Bullet RPM and performance

[Darryle]

Thanks, there is a lot to digest here

 

[dblman]

Hopefully I am not beating a dead horse here or asking an ignorant question.

I have read about twist in relation to bullet stability and velocity in relation to bullet performance at long range. I just can't recall about reading if RPM contributes to bullet performance (i.e mushrooming and transfer of energy).

I know we have all read instances of penciling, the ELD-X bullets are one I experienced first hand and at a variety of ranges.

My questions are:

Have designers taken barrel twist/bullet RPM into consideration when designing these bullets and as twist rates get faster, ranges increase, bullets get longer and velocities get higher are these contributing factors to bullet design and performance?

Can you spin a bullet too fast to inhibit performance, increase failure or increase the chances of getting penciling?

Does spin have an affect on performance and has a single design been subject to testing at differing velocities, RPMs and ranges for terminal performance or has the data been gathered?

Is there a way to know you are in the sweet spot in relation to twist and bullet/load selection other than accuracy at the range?

I am in the process of deciding on a new barrel and other than stability for the chosen bullets, I am wondering what other effects twist will play with my selection.

Thanks Darryle

A little actual experience with twists. I have two Xbolts, a 22" Pro and a 26" Hells Canyon.
Using Swarovski Z5 5-25 ballistic turret scopes on both. The Pro is 1:8 twist and the Swarovski ballistic program for the ballistic turret works perfectly. While the Hells Canyon is a 1:7 for the 143ELDX.
The faster twist just does not work with the ballistic program past 300 yards???
Faster spin rate. Does it hold the bullet up
longer? Don't know but it drops less than the 1:8 past 300. 100 to 300 = same.
Not scientific but true anyway.

 

[Radman]

Thanks, there is a lot to digest here

Lots of great advice indeed! Many folks here actually DO the walk, not just the talk. I always say that, "EVERYTHING MATTERS!"
Many people think that the faster that you can spin a bullet - is always better! This simply isn't true. In some cases yes it is, but there are so many other factors to consider, (that many here have already alluded to). You can spin a bullet apart. (Some have given examples) The point when/where a bullet goes transonic is also something to consider on distance shooting, (which probably isn't a factor for most hunting).
I learn a lot here. I've been target shooting for over half a century & I'm STILL learning! I hope that The Good Lord let's me continue to learn/shoot for a few more years!
In the meantime, when not shooting, this is a GREAT place to hangout!
Good luck in your research. Like these others, I understand your interests not only in the ballistics but in the mechanics after impact.
(Sorry to ramble)

 

[Grumpy old man]

I can assure you that that running them to fast they will blow up my bartlin 1&7 twist 22 creedmoor is blowing up 85.5 Bergers at 3260fps

 

[dblman]

Lots of great advice indeed! Many folks here actually DO the walk, not just the talk. I always say that, "EVERYTHING MATTERS!"
Many people think that the faster that you can spin a bullet - is always better! This simply isn't true. In some cases yes it is, but there are so many other factors to consider, (that many here have already alluded to). You can spin a bullet apart. (Some have given examples) The point when/where a bullet goes transonic is also something to consider on distance shooting, (which probably isn't a factor for most hunting).
I learn a lot here. I've been target shooting for over half a century & I'm STILL learning! I hope that The Good Lord let's me continue to learn/shoot for a few more years!
In the meantime, when not shooting, this is a GREAT place to hangout!
Good luck in your research. Like these others, I understand your interests not only in the ballistics but in the mechanics after impact.
(Sorry to ramble)

As far as killing. I shoot hogs. Lots of hogs here on my place in East Texas. The 143 ELDX from the 1:7 is devestating at all ranges. Most kills are 300+ out to as far as I feel good that day. It really knocks them on their butts.

 

[david g ranes]

Hopefully I am not beating a dead horse here or asking an ignorant question.

I have read about twist in relation to bullet stability and velocity in relation to bullet performance at long range. I just can't recall about reading if RPM contributes to bullet performance (i.e mushrooming and transfer of energy).

I know we have all read instances of penciling, the ELD-X bullets are one I experienced first hand and at a variety of ranges.

My questions are:

Have designers taken barrel twist/bullet RPM into consideration when designing these bullets and as twist rates get faster, ranges increase, bullets get longer and velocities get higher are these contributing factors to bullet design and performance?

Can you spin a bullet too fast to inhibit performance, increase failure or increase the chances of getting penciling?

Does spin have an affect on performance and has a single design been subject to testing at differing velocities, RPMs and ranges for terminal performance or has the data been gathered?

Is there a way to know you are in the sweet spot in relation to twist and bullet/load selection other than accuracy at the range?

I am in the process of deciding on a new barrel and other than stability for the chosen bullets, I am wondering what other effects twist will play with my selection.

Thanks Darryle

Go to a thread that I put on here it's called talk about crazy check out picture it will show you a bullet that shed the jacket about 30 yds from the end of joejack barrel very interesting. David

 

[dblman]

Go to a thread that I put on here it's called talk about crazy check out picture it will show you a bullet that shed the jacket about 30 yds from the end of joejack barrel very interesting. David

What caliber, what weight, what fps, what twist? All must fit.
Mine is 6.5 @ 2753 fps, 1:7 twist, 143 gr, devastating 100 to 600 on hogs, deer and coyotes all actual kills.

 

[lastshot]

So, you can't over stabilize a bullet...
But you can over rpm a bullet?...cup and core that come off In flight.

 

[jasent]

I've never blown up a bullet my self. I "over spin" everything I shoot. I like an sg of 2 or more. My 210gr vld load is 3.14 sg. I've even shot 58gr vmax from my 28" 1:7 243 at almost 4K and they hit my 800 yard plate no problem. Maybe rifling plays a big role in this. All my barrels are 6 groove button.

 

[lastshot]

So I'm guess I. Asking aren't they one in the same?

 

[azsugarbear]

Geting old is a double-edged sword for me. It's great for knowledge accumulation. On the other hand, you often forget where the source of that information came from. Such is my plight here. I think most of us have heard about over-rotating cup and core bullets to the point that the jacket separates from the lead core soon after leaving the barrel - resulting in catastrophic bullet failure.

Somewhere I read about a secondary problem with the 'over-stabilization' a bullet. We all know that a bullet leaves the barrel on a flat plain and begins to drop immediately. To hit targets at distance, we end up compensating for this by rasing the barrel above the taget, while keeping the sights/scope on a level plain with the target, creating the illusion of an arc in terms of the path that the bullet takes to arrive on target. With correct rotation. not only do we stabilize the bullet in flight, but we also keep the nose or point of that bullet tracking the same arc. In other words, the nose leads the bullet to the target. When we over-rotate a bullet, it still stabilzes the bullet, but the nose/point of the bullet begins to no longer track the same path as the bullet. Some call this the attitude or position of the bullet as it begins its downward arc toward the target - resulting in the belly or side of the bullet leading the way to the target as it drops. When this happens, the bullet tends to hit the target a little flat or sideways. In turn, this results with the bullet not opening correctly.

I can't remember where I read this, but we have all seen similar results in a long pass or kick of a football down the field. With the correct twist to stabilize the football, it comes down nose first into the arms of the receiver. Too much spin, results with the football arriving on target, but in a 'nose-up', belly first attitude into the arms of the receiver.

If I am wrong, feel free to correct an old man. If I am right, please let me know where I read this. It will make my day and confirm for me I am not yet too far gone.

 

[Grumpy old man]

Please elaborate; was this through a ballistic gel test? Thanks!

The purpose of say faster spin is bullet stabilization a 85 gr bullet doesn't need a fast spun barrel to stabilize, 112 gr bullet needs it a 6.5 153.5 gr bullet needs a least a 1 8 or 1 7.5 twist to stabilize cause it pencils !Some bullets that are not solid lead will come apart easier than others fragmenting so spinning fast 3000 +fps tells me from experience to get a projectile that can hold together at that velocity ! That speed turning to fast will fragment the projectile if it's construction is susceptible to coming apart!

 

[FEENIX]

The purpose of say faster spin is bullet stabilization a 85 gr bullet doesn't need a fast spun barrel to stabilize, 112 gr bullet needs it a 6.5 153.5 gr bullet needs a least a 1 8 or 1 7.5 twist to stabilize cause it pencils !Some bullets that are not solid lead will come apart easier than others fragmenting so spinning fast 3000 +fps tells me from experience to get a projectile that can hold together at that velocity ! That speed turning to fast will fragment the projectile if it's construction is susceptible to coming apart!

I am fully familiar with the concept, but I am more concerned if he did the gel test to prove it.

 

[jasent]

Geting old is a double-edged sword for me. It's great for knowledge accumulation. On the other hand, you often forget where the source of that information came from. Such is my plight here. I think most of us have heard about over-rotating cup and core bullets to the point that the jacket separates from the lead core soon after leaving the barrel - resulting in catastrophic bullet failure.

Somewhere I read about a secondary problem with the 'over-stabilization' a bullet. We all know that a bullet leaves the barrel on a flat plain and begins to drop immediately. To hit targets at distance, we end up compensating for this by rasing the barrel above the taget, while keeping the sights/scope on a level plain with the target, creating the illusion of an arc in terms of the path that the bullet takes to arrive on target. With correct rotation. not only do we stabilize the bullet in flight, but we also keep the nose or point of that bullet tracking the same arc. In other words, the nose leads the bullet to the target. When we over-rotate a bullet, it still stabilzes the bullet, but the nose/point of the bullet begins to no longer track the same path as the bullet. Some call this the attitude or position of the bullet as it begins its downward arc toward the target - resulting in the belly or side of the bullet leading the way to the target as it drops. When this happens, the bullet tends to hit the target a little flat or sideways. In turn, this results with the bullet not opening correctly.

I can't remember where I read this, but we have all seen similar results in a long pass or kick of a football down the field. With the correct twist to stabilize the football, it comes down nose first into the arms of the receiver. Too much spin, results with the football arriving on target, but in a 'nose-up', belly first attitude into the arms of the receiver.

If I am wrong, feel free to correct an old man. If I am right, please let me know where I read this. It will make my day and confirm for me I am not yet too far gone.

If that was true it would affect the bc. Flying point up. Most of my shooting is well beyond 1000 yards yet the bullets hit where they should. I've read this too but I believe it's a myth. Every bullet I shoot is "over spun"