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Thread: 2500 fps w/gas check .308 What Alloy will I need????

  1. #21
    Boolit Grand Master


    Larry Gibson's Avatar
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    Since we're back on topic....what can be done with 10 and 12" twist .308Ws;

    http://noebulletmolds.com/smf/index....pic,533.0.html
    Larry Gibson

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  2. #22
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    Larry thanks for your write-up. Just what I need, as I have a M1A NM with an 11" twist, and a M700 .308 with 26 Heavy barrel and a 12" twist, and the aforementioned 700 with 24" barrel and 10" twist.

    Should be interesting to get results from these rifles!
    Maker of Silver Boolits for Werewolf hunting

  3. #23
    Boolit Grand Master popper's Avatar
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    Larry, no, I don't have a place to shoot past 100 - unfortunately. My point is that the alloy he wants to use is wrong. Your testing showed lino is not a HV alloy. My attempts with #2 weren't successful either. But it's an AR so I can't jam the lands or other tricks. Oh, 4% Sb with S as a hardener worked pretty good bout the same as #2) but man the stink is bad.
    Whatever!

  4. #24
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    Quote Originally Posted by HappyWarrior View Post
    Larry........As for 10 shot sub MOA groups at 200 yards, it would be nice to see some proof that this is not difficult and easily repeatable.
    The accuracy criteria established by those of us who actually shoot ternary cast bullets at HV has never been "sub moa 10 shot groups". While a laudable goal and many times accomplished it can not be said with certainty that we can consistently do it across the longer 200 to perhaps 500 yard ranges. Though we do shoot sub moa 10 shot groups at 100 yards consistently that in and of itself is not the criteria. We understand that as the range increases the wind and other variables will take their toll on the cast bullets we use with relatively poor BCs. What is important are two fold; usable accuracy and linear dispersion as the range increases. If the groups size increases in a non-linear fashion as the range increases the load is over its RPM Threshold. Non-linear expansion of groups can be quite radical from 100 to 200 and then to 300 yards.

    Thus the realistic accuracy criteria to consistent produce accuracy on demand has been; two moa or less group size with 10 shot groups giving linear group expansion from 100 to 200 and 300 yards and perhaps even at 400 and 500 yards.

    Certain members here complain that 10 shot groups are "hard" to shoot. Yes, they are. Another member went into a nut roll because the demonstrated linear group expansion was not exactly, down to the .001", at 200 yards double the size of the 100 yard group. He could just not understand that groups sizes are not always exactly the same at any range....there is always an ES in group sizes given a sufficient sample size of groups. Some members post 50 or 100 yards groups and assume they will linearly expand as the range increases.....which is not so if the load exceeds the RPM Threshold. I will post some same targets shot at 100 to 300 yards shortly.......have an appointment to go to. But just to tantalize, this is 10 shots at 100 yards at 2900+ fps....

    Attachment 199953

    No, the rifle does not do that consistently but it does shoot moa +/- not very much consistently.
    Last edited by Larry Gibson; 07-19-2017 at 12:09 PM.
    Larry Gibson

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  5. #25
    Boolit Master
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    Quote Originally Posted by Larry Gibson View Post
    The accuracy criteria established by those of us who actually shoot ternary cast bullets at HV has never been "sub moa 10 shot groups". Though we do shoot sub moa 10 shot groups at 100 yards consistently that in and of itself is not the criteria. We understand that as the range increases the wind and other variables will take their toll on the cast bullets we use with relatively poor BCs. What is important is linear dispersion as the range increases. If the groups size increases in a non-linear fashion as the range increases the load is over its RPM Threshold. Non-linear expansion of groups can be quite radical from 100 to 200 and then to 300 yards.

    Thus the realistic accuracy criteria to consistent produce accuracy on demand has been; two moa or less group size with 10 shot groups giving linear group expansion from 100 to 200 and 300 yards and perhaps even at 400 and 500 yards.

    Certain members here complain that 10 shot groups are "hard" to shoot. Yes, they are. Another member went into a nut roll because the demonstrated linear group expansion was not exactly, down to the .001", at 200 yards double the size of the 100 yard group. He could just not understand that groups sizes are not always exactly the same at any range....there is always an ES. Some members post 50 or 100 yards groups and assume they will linearly expand as the range increases.....which is not so if the load exceeds the RPM Threshold. I will post some same targets shot at 100 to 300 yards shortly.......have an appoint to go to. But just to tantalize, this is 10 shots at 100 yards at 2900+ fps....

    Attachment 199953

    No, the rofle does not do that consistently but it does shoot moa +/- not very much consistently.
    Have followed your research/opinions/and history shooting cast boolits,learned a lot and continue too as you always post targets showing results good and bad .
    The one thing I have noticed is you are always consistent in your posts and I admire that and am glad to see you sharing your experience . And judging by your shooting I am twice as glad to not have been on the wrong side when you were occupied in a different profession !

  6. #26
    Boolit Grand Master


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    Here's some more examples of groups shot with a 30 XCB bullet cast of #2 alloy at 2900+ fps;


    This is 4 consecutively shot 10 shot groups at 200 yards.

    Attachment 199957


    Here are four 10 shot CBA match targets shot for group, 2 at 100 yards and 2 at 200 yards.

    Attachment 199958

    Here are three 10 shot groups shot consecutively at 100, 200 and 300 yards demonstrating that at 2900 fps the load has linear group expansion and did not exceed the RPM Threshold.

    Attachment 199962
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
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  7. #27
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    So what is meant by "non-linear expansion"? Here is a test I conducted to demonstrate what happens when the load exceeds the RPM Threshold. What I did was cast some 311291s out of COWW + 2% tin and let them AC. Since most here don't get too persnickety about bullet sorting I didn't either for this test. I used bullets w/o obvious wrinkles but did not weight sort or do a real visual selection. I used a standard load of 28 gr 4895 with a Dacron filler as this has proven an accurate load in the .308W. The test rifle has a 10" twist barrel of 24". The velocity was 1894 fps (M35P at 15'). The RPM was 136,400.....below the RPM Threshold. Note the 2 group sizes on the targets. I excluded the obvious flyers and just used the "core" group size as the flyers were probably from the non sorting of the bullets. Either way the first target with 50, 100 and 200 yard groups demonstrates linear group expansion from 50 yards to 100 and then 200 yards.

    Attachment 199963

    The next 2 pictures show the non-linear expansion of groups. Everything was the same in this test except the load was increased to 38 gr 4895 with a Dacron filler. The velocity was 2491 fps (probably the 2500 fps the OP asks about). The RPM was 189,300.....well above the RPM Threshold. We see with the 50 yard and 100 yard target the linear expansion seems to be consistent. If we were only hunting deer out to 100 yards this could be a usable load depending on the shooting conditions.

    Attachment 199965

    However when we look at the 200 yard target we see there is definitely non-linear expansion. If linear the 200 yard group should have been an 8 - 9" group. It wasn't, it was 14.5" group. Now given "random selection" had we just shot a 3 shot group and had picked those 3 round in the 9 and 10 rings we could have bragged about HV "accuracy". However, the load really isn't that accurate. Had we gone out another day and shot the 2 rounds to the right of the bull and the one to the left we would come back to the forum asking what went wrong. we would get all sorts of answers about bad bedding, loose scope bases or the scope went bad.......in reality the problem was the load exceeded the RPM Threshold. How many threads have we seen just like that?

    One other thing to note is though the group has gone wildly bad. the bullet holes are all still nice and round. That means the bullets were still stable and flying point forward. Loss of accuracy from exceeding the RPM Threshold has nothing to do with the loss of bullet stability.

    Attachment 199970
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
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  8. #28
    Boolit Grand Master


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    One last example sort of tongue in cheek.....this is a group I shot with my Finn M39 MN winning the Arizona CBA State military rifle match. It is at 100 yards shooting for score, not group. It's with a 314299 cast of #2 alloy in a Lyman mould (egads, a Lyman mould...) loaded over H4895 (I get a lot of criticism for my constant use of 4895.....it works, ain't broke so I use it.....) with a Dacron filler. Velocity is only 1850 fps........does this then make me a "two trick pony"........

    Attachment 199971
    Larry Gibson

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

  9. #29
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    Edward

    Thank you.
    Larry Gibson

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

  10. #30
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    Quote Originally Posted by Larry Gibson View Post
    One last example sort of tongue in cheek.....this is a group I shot with my Finn M39 MN winning the Arizona CBA State military rifle match. It is at 100 yards shooting for score, not group. It's with a 314299 cast of #2 alloy in a Lyman mould (egads, a Lyman mould...) loaded over H4895 (I get a lot of criticism for my constant use of 4895.....it works, ain't broke so I use it.....) with a Dacron filler. Velocity is only 1850 fps........does this then make me a "two trick pony"........

    Attachment 199971
    I'd say more like STUD!

    and that's a compliment from one stud to another................
    Last edited by swheeler; 07-20-2017 at 01:05 PM.
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  11. #31
    Boolit Grand Master


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    Quote Originally Posted by HappyWarrior View Post
    Nice shooting but not equal to C.W. Rowland's group with 1900s optics and black powder.
    Never said it was.......perhaps you can show us how you equal his at 2900+ fps with a cast bullet?

    The OPs subject of this thread is a cast bullet with his alloys at 2500 fps out of a .308W. What Rowland did or what you like with any other cartridge, BP and 1400 +/- fps isn't relevant to the OPs question.
    Larry Gibson

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

  12. #32
    Boolit Grand Master OS OK's Avatar
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    Gibson...I'm gonna miss your information with all your 'empirical evidence' of your work with cast.

    I can't imagine why you get so much resistance in these posts...jealousy perhaps, I really dunnoh. But, I can see the day coming when you don't bother to comment anymore...that'll be a sad day and a loss to this forum because of the few that feel the need to belittle your work.

    So...I'll thank you now for the help you've given me in the short time I've had access to your help...

    Thanks Mr. Gibson,

    c h a r l i e
    a m e r i c a n p r a v d a

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  13. #33
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    Quote Originally Posted by os ok View Post
    gibson...i'm gonna miss your information with all your 'empirical evidence' of your work with cast.

    I can't imagine why you get so much resistance in these posts...jealousy perhaps, i really dunnoh. But, i can see the day coming when you don't bother to comment anymore...that'll be a sad day and a loss to this forum because of the few that feel the need to belittle your work.

    So...i'll thank you now for the help you've given me in the short time i've had access to your help...

    Thanks mr. Gibson,

    c h a r l i e
    x 2

  14. #34
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    Hey guys, I'm not going anywhere. I'm beyond letting the naysayers get to me anymore with their claims and personal attacks. Have to admit they once did get tome but not anymore. I just afford them the opportunity to prove me wrong. Four of them have been afforded that opportunity on this thread. It should be noted that those four are always among the few who naysay but can't/don't prove otherwise.

    What is a shame about the naysayers butting in to attempt through claims ("I know for a fact that guys were doing the "impossible" long before the theory of the impossoble was created") and simply to criticize me, mostly with personal attacks/quips. They offer no help to the OP and in that we have apparently lost the OP in this thread........that my friends is the real shame of the way some have taken this thread.....just as they have so many others......if the OP is still out there perhaps he could fill us in on the rifle and exact mould he has so we may be of further real assistance?

    'nough said.
    Last edited by Larry Gibson; 07-20-2017 at 02:05 PM.
    Larry Gibson

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  15. #35
    Boolit Master Oklahoma Rebel's Avatar
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    I don't know why +2000fps with cast is such a touchy subject. I have asked several questions about getting to about 2100-2300 with 250 and 286 gr boolits in 9.3X62. and I got several lectures about how it wont work and also it is un needed. it might be un needed but I want to see what my limits are so why cant I! I plan on using a 3.5sb/3.5sn/93pb/w/.4-.5%copper. it will be in a CZ550FS with a 1:14barrel 20.5"long.
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  16. #36
    Boolit Grand Master


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    Oklahoma Rebel

    I say....go for it! All is there for success. Only potential detractors I can see is the bullet design and short barrel may not be conducive. The twist, caliber and case capacity are all compatible. Only one way for you to know....
    Last edited by Larry Gibson; 07-20-2017 at 06:40 PM.
    Larry Gibson

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  17. #37
    Boolit Grand Master OS OK's Avatar
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    It's not a touchy subject. It's about 'facts' and not about here-say...It's about limitations of the boolit metal, limitations of non perfect casts running high speed RPM's, fit within the barrel and contact length of the particular boolit design, concentricity and a host of other factors that all have physical limitations such as lube or PC.

    The touchy part is that some of the members post 'empirical evidence' and some post 'assumptions'...there is them that actually 'do' and them that actually 'BS' their way through. Armchair experts.
    a m e r i c a n p r a v d a

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  18. #38
    Boolit Master sawinredneck's Avatar
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    Quote Originally Posted by Larry Gibson View Post
    Oklahoma Rebel

    I say....go for it!
    I've got some stupid questions about the RPM limit and shot groups, so please bear with me.
    Why does the RPM threshold affect cast more so than jacketed?

    Why do you think groups open up so much more going from 100 to 200yds because of the RPM threshold?

    Then in the big scheme of things, why is the ten shot group so much more important than the three to five shot groups? Most of us aren't going combat with cast, if we need two shots most times we've done something wrong! I get you are looking for a basis of SD, but if I'm shooting game or predator, I'm lucky to even think about pulling a second shot, much less getting it off!

    This isn't a slight on you at all, you've always been extremely helpful to myself and others, I thank you for that! But little things like this bug the carp out of my OCD side!

  19. #39
    Boolit Grand Master Harter66's Avatar
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    The twist and rpm will effect jacketed . Cast is less able to stand the forces . I've had the "luxury" of blowing up cast well inside the load window . I've also put to paper 35 cal holes from an 06' with a fast twist . (Apparently the 8.5" 06' bbl on my 65' Savage doesn't exist) . It will run the same bullet to the same speed as the x39 and thats it . I've tried several ways . Meanwhile my PB 30-30 with a 12" twist runs right up to almost max loads with a 160 gr that didn't work for beans in the other 2 . 2300 fps no problems . The 12" twist 308 oddly enough runs out the same place . Powder choices help but ultimately they quit where they quit whether it is the physical forces or just the rate of spin doesn't matter because it happens within a predicable window per pressure , alloy , and shape .
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  20. #40
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    Quote Originally Posted by sawinredneck View Post
    I've got some stupid questions about the RPM limit and shot groups, so please bear with me.
    Why does the RPM threshold affect cast more so than jacketed?

    Why do you think groups open up so much more going from 100 to 200yds because of the RPM threshold?

    Then in the big scheme of things, why is the ten shot group so much more important than the three to five shot groups? Most of us aren't going combat with cast, if we need two shots most times we've done something wrong! I get you are looking for a basis of SD, but if I'm shooting game or predator, I'm lucky to even think about pulling a second shot, much less getting it off!

    This isn't a slight on you at all, you've always been extremely helpful to myself and others, I thank you for that! But little things like this bug the carp out of my OCD side!
    Not stupid questions at all. Let me answer with this;

    While the centrifugal force of RPM can and does spin some bullets apart spinning bullets apart has nothing to do with the RPM threshold. The RPM threshold occurs at a point when;

    The bullet is unbalanced or becomes unbalanced due to uneven obturation, swaging, bending or tilting in the bore during acceleration. The unbalanced bullet is forced to conform while in the barrel and its center of mass is revolving around its geometric center. When the bullet is free of the barrel's constraint, it will move in the direction that its mass center had at the point of release. After exiting the muzzle, the geometric center will begin to revolve about the center of mass and it will depart at an angle to the bore (line of departure). At 54,000 RPM to 250,000 RPM, depending on velocity and twist, the centrifugal force can be tremendous. It will result in an outward or radial acceleration from the intended flight path (line of departure) and will try to get the bullet to rotate in a constantly growing helix.


    "Try to" are the key words here as there are things we do (slower burning powders, harder alloys, better designed bullets, perfect fit, etc.) that we do to push the RPM threshold upward. Conversely, using a faster powder, softer alloy, no GC, etc) lowers the RPM threshold. When the bullet goes beyond the RPM threshold it does not lose "stability”. It still is flying point forward. Its flight path simply becomes a larger expanding helical one. This is why when the RPM threshold is exceeded the groups expansion as range increases is non linear.

    With cast bullets the RPM threshold will be exceeded long before the centrifugal force is enough to "spin the bullets apart". Exceeding the RPM threshold becomes apparent by the decrease in accuracy as velocity increases and the non linear expansion of group size as range increases.

    And yes, jacketed bullets have an RPM threshold. With quality bullets that threshold is usually higher than the attainable velocity. The exception being those thin skinned varmint bullets that can be spun apart at normal velocity with faster twist barrels. The effect of centrifugal force also is apparent with jacketed bullets. It is the primary reason we shoot groups instead of all the bullets going through the same hole. Hornady manuals have an excellent explanation on this.

    Statisticians/ballisticians tell us that at a sample of at least 7 - 8 is needed for any type of surety that the data received via the test is meaningful. The ten shot test gives a much higher level of "surety" that the data is correct. The use of ten shot test strings is the SAAMI and ammunition industry standard for testing. Also most competitions use 10 or 20 shot record strings. We see threads here complaining their 3 shot moa accuracy went south to 2+ or worse moa accuracy on the next trip.

    Read through the above and ask questions where you will. I've no problem answering.
    Last edited by Larry Gibson; 07-20-2017 at 09:14 PM.
    Larry Gibson

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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