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Very Hot Topic (More than 25 Replies) Mould/bullet recommendation for 28-30, Stevens (Read 2627 times)
JLouis
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #15 - Dec 15th, 2018 at 9:04pm
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Nice looking bullet Dellet and I tend to agree with you on stability. Having a bullet of that design for a 14 twist the rule of thumb based on how I was taught. To do what it is I am thinking you are trying to accomplish would be for it to be around .864 in length and being closer to the 134gr. weight range.
  
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Dellet
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #16 - Dec 15th, 2018 at 9:25pm
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JLouis wrote on Dec 15th, 2018 at 9:04pm:
Nice looking bullet Dellet and I tend to agree with you on stability. Having a bullet of that design for a 14 twist the rule of thumb based on how I was taught. To do what it is I am thinking you are trying to accomplish would be for it to be around .864 in length and being closer to the 134gr. weight range.


They have the same basic bullet with one less band and not tapered 130 grains.

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Schuetzendave
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #17 - Dec 15th, 2018 at 9:25pm
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Caliber      0.286      Inches            
Bullet Weight      152      Grains            
Bullet Length      1.01      Inches            
Barrel Twist      14      Inches/turn            
muzzle velocity      1470      fps            
Temperature      50      degrees Fahrenheit (59 is standard)            
Pressure      29.92      inches of mercury (29.92 is standard)            
                       
Sg =      1.36                  


Yup the longer 152 grain would be unstable when the weather changed or when the velocity was too slow.

You should have a tighter twist to shoot it or use a shorter lighter bullet as John suggests.


Caliber      0.286      Inches            
Bullet Weight      130      Grains            
Bullet Length      0.86      Inches            
Barrel Twist      14      Inches/turn            
muzzle velocity      1470      fps            
Temperature      50      degrees Fahrenheit (59 is standard)            
Pressure      29.92      inches of mercury (29.92 is standard)            
                       
Sg =      1.83                  
  
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Dellet
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #18 - Dec 15th, 2018 at 9:38pm
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Schuetzendave wrote on Dec 15th, 2018 at 9:25pm:
Caliber      0.286      Inches            
Bullet Weight      152      Grains            
Bullet Length      1.01      Inches            
Barrel Twist      14      Inches/turn            
muzzle velocity      1470      fps            
Temperature      50      degrees Fahrenheit (59 is standard)            
Pressure      29.92      inches of mercury (29.92 is standard)            
                       
Sg =      1.36                  


Yup the longer 152 grain would be unstable when the weather changed or when the velocity was too slow.

You should have a tighter twist to shoot it or use a shorter lighter bullet as John suggests.


Caliber      0.286      Inches            
Bullet Weight      130      Grains            
Bullet Length      0.86      Inches            
Barrel Twist      14      Inches/turn            
muzzle velocity      1470      fps            
Temperature      50      degrees Fahrenheit (59 is standard)            
Pressure      29.92      inches of mercury (29.92 is standard)            
                       
Sg =      1.83                  


Below 1.4 the quality of the bullet makes the difference. If the bore wasnít 125 years old it might have a better chance.

Iím sure this will have a couple failures, but too much success without work kinda takes the fun out it.
  
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frnkeore
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #19 - Dec 15th, 2018 at 10:16pm
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I like that 130B bullet better than the NOE but, I hate their min meplats of .180. It would be much better, balistically with a .08 - .100 meplat.

If you get the 130B, have them make the first band, .282, it will help with BSing.

Frank
  

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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #20 - Dec 16th, 2018 at 12:56am
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frnkeore wrote on Dec 15th, 2018 at 10:16pm:
I like that 130B bullet better than the NOE but, I hate their min meplats of .180. It would be much better, balistically with a .08 - .100 meplat.

If you get the 130B, have them make the first band, .282, it will help with BSing.

Frank

They offer the tapered design as #125M.
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Schuetzendave
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #21 - Dec 16th, 2018 at 11:50am
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Below 1.4 the quality of the bullet makes the difference.


It is not the quality of the bullet - it is the length of the bullet.
If it is too long for your barrel's twist to gyroscopically stabilize it; it will not be spinning fast enough and will tumble.
It may tumble immediately or a short distance down range and more so if the weather is colder or the atmospheric pressure is higher.
« Last Edit: Dec 16th, 2018 at 11:58am by Schuetzendave »  
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Dellet
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #22 - Dec 16th, 2018 at 1:07pm
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Schuetzendave wrote on Dec 16th, 2018 at 11:50am:
Below 1.4 the quality of the bullet makes the difference.


It is not the quality of the bullet - it is the length of the bullet.
If it is too long for your barrel's twist to gyroscopically stabilize it; it will not be spinning fast enough and will tumble.
It may tumble immediately or a short distance down range and more so if the weather is colder or the atmospheric pressure is higher.


I would argue that from personal experience, and qualify it with distance shot, and bullet construction. I shoot a lot of subsonic rifle, cast, jacketed and lathe cut solids. The smoother the bearing surface, the lower the SG number you can get away with on target. Jacketed bullet tend to be more forgiving than CNC turned monolithic bullets for this reason.

As with almost anything in loading, what the target shows and what science says are not always in sync. What I can say is that a 240 Matchking in a 1/10 at 1000 fps, will still make round holes in the target at 250 yards with an SG of less than 1.3. And most cast .125Ē shorter will have trouble at 100. Monolithic bullets with grooves are somewhere in between. Grooves cause turbulence.

Maybe if I shot better I could see the difference in group size due to stability, but the 1.6 SG number is there as guideline for maximum BC as well. Just because the bullet is not reaching maximum BC potential, does not automatically mean it is not stable.

Just what I have experienced on target.
  
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JLouis
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #23 - Dec 16th, 2018 at 1:36pm
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Truer words could not be spoken: " From personal experience. " All though there are several programs out there that seem to be providing good, honest and trusted information. My own personal experience has proven that it has not always been so and one can end up purchasing the wrong bullet design to fit his or her needs. If you can come across someone who is already doing what it is you are wanting to accomplish and having great success. I have found it is has been by far the better way to achieve the same type of success.
  
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frnkeore
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #24 - Dec 16th, 2018 at 5:02pm
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Quote:
As with almost anything in loading, what the target shows and what science says are not always in sync. What I can say is that a 240 Matchking in a 1/10 at 1000 fps, will still make round holes in the target at 250 yards with an SG of less than 1.3. And most cast .125Ē shorter will have trouble at 100. Monolithic bullets with grooves are somewhere in between. Grooves cause turbulence.

The major reason that what your saying is true, is because the Match King and all most all, cast bullets in that weight range, being shorter will have a much different CG.

Regarding smooth bullets, at subsonic. The surface will make some difference in the BC, because at subsonic, laminar flow, as to be maintained, for maximum airflow, lowering the air friction and turbulence, over the surface.

Frank
  

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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #25 - Dec 16th, 2018 at 5:20pm
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frnkeore wrote on Dec 16th, 2018 at 5:02pm:
Quote:
As with almost anything in loading, what the target shows and what science says are not always in sync. What I can say is that a 240 Matchking in a 1/10 at 1000 fps, will still make round holes in the target at 250 yards with an SG of less than 1.3. And most cast .125Ē shorter will have trouble at 100. Monolithic bullets with grooves are somewhere in between. Grooves cause turbulence.

The major reason that what your saying is true, is because the Match King and all most all, cast bullets in that weight range, being shorter will have a much different CG.

Regarding smooth bullets, at subsonic. The surface will make some difference in the BC, because at subsonic, laminar flow, as to be maintained, for maximum airflow, lowering the air friction and turbulence, over the surface.

Frank


This is why I say bullet construction or shape can allow for a larger window of stability.

The problem with radial grooves in a bullet is that they will actually speed up the air moving over the bullet at that point. When you get into the trans sonic speeds you get turbulence at the grooves that tend to be at the base. The nose can be sub sonic not creating a shock wave, the base can be super creating a wave off the grooves. This idea has actually been filmed.

About the 5 min mark.
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One of the things I am finding out shooting subsonic is the amount of in flight bullet noise there is. Noise is basically turbulence. Turbulence causes instability. Unless you have a program that can simulate a wind tunnel, the stability calculators will not factor in bullet shape.

Guys that can get cast bullets flying well in some ways beat science all to death. They knew what worked well 100 years ago, in some ways science is just now explaining what the smart guys simply figured out worked.

Itís that knowledge base Iím hoping to tap into.
« Last Edit: Dec 16th, 2018 at 6:46pm by Dellet »  
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Schuetzendave
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #26 - Dec 16th, 2018 at 7:07pm
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You are jumping between dynamic stability and gyroscopic stability.

Your arguement is about bullet shapes and effects on center of gravity etc.

However you first need gyroscopic stability first before dynamic stability comes into play.

The barrel twist and bullet length determine gyroscopic stability and it has impacts on bullet stability before dynamic stability from forward motion has an effect.
  
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #27 - Dec 16th, 2018 at 7:11pm
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Dave who's comments are you referring too and what was the information being shared.
  
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Dellet
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #28 - Dec 16th, 2018 at 8:34pm
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Schuetzendave wrote on Dec 16th, 2018 at 7:07pm:
You are jumping between dynamic stability and gyroscopic stability.

Your arguement is about bullet shapes and effects on center of gravity etc.

However you first need gyroscopic stability first before dynamic stability comes into play.

The barrel twist and bullet length determine gyroscopic stability and it has impacts on bullet stability before dynamic stability from forward motion has an effect.


I think my argument would be that gyroscopic and dynamic can work with or against each other, and that is where shape comes into play. Otherwise if you took it to an extreme, you could shoot the same bullet backwards and forwards with equal results and performance.

A bullet could be designed that way, and many actually do fly reasonably well backwards, but itís just not the same.
  
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Schuetzendave
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Re: Mould/bullet recommendation for 28-30, Stevens
Reply #29 - Dec 16th, 2018 at 11:39pm
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Pretty simple.

Ballisticians state it is impossible to have dynamic stability until you first have gyroscopic stability.

So you need the proper selection of bullet length for your barrel twist before it will be gyroscopically stable.

No bullet shape will restore a bullet that is  gyroscopically unstable.
  
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