Having one of these built at the moment. On a trued M700 action shooting (hopefully) 87gr VLDs.

Will report on loads and accuracy when I get to the range with it.

Blair It will be interesting to see what velocities you can achieve with this cartridge. There is not significant increases in velocity when you move up from a 26 in barreled 6mm Rem to the 6mm/284,240 Wby,6mm/06 class so the 6mm/257 Bee may be a lot more powder and a short barrel life for very little velocity gain. What powders are you hoping to use?

Will you be ordering extra barrels?

Here's the computer simulation from Load from a Disk on the old 6mm Atlas. Not a huge improvement over the 6-06. Looks like it tops out ~3900fps.

Good Luck!

Rifle Load Results
Load From A Disk v5.0
Date: 5/4/15
Cartridge Type:
__________________________________________________________________________________
Bullet Type = .243 (6MM) 88-GR Match Varmint Bullet Weight = 88.0 grains
Bullet Diameter = 0.243 in Bullet Length = 1.065 in
Bullet BC = 0.391 Sectional Density = 0.213
Case Type = 6mm Atlas Case Length = 2.475 in
Full Case Capacity = 80.641 grains water Est. Overall Cartridge Length = 3.020 in
Net Case Capacity = 74.554 grains water Bullet Seating Depth = 0.520 in
Rifle Type = 123 Barrel Length = 26.0 in
Effective Barrel Length = 24.045 in Barrel/Case Volume Ratio = 4.7
Cartridge Temperature = 70.0 °F
__________________________________________________________________________________
Powder: H4831
Calculated Powder Charge = XXXX grains
Load Density = 80.0%
Charge/Bullet Weight Ratio = 0.677
Estimated Muzzle Velocity = 3492 ft/sec
Estimated Chamber Pressure = 45031 CUP

Ah, thanks guys.

I'm using a 28" 1:10 Maddco barrel. There are two of them at my gunsmiths!!

And I have 900 257 Wby cases lying around so, they won't be a problem.

Will probably be working with RL-25 for the 87's And 80gr BT's. It is hopefully going to be a long range 'roo gun

A guy has to build what a guy has to build. Seems like a lot of work, barrel wear and powder for 100fps over a basic 6-06 or even the plain jane 240Wby.

Not really.

The reamers were the main cost......the brass was there. I think it might go harder than 100fps over a 6mm-06.

Just curious -
Did you replicate the Weatherby double radius shoulder? Or go with a conventional angled shoulder.

Cartridge Type:
__________________________________________________________________________________
Bullet Type = .243 80 GR SB BT V NOSLER Bullet Weight = 80.0 grains
Bullet Diameter = 0.243 in Bullet Length = 0.890 in
Bullet BC = 0.329 Sectional Density = 0.194
Case Type = 6mm Atlas Case Length = 2.475 in
Full Case Capacity = 81.0 grains water Est. Overall Cartridge Length = 3.020 in
Net Case Capacity = 76.962 grains water Bullet Seating Depth = 0.345 in
Rifle Type = 1234 Barrel Length = 28.0 in
Effective Barrel Length = 25.87 in Barrel/Case Volume Ratio = 4.9
Cartridge Temperature = 70.0 °F
__________________________________________________________________________________
Powder: RL-25
Calculated Powder Charge = XX.X grains
Load Density = 86.0%
Charge/Bullet Weight Ratio = 0.827
Estimated Muzzle Velocity = 3754 ft/sec
Estimated Chamber Pressure = 46608 CUP

Straight neck down............

I think you will find that the real "gain" will come from being able to shoot a heavier bullet (95-105gr) at the same or slightly higher velocity than the 6/06 or 240 can with the 80, flatter trajectory and more impact energy.

I sure hope it works for you. Years ago I built a 240PDK my blown out shoulder forward 280case. Pretty much a 240Gibbs plus. I didn't use anything above a 90gr and only had a 26". I burned 50% more powder for about 75fps.

Don't even want to think about the number of Wby cases I trashed trying to neck them down.

Please keep us informed of your progress and results.

That should obliterate a kangaroos head if you know someone with roo tags.

Sounds like a hell of a neat round.

Guns&Ammo Nov of 93, Seyfried has a write up on the 6mm/7mag imp.
75 grn bullet, 73 grns IMR 7828 = 3995 in a 25" barrel, 4150 in a 28" barrel.
100 grn bullet and surplus ww 872 he reached
3780 in the 28" barrel.
Carbon build up was a problem, and he recommended cleaning every 10 rnds.
His rifle at the time of the article had 580 rds through it and still shot under 3/4".
He figured in would likely go to hell at around 1000 rounds.

quote:

Originally posted by Big Wonderful Wyoming:
That should obliterate a kangaroos head if you know someone with roo tags.

Sounds like a hell of a neat round.

The property owner who I shoot with has 500 with more to come

1000 rounds is ok. When you drive a Ferrari, you have to expect high fuel consumption!

quote:

Originally posted by theback40:
Guns&Ammo Nov of 93, Seyfried has a write up on the 6mm/7mag imp.
75 grn bullet, 73 grns IMR 7828 = 3995 in a 25" barrel, 4150 in a 28" barrel.
100 grn bullet and surplus ww 872 he reached
3780 in the 28" barrel.
Carbon build up was a problem, and he recommended cleaning every 10 rnds.
His rifle at the time of the article had 580 rds through it and still shot under 3/4".
He figured in would likely go to hell at around 1000 rounds.

Thanks for that mate, I remember the article but couldn't find it.

The advantage with using the 257 Wby case as the parent is less of a neck down, less split necks etc.

quote:

Originally posted by ramrod340:
I sure hope it works for you. Years ago I built a 240PDK my blown out shoulder forward 280case. Pretty much a 240Gibbs plus. I didn't use anything above a 90gr and only had a 26". I burned 50% more powder for about 75fps.

Don't even want to think about the number of Wby cases I trashed trying to neck them down.

Please keep us informed of your progress and results.

Will do. My gunsmith John Clapham has a backlog, but he is very interested in how it goes.........

quote:

Guns&Ammo Nov of 93, Seyfried has a write up on the 6mm/7mag imp.
75 grn bullet, 73 grns IMR 7828 = 3995 in a 25" barrel,

GS-custom has .240wby pushing 69gn-HV pill approaching 3900mv.(24")

quote:

Originally posted by Blair 338RUM:

quote:

Originally posted by Big Wonderful Wyoming:
That should obliterate a kangaroos head if you know someone with roo tags.

Sounds like a hell of a neat round.

The property owner who I shoot with has 500 with more to come

1000 rounds is ok. When you drive a Ferrari, you have to expect high fuel consumption!

My Canberra gunsmith mentor and I built a 7.82 warbird. Killed the barrel in under 400 rounds.

Not a 1000 yard bench rest gun as we thought.

quote:

Originally posted by Blair 338RUM


1000 rounds is ok. When you drive a Ferrari, you have to expect high fuel consumption!

Fuel aint the real problem, its the Ferrari servicing costs,chewing through sets of P-Zero rubber-bands,
and possibly breaking a clutch or worse,transmission...$$$$ ....if it doesn't infamously burst into flames first....

quote:

Will probably be working with RL-25 for the 87's And 80gr BT's. It is hopefully going to be a long range 'roo gun

And here I was thinking that my wildcat was the bee's knee's long range 'roo rifle. I used a 6mmAI reamer and had it run in to the same body length as the .30-06, 70gn HP's 3800fps with no pressure, and it's a dead hold almost out to 300 yards

quote:

Originally posted by Big Wonderful Wyoming:

quote:

Originally posted by Blair 338RUM:

quote:

Originally posted by Big Wonderful Wyoming:
That should obliterate a kangaroos head if you know someone with roo tags.

Sounds like a hell of a neat round.

The property owner who I shoot with has 500 with more to come

1000 rounds is ok. When you drive a Ferrari, you have to expect high fuel consumption!

My Canberra gunsmith mentor and I built a 7.82 warbird. Killed the barrel in under 400 rounds.

Not a 1000 yard bench rest gun as we thought.

Speaking of barrel life. My Lilja barrel .270Wea lasted less than 600 rounds. I never fired more than 3 shots at the shooting range before letting it cool of. Always cleaned the barrel after 10 shots. Yes I did load the rounds to max.

quote:

Originally posted by jens poulsen:

quote:

Originally posted by Big Wonderful Wyoming:

quote:

Originally posted by Blair 338RUM:

quote:

Originally posted by Big Wonderful Wyoming:
That should obliterate a kangaroos head if you know someone with roo tags.

Sounds like a hell of a neat round.

The property owner who I shoot with has 500 with more to come

1000 rounds is ok. When you drive a Ferrari, you have to expect high fuel consumption!

My Canberra gunsmith mentor and I built a 7.82 warbird. Killed the barrel in under 400 rounds.

Not a 1000 yard bench rest gun as we thought.

Speaking of barrel life. My Lilja barrel .270Wea lasted less than 600 rounds. I never fired more than 3 shots at the shooting range before letting it cool of. Always cleaned the barrel after 10 shots. Yes I did load the rounds to max.

What?
600 rounds?
I've gotten over 2,000 rounds easily before it open up to 1/2 inch groups with a Dan Lilja barrel. I even had it shorten down and rechambered it to a 270 WSM and donated it to my niece.
I suggest you call Dan.

In my opinion, You would be just as well off with the 240 WBy, I doubt that the 6mm/257 Wby would produce enough additional velocity to justify a wildcat..

I think todays "Wildcatters" are mostly chasing rainbows, the day of the wildcatter has about run its course, but then again, to each his own, and let the games begin!

quote:

Originally posted by Atkinson:
In my opinion, You would be just as well off with the 240 WBy, I doubt that the 6mm/257 Wby would produce enough additional velocity to justify a wildcat..

I think todays "Wildcatters" are mostly chasing rainbows, the day of the wildcatter has about run its course, but then again, to each his own, and let the games begin!

Don't bet on that as I had the 6mm/264.

It's really the same sort of comparison as the 257 Wby to the 25/06 or even 270 Wby to 270 Win.

Id probably bet on it, most wildcatters live in an overbore capacity la la land!