Ideal twist rates for cast boolits vs. jacketed. Different? Why?

[MBTcustom]

I will view this with interest and any PM to delete off topic posts will be done,

Thank you for your help.

Now you have two moderators who will watch your back.
What do you say Geargnasher?

[geargnasher]

You have my answer, Brad.

[MBTcustom]

Well if we aren't here to collaborate, learn from each other, and try to advance, then why are we here?
Why do each of you log on here?
What are you really looking for from cast boolits?
Why here and not some other forum?
If you're here to learn and teach then this is my olive branch. If you are here to settle a score, make money, gripe about what all is wrong, or just sit there like a bump on a log, then you might as well not have ever logged on.

[geargnasher]

It's been done here many times, at least once with some very specific instructions. The reason you don't see that is too many distractions by detractors, and lack of interest by participants. Nobody's going to go through all mess of drama that always gets thrown in their faces when it comes up. Just look what happened the last time I posted a good HV group. That sort of nonesense has to stop, then I might tell how I did it so that YOU can do it, too.

Gear

[Love Life]

I'll get it figured out. It's not rocket science to be honest. It just requires effort and dedication. I'll need something to keep me busy on the super long range 200 yard range I'll be using in Georgia.

[357maximum]

Brad



I admire your effort here but it ain't ever gonna work the way you want it to. If you make everyone sign a "I have read and understand what Tim wrote in the most excellent post #68 on this thread" you might have a fighting chance, but

Two big things are against you.

1. One of your coherts (the one that went from asking newbee questions to being THE SELF ANNOINTED EXPERT in a years time) is still grinding axes and taking jabs apparently. His last couple of posts in this very thread show that with GIN CLEAR clarity. One of his last posts on this thread would be classified as a personal attack had it been written by anyone other than him and would have come with consequences to anyone else had they posted the same. The same fella is now taking pages from his mentors handbook with cryptic answers and scapegoating I see. It is posted right above this post that HV is not rocket science, and LoveLife is 100% correct in that statement. One can not gain prestige and notariety that some apparently seek unless they make something look waaay harder than it is and making up terms for techniques that have been posted over and over in a different word/form on this forum this same fella excels in that skill/desire/ whatever you wanna call it. Going fast with cast in all but the most disagreeable guns simply ain't that tough......the answers you seek are already typed out in this thread and scattered all over this forum. It simply comes down to using the already proven methods and merely doing the work with each toy.

2. Most the guys that already can do cast at HV in most their toys they desire to so with have been kicked in the teeth so many times for trying to help others that they have simply quit trying and have basically went radio silent, have passed on, or simply went away.

You know what they say about insanity and doing the same things over and over and expecting different results right?


I wish you good luck, you'll need it.

[nanuk]

I am new to casting, and I came here (as redirected from other sites) to learn about casting and shooing cast.

one thing I HAVE learned, is who offers information freely, who speaks in bafflegab, and who here has such a huge ego that they believe ONLY they have the right to the information, and to make money off of it.

The old, "I know something You don't know" schoolyard taunt is getting very old.

I once suggested everyone lay them out on the table alongside a ruler, take a pic and post it so everyone'd know.... as there are some who are Definitely OVERCOMPENSATING for their "Short" comings.

this used to annoy the heck out of me, but one day I had an epiphany

castboolits.gunloads.com is NOT a place of sharing information

now that I have come to understand that, I can go back to learning. (I just need to do better at searching)

[Larry Gibson]

Wait a minute.

When I mentioned that I got near 2400 fps out of a ten-twist, with "useable accuracy" (1.25 MOA for multiple, ten-shot groups at a hundred yards on different days is pretty usable), you demanded, rather rudely, to see it done in person. The implication was obvious, I think.

Now you're telling others how to do it. I can show how I did it, but I'd like to see you go first here. Please give some details, pics of groups and load details, including what tolerances or anything else specifically that you changed to "push up" the threshold compared to what you could do with your normal loading routine that limited-out at the top of the threshold. This is the sort of stuff a lot of people are interested in right now and following hoping to learn. Maybe you could start a new thread, titled "How to get good groups past the RPM threshold" or something.

Also, I'm getting a distinct vibe that you are starting to assimilate the term "pushing the rpm threshold up" with stretching the twist rate out and loading to higher velocity. I DON'T THINK SO. That would be called "lowering the RPM and increasing velocity to stay within the threshold". The threshold remains the same for the equivalent loading techniques the way I read your theory.

Gear

I would ask that you read the thread that btroj posted in the next post of two; http://castboolits.gunloads.com/show...velocity-chart

If you'll note in there I say the threshold can be pushed up, and it can. As to the '06 with 10" twist being accurate "near 2400 fps" it was not with multiple 10 shot groups at 1.25 moa. The complete details can be found with a search. The testing was done several years ago by my self and bass ackwards and was quite well documented on this forum. All of the techniques used you describe on the other thread now running were mostly used plus a bullet of proper design for HV in the '06 case was used. In that concurrent thread I see little to no discussion of proper cast bullet design for HV, especially in faster twists to push the RPM threshold up. I would interject some helpful comments in that thread but I haven't because I suspect the response would be similar to that when I offered advise in your design for the 30x57 thread. Yourself and 2 - 3 others would simply come back with the same old arguments instead of looking at it with an open mind considering what I've demonstrated at HV with cast bullets in 10 and 12" twists also. Thus I simply choose not to comment as I am very tired of it all. That is why, in this thread, I was adamant with btroj not to go into a discussion of the RPM threshold.

I didn't "demand to see it done in person" rudely or not. To "demand" requires authority and I have no authority to make you do anything. I asked, numerous times, for you simply to show me how you do it.....not that it could be done but rather how you do it. You refused even though I was at Kerrville. It is your refusal to show me how you do it that lends credence of many to doubt you can. I do not doubt it can be done as I have done it. It is the "how" I wanted to see because I like to learn and expand my knowledge to better understand cast bullet ballistics. I have the impression I could learn from you the same as you could learn from me but that needs to be a two way street.

Also you are misinterpreting your "distinct vibe". I often describe how to push the RPM threshold up when they have faster twists in their rifles and offer that advise to many here. However, the topic of this thread is the "ideal" twist as goodsteel stated with the implication if building a rifle why not use the "minimal" necessary twist so as not to spin the bejesus out of the cast bullet. That is the difference; if you already have a rifle with a given barrel twist then you must deal with that. If you are building a rifle then you don't have to "deal" with a given twist. You can have a twist that is best suited or "ideal" for the bullet(s) you intend to use. Thus I am not assimilating one term into the other as they are two separate and distinct situations.

BTW; "lowering the RPM and increasing velocity to stay within (actually under) the threshold" is a very easy way to accomplish accuracy at HV with cast bullets if one is building the rifle. That is the real point of being able to select the "ideal" twist, eh?

Larry Gibson

[Larry Gibson]

How do we get decent 2200 to 2400 fps accuracy from a 10 twist barrel when this far ascends the 1944 fps that gives us the upper rpm limit of 140,000?

http://castboolits.gunloads.com/show...velocity-chart

Are you saying that with good load technique, a good chamber and throat, and good bullets that the threshold can be beaten?

If you read my post #1 in that thread you'll find it says; "The RPM threshold is not a set “limit” of RPM or velocity.". A complete reading of that post explains that in detail. Basically there is no "upper limit" of a specific RPM. Goodsteel's synopsis in his last post of what I said in that thread is correct.

And no, I am not saying the RPM threshold "can be beaten". I am (my opinion on this is changing, read caveat below) saying it can be pushed up with "good load technique, a good chamber and throat, and good bullets" plus several other techniques. The RPM Threshold can also be easily lowered by the use "poor" of improper of any of those things or techniques.

Caveat; I am coming to find, as I measure the psi, that when the pressure gets to the point the alloy begins to plasticize (I believe geargnasher mentions this in a post) that the RPM threshold becomes apparent with lost accuracy. It appears that plasticization of the bullet has the effect of lowering the RPM Threshold regardless of the velocity/RPM. For example; with my 14" twist .308W Palma rifle 2700 fps is giving 138,850 RPM. Shooting a 311466 I can hold accuracy to 2600+ fps with AA4350 which is 105% load density. The psi runs around 41-42,000 psi +/-. Going to a faster powder such as Varget or RL15 is needed to push the velocity upwards (haven't tried LeveRevolution yet) but the psi increases above 42,000 before velocity reaches 2600 fps and accuracy is lost. Thus the concept of the slightly increased case capacity of the 30x57. That should enable enough slower burning powder such as AA4350, RL19, H4831SC or RL22 to be used to increase the velocity and keep the psi (to keep the bullets from plasticizing) under 42,000.

That's the idea anyway. I'm waiting to find a 16" twist barrel so goodsteel can barrel a rifle for me. If the 30x57 doesn't have the case capacity I will lengthen the chamber to 30-06 (another potential benefit of the 30x57 cartridge design when used in an '06 length action).

Larry Gibson

[Larry Gibson]

At least YOU know how to capitalize my nickname, thank you.

Now, you want the truth? Here it is: This will not be possible as long as Larry Gibson participates. The reason is simple, he has dug himself into a theory which originally (though it has and continues to evolve greatly over time) stated that what we are doing with HV cast is impossible, and he doesn't want us to succeed.

If you don't believe that, look at past history. Every time someone claims to have busted the RPM threshold, he goes berserk and destroys the thread through many clever techniques, the last of which is by insulting members to the point that they get themselves banned by trying to defend themselves. Those who don't want to get banned just go away. It works every time, and his theory is safe. Now, granted, he's modified his theory over the years to gradually accept that maybe, just maybe, there are ways to "push it up", so it might be possible for him to help prove that and save "face", but basically, if you learn to do what he can't yet do, you don't really need to worry about RPM at all and his theory becomes moot. That would be devastating to him, ego-wise and credibility-wise. So I ask again, do you really think he wants us to succeed? And further, do you really think he's going to give it his best effort to prove that there was a lot about HV shooting he didn't know?

Brutal honesty, and truth. There needs to be a lot more of that around here.

Gear

Well, I made my last 2 posts above with the air of getting on with a reasonable discussion of all this so we could all learn and succeed. With this post from geargnasher, who has quite clearly now stated his position, and btroj's desire to leave an important ballistic part out of the discussion (RPM) I see we still aren't going to discuss anything as their minds are certainly made up; their way or the highway.

Not much to say other than I am very tired of the continual personal attacks by these two and a couple others. So let's just make them happy. Adios to everyone here, especially the many good friends I've made. The forum is theirs.

Larry Gibson

[MBTcustom]

Well, I made my last 2 posts above with the air of getting on with a reasonable discussion of all this so we could all learn and succeed. With this post from geargnasher, who has quite clearly now stated his position, and btroj's desire to leave an important ballistic part out of the discussion (RPM) I see we still aren't going to discuss anything as their minds are certainly made up; their way or the highway.

Not much to say other than I am very tired of the continual personal attacks by these two and a couple others. So let's just make them happy. Adios to everyone here, especially the many good friends I've made. The forum is theirs.

Larry Gibson

Don't leave just yet Larry.
The olive branch has been extended, and it takes a very special type of person to slap that to the ground and spit on it. I don't think that Gear, or Brad are that low.
However, you can't just throw years of hard feelings out the window at the drop of a hat. Especially if you're from Texas. LOL!

[Love Life]

Well...this didn't turn out well.

Anywho, while everybody is busy trying to figure out who has the biggest...ummm...caliber, I have been kicking thoughts around in the ol' brain housing group.

Where I plan to start:
When I get the 308 barrel screwed back on: Get a chamber cast and chamber pound done. Why both? Why not? This will give me my optimal case OAL so I can trim just enough to where I won't pinch a case neck and there won't be a canyon between the case mouth and the goods. It'll also give me the info needed for ordering a mould.

Boolits: Once I have my measurements then I'll order a custom mould. I plan to order it big and then bug Buckshot to make me a set of push through sizers so I can size down as needed. Maybe a good size reduction will help in eliminating those unseen voids...maybe not. You never know until you try. I may even order a mould with different sized (diameter) cavities so I have a lot to play with.

Alloy: I'll order from rotometals so I have foundry certified. I'm debating between hardball and lino, but I'll probably order both.

Lube: I have speed green so that ought to do the trick. Love me some Speed Green.

I want to test a bunch of things here. Bullets sized to bore, .001 over, .002 over, etc.

I've got to measure 308 blank neck thickness as that may allow me somewhere to play if the neck of the 308 tube is huge.

Powders: I have a bunch, and I'll play with them all.

This rifle barrel was an easy sub MOA performer and is chrome lined. Should be fun.

Ya'll keep fighting (even though I wish you wouldn't) and I'll keep on pushing.

[geargnasher]

Well, I made my last 2 posts above with the air of getting on with a reasonable discussion of all this so we could all learn and succeed. With this post from geargnasher, who has quite clearly now stated his position, and btroj's desire to leave an important ballistic part out of the discussion (RPM) I see we still aren't going to discuss anything as their minds are certainly made up; their way or the highway.

Not much to say other than I am very tired of the continual personal attacks by these two and a couple others. So let's just make them happy. Adios to everyone here, especially the many good friends I've made. The forum is theirs.

Larry Gibson

I did not state my position there. Only Brad and Tim know what it is exactly, as I have responded to PMs fro them. You do not know what it is, and cannot imply from my post what it is. I can tell you that what you assume about me is wrong, though.

That was not a personal attack, it is a viewpoint of a situation, backed up by some ten years worth of recorded history on the subject and a great deal of study about how to make something productive out of discussions that DO get personal, and DO turn into actual verbal fights. Anyone who cares to look into that can draw the same conclusion I have, and who it is who starts the attacks in the first place. I mean attacks, not valid and well-intentioned questions or devil's advocate scenarios.

Gear

[Mooseman]

You cannot solve basic engineering / ballistics/ aerodynamics/ accuracy issues without taking ALL the variables into account.
Long range shooters know that wind, humidity, temperature also play into accuracy as well as bullet design, powder used etc. The list goes on and on. Some of us have discovered other factors not expressed here... Like Bullet bases affecting accuracy.
Agreeing to disagree and remaining civil while collaborating Data is what any true Team of engineers/scientists will do to achieve the goal set forth , anything else is a just banter back and forth with ego and drama in the mix...
The first thing I was taught was the ABC's. A affects B which affects C !
Talk is cheap , the proof is in the X ring blown out of the target at extreme yardages...
Rich

[MBTcustom]

You cannot solve basic engineering / ballistics/ aerodynamics/ accuracy issues without taking ALL the variables into account.
Long range shooters know that wind, humidity, temperature also play into accuracy as well as bullet design, powder used etc. The list goes on and on. Some of us have discovered other factors not expressed here... Like Bullet bases affecting accuracy.
Agreeing to disagree and remaining civil while collaborating Data is what any true Team of engineers/scientists will do to achieve the goal set forth , anything else is a just banter back and forth with ego and drama in the mix...
The first thing I was taught was the ABC's. A affects B which affects C !
Talk is cheap , the proof is in the X ring blown out of the target at extreme yardages...
Rich

I couldn't agree more. The whole point of a collaborating thread is to reach a mutual understanding. Asking one participant to change the basic way they view this sport, is not just childish, unreasonable and selfish, it's downright unfair.
Larry does not understand the opposing position (frankly, neither do I) but it's equally obvious that Ian and Brad do not understand Larry's position either (which I feel I have a better grasp of right at the moment because it is explained more clearly.)

Fighting over it has not rendered a positive outcome for the last ten years, (no big surprise there) so why not do like everyone else throughout history who wanted to advance their knowledge, and WORK TOGETHER?

[Love Life]

Kestrel 4000 and wind flags...Mmmmm good.

Boolit bases or bullet bases? Which are you talking about? FB VS BT VS RBT?

Don't forget Altitude and DA.

[Mooseman]

Cast Boolit bases, j word bases, etc. there is more to it as many documented experiment from the 1800's forward have proven if one would read what has been done by people like Whitworth , and Mann , and others.

[Love Life]

Indeed.

[RoyEllis]

..... gripe about what all is wrong, or just sit there like a bump on a log, then you might as well not have ever logged on.

Hope it don't make anyone mad, but I'm here to gripe about what is wrong, (without taggin & baggin boolits with paper I can't get GOOD accuracy past approx 2150-2200fps with cast) and I'm firmly planted on my log, even if I do look like a bump on it cause I want to be close enough to the fire to hear what everyone has to say.
Since I can't figure out what I'm doing wrong (or not doing right) to hit accurate HV cast loadings, all I got is ???s to offer...so I figger to shut up, sit back & soak up all the knowledge I can.
So there Tim....neener, neener, I ain't giving up my log!

[MBTcustom]

True, except you forget one significant item.

I am speaking of ONE specific gun in my case. The barrel twist is what it is. That isn't changing, ever. I also have a set velocity goal for it.

Those are no longer variables, they are set in stone.

What I want to discuss is how to get to my goal with a cast bullet and good accuracy.

I am not interested in discussing what my goal should be, I have set it.

People can either help me reach my goal r decide that it is a fools errand and bow out. I have stopped caring what others think.

So, do people want to help ME and MY gun reach a specific goal or would they rather tell me what gun I should be using and what my goal should be?

It really is that simple. The gun is what it is. Period. Can't be changed. Twist rate was set long ago by Kreiger. My velocity goal is what I want to ACHEIVE. How we get there is the ONLY thing I am interested in discussing.

Brad, why do you continually look at the RPM threshold as a limit, or a way to say this far and no further?
I don't see it that way. I see the threshold as a schoolmaster that will teach you how to push further. You start with your best guess for a load and start working up. At a certain point you hit a wall (the RPM threshold) at that point, I'm not saying you throw in the towel and give up. What I'm saying is that you recognize what is happening and set up shop right there changing one thing at a time till you see what tightens the group up. Then you push further till you get stopped again. You know its imperfections that are jerking the rug out from under you somewhere, so you can progress.
To say that the RPM theory is bunk is to blow right past that stopping point, or start well past the RPM threshold and start playing cleanup. Seems that is a very haphazard way to cast about (pun intended) for answers. Nobody is asking you to change your twist rate (Personally I think you picked the perfect one to learn from) and no one is asking you to give up on anything. All I'm saying is that the RPM theory is not the only way, but it's a way of thinking about this in a straightforward scientific manner, that definitely works for some people. I'm not asking you to buy it hook line and sinker, just quit laying your hand over the mouths of people who think that way. It costs you absolutely nothing to hear another point of view and while you may disagree with Larry on this issue, you would be an absolute fool to throw everything he says in the trashcan, just as he would be a fool to ignore anything you have observed, measured and tested.
Why does the RPM threshold and the discussion of it threaten your personal constitution so much? It's just a way of looking at things just like algebra, calculus, or trig. Nobodies trying to make you change your mind on anything. All I'm asking is that you find a way to share information in a professional manner and quit lambasting Larry every time he thinks about breathing the words "RPM threshold".

I went 20 rounds with a guy at work who was a flaming liberal. I detest everything he stands for, and the basis of his every thought. I argued with him respectfully as a peer. Went round and round with him, and I learned quite a bit about the liberal agenda and several times he gave me pause for thought, and I had to reassess my values (which is why I kept going round and round with him). It was obvious that I was talking to the very guy that was going to cancel out my vote at the poles, but I kept my cool and discussed things. I never felt a compulsion to knock him out, or jerk his underwear over his head (OK, I lied) but I worked with him effectively for months. We built some cool stuff together. Does that make me less of a man? Did I feel the need to vote for Obama? NO. I could carry on an adult conversation without ramming my opinion down his throat.
That's all I was asking of you and Ian, and I didn't think that was an unreasonable request.
In this thread, Larry has been nothing but civil and helpful, unless he was answering a direct, unwarranted attack on his character. Who could blame him?