7mm barrel twist ?

[bighorn06]

Need input to make decision if I can go with less than 1-9 twist using the berger 180VLD & 180 Hybrid at 1000 yds. MV 2900 fps min, generaly 2975 to 3000+ Thanks, Mike

 

[TonyR]

I have fired thousands of the Berger 180VLD in 1000 Yard F-Class using the 1:9 twist at 2900 fps without problems but rarely at temps below 50 degrees. No stability problems. I also have a 1:8.5 and I don't see any difference.

 

[Jeffvn]

I have shot the Berger 180 VLDs from my 7WSM with a 28" 1:9 twist in all conditions in Vegas, down into the 20s, with no stability issues.

JeffVN

 

[bighorn06]

Thanks guys, I also have not had any problems with the 1-9 twist. In my endeavor to improve my competion shooting ability I propose the theory that a slower twist, say a 1-9.5, or 1-10 would reduce the torque and help the gun to track better for faster follow up shots. I know the 1-9 recomendation has to cover slower calibers, so there should be some room here for the faster ones to still stay stable at 1000 yds. Hoping some of you long timers have been here before or have the programs to predict the outcome. Thanks for any shared knowledge, Mike

 

[TonyR]

Here is a link to an article about bullet stability including the Miller Twist Rule

http://www.jbmballistics.com/ballistics/bibliography/articles/miller_stability_2.pdf

 

[Kyle Schultz]

The following thread had a strong influence on me chosing a 1:9 twist.

http://www.accurateshooter.com/forum/index.php/topic,3737115.0.html

 

[lurcher]

Sorry to drag this off topic a little. I bought a 7mm barrel with a 1in8 twist from a guy who folded on a project. I have a 7mm saum and I'm currently shooting 140 and 160 grain bullets out of it. It is a hunting rifle with a 22 inch barrel. If I rebarrel I probably won't want to go over 24 inches due to the portability factor (I use a supressor which extends beyond the barrel by about 4 inches)


Is the 1in8 twist rate too quick to stabilise they lighter bullets? would I be best to use this barrel for another project involving heavier bullets?

 

[smoking-brass]

Yes....and Yes

 

[Erik Cortina]

Sorry to drag this off topic a little. I bought a 7mm barrel with a 1in8 twist from a guy who folded on a project. I have a 7mm saum and I'm currently shooting 140 and 160 grain bullets out of it. It is a hunting rifle with a 22 inch barrel. If I rebarrel I probably won't want to go over 24 inches due to the portability factor (I use a supressor which extends beyond the barrel by about 4 inches)


Is the 1in8 twist rate too quick to stabilise they lighter bullets? would I be best to use this barrel for another project involving heavier bullets?

No... And No! ;D

I had a 280 AI and it had a 1:8" twist barrel, I shot 160 gr. Nosler Accubonds out of it and 175 gr. Matchkings, it was very accurate with both bullets. Just use what you have, it will work just fine!

 

[bighorn06]

I went on JBM and run some variables. I had never used this before as I didn't think that I knew enough to use it. It wasn't that hard. My results say that 1-9.5 is probably ok, but 1-10 is probably marginal except in warm higher elevations. Thanks for the help, Mike

 

[RossL]

If you want less torque,how about going with a 1 in 10 maybe 1 in 11 and using the 168 VLDs instead of the 180s?

I used JBM's program, Bryan Litz's G7 BCs and cannot little difference in wind drift out to 1000 yd. The 180 may have higher BC but 168 makes up for its slightly lower BC with higher velocity. Am I missing something?

 

[bighorn06]

Thanks Ross, I haven't shot any of the 168vld but have shot the 175 xld, and they have done well. I, like every one need some good weather to make some factual determinations. Based on JMB, I believe I could go to a 1-10 for the 175 xld. Berger recomends a 1-10 for the 168 vld. I think I will try and see what happens. That is the only way to find out. I have been waiting for a very experienced barrel builder to calculate his opinion, but am not very patient, so will try to get it built.

 

[AckleymanII]

Here's your sign!!!

If your barrel will stabalize a 180g Berger VLD, it will stabalize any bullet lighter than that in the Berger, Nosler, Sierra, Speer, and Hornady line.

 

[bighorn06]

Thanks Keith, Berger recomends a min of 1-10 for the 168 VLD so that pretty well says that anything lighter will stabilize for 1-10. I believe the 180 Hybrid will be the dominate bullet for 1000 yd and as stated in my origional post would like to use a 1-9.5 or even a 1-10 for it to reduce the torque so to stay on target better. So far no one seem to know for sure so I am ordering both to find out. I should know in about 6-12 months. Mike

 

[sailhertoo]

6 to 12 months ! ?

You sound like some of our suppliers!

We need info now!! Just kidd'en

 

[Erik Cortina]

Thanks Keith, Berger recomends a min of 1-10 for the 168 VLD so that pretty well says that anything lighter will stabilize for 1-10. I believe the 180 Hybrid will be the dominate bullet for 1000 yd and as stated in my origional post would like to use a 1-9.5 or even a 1-10 for it to reduce the torque so to stay on target better. So far no one seem to know for sure so I am ordering both to find out. I should know in about 6-12 months. Mike

A 1:9" works for sure, no need to re-invent the wheel, is there?

My 284 Shehane has a 1:9" twist and it does not torque, it used to, but not anymore. It's all about learning how to shoot your gun. My gun tracks so well that as long as conditions hold I don't even have to move my joystick, just push the gun back to the bump stop and squeeze trigger again, it tracks that good!

I just don't think 1:9.5" will make enough difference to be able to tell, most guys that shoot the 180's are using 1:9" and some 1:8.5", and most can get their guns to track well.

Just my $0.02

 

[bighorn06]

Thanks Erik, Some times we need a reminder that it isn't the gun at fault. I have definatly seen an improvment. My slower loads from 2900 to 2950 don't torgue bad at all, but for the 3000 to 3050 I would like to improve. Maybe it's time to work on the bag lube to get the rifle to slide better. I havn't given that much thought, but your post got me to think about that. If I may ask what speed are you running at? Thanks again, Mike

 

[Erik Cortina]

I'm running the 180's at 2930 fps., and after working on my setup, I can now free recoil my Shehane and it track great. I have a Magnum in the works, it should be going 3000 fps. with the 180's, I hope my gun still tracks good at those speeds, if not, trigger time will cure that! ;D

 

[bighorn06]

Mine is a SAUM and 3000 to 3050 is not hard to get. I had my barrel Nitrided and it seems to be getting faster. Mike