338 LM Improved gain twist barrel

[Jeffvn]

Re: 338 LM Improved gain twist barrel

I will be there Wednesday all day and part of thursday. Happy to meet. sending you a PM with my cell number...

JeffVN

 

[groper]

Re: 338 LM Improved gain twist barrel

Ok, before i go into the long noses and pitching moment, i might stick with the boattail theme a little longer and its relationship with pitching moment first. I only offer these "presentations" in an effort to bring value and understanding... if its not appreciated, simply dont read it...

Keep in mind that again, these forces are again symmetrical at zero yaw and therefore only apply once you have an angle of attack or yaw (which all bullets have unfortunately) directly applying to the epicylic or limit cycle precessional yaw that begins immediately upon exiting the muzzle (the wobbling football pass).

So not only does the boattail generate destabilizing magnus forces, boattails also generate negative lift or normal force, which acts in a vector that increases the pitching moment aswell (further reducing stability). The mechanism by which this occurs can be visualized by imagining a projectile flying with a small amount of yaw and realizing the angles of the fore and afterbody (ogive and boattail) and the lift vectors they generate by presenting an angle of attack to the oncoming airstream. The vector of the nose force is directly opposite the vector of the boattail force due to one having a net positive angle of attack and the other a net negative angle. So you get positive force/lift from the nose and negative from the tail. However the vectors complement rather than cancel due to them acting on opposite sides of the center of gravity- which incidentally determines the length of the moment arm. The moment arm lengths are measured from the center of gravity to the center of pressure of whatever force we are talking about, being magnus or normal force/lift etc. Therefore the sum of these lift/normal forces and moment arms determines the overall total center of pressure and the moment arm length acting upon it... collectively termed, the pitching moment. This acts to turn the bullet around rather than fly straight of course.

Now the nose length...

This shouldnt need much explanation of one can visualize the above with regard to the boattail. The Center of Pressure for the ogive section alone, lies almost exactly half way along its length at velocities around mach 2 to 4, regardless of whether its a secant, tangent, von karman, or whatever ogive.. There are subtle variances, but lets keep it simple for now. So if you increase the length of the nose, you get a greater pitching moment in at least 3 ways... First, the CoP gets further from the CoG due to the half length (CoP arm) of a longer ogive being physically longer. 2nd, you get a greater normal force due to the nose having more surface area and thus a larger lifting surface. Third, you move the overall CoG of the entire projectile REARWARD due to the volume/mass dimensions of longer ogives and pointier tips distributing less mass at the nose tip compared with their overall length.

Another destabilizing feature of the long nose but not relating to pitching moment, but which is similar to the third point in mechanism, in that it redistributes its mass and therefore axial and transverse inertias in a similar fashion. So it reduces the axial inertia and increases the transverse inertia and radii of gyration. - This happens to be compounded implicitly by less gyroscopic inertia (which is axial inertia of course ) so you must spin it faster to achieve the same gyroscopic effect. *As a side note on the same mechanism, Bore riding shanks with raised drive bands reduce available gyroscopic inertia also by having less mass along the axial extremities of the shank...

So you run into stability problems when designing long noses very easily, however the longer nose is a design parameter worth going after due to the VERY significant reductions in wave drag offered by long noses.

So increasing the length of the boattail, increasing the negative ANGLE of the boattail, and increasing the length of the nose etc. ALL act to increase the pitching moment and reduce stability, both static and particularly dynamic. So for one to be successful, one must not just find a way of reducing drag and providing adequate spin, but also very important is mitigating these moments and forces.

So these are some of the challenges faced when trying to design a projectile of +6.5calibers length and why we dont see many in existence. Not to say that its impossible, and in no way am i trying to discredit Noel Carlson, GSC or anybody else, nor prod you beta testers??? Much of what ive posted would be helpful to interested parties and i meerly offer information to those interested, certainly free information is better than living in the dark?

 

[Jeffvn]

Re: 338 LM Improved gain twist barrel

Groper

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> "I only offer these "presentations" in an effort to bring value and understanding... if its not appreciated, simply dont read it...</div></div>

I am throwing the BS Flag on this crap. With due respect, start your <span style="font-weight: bold"><span style="color: #FF6666">OWN THREAD</span></span> for your "presentations". I started this thread to report on my bullet testing results and my gain-twist rifle, not for these lectures by you. Take your "presentations" to a different thread.

JeffVN

 

[Noel Carlson]

Re: 338 LM Improved gain twist barrel

"Free information is better than living in the dark"... provided it is accurate, I agree with this statement entirely. In reading your last post, it dawned on me why you are actively seeking off-line help. Might I suggest, to any interested, an excellent essay tailored to non-academics titled "How do Bullets Fly" by Ruprecht Nennstiel. It will come in at the top of a search.

As for your conclusion, that 6.5+ caliber projectiles present advantages sufficient to justify a solution of their unique design challenges, I hope it is clear that this is what Jeff, Augustus, and LRS50BMG have been reporting on for over two years now. This information has a direct application to 6.0- caliber projectiles also... hence the delay in release of bullets designed to function from conventional twists, and magazines.

 

[Augustus]

Re: 338 LM Improved gain twist barrel

Groper, this is very interesting reading; however, have you missed my report on the ZA .375 400 gr 6.5 cal that is stable and still has a super-sonic signature at 2560 yds. Sooo, what you are trying to do has already been done. Upon more extensive testing there may changes to the design prior to release. Anyway the more people working on this class of projectiles the better. You guys dont jump all over me about the statement regarding the super-sonic signature. I realize putting a guy in a ditch and firing over his head is a fairly low tech way of determining if a projectile is traveling faster than the speed of sound. This method will just have to do until we can get it checked with radar. I have posted its BC based on drops out to 2560 yds, the testing has been limited and this also may be tweaked.

Anyway the only problem I have with your post is that it reads as if the development of these projectiles are still in the realm of theory, I can attest to the fact that is not the case. They already exist, they have been tested, they work and they are going to be available soon. The big hurdle is the availability of barrels.

 

[groper]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Augustus</div><div class="ubbcode-body"> the ZA .375 400 gr 6.5 cal that is stable and still has a super-sonic signature at 2560 yds. </div></div>

Upon making this statement, i made the comment 'looks like the ZA is winning the race...'

What i should have done is congratulated Noel on this success as it is a significant achievement in it own right. So ill take the time now to say well done, and following this success, im confident the ZA .338 version wont be too far behind it.

I beleieve some parties are interpreting my posts and particularly their intent, for more than what they actually are... which is nothing more than simple information...

 

[Noel Carlson]

Re: 338 LM Improved gain twist barrel

... And I believe you Groper, just don't do it again.

The problem with speculating, over details on which you hear resounding silence, is that you have limited yourself to an audience of one. I told you early on that I would share information at an appropriate time. This will come initially in the form of general public disclosure of field results... and only later as a high-order technical analysis of *why* the design works.

I hope that realization will temper some of your on, and off-line inquiry... in all of its variety.

 

[killer_penguin]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jeffvn</div><div class="ubbcode-body"> start your <span style="font-weight: bold"><span style="color: #FF6666">OWN THREAD</span></span> for your "presentations". </div></div>

Good advice right there.

 

[goober]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Augustus</div><div class="ubbcode-body"> the ZA .375 400 gr 6.5 cal that is stable and still has a super-sonic signature at 2560 yds. </div></div>

Upon making this statement, i made the comment 'looks like the ZA is winning the race...'

What i should have done is congratulated Noel on this success as it is a significant achievement in it own right. So ill take the time now to say well done, and following this success, im confident the ZA .338 version wont be too far behind it.

<span style="color: #FF0000">I beleieve some parties are interpreting my posts and particularly their intent, for more than what they actually are... which is nothing more than simple information...

</span>



</div></div>I have found this thread very interesting and am following it -Groper I am reading your words also and don't know why others are so titchy-I say that meaning no disrespect to the OP and Noel .
Really good reading guys and I am inspired to getting another stick just a little bigger like the 338LM Imp.
Jeff I would like to know a little more about this round as I want to go from 1km which I shoot now up to 2km.I don't have deep pockets but support my habit when the wife isn't watching .What kind of barrel life does one get from the imp LM round ? I don't know much about turned rounds either or if one can use off the shelf heavier projectiles -all info appreciated

 

[groper]

Re: 338 LM Improved gain twist barrel

Jeff,
I thought this was a FORUM, where ideas, opinions and discussions took place? If im mistaken, then what are we all doing here? Why not simply post 'updates' where difficult questions need not be answered on a twitter page or such like? And if you believe i should not be posting in this thread, then by your own reasoning you forfeit your right to post in my forthcoming threads... which would be disappointing.

Noel,

I really dislike being told what to do by complete strangers, and whilst i wont tell you the same, just know that it kinda pissed me off...

Giving away proprietary information is one thing, but the problem with "resounding silence" on questions that are clearly NOT proprietary information, <span style="font-style: italic">speaks a thousand words</span>...

So i shall rephrase my prior form, back on topic, and put it like this: - In your own mind, why do you beleive that noone to date, has designed and successfully implemented, a rifle system whereby very long projectiles are stabilized from very tight twist rate barrels? Did all the great minds miss something?

A plausible answer to the above would end all the speculation your so paranoid about... And you may omit all proprietary information, just in case all your academia missed that part...

 

[Noel Carlson]

Re: 338 LM Improved gain twist barrel

Che,

No offence taken at all.


Groper,

You are free to be "pissed off" all you like. You are not free to draw conclusions from thin air on a projectile on which you have limited knowledge without being called out. Your off-line communications only compound a general concensus that you are peddling smoke, and mirrors.

As to your question; I believe the "great minds" have been engaged in other disciplines for many decades now, which makes picking up the low fruit in small arms development rather easy.

Best to you on your April 1st release. Does that date have the same significance in Australia as it does here?

 

[groper]

Re: 338 LM Improved gain twist barrel

Once again, more avoidance and irrelevance...

Would the 'general consensus' to which you refer, be similar to that of your 2+ year project that still isnt ready for public release yet? Wow, sounds special... sounds about as likely as finding someone to supply your 55% cobalt alloy/ rhenium bore barrels... when should we be expecting those... next week, another 2 weeks, end of summer, just in time for hunting season, maybe xmas 2013?

The viability of your system is assured failure, REGARDLESS of whether the bullets fly or not, due to an unworkable and unprofitable business model. When the business fails, what will happen to all the people with expensive tomato stakes that wont be able to shoot any other bullet, have you spared a thought for them? - You might consider a contract with your customers guaranteeing supply, and that they wont be held to ransom by the cost of projectiles in your tiny captive market.

Good luck mate, your gonna need lots...

 

[Noel Carlson]

Re: 338 LM Improved gain twist barrel

Ah,

Now that is the Groper that we have been seeing behind the obsequiously engratiating door-rattling.

Thankyou for the best wishes, but "luck" is not a part of my business plan. I trust you have all of the information that you need at this point?

 

[Jeffvn]

Re: 338 LM Improved gain twist barrel

Groper

Thanks for turning my thread into another rant so full of crappy arguing that I no longer want to read it, much less participate in it.

JeffVN

 

[jrob300]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">So i shall rephrase my prior form, <span style="font-weight: bold">back on topic</span>, and put it like this: - In your own mind, why do you beleive that noone to date, has designed and successfully implemented, a rifle system whereby very long projectiles are stabilized from very tight twist rate barrels? Did all the great minds miss something?</div></div>

Groper,

Perhaps you're lost and have wandered into the wrong thread...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jeffvn</div><div class="ubbcode-body">I have been posting <span style="font-weight: bold">about my new rifle</span> in a different forum, but thought you guys might like to see it also.</div></div>

I'm pretty sure that was the OP's topic. Jeff, feel free to correct me.

From what I can see, in every thread where you show up, you turn it into a conversation about you. You might want to take the polite suggestion to start your own thread so the rest of us can enjoy the topic at hand.

You're not the only one guilty of this, even in this thread, perhaps just the most persistent or desperate to be heard.

John

 

[Augustus]

Re: 338 LM Improved gain twist barrel

When Noel and I started the development and testing on the ZAs we decided to keep the process completely transparent. It was decided that the info would be made public on each succeeding test and that the failures as well as successes would be reported. Up to this point that philosopy has been followed to the letter. From the very beginning I have warned individuals to refrain from running out and ordering barrels until the testing is complete and the questions concerning what works and what dont have been answered. I now believe the avenue of transparency was a bad idea and has served no purpose other than cause unnecessary controversy. Anyway the end of the process is very near and everyone can expect a comprehensive statement concerning twist rates,projectile demensions,BCs, availibility of componants etc. Everyone needs to take a deep breath and relax. Hell,once perfected there wont be more than a handfull of cavilians interested in this stuff anyway.

 

[killer_penguin]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body">You might want to take the polite suggestion to start your own thread so the rest of us can enjoy the topic at hand.</div></div>

THIS!

I'm sick to death of seeing groper's name next to posts where he's preaching shit to people that obviously don't need to be preached at.

Groper, is it so hard to share your views in YOUR OWN THREAD instead of crapping up everyone else's? Just so you know, to the 3rd parties here, you just come off as you enjoy being a thorn in the side.

 

[goober]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Killer Penguin</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body">You might want to take the polite suggestion to start your own thread so the rest of us can enjoy the topic at hand.</div></div>

THIS!

I'm sick to death of seeing groper's name next to posts where he's preaching shit to people that obviously don't need to be preached at.

Groper, is it so hard to share your views in YOUR OWN THREAD instead of crapping up everyone else's? Just so you know, to the 3rd parties here, you just come off as you enjoy being a thorn in the side. </div></div>
Killer Penguin stop barking like a Chihuahua it is annoying .
Groper is participating in a forum like I am and you are and expressing ideas which he obviously has even if they annoy the OP .
I am not picking up still from this thread why the need for aggro- academic ego maybe , no offense intended ?? I don't know Groper at all but so what if Groper pitches in his ideas also -more of you guys testing at gear at ELR range the better for us all cause I sure cant afford to do it .It is not a bad thing to hear an academic argument based on testing and concepts from two or more people even if their views are different .

I hope you keep this particular forum up to date Jeff ,Noel and Augustine with your findings as I do Groper as it is actually real important .
There isn't to many guys around that do this stuff well and that share their valuable findings with others like myself who have an interest in ELR shooting .
your work leads many like myself through the darkness of the ballistics quagmire to a place where a positive decision on gear combination's can be made .
just my 2 cents gentleman and I value yours obviously greatly

 

[jrob300]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ch'e</div><div class="ubbcode-body">Groper is participating in a forum like I am and you are and expressing ideas which he obviously has <span style="font-weight: bold">even if they annoy the OP </span>. </div></div>

That's *your* opinion.

Here's what the conduct rules have to say about that:

2. Do not post off-topic. Please keep your comments consistent with the subject and purpose of the conversation thread. Deliberate disruption -- such as consistent off-topic commentary -- will not be tolerated.

John

 

[goober]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ch'e</div><div class="ubbcode-body">Groper is participating in a forum like I am and you are and expressing ideas which he obviously has even if they annoy the OP . </div></div>

That's *your* opinion.

Here's what the conduct rules have to say about that:

2. Do not post off-topic. Please keep your comments consistent with the subject and purpose of the conversation thread. Deliberate disruption -- such as consistent off-topic commentary -- will not be tolerated.

John
</div></div>

John , when talking about these things other ideas have relevance and pertain to the general subject .Please show me how Groper is consistently contravening these rules with an obvious bad intent

 

[jrob300]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ch'e</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ch'e</div><div class="ubbcode-body">Groper is participating in a forum like I am and you are and expressing ideas which he obviously has even if they annoy the OP . </div></div>

That's *your* opinion.

Here's what the conduct rules have to say about that:

2. Do not post off-topic. Please keep your comments consistent with the subject and purpose of the conversation thread. Deliberate disruption -- such as consistent off-topic commentary -- will not be tolerated.

John
</div></div>

John , when talking about these things other ideas have relevance and pertain to the general subject .Please show me how Groper is consistently contravening these rules with an obvious bad intent </div></div>

Now we ARE off-topic... but perhaps it would be good for the lot of us to discuss this in the open, because the usual suspects end up in each others' threads and end up annoying each other a LOT.

In my mind, homage is paid to the OP and his thread. He dictates whether something is on topic or off topic. Some OP's moderate their threads better than others. But most contributors to a thread came to read about and contribute to the topic. NOT SOMEBODY ELSES AGENDA!!

What I see Groper and OTHERS (most have all showed up in this thread) do consistently, is turn any thread about ELR back towards their little squabble. I seriously wish you guys would just get a room. The foreplay is killing me.

 

[jrob300]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ch'e</div><div class="ubbcode-body">Please show me how Groper is consistently contravening these rules with an obvious bad intent</div></div>

In answer to your specific question...

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">Once again, more avoidance and irrelevance...

Would the 'general consensus' to which you refer, be similar to that of your 2+ year project that still isnt ready for public release yet? Wow, sounds special... sounds about as likely as finding someone to supply your 55% cobalt alloy/ rhenium bore barrels... when should we be expecting those... next week, another 2 weeks, end of summer, just in time for hunting season, maybe xmas 2013?

The viability of your system is assured failure, REGARDLESS of whether the bullets fly or not, due to an unworkable and unprofitable business model. When the business fails, what will happen to all the people with expensive tomato stakes that wont be able to shoot any other bullet, have you spared a thought for them? - You might consider a contract with your customers guaranteeing supply, and that they wont be held to ransom by the cost of projectiles in your tiny captive market.

Good luck mate, your gonna need lots...
</div></div>

This has NOTHING to do with OP's topic...

John

 

[killer_penguin]

Re: 338 LM Improved gain twist barrel

Bingo. Jrob hit it nicely. Call me whatever you like, it doesn't change the facts.

Fact is that nearly every thread groper is involved in turns into a shitstorm from which we have to pick out useful data from in between his tired ramblings.

If someone's true intent is to simply share knowledge, they have very little emotional attachment to whether someone agree's with them or not. This is NOT the case with groper. He has no desire for a conversation, and thusly does not LISTEN but rather just wait's to talk.

 

[goober]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Killer Penguin</div><div class="ubbcode-body">Bingo. Jrob hit it nicely. Call me whatever you like, it doesn't change the facts.

Fact is that nearly every thread groper is involved in turns into a shitstorm from which we have to pick out useful data from in between his tired ramblings.

If someone's true intent is to simply share knowledge, they have very little emotional attachment to whether someone agree's with them or not. This is NOT the case with groper. He has no desire for a conversation, and thusly does not LISTEN but rather just wait's to talk. </div></div>

Guys , Groper may have challenged others on this thread as noted with John's copy of a groper quote -but so what if a few academic sparks fly .To date his post's have been polite just not in agreement with the op's-No big deal-lets thicken our skin up a little guy's !I went back and read a few of his post's and find him to be -like me ??? lol
Now lets get back on line of this thread as I really want to hear more from the OP and friends .

 

[killer_penguin]

Re: 338 LM Improved gain twist barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ch'e</div><div class="ubbcode-body">Now lets get back on line of this thread as I really want to hear more from the OP and friends . </div></div>

Agreed, however its a virtual guarantee that groper will not allow that to happen without firing back. Perhaps I can be proven wrong.

 

[Noel Carlson]

Re: 338 LM Improved gain twist barrel

KP, John, Ch'e,

We are preparing for SHOT, and will not be doing any more testing for awhile. When the thread resumes, it will be for publication of final test results, not be for the purpose of generating "academic sparks". The more astute already know Groper is not a fountain of academic wealth in any case, and I would put Ch'e on notice that if he decides to emulate Nick, it will not be well received. I have already provided a good reference for those whose interests are technical.

We appreciate that current interest is focused now upon what we are doing that is different, and that explaination will have to wait a little longer. For now, we will be restricting reporting to performance based observations only. I genuinely wish it could have been different. I hope you will be understanding, especially those that have been waiting a very long time for projectiles compatible with standard twists.

Best,
Noel

 

[goober]

Re: 338 LM Improved gain twist barrel

Noel , thank you for the update concerning testing and shot show ! As far as emulating Nick "aka Groper " no that will not be happening as I know far less than all of you about your subject matter and wouldn't think of putting an uneducated opinion forward .
I am happy listening to those actually doing it and taking their advice which ultimately will be yours, Jeff's and Augustus and if Groper comes up with something his also .As mentioned the work and info are much appreciated and I await the finish of the story once its written.Many thanks

 

[Noel Carlson]

Re: 338 LM Improved gain twist barrel

Thankyou Ch'e

 

[C.K]

Re: 338 LM Improved gain twist barrel

Noel, don't take this wrong.

FWIW these need to me tested at sea level and in -degree temps before release, we both know what can happen if there running on the edge and what a 20degree change will do. I'm not saying there running on the edge but it would be an easy way to check if they are.

 

[Augustus]

Re: 338 LM Improved gain twist barrel

CK, it was 15 deg F this morning and the elevation is 550 ft here at my house. I saw no indication of instability at 2560 from the 6.5 cal.

 

[Augustus]

Re: 338 LM Improved gain twist barrel

Uh, maybe I should also so add that I did not get out of bed this morning either.