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October 30, 2012, 10:22 AM | #26 | ||
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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. Quote:
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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October 30, 2012, 11:28 AM | #27 | ||
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October 30, 2012, 11:31 AM | #28 |
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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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October 30, 2012, 10:06 PM | #29 |
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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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October 30, 2012, 10:52 PM | #30 | ||
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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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October 31, 2012, 01:06 AM | #31 | |
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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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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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November 1, 2012, 12:02 PM | #33 |
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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. |
November 1, 2012, 02:39 PM | #34 | |
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Sierra GK .253 Barnes TSX .249 Barnes website lists 1/9 or faster for that bullet. |
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November 1, 2012, 02:54 PM | #35 | |
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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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November 1, 2012, 03:40 PM | #36 | |
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November 2, 2012, 09:13 AM | #37 | ||
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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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November 2, 2012, 09:38 AM | #38 |
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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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August 31, 2016, 12:10 PM | #39 |
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Barnes TTSX Keyholing in 257 Roberts
I have three 257 Roberts rifles that I am hand loading for. I tried some Barnes TSX FB bullets in 115Gr and this is the first time I ever experienced key holing while shooting from my Nosler Trophy Grade rifle (1/10 twist). These were loaded with 40g of IMR 4831 and OAL was 2.80. I shot the same load from my Savage 257 Roberts (also 1/10 twist) and no key holing (though poor grouping). After trying about 6 different load combinations I found a load that shoots 3/4" or better in all three rifles. That load is the 100 GR Barnes TTSX BT (with the blue tip) with 42g of RL19 at OAL 2.80. I also got similar accuracy using the 100GR Nosler ballistic hunting tip with 40g of IMR 4350.
I have not tested in the Winchester yet but am hoping the 100 GR Barnes TTSX BT with the 42g RL19 may be my go-to load for all 3 rifles. When you combine all the possible combinations of bullets and powders and then add the factor of 3 different rifles, this stuff can drive you insane. I wanted to post this in the event that it helps somebody looking for a Roberts load and also, cause the key holing was a whole new experience for me that I don't want to repeat. |
August 31, 2016, 05:47 PM | #40 |
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If you look at the stability/twist calcs for that bullet, you need
at least a 1:9 for it to function at any reasonable velocity -- -- even for a Weatherby. |
September 1, 2016, 08:01 AM | #41 | |
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I have measured free bore, I have found chambers that allowed the bullet to leave the case and travel .300" before hitting the lands; now that is huge. At the same time I found 300 Win Mag shooters that wanted to jack up the 300 WM. F. Guffey |
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September 1, 2016, 12:41 PM | #42 |
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Barnes
As others have said this might be a free bore issue in conjunction with an elongated bullet.
Have you tried to slightly seat your bullet in a case and chamber it to see where it encounters the lands/grooves? Try this and adjust your seating die to approximately 1/10th inch before bullet contact and see what happens. My experience with Barnes TTSX in 7mm out of a 7x30 Waters have been -1/2-inch MOA at 100yds. Good luck and let us know what happens.
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September 1, 2016, 06:05 PM | #43 |
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It's a Weatherby, right? Good luck seating it out to touch the lands. With the high intensity Weatherby rounds, the freebore is there for a reason. It's the running start of which Mr Guffey speaketh.
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September 1, 2016, 06:16 PM | #44 |
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What is the length of the two bullets??? I would expect the TSX bullet to be quite a bit longer?? William
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September 1, 2016, 06:39 PM | #45 |
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1.228"
http://www.midwayusa.com/product/112...free-box-of-50 Which is why I said it required at least a 9 twist rate -- or faster -- even with a Weatherby |
September 1, 2016, 07:57 PM | #46 |
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The shorter flat base Sierra bullet would/should give considerable better accuracy than an all copper longer length TSX bullet, I wouldn't be surprise the TSX bullet would be .050" or longer than a lead core hunting bullet!! William
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