I'm a fan of the 8mm.
I was curious. What do you think an 300 ultra mag could do necked down to 8mm?
What do you think the 8mm WSM could do?

Matt,

Assuming equal pressure and equally suitable powders, a .323 on the same case size as a .308 and in the velocity areas of 3000 to 3300 or there abouts, should give about 80 f/s more velocity with the same bullet weight.

Mike

I think that the 8mm Ultra Mag would be a pretty cool cartridge. I have a 26" barreled 8mm Rem Mag that does 3000-3100 fps with 220 gr Hornadies, this case should be good for 50-100 fps more. I like it. - Dan

8mmRem: My go-to rifle. For everything. The load is 89gr of RL25 in a RP nickle-plated case, with GM215M for ignition and a 220gr Hornady up top. I use this load in a Sako TRG-S, where the magazine lets me seat the bullet out to 3.725in. Seating deeper for another rifle may not be a good idea as this load is quite compressed. It generates the same pressure as the factory safari-grade 200gr Swift A-frame, but about 200fps faster with more bullet mass. It tests at 2975fps with the velocity and POI identical from 10 below to 100 degrees above zero.

I truly love the performance of the big 8 and have a plan for an 8mm WSM, only I'd call it the 325 Montana. The case, with a 220gr Hornady seated out the base of the neck is 3.094in long and will hold 77gr of V550 powder. It will fit in our M1999 SA and it's possible that we might see 2800-2850fps out of a 22in barrel.

It has been my experience on big game that 2900-3000 fps is all the Hornady 220gr can handle, especially if you take a shot under 100yards. But there is a 220gr Swift A-frame now and that might be a better answer.

Matt77:

I did some research on the probable performance of an 8mmWSM some time back.

A helpful forum member did a model on "Load From A Disk".

The "ceiling" (65,000psi) was in the neighborhood of 2950fps with a 200gr bullet, 3150fps with 180s.

I am quoting from memory, but I am pretty sure those figures are correct. Rod's estimate for a 220gr bullet would be along the same performance levels.

I was planning on useing an "intermediate length" M98 action, (VZ500) but have since aquired a M98K barreled action in like new condition. I have decided to rechamber the M98K action to 8X68S. The performance characteristics of the 8X68S would be similar to the 8mmWSM perhaps @ slightly lower pressure.

I will save theVZ500 actions for something in the intermediate length cartridge family. One will definately be an 8X57, the other perhaps a 6.5X55 or 6mm Rem. Ackley Improved.

The 8mmWSM is definately an interesting proposition. A military barrel could be rechambered to it, but would require a "setback" of about .135" to clean up the 8X57 chamber. It is feasable, but a rebarrel job would probably be more practical.

A M48 Yugo action would be ideal for an 8mmWSM IMO. It would allow a longer COL, perhaps 3.150"

Would you be useing the 300WSM case, or the slightly larger 7mmWSM case? My vote would be for the 7mmWSM case.

[ 12-02-2002, 18:10: Message edited by: wildcat junkie ]

350 Montana: probably belongs in another string, but this one would one-up the 35 Whelen. Another interesting twist for the WSM parent. Neck up from .338 when it appears.

Necking up from .300 to .323 is probably better than going the full mil from 7 to 8 for brass life. Good thing these are WW cases in any regard.