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Thread: Trailing Edge and accuracy

  1. #21
    Boolit Master


    Larry Gibson's Avatar
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    vzerone

    Nothing condescending or inflammatory there in my post. I was responding to runfiverun's remark which some might consider "inflammatory". However, I do not consider his remark that but just his usual snide remarks. Other than that my remarks are facts based on what was said in the other thread.

    The point is DrB claimed all sorts of "credentials in Ballistics" but it became quite apparent his knowledge on the topic was lacking. I do have a college degree but have learned far more from practical experience and learning by doing/experimenting than I did in college. What I did learn in the science classes I took was how to properly conduct an experiment with a sufficient sampling so that a correct conclusion may be reached. I know many highly educated people, including PHDs, who could not pour water out of a boot with out cutting the toe off to do it. Conversely I also know many highly educated people, including PHDs, who can and do use their education and knowledge correctly. I have been studying ballistics since I was in high school. I have continued through the years and have invested heavily in the study to be able to conduct and measure the results of tests/experiments. What I present is based on facts from that testing.

    Did Dr. F. W. Mann have a PHD in Ballistics? No, he was a medical physician (general practitioner including obstetrics) With a degree in science. He began studying ballistics as a young man because he was intrigued by the bullets dispersion on target (what we call groups). He learned through tests and experimentation. We are fortunate for the results of his work.

    When I first mentioned preliminary testing was indicating too much RPM might be the root cause of inaccuracy at high velocity on this forum long ago I was challenged by many on this forum. I was told by several "old sages" here that I must prove the theory. I went to great lengths of time and expense to prove the RPM Threshold was valid. Most knowledgeable shooters here believe that proof and believe the RPM Threshold is valid because they have experienced the effect of too much RPM resulting in loss of accuracy also.....at the RPM levels predicted. If you still doubt then you also are more than welcome to present actual test evidence proving otherwise. However, unless you actually post real test results with sufficient groups such as I have at 100, 200 and 300 yards then be prepared to have your results questioned. Posting what someone else says they have done, especially on the internet, without the actual test results is meaningless. Also posting cropped photos of a supposed 4 shot group at 312 yards by a relative is questionable.

    You can indeed push up the RPM Threshold. I have also proven that not only on this forum but you can still find the information on the NOE Forum. However, even though you can push up the RPM Threshold you will still bump into it. Several claim by using Cu in the alloy and heat treating they attain "accuracy" at 2400 fps +/- from .308W ARs or similar rifles with 10" twists. For sake of argument let's just agree with that. So then if there is no RPM Threshold then why are they not pushing 2500 - 2600 fps from the .308W.....it certainly is capable. The RPM Threshold of 120,000 to 140,000 RPM is the "magnitude and intensity" based on the use of bullets cast of ternary alloys. Adding Cu, PPing, and it appears some PCing are some methods to push up the RPM Threshold.

    However, all of this has nothing to do with the OP's question. I'm all for getting back on topic.
    Last edited by Larry Gibson; 11-13-2017 at 01:14 AM.
    Larry Gibson

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    ― Nikola Tesla

  2. #22
    Boolit Master
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    I have done no testing on crowns that I puposely disfigured. However, I have recrowned more than one barrel with a hacksaw, square and file, and a 1" diameter grinder ball in a hand drill and obtained groups of less than one inch at 100 yards, so it can't be that hard. On the other hand, it has been my experience that the base of a cast bullet should be as near perfect as you can make it, even if you are covering it with a gas check.
    Last edited by oldblinddog; 11-13-2017 at 04:11 AM.
    USMC 6638

  3. #23
    Boolit Master
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    sarcasm isn't snide.
    it's all an educated guess,,,, till the trigger is pulled.

    this opinion brought to you by mister low-tech solution..

  4. #24
    Boolit Bub
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    Firearm-fixed(short term,throat brrl condition)

    Target-fixed(stapled)

    Shooting station-fixed

    Skill-fixed(plateau)

    'Bout the only thing not "fixed" is the bullet flight.So don't put fixed limits on a dynamic part of the equation.Just sayin.

  5. #25
    Boolit Man
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    I have recrowned barrels and counterbored worn muzzles,not due to any theory,but because owners paid to have it done.And I have read claims that a barrel crown needs to be accurate/even to within a millionth of an inch.Now if someone was willing to pay ,I could certainly charge extra for that.Whether it was achieved or not.But I have always theorized that if all this was so critical,why isnt porting of barrels ie Pendleton Dekicker /Swedish AG42....universally applied.Venting pressure from the exit discharge should work. IMHO,the shooters most likely to pay for anything that works would be the rimfire competition crowd.Do they?I dont know.Fixing their guns is like clockmaking,i cant do that either.

  6. #26
    Boolit Master


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    oldblinddog and john.k bring up some interesting points concerning just how "precise" does the crown have to be?

    I have, many years ago, filed the bases of bullets so they were not square to the axis of the bullet. Accuracy with those was very poor.

    I believe there was a test done with the results posted in CBA's "Fouling Shot". I'll try to find it.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  7. #27
    Boolit Master vzerone's Avatar
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    Quote Originally Posted by Larry Gibson View Post
    vzerone

    Nothing condescending or inflammatory there in my post. I was responding to runfiverun's remark which some might consider "inflammatory". However, I do not consider his remark that but just his usual snide remarks. Other than that my remarks are facts based on what was said in the other thread.

    The point is DrB claimed all sorts of "credentials in Ballistics" but it became quite apparent his knowledge on the topic was lacking. I do have a college degree but have learned far more from practical experience and learning by doing/experimenting than I did in college. What I did learn in the science classes I took was how to properly conduct an experiment with a sufficient sampling so that a correct conclusion may be reached. I know many highly educated people, including PHDs, who could not pour water out of a boot with out cutting the toe off to do it. Conversely I also know many highly educated people, including PHDs, who can and do use their education and knowledge correctly. I have been studying ballistics since I was in high school. I have continued through the years and have invested heavily in the study to be able to conduct and measure the results of tests/experiments. What I present is based on facts from that testing.

    Did Dr. F. W. Mann have a PHD in Ballistics? No, he was a medical physician (general practitioner including obstetrics) With a degree in science. He began studying ballistics as a young man because he was intrigued by the bullets dispersion on target (what we call groups). He learned through tests and experimentation. We are fortunate for the results of his work.

    When I first mentioned preliminary testing was indicating too much RPM might be the root cause of inaccuracy at high velocity on this forum long ago I was challenged by many on this forum. I was told by several "old sages" here that I must prove the theory. I went to great lengths of time and expense to prove the RPM Threshold was valid. Most knowledgeable shooters here believe that proof and believe the RPM Threshold is valid because they have experienced the effect of too much RPM resulting in loss of accuracy also.....at the RPM levels predicted. If you still doubt then you also are more than welcome to present actual test evidence proving otherwise. However, unless you actually post real test results with sufficient groups such as I have at 100, 200 and 300 yards then be prepared to have your results questioned. Posting what someone else says they have done, especially on the internet, without the actual test results is meaningless. Also posting cropped photos of a supposed 4 shot group at 312 yards by a relative is questionable.

    You can indeed push up the RPM Threshold. I have also proven that not only on this forum but you can still find the information on the NOE Forum. However, even though you can push up the RPM Threshold you will still bump into it. Several claim by using Cu in the alloy and heat treating they attain "accuracy" at 2400 fps +/- from .308W ARs or similar rifles with 10" twists. For sake of argument let's just agree with that. So then if there is no RPM Threshold then why are they not pushing 2500 - 2600 fps from the .308W.....it certainly is capable. The RPM Threshold of 120,000 to 140,000 RPM is the "magnitude and intensity" based on the use of bullets cast of ternary alloys. Adding Cu, PPing, and it appears some PCing are some methods to push up the RPM Threshold.

    However, all of this has nothing to do with the OP's question. I'm all for getting back on topic.
    Well Larry those members shooting CU in the alloy aren't claims, they are facts. One member, who doesn't post much anymore, is getting full jacketed velocities with a 7mm-08. Now your mention of the AR10 with the ten twist reminds me of my cousin and you know who I'm talking about. I also wonder if you meant him, but he wasn't using CU in his alloy. Well he did 3100 fps with more then very good accuracy, but you and your minions just ran him into the ground. He done it, I've seen it, I've seen him do it again and again. Now he doesn't care about it. You've made this statement to a current member, which I won't mention, and he called it your "canned response" "about the small calibers not having enough distance away from the centerline of the bullet to be affected by the spin as much". With that said why did you fail the high velocity with accuracy test with the 6.5 Swede which can still be read here? Or did you purposely fail it to smite my cousin and another banned member? I'd say you just outright failed at it.

    Larry you just can't or won't see that gripping the rifling and alloy flow under acceleration is the problem and that the spinning just exacerbates and magnifies those issues. You know about the famous seven twist Colt HBAR my cousin has. He has done some precise measurements of that barrel's bore and groove. Mainly the groove is of his concern. The dept of the rifling groove is barely .0025. That would give you a .006 across the grooves. He surmises that when you are going to manufacture a barrel that is going to be chromed in the bore and chamber that the manufacturer makes allowances for the chroming. Maybe Colt didn't??? Or maybe they didn't feel the smaller groove measurement was going to make any difference. Well it doesn't with jacketed, but it sure does with cast. You are correct about not getting accuracy with that seven twist HBAR, but not because of the rpm theory, but because of the reason stated at the beginning of this paragraph. What's even more amazing is that I've seen you mention shallow rifling is bad for cast in another post somewhere else or even some other forum. Yet you hold onto this rpm theory.

    There are two current members, that I know of, at the present and closing in on 3000 fps velocity with reasonable accuracy using powder coat alloy bullets. So maybe Larry powder coat, paper patch, even unique alloy mixes are better gripped by shallow rifling. I know another thing that paper patch does for the alloy bullet and that is it keeps the heat from powder combustion and friction off it. Perhaps powder coat does the same, but unique alloys don't.

    If rpm doesn't have a flaw to work on, it doesn't affect accuracy.

  8. #28
    Boolit Master vzerone's Avatar
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    BTW perfect crowns and perfect bullet bases are very old knowledge.

  9. #29
    Boolit Master
    swheeler's Avatar
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    Hell, I was there!

  10. #30
    Boolit Master


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    vzerone

    If you read what you just posted (post #27) you validate the RPM Threshold and explain why it exists.

    I know a bullet with Cu in it can push the RPM Threshold.....I said that not only in this thread but in numerous other threads. I have tested bullets with Cu in it, one of those "former" members you mention sent me the babbitt and useful information. I also have tested PC'd bullets and have pushed the RPM threshold with them. I've posted the results of both on this forum. Even so, the RPM threshold is only pushed up....it is still there with those bullets. Obviously you have problems understanding the RPM Threshold of 120,000 - 140,000 RPM applies to ternary alloyed bullets not those with Cu in them or those that are PC'd.

    I have no idea what you mean by "canned response" but the higher the rotational velocity the greater the adverse affect of any defect will be given the same RPM.

    "If rpm doesn't have a flaw to work on, it doesn't affect accuracy."

    Absolutely correct. By posting such you obviously admit to the adverse affect RPM has on accuracy. Thank you for finally coming to the correct conclusion.

    I'll not enter into a discussion of your cousins, shall we say, bodacious claims as they've been discussed too many times before. The completeness of my testing on the 6.5 Swede thread speaks for itself. No one else posted any factual test evidence of doing any better.

    As to closing in on 3000 fps......I closed in on it last year using a ternary alloy (#2 alloy) cast bullet (the 30 XCB) and held 1 1/2 moa accuracy with 10 shot groups at 100, 200 and 300 yards consistently.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  11. #31
    Boolit Bub
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    "One hit wonders".... sheesh.

    I'll never forget gettin front page coverage on/in Southern Living mag.....

  12. #32
    Boolit Master


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    Quote Originally Posted by runfiverun View Post
    sarcasm isn't snide.
    Before admitting to using something you might want to look up its meaning. I was being nice and continuing to give you the benefit of the doubt using the term "snide".

    According to Webster's New Collegiate Dictionary "sarcasm" is defined as; 1. a sharp and often satirical or ironic utterance designed to cut or give pain. 2. a mode of satirical wit depending for its effect on bitter, caustic, and often ironic language that is usually directed against an individual.

    Thus your "sarcasm" is duly noted.

    Now, can you and vzerone kindly knock off what has been hashed out so many times and just let this thread get back on topic? I for one would appreciate it as I'm sure would most everyone else.
    Last edited by Larry Gibson; 11-13-2017 at 05:41 PM.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  13. #33
    Boolit Master vzerone's Avatar
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    Quote Originally Posted by Larry Gibson View Post
    vzerone

    If you read what you just posted (post #27) you validate the RPM Threshold and explain why it exists.

    I know a bullet with Cu in it can push the RPM Threshold.....I said that not only in this thread but in numerous other threads. I have tested bullets with Cu in it, one of those "former" members you mention sent me the babbitt and useful information. I also have tested PC'd bullets and have pushed the RPM threshold with them. I've posted the results of both on this forum. Even so, the RPM threshold is only pushed up....it is still there with those bullets. Obviously you have problems understanding the RPM Threshold of 120,000 - 140,000 RPM applies to ternary alloyed bullets not those with Cu in them or those that are PC'd.

    I have no idea what you mean by "canned response" but the higher the rotational velocity the greater the adverse affect of any defect will be given the same RPM.

    "If rpm doesn't have a flaw to work on, it doesn't affect accuracy."

    Absolutely correct. By posting such you obviously admit to the adverse affect RPM has on accuracy. Thank you for finally coming to the correct conclusion.

    I'll not enter into a discussion of your cousins, shall we say, bodacious claims as they've been discussed too many times before. The completeness of my testing on the 6.5 Swede thread speaks for itself. No one else posted any factual test evidence of doing any better.

    As to closing in on 3000 fps......I closed in on it last year using a ternary alloy (#2 alloy) cast bullet (the 30 XCB) and held 1 1/2 moa accuracy with 10 shot groups at 100, 200 and 300 yards consistently.
    No Larry I don't admit to your false theory. Anyone that casts good bullets, loads them properly, good lube, and the bullets start straight there is no rpm theory.

    You know I see you're nit picking on Runfiverun, so legal season then. As I mentioned your "minions" I see one showed up and put up some emoticons. I leave you with this

    Knowing the truth, seeing the evidence of the truth, but still believing the lie.

    I'll use your ploy, let's get back to the original posters questions.

  14. #34
    Boolit Master
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    Here we go again with the "this guy I know" or "my cousin did this" but never any documentation to back it up. This kind of garbage cost us more than one top notch contributor to this forum in the past! Hey Larry, for what its worth---it never pays to interact with trolls! It's sort of like trying to teach a pig to sing---frustrates you and aggravates the pig!
    R.D.M.

  15. #35
    Boolit Master OS OK's Avatar
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    Quote Originally Posted by blackthorn View Post
    Here we go again with the "this guy I know" or "my cousin did this" but never any documentation to back it up. This kind of garbage cost us more than one top notch contributor to this forum in the past! Hey Larry, for what its worth---it never pays to interact with trolls! It's sort of like trying to teach a pig to sing---frustrates you and aggravates the pig!
    Nailed it...you must be a framer! . . .

    Especially about loosing the top notch contributors, their hard to come by...Ever now and then a post like this one will get deep and danged interesting but there's always someone and his kinfolk to contend with.

    I wish some of you 'drive by commenters' would put the effort into a quality thread, jam packed with facts and pictures ever now and then...it'd make the arguments a lot more tolerable.
    a m e r i c a n p r a v d a

    Be a Patriot . . . expose their lies!

    “In a time of deceit, telling the truth is a revolutionary act.” G. Orwell

  16. #36
    Boolit Master JBinMN's Avatar
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    I am not sure I understand what some folks are saying for sure in the last 10 or so posts about other topics, but due to my own previous experience in another field, I do know that items in rotation, do show an effect of more deviation of path due to defects/changes in rotation.( in my case/experience by "doing" & "testing", aviation & "tracking" "helo" blades & propellers in particular)

    Thus, I can visualize/understand how the path of a bullet that has a certain defect would not follow the same path as others without the same defect, or others that had dissimilar defect(s) would not follow the same path as the former, nor the same as bullets without defect.

    How I see this in my head is... A set of blades/props that has one that has a defect, or is out of adjustment(OOA), can have an effect on the others, even though the others may have no defect/OOA situation, due to the same rotational path of the set. The speed is the same, the torque is the same, every thing is the same but the defect(s).
    [Or, perhaps dissimilar materials used in manufacture. I.E. - Fiberglass &/or metal construction, wood, different assembly components et al, etc.]

    In aviation,( or used to do it) we test for such situations so that we can try to find the optimal set of parameters that makes each work as a whole & not as an individual.

    To me, it is the same with bullets/boolits/projectiles of any kind. Could be a rock, or a missile. If they are not the same as each other, they will react differently due to any factor that may have influence.

    Be it "rotation" differences in lands & grooves, or differences in the powder charge or prime or combination, crimp, or lack of, etc... they are all factors to be considered.

    In the case(s) of my experiences testing & correcting blade tracking issues( in particular), I have found that even when all components are the same type & manufacturer, there may still be cases of one having a defect or being just different enough, but still in specifications from the others, that an OOA condition can be noticed as compared from the others rotational path & correction needs to be made for optimal & efficient performance.
    http://aviationmaintenance.tpub.com/...04-23-5_68.htm


    I see no difference in bullets or boolits...

    Any differences of opinion about one of the "factors" such as RPMS,etc. is likely a different topic subject than the OP here. ( & seems to be, from some time before)

    To "try" to paraphrase the OP & what I got from it's intentions...

    "What effect does a bullet/boolits shape at the "Trailing edge" have on its' accuracy as far as being different from a normal one?

    Or something along those lines...

    I said before I think it does have an effect & it appears so do more than a few here & other places...

    Are we back to the regular scheduled program?
    Last edited by JBinMN; 11-13-2017 at 09:35 PM. Reason: Yeah. Stuff happens...
    "If ya don't like my gate, ya don't have to swing on the hinges..." - L. Ackerman ( RIP)

  17. #37
    Boolit Man
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    I have no doubt that all of the research into this was done over 100 years ago,in respect to artillery projectiles.The results are probably still top secret,buried in the archives .Factors relating to the barrel are easily controlled, but once the projectile is free of the barrel,then how many variables are there?I dont know,and its certainly beyond the means of any private person to investigate in a scientific manner.......Here s one more variable...I recently fired and recovered some cast bullets,and i have noted that paper patched flat based bullets develop a small uneven bevel around the base when fired.But imagine how much Dr Mann could have achieved with a labradar and high speed video recording.Look in the archives,dont ask to reinvent the wheel.

  18. #38
    Boolit Bub
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    Let me get this straight.... if I rip off someone else's work,change a "name" and present it as fact,that anybody questioning it is somehow not paying due diligence?

  19. #39
    Boolit Master


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    For those CBA members the Fouling Shot article is "The Need for a Perfect Crown is a Myth" - John Alexander, Fouling Shot Jul-Aug 2014. I'll have to check and see if I can repost it here.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check