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Old October 30, 2012, 10:22 AM   #26
Brian Pfleuger
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It's pretty clear now that this bullet needs more "umph" for my barrel. I would never have thought that different barrels for the same caliber would have different "umph" requirements but I guess they do.
They absolutely do. That's why there are different rifling twist rates.

There is no "right" number for a cartridge and any choice is a trade-off.

Lower numbers (1:8 being lower than 1:12) will spin bullets faster, higher numbers spin bullets slower.

Lower numbers also provide more resistance to the accelerating bullet and so produce lower muzzle velocities.

Lower numbers will stabilize heavier bullets but might over-spin light bullets.

Higher numbers give slightly higher velocity but might not stabilize heavier bullets.

It's important to note that we take a few liberties in our choice of words in this discussion. We say "heavier" and it's generally true but as you've found the real issue is length. The reason your gun will stabilize a 117gr Sierra but not the 115gr Barnes is because the traditional jacketed lead construction of the Sierra is heavier per length than is the solid copper Barnes bullet. In other words, the Barnes is longer to reach the same weight.

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I just wish we could establish some direction as to which bullet shape might be most likely to be better stabilized in my barrel without needing max loads.
You can. There are plenty of bullet stability calculators in the internet. They're not absolutely accurate but they provide a good idea. I've found that they seem to be less accurate with smaller diameter bullets. They tend to be pessimistic, saying that a bullet won't be stable when it actually will. On the plus side, if it says you are stable, you can pretty well bet on it.

Here's one:
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Inputing your data, I get a low 1.xx stability factor, which is in the border region. If your velocity is significantly slower and/or you mismeasured the twist rate, you would be (and obviously are) unstable.
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Old October 30, 2012, 11:28 AM   #27
SSA
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I just wish we could establish some direction as to which bullet shape might be most likely to be better stabilized in my barrel without needing max loads
Use a shorter bullet.

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I've always had good results with the Sierra GameKing 117 gr spitzer BT.
Use that, or any lead core flat base bullet.
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Old October 30, 2012, 11:31 AM   #28
old roper
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FLChinook, I just checked Barnes site and your right on what your using as to what I have in their manual plus the 90gr and 100gr loading data is different.

The test rifle they used a Wiseman 24" long barrel 1/10 twist.

When I work up a load I never do it over a chronograph and that's just me but on the Wby's I do. the 257 Wby I had build with the 115gr TSX I got max Barnes velocity 2gr under max using IMR-7828ssc and if it was me I'd use that powder over H-1000.
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Old October 30, 2012, 10:06 PM   #29
langenc
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Call Barnes and talk w/ Randy and see what load he suggests. Explain the problem to him and he will fix it. Might want to pull those loads as the Barnes aint cheap.
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Old October 30, 2012, 10:52 PM   #30
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Sorry to belabor this, but if bullet stability is not a function of BC, what is it a function of?
No stability is not a function of BC, BC is a function of the bullets shape. Long skinny pointed bullets will have a higher BC than short blunt fat ones, to put it (ultra) simply.

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Is there some minimum muzzle velocity for any given bullet and barrel length/twist? Are we "doomed" to learn about each bullet's stability with each gun by trial and error; hopefully not...
Yes, but generally not by YOUR trial and error. Most of the work has been done for you, its in your loading manual, if you dont see a bullet weight listed, thats because its not right for the "normal" twist fort he caliber, BUT, you have to keep in mind that, #1 copper bullets introduce a new variable (long for weight). and, #2, The whole twist rate/stability thing is, to quote capt. barbossa, "more what you'd call "guidelines" than actual rules"........ That is, not ALL .257 WBY rifles with a 1in10 twist will shoot that bullet poorly. As anyone who is into guns eventually finds out, each gun is an individual as far as what it shoots good and what it shoots poorly. Its possible the next rifle off the assembly line after yours shoots 115gr barns TSX into super tight groups. (its also possible it shoots them just as poorly)

For the most part, you wont go wrong following conventional wisdom as far as bullet weight/twist, but there are always exceptions, (monolithic hunting bullets being one of them). Some rifles with "to slow" twist rates will stabilize "to heavy" (long) bullets, while some rifles with "correct" twist rates wont stabilize "correct for twist" bullets..... And even when the twist and bullet length are perfectly matched, sometimes your gun just plane wont like a bullet/powder/primer/brass combo.... we just have to keep plugging along till we find one our gun likes...
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Old October 31, 2012, 01:06 AM   #31
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we just have to keep plugging along till we find one our gun likes...
Thanks. I probably could get the Barnes TSXs to work by changing powders and increasing loads. But, to be honest, my heart isn't in it anymore. I only have about 20 of the bullets left and I'm going to just give them away

Opening Day is only 4 days away now and time is fleeting. I know, I should have planned ahead more..

All the bullet makers have excellent call support. I called Sierra today because I have Sierra bullets. I told him what powders were in my larder; he chose the one he felt would do best with my GameKing 117's. I loaded a batch with his recommended load and then another batch at the max recommended load. Off to the range I went...

The recommended load gave me 0.7" three shot groups and the max load gave 1.3" groups. I'm now set for OD. I can experiment with other bullets and loads after my freezer is full of venison..

Thanks again for everyone's help. I have learned a HUGE amount from this thread!
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Old October 31, 2012, 10:19 PM   #32
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good luck! our season ended sunday.... we saw 5-8 deer and a moose in the first 2 days, then the weather turned and we didnt see anything but tracks from then on
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Old November 1, 2012, 12:02 PM   #33
RC20
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Hmm, poor choice of a title, this is not a disaster.

A disaster would be a blown up gun.

Merely a minor problem to be sorted out or just give up and go with something else.
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Old November 1, 2012, 02:39 PM   #34
thinkingman
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Is the tendency to keyhole a function of Ballistic Coefficient?
No, it is a function of sectional density (SD)

Sierra GK .253
Barnes TSX .249
Barnes website lists 1/9 or faster for that bullet.
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Old November 1, 2012, 02:54 PM   #35
FrankenMauser
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Barnes website lists 1/9 or faster for that bullet.
Barnes isn't always consistent with their twist rates.
The bullet is listed as needing a 1:9" twist or faster, but the load data is all based on a 1:10" twist barrel (with no notes about a recommended twist).
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Old November 1, 2012, 03:40 PM   #36
FLChinook
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Hmm, poor choice of a title, this is not a disaster.
The point of exaggerated word-usage is well taken... We all are very sympathetic and concerned about the many folks affected by the true disasters associated with the recent storms.
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Old November 2, 2012, 09:13 AM   #37
three-fifty-seven
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I also had a new Zeiss 4.5-14 50 scope with Leupold rings on my previously-installed Leupold one-piece base.
I think I found your problem; see the quote below.

Quote:
A guy had a keyholing problem a while ago on another forum with his remington in 308. He racked his brain along with everyone else who offered up a possible reason for it. In the end it turned out that his scope was so far out that the bullets were actually hitting the ground in front of the target and skipping to the target.
http://w.snipershide.com/forum/ubbth...Number=2444749


I had a similar problem where it appeared my friend's rifle was keyholing but in reality it was an issue with scope adjustment.
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Old November 2, 2012, 09:38 AM   #38
rogn
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dont forget

Don't forget that if you have a marginally stable load and the temperature drops significantly, your stability may go right out the window. Temperatures below freezing can start the problem all over again.
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