Just trying to get some conversation going about twist rate for current Berger/Matrix 180's 190's. The standard now seems to be a 9 twist for the 180 VLD but how about the Hybrid Target or the 190 Matrix? Is the 9 twist still working? And with the 195gr possibly coming from Berger would it make sense to go 8.5 or 8 twist just in case? Does anyone use 8 twist with the 180's now? I read somewhere that the 180 VLD would come apart in an 8 twist at as low as 3100fps, can anyone confirm this? Seems to me like there would have to be some other variable at work for a bullet to come apart due to spin at that velocity. But if it is true what would that mean for bullets in the 168 range out of an 8 twist??
7mm...What twist rate for the heavies?
- Thread starter cdn shooter
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I am shooting a 190 Matrix from a straight up 284 winchester and a 9 twist barrel. So far I have not had positive results, I have talked to Marshall at Matrix and he thinks I will not be able to push it fast enough to stabilize, so far I would have to agree. I am going to try one more series of loads and see what happens and if I can not get decent groups I will go down to the Matrix 168s. I have not chronied them yet so I can not say what velocity I am getting, and the only powder I have tried is H4831SC although I do have a couple pounds of Reloader 17 that I will try too.
I have some 190 Matrix VLD's in the mail right now. I spoke to Marshal a while back and he said I should have no problem stabilizing them in my 7STW with a 1:9 twist barrel.
Unfortunately I probably won't have a range report until spring. Hopefully I can get them out over 3000fps.
Unfortunately I probably won't have a range report until spring. Hopefully I can get them out over 3000fps.
Mystic Precision
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In anticipation of the new Bergers and heavier 7mm, I have 8 twist barrels in the works.
All the 180's work with the 9 twist.
If you need to push the velocity to stabilize a bullet, the twist is certainly not to its liking (too slow). The only reason to consider using a slower then desired twist is if pushing so fast, concerned about jackets blowing up. That is not likely an issue with the 7mm jackets out of anything we would consider shooting.
Jerry
All the 180's work with the 9 twist.
If you need to push the velocity to stabilize a bullet, the twist is certainly not to its liking (too slow). The only reason to consider using a slower then desired twist is if pushing so fast, concerned about jackets blowing up. That is not likely an issue with the 7mm jackets out of anything we would consider shooting.
Jerry
Jerry, Would you expect any negative effects of running 180's out of an 8.5 twist? I've heard reports of consistency problems with the 8 and 180's but can't find anything on the 8.5. Another thing, have you heard anything regarding the release of the 195's. In other words, would a person want to build in anticipation for them now?
My barrel is a Broughton and 24" so I think it might be a little short to get the maximum velocity from this set up, however I wanted something that I could still carry in the field with relative ease. I don't know if more velocity will straighten it out or not, I am already at or very near the maximum that I am willing to go with H4831SC, thats why I mentioned Re17, apparently it gives more velocity but I am not sure about it's temperature stability. Will have to see how it plays out.
Nice! Who's the barrel maker? And what sort of accuracy are you finding with it?
The 180 VLDs that came apart were the hunting bullets, I believe. They use a thinner jacket than the target bullets. I had the same issue with Matrix 117gr. in 6mm when they first came out. At 3150 fps, half of them didn't make it to the target at 500 yards. Then Marshal changed the jacket and I was able to lauch them at 3250 fps without any issues. The new bullets have a much higher BC too.
I got an 8.5 twist in anticipation of the new Berger. But, this is a big magnum. I would go with an 8 twist with a 284 sized case. Bryan has said that 8.5 is the slowest he recommends for the 195.
I got an 8.5 twist in anticipation of the new Berger. But, this is a big magnum. I would go with an 8 twist with a 284 sized case. Bryan has said that 8.5 is the slowest he recommends for the 195.
Mystic Precision
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the issues are likely more tied to pressures and trying to hit a certain speed then anything else. The tighter the twist, the sooner you are going to max out useable pressures for any given case volume.
1" faster twist is not going to hurt these big bullets at 284 type speeds. I doubt it would make a difference even if pushing 200fps faster. BUT when shooters try to make a small case run like a big case, you can have some real fussy set ups.
When we set up Open rifles, we are trying to be super picky about every single variable and with the performance desired, every little bit helps. A growing number of shooters are moving away from the 284 case simply because hitting the 2900fps node is not always possible and some even want to go faster.
Larger cases like the 280/improved, RSAUM, and WSM can hit these speeds without breaking a sweat and allow more top end if desired.
the quirks and likes of any one barrel is going to limit what the max ACCURATE speed is. Keeping pressures lower by pushing more slow burning fuel down the bore almost always leads to higher speeds without a lot of fussy tuning.
YMMV.
Jerry
Mystic Precision
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Here is a prime example of what I mean. Burning over 10grs more slow powder to reach similar speeds then the 284/Shehane. Tuning is a breeze.
I went 8 twist instead of 8.5 cause we have no idea what the final super monsters are going to like AND being 1/2 twist too much is better then 1/2 twist too little.
This new Bergers, and of course Matrix, Sierras and others to follow may change the landscape for what is "the best" F Open set up. Should be a very interesting couple of seasons.
Jerry
gunrunner8
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All this mumbo jumbo and guessing would be avoided if producers would state the minimum RPM (and maximum) on each and every one box of bullets.
Lets say for instance 7mm 175gr SP bullet needs 180 000 RPM to stabilise. I have 7mm Weatherby Mag with 12" twist so I must achive min 3000FPS to get that 180 000RPM. The other shooter has 7mm RM with 10" twist so he has to push the same bullet min 2500FPS to stabilise it.
Without full disclosure from bullet makers all our guessing doesn't make any sense.
Lets say for instance 7mm 175gr SP bullet needs 180 000 RPM to stabilise. I have 7mm Weatherby Mag with 12" twist so I must achive min 3000FPS to get that 180 000RPM. The other shooter has 7mm RM with 10" twist so he has to push the same bullet min 2500FPS to stabilise it.
Without full disclosure from bullet makers all our guessing doesn't make any sense.
Really seems like there are intangibles though that cause one set of variables to produce accurate results where another setup that "should" work, doesn't. A 180 vld should work perfect with an 8 twist but is seems (results show) that it works best at 9 twist, which is right at the edge of not having enough rotation. I'm going to gamble and go 8.5, I will only shoot a couple matches this year so I can definitely afford to experiment. I'll be sure to post my results as it seems there is very little data out there at the moment.
I'm using a krieger and it drops them on top of each other when I'm doing my part. Rem action, MDT TAC 21 chassis with a bench rest adapter. Sightron 10-50. Rem brass. Mcphee did the work. It's a riot to shoot. I could have pushed it harder but didn't see the point. I have it's twin in a SA in 6 BRX.
You're going to have to share some more info on the rifle, barrel length, twist, chambering, load?
The red chassis is the following: Rem 700 LA in 7 Rem Mag, Krieger 32" x 1.30, 1-8.5, Sightron 10-50x60 in a 20 min alpha mount. Rem brass, fed 215M, 69 gr of retumbo, 180 gr Berger VlDs @ 2950 fps. MDT Tac 21 chassis with custom bench rest adapter, PRS stock with MDT adjustable butt system, Ergo grip. All groups are shot @ 200 yds.
The green is a Rem 700 SA, 6 BRX, Krieger 28" x 1.3, 1-7. Load info is on the target.
Hope that satisfies your curiosity, Piper.
The green is a Rem 700 SA, 6 BRX, Krieger 28" x 1.3, 1-7. Load info is on the target.
Hope that satisfies your curiosity, Piper.
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The red chassis is the following: Rem 700 LA in 7 Rem Mag, Krieger 32" x 1.30, 1-8.5, Sightron 10-50x60 in a 20 min alpha mount. Rem brass, fed 215M, 69 gr of retumbo, 180 gr Berger VlDs @ 2950 fps. MDT Tac 21 chassis with custom bench rest adapter, PRS stock with MDT adjustable butt system, Ergo grip. All groups are shot @ 200 yds.
The green is a Rem 700 SA, 6 BRX, Krieger 28" x 1.3, 1-7. Load info is on the target.
Hope that satisfies your curiosity, Piper.
You have some issues there, better look into that vertical stringing of the 6 BRX. LOL. Nice groups and nice rigs!
