Barrel length and twist question

[Gerard Schultz]

Longer barrel = higher speed = more rpms = better terminal performance. Shorter barrel = lower speed = lower rpms = lesser terminal performance.

The further he shoots, the more Sg he has, using the same load. So, yardage has a telling effect, even if the same load is used.

One bullet will not do the job at all distances. That is why we need to know at what average distance he shoots and whether he is hunting or target/tactical shooting.

A 300 Weatherby will not work up the speed to disintegrate a 150gr Accubond, even if the barrel is 28" and the twist is 1:9", it is a moot point.

 

[L.Sherm]

I've had 55 Sierra's blow up in a 8tw 22 Dasher, didnt even make it to the 100 yard target.

 

[Gerard Schultz]

"A 300 Weatherby will not work up the speed to disintegrate a 150gr Accubond, even if the barrel is 28" and the twist is 1:9", it is a moot point."

 

[L.Sherm]

I suggest if all of this confuses the O.P is he gets Brian Litzs book and read it and come to his own conclusion.

 

[L.Sherm]

This is a thread on accurateshooter Bryan Litz was responding to and why I'm a firm believer in not over spinning a bullet more than necessary.

 

[Gord0]

Yes it is. Excessive spin exacerbates any mass distribution inconsistencies in the bullet itself which causes group sizes to grow. In extreme cases bullets can come apart from the gyroscopic stresses induced by spinning too hard. There's just no need to twist something for the sake of twisting. It either is or is not stable darned near right out of the muzzle.

OP: A 12 twist is sufficient up to 180gr bullet from that rifle. Any faster twist only enables you to use heavier bullets if you happen decide you haven't had enough recoil for a lifetime.

Yes, I know this. The OP is talking about faster twist than 10 in his 300wby. I could have went further in my explanation, but you also only took out one tiny portion of my post. I went with a 9 because I want to shoot the 215, and possibly the 180 hammer. Those require at least a 10, but start to get close to marginal at my elevation. I'll get a more consistent BC, and terminal performance with the faster twist. Most modern bullets are much more consistent than bullets if 20yrs ago. They'll generally take more rpm before bad stuff happens. Now if you take a standard 14twist 22-250 that's shooting a 40gr at 4300fps and make it a 7 twist for some 90gr vld's you're probably going to have a problem with the 40's.

 

[LVJ76]

This is just an opinion, the OP is entitled to use what ever bullet he likes. We may offer some advise but no need to imply he is wrong on what he is doing because he is not, its a personal choice.

The longer the Barrel the faster the bullet will leave the muzzle since more powder can be burnt when using the appropriate powder. The twist will determine what bullets he can use, a slower twist like a 1 in 12 means he won't be able to use some heavy for caliber bullets like say a 230gr bullet because, it might not be able to stabilize it, but will stabilize a 150gr bullet perfectly. A fastet twist like a 1 in 8" will stabilize the high for caliber bullets but might not stabilize the lighter ones. No, it won't cause a blow up on this caliber, but it might cause some accuracy issues.

A 1 in 10" is the middle ground and just in case he decides to go with something heavier like a 180gr bullet he will be able to, and also be able to use the 150gr with good results.

 

[Randy Tidwell]

Of course any change to a bullets weight, shape, lenght is going to affect its stability, but I stand by bullet length has allot more affect than weight.

Example, a 105 grain 6mm VLD bullet (long) needs a much faster twist than a 100 Spitzer.

Same applies to Copper vs Lead Core, your typical copper 180 grain bullet is much longer than a 180 lead core. The coppers shoot much better with the faster twist. Even being the same weight.

I have a 257AI that will not stablize a 100 grain Barnes, yet the 25 Souper with a 9 twist bullet does. The 257 AI shoots the 100 grain Balistic tips great. Much shorter bullet.

So I contend, longer the bullet, the faster it needs to spin. Has very little to do with weight.

JMHO

 

[Rainy]

I have the same gun and I put an lilja mark 13 on it 28" stock in cut and finished out at 28.75" its 1:10 twist 6 grove shoots great with 210 nos accbound LR with 80.6 gr of RL26 @3080ish. But the action is metric thread tell the gunsmith SK he will know before hand mine found that out and it cost me a lil extra for the time to set up the lathe and equipment. You will live the barrel

That's a nice piece of machinery you have there!

 

[Rainy]

That is only true if you use jacketed lead bullets. With copper monos it does not happen and you get the best of both worlds: Very close to the BC of the heavier bullet but the speed of the lighter bullet. Given that BC is a combination of form factor and speed, copper monos translate into very much the same wind drift as a jacketed lead bullets but much flatter trajectory and sometimes a shorter time of flight.

Under 500 a 1:9" twist will not hurt anything and over 500 he can use bullets as long as he likes, a 300 Weatherby will not work up the speed to disintegrate bullets but he will get correct terminal performance on animals.

For one load to work, we will need to know how far the average shot is and what type of shooting is done: target/tactical or hunting.[/QUOTE This is my hunting rifle. I shoot it regularly though. I have found that 180s do far too much damage to the meat and I often lose an entire quarter when I don't get that perfect broadside andle. I chose the 150 for velocity and still having the "hit" at 800+. The farthest shot I'd responsibly take at the moment would be 550yds. I shoot elk and smaller game. Mostly deer.

 

[LVJ76]

Of course any change to a bullets weight, shape, lenght is going to affect its stability, but I stand by bullet length has allot more affect than weight.

Example, a 105 grain 6mm VLD bullet (long) needs a much faster twist than a 100 Spitzer.

Same applies to Copper vs Lead Core, your typical copper 180 grain bullet is much longer than a 180 lead core. The coppers shoot much better with the faster twist. Even being the same weight.

I have a 257AI that will not stablize a 100 grain Barnes, yet the 25 Souper with a 9 twist bullet does. The 257 AI shoots the 100 grain Balistic tips great. Much shorter bullet.

So I contend, longer the bullet, the faster it needs to spin. Has very little to do with weight.

JMHO

The reason why I posted: "Some" high for caliber bullets.

The larger the bearing surface the faster the twist needs to be.

 

[FEENIX]

Of course any change to a bullets weight, shape, lenght is going to affect its stability, but I stand by bullet length has allot more affect than weight.

Example, a 105 grain 6mm VLD bullet (long) needs a much faster twist than a 100 Spitzer.

The weight and length are directly proportional (reduction in length = reduction in weight, increase in length = increase in weight). In your example, you are restricted (fixed) to 6MM diameter of the bullet so the only way for a bullet increase in weight is an increase in length.

Below is another example to keep it with the same bullet manufacturer and design (information extracted from Berger), also not sure which 100 spitzer bullet you are referencing ...

SOURCES:
https://bergerbullets.com/product/6-mm-95-gr-vld-hunting/
https://bergerbullets.com/product/6-mm-105-gr-vld-hunting/

To increase the weight from 95 to 105 grain, length has to be increased by .093".

BTW, I am not disputing that the longer the bullet, the faster the twist requirement for stabilization but you cannot ignore the bullet weight and length relationship that exist.

Cheers!

 

[Randy Tidwell]

Feenix, I agree, can't ignore the weight.

How ever, two bullets of the same diameter and weight that are different lengths will perform better with different twists.


Compare a 180 grain 30 cal round nose, Spitzer, VLD, for optimum stability you different twist rates.

The bullet weight is only 10-20% of the equation. Just a guess on the %.

I understand why everyone relates it to weight, it's easier than keeping track of bullet length.

I had a long discussion/debate with Barnes at the Shot Show a few years back about this. They finally conceded that their bullets benefited from a faster twist for the same weight lead core bullet.

JMHO

PS: OP, sorry we kind of high jacked your post., just order a 10 twist you will be fine.

 

[FEENIX]

lHow ever, two bullets of the same diameter and weight that are different lengths will perform better with different twists.

Compare a 180 grain 30 cal round nose, Spitzer, VLD, for optimum stability you different twist rates.

The bullet weight is only 10-20% of the equation. Just a guess on the %.

I understand why everyone relates it to weight, it's easier than keeping track of bullet length.

Sorry but your 180g round nose, Spitzer, VLD analogy does not make sense. The reason they require different twist for stabilization is because by design they have different lengths and BCs, two essential element of the bullet parameter necessary input to the twist rate calculator. The other two is weight and caliber/bullet diameter. As previously noted, any changes in bullet parameters (BC, caliber/bullet diameter, weight, and length) will have a correlational effect to twist rate/SG relationship.