7" twist 6x47L - did I choose poorly?

[kevwil]

I ordered a 25" Pac-Nor barrel a few weeks ago, chambered in 6x47L with the intent of shooting 105gr-108gr bullets such as Berger Hybrid, Nosler RDF, and Hornady ELD-Match. I went with a 3-groove 1-7" twist, based on Berger's "optimal" recommendation for the Hybrids. I see a lot of posts here where people use 8" twist with great success, and I'm a bit worried.

For what it's worth, I'm usually shooting between 5000 and 9000 ft elevation.

Am I going to be tearing bullets apart with such a fast twist? Or did I make the right choice for my bullet weight and elevation?

 

[Grimstod]

Good choice. You have to rip those bullets at 3400fps to get them to explode.

 

[SG4247]

My 6x47 is 7.5 twist Bartlien and its perfect for the 105s, 7.0 would be just as good.

This barrel seems to be a little slow (due to the twist rate?), or it might be some other factor.

 

[hogpatrol]

At those altitudes, an 8 would have worked but now you have the option to go with heavier custom bullets.

 

[kevwil]

At those altitudes, an 8 would have worked but now you have the option to go with heavier custom bullets.

I asked because it might not be too late to change my order, given their 10 week estimate. Ideally, I'd rather not leave speed on the table if I can be confident of the bullet stability at all distances. On the other hand, there are 125gr match bullets out there that I wouldn't try with an 8" twist.

 

[kevwil]

Good choice. You have to rip those bullets at 3400fps to get them to explode.

I figure with this barrel and 105gr projectiles I'll be in the 3000 - 3050 range.

 

[lawman29]

http://bulletin.accurateshooter.com/2016/01/the-effect-of-barrel-twist-rate-on-muzzle-velocities/

 

[XTR]

You will be fine, and if you ever want to shoot 115s your all set

 

[Cool Tool]

I asked because it might not be too late to change my order, given their 10 week estimate. Ideally, I'd rather not leave speed on the table if I can be confident of the bullet stability at all distances. On the other hand, there are 125gr match bullets out there that I wouldn't try with an 8" twist.

I have never waited 10 weeks for a gun barrel.

 

[Frankr]

I have a 1-7 twist in 6XC and I have not had any problems with it just as accurate as my 1-8 but I mostly shoot the 115's in it. I waited a year for it....Back when things were had to get...I ordered the barrel and they said around 10 months...SO I waited...

 

[TAJ45]

I ordered a 25" Pac-Nor barrel a few weeks ago, chambered in 6x47L with the intent of shooting 105gr-108gr bullets such as Berger Hybrid, Nosler RDF, and Hornady ELD-Match. I went with a 3-groove 1-7" twist, based on Berger's "optimal" recommendation for the Hybrids.QUOTE]


Don't forget the new
Sierra 110s.........needing a 7 tw. I have a 7.5Krieger set aside for a 6XC Long that I hope will stabilize them. Hoping to find a node at 3200 for F Class.

 

[hunter243sgk]

http://bulletin.accurateshooter.com/2016/01/the-effect-of-barrel-twist-rate-on-muzzle-velocities/

I would like to see a test like that done but with different grove rates. Like the 3 groove then a 5r ect,ect.

 

[missed]

I went 7" for the 105 hybrid's so far so good. Hopefully I'll finish load development next weekend

 

[XTR]

I would like to see a test like that done but with different grove rates. Like the 3 groove then a 5r ect,ect.

I don't think it's going to make a whole lot of difference, do you? It would be quite expensive in terms of barrels, components and time to generate a properly supported statistically valid study.

Bryan has alluded to, but I haven't seen him publish (doesn't mean he hasn't just I haven't seen it) is a study that evaluates spin decay as it relates to rifling type and groove count. That data would relate to stability and, at least for long range shooters, that might have a whole lot more value than determining which barrel is 8 FPS faster than another.

 

[hunter243sgk]

I don't think it's going to make a whole lot of difference, do you? It would be quite expensive in terms of barrels, components and time to generate a properly supported statistically valid study.

Bryan has alluded to, but I haven't seen him publish (doesn't mean he hasn't just I haven't seen it) is a study that evaluates spin decay as it relates to rifling type and groove count. That data would relate to stability and, at least for long range shooters, that might have a whole lot more value than determining which barrel is 8 FPS faster than another.

Do I? Well honestly I don't know. I have heard of people saying they did get higher velocity with a 3 groove. But I have not experimented with it so I honestly don't know. But I would bet there is at least a small amount of difference.if not more.

 

[XTR]

I'd personally like to see a lot of stuff in this sport/game tested with results that would stand up to be statistically valid, and I'd agree with you that grooves is one of them, though based on the results of the study listed above I don't think it will yield much.

 

[missed]

Mine is a 5R, I'll post my results next week

 

[swd]

Great choice in my opinion. Get some of the new 110 Sierras along with Reloader 16 and have fun!

 

[nvbroncrider]

I asked because it might not be too late to change my order, given their 10 week estimate. Ideally, I'd rather not leave speed on the table if I can be confident of the bullet stability at all distances. On the other hand, there are 125gr match bullets out there that I wouldn't try with an 8" twist.

I ordered a 26" with the same specs. I'm sure it will shoot like a house on fire what freebore did you go with? I went a .126 which starts a RDF @ -.018 @ 2.745" COAL

 

[kevwil]

I ordered a 26" with the same specs. I'm sure it will shoot like a house on fire what freebore did you go with? I went a .126 which starts a RDF @ -.018 @ 2.745" COAL

I didn't give a freebore specification because I wasn't sure what bullet I want to run.