6 dasher is 7 twist too much

[shoot4fun]

I don’t think the two are connected. Stability is affected by the air density, but blow ups would be purely an issue with rpm and centrifugal force.

Berger uses the work stability in providing data on whether or not your TWIST RATE is proper for the bullet you are using. My examples above show the effect of air density (altitude) on twist rate. I can say my overall results with the 6's improved when I went from my old standard 8 twist to a minimum of 7.5 in selecting barrels.

 

[Evan]

Lower velocity is one

I'm curious just how much we're talking here with a Dasher. Most guys find best accuracy well below max speed, so does a faster twist mean that you just add another 0.2gns and you're still in the sweet node anyway?

 

[Evan]

After my experience with my 22BR I don't think I will ever setup another rifle that spins heavy bullets with a long bearing surface faster than 300k rpm. I think that's the red line where you cross into bullets going poof.

 

[Dusty Stevens]

I'm curious just how much we're talking here with a Dasher. Most guys find best accuracy well below max speed, so does a faster twist mean that you just add another 0.2gns and you're still in the sweet node anyway?

Probably. Im the guy that uses the slowest twist that will stabilize the bullet. It comes from hanging around br guys. They could shoot 10tw but why do they use 14 or 15?

 

[Evan]

Probably. Im the guy that uses the slowest twist that will stabilize the bullet. It comes from hanging around br guys. They could shoot 10tw but why do they use 14 or 15?

Agreed. I've seen the light, <300k rpm and Sg of >1.2. If you can't hit those parameters then be ready for trouble.

 

[shoot4fun]

Probably. Im the guy that uses the slowest twist that will stabilize the bullet. It comes from hanging around br guys. They could shoot 10tw but why do they use 14 or 15?

100/200 (rarely 300) yards in one case v. 600/1,000 (or farther for PRS) yards in the other. Lot of things happen past that 200 yard marker.

 

[Dusty Stevens]

100/200 (rarely 300) yards in one case v. 600/1,000 (or farther for PRS) yards in the other. Lot of things happen past that 200 yard marker.

If you think a shortrange rifle not need to be near as precise as a prs rifle you should tune one up and try to compete or even agg for fun at 100/200. If what you say is true then it shouldnt be an issue shooting a 68gr bullet in a 7tw barrel and win all the prizes

 

[spclark]

I don’t think the two are connected. Stability is affected by the air density, but blow ups would be purely an issue with rpm and centrifugal force.

Stability can be affected by twist rates faster than what are considered as ‘optimum’ for bullet length. Problem being the faster the twist the greater impact centrifugal force has on bullet jackets and the center of gravity for the cores. Inherent defects are magnified by twists faster than ‘normal’.

Velocity of course play a part; push bullets fast through too-fast a twist you’re only making things worse for those projectiles.

I’m messing with a 7mm wildcat right now that I first fired in a 1:9 30” Brux. With Berger 180 Hybrids @ 2,800 fps I fired 200-15x in 2016. New barrel’s a 1:8.5, I want to see if I can maybe find a lower node w/o sacrificing accuracy at a lower chamber pressure by going to a faster twist.

Go too fast, bullets can’t hold it together going down-range.

 

[spclark]

Probably. Im the guy that uses the slowest twist that will stabilize the bullet. It comes from hanging around br guys. They could shoot 10tw but why do they use 14 or 15?

I know a Palma Team member likes to shoot 155 Hybrids in 1:15 twist barrels. Everybody else goes to 1:12 or faster.
He has his barrels made with very shallow lands so bullet deformation is significantly less, then loads Palma brass to (what some would consider insane loads) provide 3,200 fps muzzle velocity.
Works for him really well! Hard on brass though.

Maybe BR folks take the same philosophy? Slow twist for bullet length but push ‘em hard?

 

[shoot4fun]

If you think a shortrange rifle not need to be near as precise as a prs rifle you should tune one up and try to compete or even agg for fun at 100/200. If what you say is true then it shouldnt be an issue shooting a 68gr bullet in a 7tw barrel and win all the prizes

I shot short-range for quite a few years my friend. I know cousin Billy and Bart well and was schooled by the likes of Jeff Graves and Steve Lee. oh, and I've never shot a PRS match and have no intention of doing so.
You misunderstand my point sir. I totally agree that inside 300 yards the 14 twist with 68's was and is the king. I still have a CZ527 wearing an old PPC barrel that will hammer prairie dogs out past 400 yards on a calm day.
The much longer distances require a different though process. Technically, a 10 twist 6mm barrel would stabilize the 105's but it isn't ideal for launching them way out there. For that I'll choose the 7 or 7.5 every time.

 

[steve123]

It's quite funny you said that bought Berger 55grain 20 caliber back in the day recommendations was an 8 twist I was shooting 20x47 lapua at 3920 fps at 700 ASL an proof bullet blows up made a 9 twist guess what happy camper.Thanks for your comment.

My 20x47 was blowing up those same bullets in a 9 twist Krieger in less than 300 rounds. It was fine at first...
Had to go with 40vmax slowed to 4100 fps, that worked but for how long?? I haven't used that barrel in years so I might not find out.

Now my 223AI is starting to do weird things with 88's in a 7 twist.

Darn, I guess Murphy has it out for me??!!

I'm with Evan on this subject. I'm just going to stick with normal bullets weights and lengths and aim a little farther out for wind. Well unless I want to try solid alloy projectiles for whatever reason.

 

[Evan]

I'm with Evan on this subject. I'm just going to stick with normal bullets weights and lengths and aim a little farther out for wind. Well unless I want to try solid alloy projectiles for whatever reason.

Yep. Need more BC? Step up a caliber. I'm thinking it goes like this: 80s in 22, 105s in 243, 140 in 264, 180 in 284, and 210 in 308.

 

[FrankG]

Bryan Litz put that to rest a few years back. The amount it reduces velocity is insignificant from an 8" to a 7". I was as surprised as anyone..
http://bulletin.accurateshooter.com/2015/02/does-barrel-twist-rate-affect-muzzle-velocity-litz-test/

Correct. For the most part twist does not effect pressure and or velocity. It might but as has been pointed out it’s virtually insignificant. The bore and groove size varying and or the difference in chambers will effect you more.

We’ve done test barrels in multiples of different calibers using the same chamber reamer etc...and the only difference being was the twist rate and all of the data supported that as well.

Calibers that have been done in and not in any particular order... .223/5.56mm, 6.5CM, .260 Rem., .308win, .300wm, .300 Norma, .338 Lapua, .338 Norma are some that come to mind.

Later, Frank
Bartlein Barrels

 

[dcali]

I've said it before, but I believe most shooters outside of BR circles spin their bullets too fast. The benchrest guys get it.

 

[FrankG]

I've said it before, but I believe most shooters outside of BR circles spin their bullets too fast. The benchrest guys get it.

In some cases I’ll say yes that the bullets can get spun to fast.

That being said even some of the BR guys are going to a slightly faster twist and if I recall correctly the late Mike Walker when they came out with the 6BR originally recommended a 1-13 twist (if I recall correctly) and not the 14 and 15’s that where being run.

I’ve said it before and I’ll say it again....you can run the twist to slow/be on the ragged edge of stabilizing the bullet. The old saying around BR stuff is at the ragged edge is where you find your best accuracy but you get into different climate conditions, elevation and or lower than expected velocities etc...and you then run into accuracy issues as well.

Also in a really fast twist if you shoot poor quality bullets and or your loaded ammo has too much runout a faster twist can work against you but my experience is good bullets/good ammo and you don’t get hurt as much as some think.

Not a BR comparison but 30+ years ago when shooting Service rifle. I was just starting to load/shoot AR15’s and AR’s where in they’re infancy back then. The heaviest bullets you could find where 68 Hornady’s, 69SMK and 70 VLD’s. I had a rack Colt AR15a2 with a factory 1-7 twist barrel. That gun would shoot the 69SMK at 3/4moa at a 100 yards. Shoot 55gr ball ammo and on average 2 out of 5 bullets would go thru the target sideways at a 100 yards. Loaded up some 52gr Hornady HPBT match bullets and those would shoot 3/4moa just like the 69SMK would do. Yes I tested the bullets/ammo on the same day in the same conditions. Those 52gr bullets would fly thru a 1-9 twist and even 14 twist barrel as well as I shot them in Prairie dog rifles. The difference here was the quality of the bullets/ammo more than anything else.

Later, Frank
Bartlein Barrels

 

[kyreloader]

My last 600 yard midrange Fclass match, I won with a 597 shooting 115g Berger VLDs out of my 1:7 twist Dasher.

 

[johara1]

In some cases I’ll say yes that the bullets can get spun to fast.

That being said even some of the BR guys are going to a slightly faster twist and if I recall correctly the late Mike Walker when they came out with the 6BR originally recommended a 1-13 twist (if I recall correctly) and not the 14 and 15’s that where being run.

I’ve said it before and I’ll say it again....you can run the twist to slow/be on the ragged edge of stabilizing the bullet. The old saying around BR stuff is at the ragged edge is where you find your best accuracy but you get into different climate conditions, elevation and or lower than expected velocities etc...and you then run into accuracy issues as well.

Also in a really fast twist if you shoot poor quality bullets and or your loaded ammo has too much runout a faster twist can work against you but my experience is good bullets/good ammo and you don’t get hurt as much as some think.

Not a BR comparison but 30+ years ago when shooting Service rifle. I was just starting to load/shoot AR15’s and AR’s where in they’re infancy back then. The heaviest bullets you could find where 68 Hornady’s, 69SMK and 70 VLD’s. I had a rack Colt AR15a2 with a factory 1-7 twist barrel. That gun would shoot the 69SMK at 3/4moa at a 100 yards. Shoot 55gr ball ammo and on average 2 out of 5 bullets would go thru the target sideways at a 100 yards. Loaded up some 52gr Hornady HPBT match bullets and those would shoot 3/4moa just like the 69SMK would do. Yes I tested the bullets/ammo on the same day in the same conditions. Those 52gr bullets would fly thru a 1-9 twist and even 14 twist barrel as well as I shot them in Prairie dog rifles. The difference here was the quality of the bullets/ammo more than anything else.

Later, Frank
Bartlein Barrels

Frank, We were testing the M-16 in the mid 60's.... that is almost 55 years ago....... jim

 

[FrankG]

Frank, We were testing the M-16 in the mid 60's.... that is almost 55 years ago....... jim

Yep and the stuff comes around full circle every once in a while! LOL!

 

[johara1]

Frank, we were testing it against the Stoner and the M14..... how time flies ...... jim