Why do we need slow twist barrels again?

[Big Sky]

Originally Posted by chuck

It is a lot more than two groups from me that says there is evidence in support of this.

How many groups from you is it?
How many different bullet weights and twist rate combinations have you experimented with?

[260 Rem]

Here's a three shot group (100M) from a hunting rifle shot about noon today. As much as I would like to attribute the result to "appropriate twist", I suspect it could be related to blind luck or perhaps a friendly gust of wind


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[Pathfinder76]

Originally Posted by Bushrat

Did you change your zero between groups?

Yes

[Pathfinder76]

Originally Posted by Big Sky

How many groups from you is it?
How many different bullet weights and twist rate combinations have you experimented with?

I’m talking hundreds if not thousands of rounds from various rifles. And I am far from the only one with that experience.

[Pathfinder76]

Originally Posted by 260 Rem

Here's a three shot group (100M) from a hunting rifle shot about noon today. As much as I would like to attribute the result to "appropriate twist", I suspect it could be related to blind luck or perhaps a friendly gust of wind


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This is not a thread about attribution of group size to twist rate. This is a thread about why in the wide world of sports would i hamstring myself with a ridiculously slow twist rate when I don’t have to. I’m quite confident that you can shoot 1/2” groups with 40 gr bullets in a 1-14 twist 223. I’m also quite confident that you can’t shoot 1/2” groups with 75gr bullets 1-14 twisted 223.

[dogslayer403]

I had an interesting experience today with the same 22-250 mentioned earlier was testing some 62g varmagedon i wanted to see if i could get a load with cfe223. 2 loads on the upper end of my test had bullet failures out of 10 shots with the 2 groups i had 4 bullets come apart i thought i seen dirt fly when shooting about 40yds in front of me. Sure enough when i walked up to check groups i seen where parts of them hit the ground and missing 4 holes on paper for those groups.
Now im not saying this was my fast twist as it could just be a bad batch of bullets or their construction but none the less interesting i forgot my chronograph but estimated around 3400-3500 on the ones that failed. Disappointing as the groups were getting better the faster i pushed em

Im gonna test them in my 1/9 223 as well see if i have better luck

[260 Rem]

Sorry Chuck, I must have missed the point about the relationship between twist rate and group size because of the pic in your OP. And you must have missed my point that twisting a bullet with the least rotation required to stabilize it, might work even better? So, here is a pic of some consecutive groups I shot with a hunting contour barrel I used last year ... with the least twist required to stabilize the bullet ... which I think provides some support for the practice of not over rotating bullets. I don't think it is credible to suggest that a single/fast twist rate is a "fits all" solution.

[Pathfinder76]

Originally Posted by 260 Rem

Sorry Chuck, I must have missed the point about the relationship between twist rate and group size because of the pic in your OP. And you must have missed my point that twisting a bullet with the least rotation required to stabilize it, might work even better? So, here is a pic of some consecutive groups I shot with a hunting contour barrel I used last year ... with the least twist required to stabilize the bullet ... which I think provides some support for the practice of not over rotating bullets. I don't think it is credible to suggest that a single/fast twist rate is a "fits all" solution.

You have missed the point. By a country mile. Again.

[duceman]

here's the follow up question:
what the hell is the draw toward dink bullets with high powder capacity cases; for example 50 gr bullet in a 40 gr powder capacity 22-250.

[propliner]

Originally Posted by Full Curl Earl

Where did you arrive at 10 fps? Or did you mean 10%? There are a lot of variables to consider to have been able to arrive @ 10 FPS. For instance, the differenace in a 1:8 vs 1:14 will not be the same. Putting a projectile into a forced tight spin is detrimental to bullet skins, speed and barrels, and lighter projectiles in a good barrel don't require it, in my opinion, so what would be the positive trade off? I can't think of one really, but there may be
.
Twist rate has a negligible effect on bullet speed, under 10fps. As stated earlier, slower twist rates prevent thin-jacketed bullets from spinning apart under excessive centrifugal force.

The Litz test.

http://bulletin.accurateshooter.com/...ity-litz-test/

[dogslayer403]

Originally Posted by duceman

here's the follow up question:
what the hell is the draw toward dink bullets with high powder capacity cases; for example 50 gr bullet in a 40 gr powder capacity 22-250.

Why not? Perfect for coyote calling very broad PBR with the flat trajectory of a fast light bullet. Heavy high bc bullets in .224 arnt gonna shine till they get way out there and seldom do I need that yote hunting plus hard on fur with a 70-80g bullet. Kinda the staple of varmint hunting is frangible fast light bullets and flat trajectory is it not? Target shooting is another story I suppose

[duceman]

i shoot coyotes to 400 pretty routinely with a 222 running a 50 gr bullet at 3100. if your not shooting long, why burn twice the powder for another 6-700 fps with the same bullet? coyote tips over regardless....

[dogslayer403]

Originally Posted by duceman

i shoot coyotes to 400 pretty routinely with a 222 running a 50 gr bullet at 3100. if your not shooting long, why burn twice the powder for another 6-700 fps with the same bullet? coyote tips over regardless....

Each to their own could argue this for days why shoot a 222 with double the powder of a hornet or a bee for 6-700 fps of gain

I have good success my way and you do your way. Have a good winter on the dogs

[Delavan]

I got a 1-9 twist .223. Better to stabilize 40-69 grain projectiles if I rely on what I read.
As I'm not extremely knowledgeable, I just use this as my baseline.
I remember reading that 1-7 & 1-8 twists are to stabilize heavier/NEWER military rounds.

[DiabeticKripple]

I have a 8 twist Tikka. Never really saw a downside to having a higher twist rate than required.

[Unregistered user]

Some say that if you're shooting bigger bullets in bigger calibres you feel torque twist and can throw you off a bit, some claim quicker fouling in the quicker twist rate. I don't know, is slow twist cheaper to make?

[Pathfinder76]

Maybe there is something to this match the weight to the twist thing.

Another fluke perhaps?

[Big Sky]

Originally Posted by chuck

Maybe there is something to this match the weight to the twist thing.

Another fluke perhaps?

This is pretty obtuse.
What exactly, are you trying to say?

[Pathfinder76]

You’re guessing and I’m not? I don’t know.

[260 Rem]

Nice to see that last group with the long Bergers that are appropriate for the 8 twist. As you have demonstated, they group much better than the “shorties” pictured in your OP which might group better with a slower twist.
IMO, the best way of testing consistency is to shoot some consecutive 5 shot groups. These are nice temperatures for longer strings.

[Pathfinder76]

There are three other variables involved. Bullets, brass, and powder. Down here wind is the biggest weather issue for shooting groups.

[6.5 shooter]

6MM br 1 in 8 ...105gr bullets bug holes, 87 gr v max 20 yards past muzzle they were mist..........over stabilized....me thinks

[Pathfinder76]

I have shot a boat load of 55gr 6mm BT’s in nine twist barrels at 4K to know better than the mist theory.

[6.5 shooter]

Originally Posted by chuck

I have shot a boat load of 55gr 6mm BT’s in nine twist barrels at 4K to know better than the mist theory.

So happy for your luck...I can provide witnesses if you would like to call me a lair again???

[Pathfinder76]

Originally Posted by 6.5 shooter

So happy for your luck...I can provide witnesses if you would like to call me a lair again???

[RickF]

Originally Posted by 6.5 shooter

6MM br 1 in 8 ...105gr bullets bug holes, 87 gr v max 20 yards past muzzle they were mist..........over stabilized....me thinks

With that combo you aren't anywhere close to enough velocity to make a V-Max come apart. It is possible you have an incredibly rough or flawed bore that is causing that thin-jacketed bullet to fail.

[PartTimeHunter]

Originally Posted by chuck

I was shooting 40gr Ballistic Tips in an 8 twist 223 yesterday. Once again, light bullets seemed to do just fine in a quicker twist barrel. Is there a good reason why manufacturers continue to use slow twist barrels in many of their offerings?

I think the slower twists are to conform with the manufacturers offerings of bullet weights in factory ammo and don't take handloaders into account. Why they don't consider other choices I can't answer. My understanding is that you can over twist for lighter bullets. In my 20 Extreme with an 8 twist barrel I can shoot the 55 grain Bergers lights out, 40 grain works good too. I have not been able to work up a load with 32 grain bullets for that rifle and didn't even try the 26. I also have a 10 twist in 20 Extreme that works fantastic with 40 grain but can't stabilize the 55's. I have heard and read of bullets "misting" on the way down range. There is a guy on the other site for nutz that posted a formula for maximum bullet rotation. He experimented with some wildcats and used this to find the right twist for the chosen bullet.

[260 Rem]

The “greenhill formula” (and its fine tuned offspring) using the bullet diameter, length, specific gravity, and velocity ... provides the basis for calculating the optimum rotation required for stabilization. Although rotating a bullet faster than the “optimum” has no theoretical deleterious effect itself, bullet construction that is not “perfect” ... say in weight distribution, uniform jacket thickness, and a host of other factors... will amplify the imperfection and may result in poor performance. Consequently, the best advice is to choose bullet/characteristics that fit in the range of optimum stability provided by a given twist.
So, to address the issue posed in the OP, it is evident that maqnufacturers make slow twist barrels for specific (shorter) bullets, and faster twists for their longer cousins. Yes, we still need slow twist barrels because over rotating a bullet with deficiencies, is unlikely to give the best results.
It is quite possible that a well constructed bullet may shoot “decent”, which does not rise to the standard of shooting “well”.
If manufactures thought their barrels would shoot every length of bullet well with a fast twist ie: 1:7 ...they would just make them all that way and not bother with extra retooling costs.

[elkhunter11]

So shooting the same load in two rifles with different twist rates produced a difference in velocity of only 10fps? Has anyone actually measured the pressure produced in both barrels with the same load? If the fast twist barrel is producing more pressure , then you would need to change the load to produce equal pressure in both barrels to determine the true effect of twist rate on velocity. And even if the same pressure only produces 20fps more with a slow twist barrel, why not take advantage of that 20fps if the accuracy is the same? If I am only going to shoot a 55gr bullet , why use a twist that is optimum for 80gr, and give up 20fps that I can have for nothing?
I have owned six 7mmstw rifles, four with a 1 in 10" twist, and two with a 1 in 9" twist. All shot 140-150gr bullets well, but the 1 in 9" rifles did not shoot the 140gr bullets as well as they shot 150 gr bullets. The 1 in 10" rifles preferred the 140gr bullets. So is this simply coincidence, or is the twist rate a factor? And this is with only a 1" difference in the rate of twist.

[densa44]

The rub is of course, no matter how hard you try you can't keep all the variables constant while you manipulate rate of twist.

Some of the posts are very scientific and I really appreciate that. The Litz test (I think that is what it was) and Elk's last post may be showing that the small difference in MV moves the point of impact due to harmonics not bullet stabilization.

I calculated the rpm of bullets exiting the barrel once and they were extremely high and it is hard to believe that a higher rpm makes them more stable.

Maybe the different twists rates are just a marketing tool? As others have said, its how they shoot that counts.

Good stuff.