Another ladder test: .257 Weatherby Mag, IMR 4831, 100gr Nosler Partition

mikeyb

mikeyb

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Nothing fancy here, a pretty standard combination for the .257 Weatherby. Partitions to survive the impact and outrageous velocity to impart hydrostatic shock. This is not to book max (68gr).

Rifle: Weatherby Vanguard, 24" barrel 1:10 twist
Bullet: Nosler Partition 100 grain
Brass: Weatherby(once-fired)
Powder: IMR 4831
Primer: Federal 215M Match
COAL: 3.250"

65.5gr Velocity 3315/3331/3324 min/max/average
66.0gr Velocity 3340/3366/3354 min/max/average
66.5gr Velocity 3391/3411/3398 min/max/average
67.0gr Velocity 3390/3474/3425 min/max/average
67.5gr Velocity 3439/3479/3454 min/max/average

I tend to be fairly cautious with hugely overbore magnums and approaching their maximums as they can be very sensitive to slight variations in loading. Needless, I definitely prefer the metering of ball powder to stick but I have two pounds of this on the bench. The data at 66.5 looks best IMO, right around 3400 fps and very consistent velocity. I had 3 shots register 3391! Not bad.

I'd love to see what this could do through a 26" barrel, with overbore cartridges like the .257 Weatherby I would expect an easy 40-50 fps per inch. Published maximum for the 100 grain Nosler is 68 grains, but at these speeds I'm kind of not really concerned with maxing it out - 3400 is a laser!
 
Looks good/promising
I have a 240 wby my scope rings should be in this week can not wait to shoot the first 20 rounds (break-in) as per the store I bought it and also the company that made the rifle. If it shoots as well as it looks - you will see some EE ads in order to help me fund a Mark V (257 wby)
 
That 66.5 grain load sounds like a real winner!
I had a Vanguard in 257 a few years ago and it's favourite bullet seemed to be the 100 grain TSX in front of H870 which was discontinued at the time but I had several lbs of to use up.
My current favourite Weatherby's are a 270 on a MkV and a 240 in a custom M17, both are great performers!
 
The 65.5 load gives an ES of 16 and a SD of 6.5.
The 66.5 load gives an ES of 20 and a SD of 8.2.

Therefore your 65.5 load is the better one. All you have to do is work on your seating depth now, if needed.
 
I had a 257 STW and with 100 gr bullets it liked Reloder 33. Other powders that provided close to a 100% fill (e.g. US869) provided much higher MV's than 4831, but of course this is a 257 Wby not a 257 STW, and it's MV and accuracy that matter.
 
mikeelliot said:
ES of 20 is bad? Or am I reading his numbers wrong?
Click to expand...

Sorry, I was on crack there, ( not real crack but you know what I mean ), I should have said the velocity increase from 66.0 - 66.5 is fairly large on average compared to 66.5-67. Maybe a bit above 66.5 would be even better.
 
I’ve been getting good results with H1000. Nosler book sez 3572fps with 75.5gr - 26” barrel
Same book sez 25-06 same bullet gets the best speed with RL19 at 3361fps. - 24” barrel
 
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