has such a large case it didn't seem worth the extra expense on brass, rifles,ect. now the sa mag cases are readily available and it still may be to much of a good thing. Nate

shortmags.org says the 300SAUM case will hold 75.1 grains of water and the 300WSM holds 82.6 grains, so that's about 10%.

It'll probably be easier to to just neck the 7 Mag case down to 25 and go from there.

quote:

Is there any conventional/factory round that makes the 257 Roy look slow?

NO! About the closest is the .25/'06, and it is plenty fast enough!!

Thanks Frank, I see your point. (took off your hat? )

The SAUM may be something to play with. I just wonder how long cases will be available. Nate

The 6,5x68 - quite well-known factory cartridge in Europe - is certainly a notch above the .257 Weatherby Magnum. But I see no need for that. Overbore.

Carcano

quote:

Originally posted by carcano91:
The 6,5x68 - quite well-known factory cartridge in Europe - is certainly a notch above the .257 Weatherby Magnum. Carcano

I believe that is a European myth, Carcano. The "warp speed" (about 1100mps ~ 3600 fps) data you see for the 6.5x68 are always achieved with the lightest possible bullets - and if you are happy to go as light (i.e. low sectional density) as that, the .257 Wby still has the edge. Either cartridge is faster than what you need, and overbore, as you correctly point out.
- mike

257 Condor. The 6.5 X68 case necked down to 25 and improved if memory serves. Shot next to one at the range years ago, it was quite the cartridge. A little more case capacity then the 257 Wby, but less then the 257 STW (which is a screamer). - dan