Potential downsides to fast twist barrel?

[Wilderness Blacktail]

Thanks J.E!
Gettin good info on the nuances of twist rate for sure.
I'm lookin at 7twist in 25 caliber, for the heavier hammers as well as 110 Badlands bullet available at present.
7inch in the 6.5 for all the stuff I shoot now (in 1:7) plus what's coming.
27 & 28 cals I'm leaning towards 8 in both but not as sure.
The .277 heavies are there with more to come but not sure if I wanna shoot the heaviest bullets as then recoil and muzzle jump come into play and make seeing hits much harder. The 28, I'm sure I don't wanna twist myself out of shooting 140 class bullets.
Hence the post. Lol

 

[Craig Miller]

This is something I am still undecided about the advantages and disadvantages.

In theory the gain twist appears to have all the advantages, but in actual use that doesn't appear to prove out.

I have had several and still do own one, and being anal I try to look at fired bullets to inspect the engraving on the bullet and find that the best, most uniform engraving Is with slower twist rates and the worst looking is the gain twist. The fast twist rates are in between in quality and uniformity.

As far as the most accurate, the standard rifling, proper grove count and twist rate has been the best for me.

Just my experience with different twist designs.

J E CUSTOM

Thank you very much. That generally tracks with what I have been reading elsewhere but it's never been an actual rifle smith giving his experience.

 

[J E Custom]

There is another video on this that he made but I have to search more.

That is a very good VIDEO !!!! and should help explain some of the pitfalls of fast twist rates.

J E CUSTOM

 

[AZShooter]

I can tell you based on experience that with a 1 in 7 twist 3 groove barrel was too much for 180 VLD Bergers both hunting and target versions. My friend made a 7 STW and I made a 7 Rem mag. We used 30" Lilja 3 groove 1 in 7 twist barrel as that was all he offered at the time that would stabilize the 180 Bergers. I see now that there is a 1 in 8 which is also a 3 groove.

Friend's rifle began to damage the 180 hunting VLDs around round count 100 and mine did the same at approximately round count 200. The result was bullets that diverged many inches from the point of aim at 100 yds.

Dan quit on this project and rebarreled to another configuration. I switched to the thicker 180 target VLDs. After another 75 rounds or so the barrel began to damage the bullets. I then tried moly which helped for a while then quit working.

Switched to an 140 accubond and also a Barnes TTSX and issue didn't show again.

Our conclusion on why those bullets failed is a combination of faster than required twist and being a 3 groove barrel. Why the delay in damage? We think the throat became rough and the amount of shots fired with the STW with its greater powder charge caused it to go first. Perhaps the 30" barrel was also a factor as it can create more friction heat transferred to the barrel. See this article written by Berger:

Bullet failure article

Found this over on BR Central in the 1000 yd forum. Interesting. [ QUOTE ] Bullet Failure Causes and Solutions Defined -------------------------------------------------------------------------------- As many of you know we have been working on the bullet failure (blow up) situation for...

www.longrangehunting.com

FYI RPMs for the two rifles:
7 STW 318, 857
7 Rem mag 303,428

If you shoot monos you will avoid this issue of bullet failure should you get a faster twist barrel. I remember decades ago Steve Shelp and a friend both made 6.5-300 Weatherbys for hunting. It was a wildcat back then. Steve remarked that he had a faster twist barrel than his friend's and he swore the faster twist rifle killed more dramatically.

 

[MagMan]

I had the same barrel in 7RUM. Tore up a lot of bullets but the 160 AB's shot great at 349,000.

 

[J E Custom]

Thanks J.E!
Gettin good info on the nuances of twist rate for sure.
I'm lookin at 7twist in 25 caliber, for the heavier hammers as well as 110 Badlands bullet available at present.
7inch in the 6.5 for all the stuff I shoot now (in 1:7) plus what's coming.
27 & 28 cals I'm leaning towards 8 in both but not as sure.
The .277 heavies are there with more to come but not sure if I wanna shoot the heaviest bullets as then recoil and muzzle jump come into play and make seeing hits much harder. The 28, I'm sure I don't wanna twist myself out of shooting 140 class bullets.
Hence the post. Lol

I have re barreled a few different rifle calibers 1 in 7 twist rifle because they went to fast on the twist rate and did not perform as good as they should. (There could be many reasons for this) but with a 1 in 8 twist they all shot better according to their owners. I assume that they loaded the same way and used the same bullets that they wanted to in the first place.

I would think that a 1 in 8 would be a good twist for what you want and with the cartridges you will use. you don't have to go with a fast twist to get accuracy, you do have to load good ammo though.

This is just My opinion.

J E CUSTOM

 

[J E Custom]

I can tell you based on experience that with a 1 in 7 twist 3 groove barrel was too much for 180 VLD Bergers both hunting and target versions. My friend made a 7 STW and I made a 7 Rem mag. We used 30" Lilja 3 groove 1 in 7 twist barrel as that was all he offered at the time that would stabilize the 180 Bergers. I see now that there is a 1 in 8 which is also a 3 groove.

Friend's rifle began to damage the 180 hunting VLDs around round count 100 and mine did the same at approximately round count 200. The result was bullets that diverged many inches from the point of aim at 100 yds.

Dan quit on this project and rebarreled to another configuration. I switched to the thicker 180 target VLDs. After another 75 rounds or so the barrel began to damage the bullets. I then tried moly which helped for a while then quit working.

Switched to an 140 accubond and also a Barnes TTSX and issue didn't show again.

Our conclusion on why those bullets failed is a combination of faster than required twist and being a 3 groove barrel. Why the delay in damage? We think the throat became rough and the amount of shots fired with the STW with its greater powder charge caused it to go first. Perhaps the 30" barrel was also a factor as it can create more friction heat transferred to the barrel. See this article written by Berger:

Bullet failure article

Found this over on BR Central in the 1000 yd forum. Interesting. [ QUOTE ] Bullet Failure Causes and Solutions Defined -------------------------------------------------------------------------------- As many of you know we have been working on the bullet failure (blow up) situation for...

www.longrangehunting.com

FYI RPMs for the two rifles:
7 STW 318, 857
7 Rem mag 303,428

If you shoot monos you will avoid this issue of bullet failure should you get a faster twist barrel. I remember decades ago Steve Shelp and a friend both made 6.5-300 Weatherbys for hunting. It was a wildcat back then. Steve remarked that he had a faster twist barrel than his friend's and he swore the faster twist rifle killed more dramatically.

I also built a 7 STW For speed that had a 31" barrel. it had a 1 in 9 twist and was a 6 grove Lilja.
It was intended to shoot 140 grain bullets at blazing speeds and flat trajectories.

As I worked up to top velocities It got better and better until I reached 3800 ft/sec, then things went south, I backed off and regained the accuracy at just over 3750 ft/sec. so I decided to do a impact test at 100 yards to 600 yards to see if I could find the problem. (I still wasn't getting high pressure signs).

It all came to light at 100 yards. I was throwing the jackets at the muzzle. it was very clear with two odd looking holes in the target, I tried the 3700 ft/loads and they produced beautiful little bug hole groups. I also did my digging trick in the berm to try and recover a decent bullet to look at the engraving. I did find a few but they were well destroyed, so no real rifle engraving results.

With jacket loss I decided the same as many others have suggested and went to a mono metal bullet. They held up well but I could never get the accuracy out of them because apparently I was reaching near 400,000 RPM and there balance was not perfect (To bad Hammer Bullets were not around at the time). After realizing I had reached the bullets limit, I backed off to 3700 ft/sec velocities and they performed well. The longest shot that I made with this rifle and load was just over 800 yards and the hog looked like he was hit by lightning.

I did recover some of these bullets from this load and the engraving on the bullets looked great with the 6 grove barrel. I have many 3 grove barrels that perform well but they are slower twist at higher velocities and most bullets are able to handle the velocity in the slower twist, The only rifle that reached bullet destruction at/in the barrel is a 223 wssm in a 1 in 15 twist @ 4600+ft/sec velocity.

So depending on what velocity and caliber you choose, twist rate and grove count can be important for best performance.

Chose wisely!!.

J E CUSTOM

 

[BKM]

Good info guys. This issue has been debated amongst the smokeless muzzle loader community as well.

While most SML's are 40's & 45's they are achieving velocities well over 3000 fps.
With too fast of twist barrels the spin drift is terrible even if the bullet stays together and doesn't spin the jacket off


Many of the modern mzl bullets come with the aluminum tips. When shooters try to figure their Miller stability they measure the entire length of the bullet (tip included) and this skews their information.

This was a very good video and explains the negatives of a bbl with too fast of twist very well.
Think about it , if too much twist wasn't a problem, barrel manufactures could simply make all barrels with a fast 6 twist and that would cover any bullet we choose to shoot.

I apologize OP. Didn't mean to derail ur post.

 

[Wilderness Blacktail]

I can tell you based on experience that with a 1 in 7 twist 3 groove barrel was too much for 180 VLD Bergers both hunting and target versions. .. I see now that there is a 1 in 8...

Our conclusion on why those bullets failed is a combination of faster than required twist and being a 3 groove barrel. Why the delay in damage?

Great info AZ. That must have been a major bummer to find that out like that.
So what twist is recommended for that bullet? You were 1inch too fast?

How much slower do you think you would have to run them to not have that issue? Thinking about case size/velocity vs twist to switch up the acceptable combinations.
As in my 26" 7twist 6.5CM shoots everything well tho I havent shot a 7 twist bullet yet, but I dont thing the same would be true of my 6.5-300wby right?

 

[Wilderness Blacktail]

I have re barreled a few different rifle calibers 1 in 7 twist rifle because they went to fast on the twist rate...
I would think that a 1 in 8 would be a good twist for what you want and with the cartridges you will use.
J E CUSTOM

J E,
Great info, this is exactly why I posed the question here.
Miles of BlackJack bullets has cautioned the same line...too fast and you risk integrity issues, too slow and you negate the benefits of long accurate high BC bullets.

 

[IHFarmer07]

Found the other video on this.....probably not as good as the other like I thought.

 

[sedancowboy]

Very good discussion! Thanks to all who have contributed.
With my limited mind. I don't think there is such a condition as over stabilization. Can we spin the bullet too fast for conditions, absolutely we can but that does not mean that the bullet is over stabilized. It means that the bullet failed in its construction at the speeds we are pushing them.
We have in several instances reached the point of failure in the integrity of the bullets. Several factors contribute to this failure. Rough bores or throats, possible long barrels which heat the bullet more as well as air resistance heating them. Remember Hornady discovered that their plastic tips were heating up and failing at high speed and distance from air resistance.
When I wrote post #2 I was simply stating a fact. I was not stating that bullets do not fail because we are spinning them too fast. Simply put we need to optimize the spin rate/twist to match the bullet we select at the speed we intend to shoot it at.
As we push the envelope of the ballistics and projectiles we use we will find their weak points and find ways around them hence the monos. I am not convinced that the RPM rate causes the bullet to approach a distance target at a
drastically different attitude than a slower one that is only barely stabilized. I would need to see more proof than the video provided. I am not saying he is wrong just that I personally need more evidence. I think a bullet will always approach a distance target at a nose up attitude until it is unstable or falling straight down.
We are so used to thinking in terms of Revolutions per Minute and Feet per Second till I think we need to think in the same measurement of time. RPS and FPS. An example is a bullet at 3200 FPS with a 1/8 twist is 4848 RPS.
I also wonder if heat from air resistance is not playing a larger roll in bullet failure that we first thought. I suspect that the bullets are getting very hot at the speeds that are causing complete disintegration. Think space shuttle tiles. I have also been convinced that a fully stabilized bullet will have better terminal ballistics than a marginally stabilized one. Steve at Hammer Bullets backs that up. There is a difference in terminal ballistics and accuracy. Just because a slower twist will shoot more accurately does not mean that it will preform better terminally.
I admire those who test the limits not just talk about them. Thanks JE.
Henry

 

[Jon Bischof]

How do ya delete a stupid post?

 

[Jon Bischof]

It becomes a trade-off between the durability of the bullet in flight and the amount of expansion after impact. I guess if we ran everything above 300,000 rpm's, it would eliminate a lot of bullet construction choices because it would spin the jackets off of many older designs. Plus I think the gyroscopic effect of super fast spins really does affect the flight characteristics. It has to; centrifugal force is a real thing, so it puts a disrupting force upon the bullet as it drops.