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Perplexing chrono results with my 257wby...

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So I spent the day at the range, finally able to work on a bunch of loads that I've been working up since I got home. Found a sweet spot with 105 amax's out of my 243: 3146fps, .6" and single digit ES. Wish I could say the same for my 257 wby(Vanguard S2). I shot 5 strings of H1000 ranging from 68-72gr pushing a 115 Berger HVLD, and my average velocity between the strings was very close. 2945fps @ 68gr and only 3054fps @ 72gr. This is the first time I've ever come across such a small gain in velocity between charges of this size. Would the free bore have anything to do with this(I did load quite long, and Bergers are picky)? Makes me curious if I could push this any faster with H1000 or if I need to switch to RL25. Thoughts?

 

Thanks.

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Any signs of pressure at 72 grains?

Barrel length seems like 24"?

How was accuracy?

 

Seems like the .257 Weatherby should be pushing the 115 VLD faster than 3054fps. Try RL22 also. My .25-06 Ackley pushes the 115 HVLD at 3400 from a 28" barrel using 58 grains of RL22. And RL22 always gives me good velocities in 7RMs pushing 140 To 168 VLDs too. Even worked very well in my .300RUM w. 175-215 bullets.

 

My .300RUM had a velocity spread from 2956 to 3100 pushing 210 VLDs with charge weights from 85.5 to 91.5 grains of H1000. So about 150 fps over 6 grains of charge weight difference. Right in line with your 100+fps gain over 4 grains of charge weight difference.

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Higher capacity cartridges see little velocity gain with adding powder a grain at a time, especially with slower powders. 1 grain at a time at 70 grains is only 1.3% more. Nature of the beast...

 

I'd switch powders. You may have a slow barrel too...

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With my 7mag I get 3160 with 69.5 grains H1000 and a 162 Amax. I would figure a lot higher FPS with your 257wby and a 115 grain bullet.

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WeRE the loads accurate? Was the velocity spread consistent? Dont worry so much about velocity if the accuracy is there. I shoot basically the same load you were testing in my 257 van guard series 1 and it is accurate so I shoot it. I have shot groups consistently sub MOA with mine, and even shot a couple groups sub .5 moa. I have shot sub MOA groups at 500 yards with this load combo in my weatherby.

 

My cow elk didn't care how fast the bullet hit her this year, I hit her were it counted and she fell down. The shots were roughly 270 yards and I drilling her twice with great results.

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No pressure signs, 24" barrel, and sub par accuracy. Best grouping I had was 1.12"@100yds with the 68gr load. My ES was 30-70 fps, depending on the load. The average velocities for the 5 strings were 2895, 2967, 3026, 3039 & 3054. I guess what really surprised me was the spread from 70-72gr.

 

I think I'll try another powder or two, and if that doesn't work, I'll switch to some tsx or ttsx bullets.

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Anytime you get a "flat liner" load you're dangerously close to, or past, maximum pressure. I ran your load in my QL program and yep it confirmed at 71gr., you're at max. . Going to RL22 will increase velocity but will also increase pressure. You might try RL25 and see what it will do in your rifle. It is my favorite in the 257 WBY. with heavy bullets. BTW those 115 Bergers really perform better an 8 twist for good groups. Your rifle is probably a 9 twist.

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What are you using for COAL? do you know how far off the lands you are? You might need to play with seating depth too.

 

My rifle loves berger 115gr hvlds, and hornady 117gr btsp bullets. It shoots both very well. It didn't shoot nosler ballistic tips great. No bad, but not like the other 2.

 

It shoots SSTs pretty decently too but I have not played with the load much so I bet it could get better.

 

Harley

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Rifle is listed as a 10 twist, but I've not ran a rod through it to confirm. Never messed with QL, but I figured 72gr would be about max. My coal 3.295", which is as long as I could seat out and still support the bullet with the full length of the case neck. I wasn't able to seat to the lands when trying to figure out my coal. I'll try RL25 tomorrow.

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I found in my old 300 rum that 1 grain more or less of H1000 yielded about 30fps. Yes, it took a lot more powder to get a little increase in horsepower.

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i only have 16 rounds through my .257. i have not chronod yet. are you using fed 215 primers? Imr 7828 shows the highest velocity in the nosler manual. I asked a guy on 24hourcampfire about loading .257, he has three. He said that according to Weatherby they use Re-22/Mrp in their factory ammo.

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Keep trying different combos until you find what your rifle likes. Mine likes h1000 and bergers so I bought an 8lb keg of h1000 and plan to buy a 500ct box of bergers soon.

Re22 has shown promise in my rifle but h1000 was better so I went that route. Each gun is different though.

 

 

Harley

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