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Thread: Velocity threshold for cast rifle boolits.

  1. #21
    Boolit Master
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    Someone tell me when to start the popcorn. These RPM threads get rowdy, usually within the first page.

    I gotta agree that what Larry says may have merit. I know that 1600-1800 FPS with most rifle calibers remains tractable and accurate for me. Most of my twists (223 to 8 x 57) run 1-9" to 1-12". The 9.3 x 62 is 1-13.1" (metric monster.....), the 45-70 is 1-20", and the soon-to-arrive 38-55 will be pitched at 1-18". The untried 22 Hornet is 1-16". Early runs at 2000 FPS+ with the 30-06 and 9.3mm have been uneven using 50/50 lube--I have test loads assembled with Carnauba Red, awaiting the wind's departure......which hereabouts stops for about 15-20 minutes per week.

    My thoughts on the RPM matter are that if you are dealing with a faster twist--and it puts up a speed limit--isn't the best resolution to add boolit weight, keep the velocity at its established "upper constant"/speed limit, and thereby increase striking energy and penetration potential?

    Orville Redenbacher, butter, and lightly salted. (Col. Mustard, The Conservatory, and the dagger).
    Last edited by 9.3X62AL; 09-25-2013 at 01:51 AM.
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  2. #22
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    My thoughts on the RPM matter are that if you are dealing with a faster twist--and it puts up a speed limit--isn't the best resolution to add boolit weight, keep the velocity at its established "upper constant"/speed limit, and thereby increase striking energy and penetration potential?
    This is my philosophy. I'm heading toward hunting with cast (have hunted before but didn't get anything) so I'm all ears.

    From what I have gathered, 1800 - 1900 fps is a good starting point for cast and is the RPM limit for a 1 in 10 twist 30 cal.

    I'm planing on doing some target shooting and for that I'd prefer a high BC which translates into heavy for caliber which is fine for that 1800 to 1900 fps range.
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  3. #23
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    Quote Originally Posted by 9.3X62AL View Post
    Someone tell me when to start the popcorn. These RPM threads get rowdy, usually within the first page.

    I gotta agree that what Larry says may have merit. I know that 1600-1800 FPS with most rifle calibers remains tractable and accurate for me. Most of my twists (223 to 8 x 57) run 1-9" to 1-12". The 9.3 x 62 is 1-13.1" (metric monster.....), the 45-70 is 1-20", and the soon-to-arrive 38-55 will be pitched at 1-18". The untried 22 Hornet is 1-16". Early runs at 2000 FPS+ with the 30-06 and 9.3mm have been uneven using 50/50 lube--I have test loads assembled with Carnauba Red, awaiting the wind's departure......which hereabouts stops for about 15-20 minutes per week.

    My thoughts on the RPM matter are that if you are dealing with a faster twist--and it puts up a speed limit--isn't the best resolution to add boolit weight, keep the velocity at its established "upper constant"/speed limit, and thereby increase striking energy and penetration potential?

    Orville Redenbacher, butter, and lightly salted. (Col. Mustard, The Conservatory, and the dagger).
    Your a d***ed keyboard comedian Al. You said the same thing when you were a mod. I can't help people when they insist on using 1970's cast boolit knowledge or blaming something inanimate for their problems. Same ole same ole stuff out of them. I just consider the RPM business an excuse for not doing their homework and being lazy. Quite a few people have posted groups at high velocity, far outside some folks wildest dreams, that are very good. You guys have been told what causes the problem, but no one seems to know how to do better among the go slow crowd...... and that's just fine with me, but don't say that no one can do any better because the posts where they did better are on this site...... you just have to read and ask questions to those that do know because the go slow crowd can't answer how to go fast with accuracy.

  4. #24
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    I would like to know more about this.
    I dont rank myself in amongst the casting elite, and those that know what's really going on with HS cast lead, but I have driven boolits pretty darn fast. I've been casting since I was 16 and I'm just plodding my way closer to being an expert (someday, hopefully).
    I am a gunsmith, so I'm like a guy with a shiny new hammer, every propblem looks like a nail LOL!
    I theorize that if I can build a rifle with a perfectly straight barrel, reamed perfectly straight, with perfectly fitting brass, then I can push much faster, and so far, it seems like I am onto something.
    When I was trained to make ultra precision bearing assemblies, I learned that "Accuracy starts in the parts" ie. you have to have a precision unit from the ground up. If your barrel is slightly out of straight, and your chamber was reamed slightly crooked, and your boolits are pretty close to being right, and your........fill in the blank, I think that the further you are from perfection, the speed that you can shoot with a soft boolit degrades exponentially.

    It's just like the theory that glass is one of the strongest substances on earth, because it needs a flaw to start a crack. Theoretically, if there are no flaws, then there is no place for a crack to start, and it wont crack, no matter how much pressure you put on it.
    I look at HS cast lead boolits in a similar way. I have no proof to back this theory up whatsoever, but I am experimenting, and hoping I can understand what I cannot see.

    I have studied the rifle barrel very closely, and I can see definite flaws in all but the best rifled barrels, and factory barrels and chambers are a joke. It doesn't surprise me that most folks with factory rifles are unable to achieve any better than 1800FPS when they slam their boolits sideways into a warped hole, which sizes the boolit down as it is rolled against the wall of the barrel as it traverses chamber to crown.

    Anybody know if I'm on the right track, or am I majoring in the minors here?
    45 2.1, I would value your opinion.
    Last edited by goodsteel; 09-25-2013 at 11:16 AM.
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  5. #25
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    Quote Originally Posted by goodsteel View Post
    I would like to know more about this. (Typing, gimme a sec...)
    Take your time......

    Larry Gibson

  6. #26
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    My feeling is that faster twist=higher resistance that creates lead sheering. But PSI and CUP total numbers dont mean a thing. Its about pressure curves that can be tailored through powder changes. With jacketed bullets powder changes turn a less than MOA rifle into a .75" MOA if done right, and in cast they can turn a 6" group into MOA. So a slow twist like you say can be pushed faster through the high point of a pressure curve without sheering. I also believe this what helps in paper patching. Those fibers hold that thin skin of lead together to prevent sheering and go faster.

    Thants the best I've come up with.

    Quote Originally Posted by Larry Gibson View Post
    NVScouter

    Call it what you want but the fact is with the .308W using regular cast bullets you'll start losing accuracy around 1650 - 2000 fps with a 10" twist barrel, around 1950 - 2350 fps with a 12" twist and around 2450 - 2700 fps with a 14" twist barrel. The same holds true with 10, 12 and 14" twist .223 Remingtons. It's not the psi because as the velocity increases so does the pressure. What do all those different velocity ranges have in common? The RPM is between 120,00 and 140,00 with all of them. Consider also that the inaccuracy is caused in flight as the centrifugal force acts upon the imbalances of the bullet above the threshold within those RPM ranges. The higher the RPM is above the RPM threshold the greater the inaccuracy caused by centrifugal force will be.

    If it is pressure as you suggest(?) then ask yourself; how is it we can shoot a 311359 at 40,000 psi out of an M1 Carbine with excellent accuracy equal to jacketed bullets yet when we load that same bullet to the same 40,000 psi in a 30-06 accuracy will be so poor as we may not even keep the bullets "on target" at 100 yards let along shoot a "group"?

    Now before 45 2.1 goes into a nut role again let me say the RPM threshold is not a "limit". With the correct cast bullet design for the cartridge used, the correct alloy, the correct fit, the correct lube, the correct powder, the correct loading technique, etc. ad nauseum, the RPM threshold can be raised by keeping the cast bullet as balanced as possible during casting, loading and the internal ballistic phase. Conversely the RPM threshold can easily be lowered by with the "wrong" of anything mentioned and further unbalancing the bullet. However, as the OP has found the RPM threshold with regular cast bullets will most often be between 120,000 and 140,000 RPM with normal care in casting and loading.

    Larry Gibson

  7. #27
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    I'm talking hunting/expanding alloys, this is also in track with the OP's query. How far/fast does a cast hunting boolit need to be to hit, expand, and give that nice WACK on critters. If its just punching paper over a chrono with hard boolits I dont see how it applies to the OP's thread. Sorry if that sounded rude I just see this thread heading sideways and I think I'm the one that opened the door.....

    My 30-06 I'd say 200y, my 375 H&H 315g load I'd say 350-500y.

  8. #28
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    Tim, you are on the right track!

    Larry, it's not the RPM per se, but it's affect on circumference speed. That's why small diameter boolits can be shoved faster, i.e., 22's easier than 30's, than 45's, etc. Smaller boolits have less resistance for Getting a boolit to higher RPM. Larger boolits, more resistance, but after launch, the larger boolits can go much further than the smaller boolits because of that resistance (inertia, electrical back EMF, etc.). ... felix
    Last edited by felix; 09-25-2013 at 12:00 PM.
    felix

  9. #29
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    I thought that was called recoil/Ouch factor. I dont buy that smaller bullets have less resistance since the ratio of the same style bullets in any caliber are going to be the same. Bearing surface to to rifling/groove area if all things scaled the same
    Quote Originally Posted by felix View Post
    Tim, you are on the right track!

    Larry, it's not the RPM per se, but it's affect on circumference speed. That's why small diameter boolits can be shoved faster, i.e., 22's easier than 30's, than 45's, etc. Smaller boolits have less resistance for Getting a boolit to higher RPM. Larger boolits, more resistance, but after launch, the larger boolits can go much further than the smaller boolits because of that inertia. ... felix
    Also 22 casts are notorious for needing harder alloys since they need to build higher pressures faster. This supports lead sheering of bearing surfaces and pressure curves. RPM=accuracy only.

  10. #30
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    You can only supply so much current to start a motor with cheap components without blowing one or both up. Needed is a soft start mechanism to compensate for the motor's inertia (B-EMF). Unfortunately, the cost of a soft start mechanism sometimes out-costs the motor by a long shot. BR nuts, me being one, will spend umpteen bucks for that soft start gun for that 22 or 24 caliber. That "motor" is a small motor compared to a 50 BMG bullet/boolit. Such a big motor as the 50, the BR gun would weigh tons when compared to the SAME for the 24. ... felix

    It's the acelleration curve involving ALL physical apparatus. That's the physical constraint we all face. ... felix

    The analogy:
    Primer = voltage
    Powder = current
    Gun = soft start
    Projectile = motor
    Last edited by felix; 09-25-2013 at 02:53 PM.
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  11. #31
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    While confusingly worded I think your saying that: pressures are limited to lead's yeild strength. And you want a slowly rising pressure curve to "slow start" your bullet. Then you mention 22 VS 50 cal scale size difference not mattering due to weight. Did I have that correct?

    I agree that a slowly building pressure curve is idea. I dont see how if everything is on scale how there would be any difference, Bearing surface and rifle groove ratios on scale. With a bigger caliber and equal ratios the amount of surface area on the boolit base would also be equal. Add an equal pressure curve and it would be equal. Scale only would matter to the poor schmo that had to carry it.

    With the chemical properties and grain shape of powders I think you could get a slow start pressure curve easier with larger calibers. Granual shape has a lot to do with burn rates.

    Quote Originally Posted by felix View Post
    You can only supply so much current to start a motor with cheap components without blowing one or both up. Needed is a soft start mechanism to compensate for the motor's inertia (B-EMF). Unfortunately, the cost of a soft start mechanism sometimes out-costs the motor by a long shot. BR nuts, me being one, will spend umpteen bucks for that soft start gun for that 22 or 24 caliber. That "motor" is a small motor compared to a 50 BMG rifle. Such a big motor as the 50, the BR gun would weight tons when compared to the SAME for the 24. ... felix

    It's the acelleration curve involving ALL physical apparatus. That's the physical constraint we all face. ... felix

  12. #32
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    Quote Originally Posted by felix View Post
    You can only supply so much current to start a motor with cheap components without blowing one or both up. Needed is a soft start mechanism to compensate for the motor's inertia (B-EMF). Unfortunately, the cost of a soft start mechanism sometimes out-costs the motor by a long shot. BR nuts, me being one, will spend umpteen bucks for that soft start gun for that 22 or 24 caliber. That "motor" is a small motor compared to a 50 BMG rifle. Such a big motor as the 50, the BR gun would weight tons when compared to the SAME for the 24. ... felix

    It's the acelleration curve involving ALL physical apparatus. That's the physical constraint we all face. ... felix
    That's the carrot on the end of the stick, ain't it Felix?
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  13. #33
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    I happen to know a lot about motors. If everything was perfect (bearings, winding, shafts, collars, brushes/etc.) then you could pump as much current into it as you want with 100% efficency is the theory. The RMP would rise and fall in harmony with the current supply and/or load. Thats theory and what we aspire to.
    Real world brushes wear and foul, winding fuse, bearings eat themselves alive, and shafts turn oblong. Power is dirty and we lose energy as heat so our loss many times outweighs our gains. This is why motors have peak ratings. As our alloys, molds, rifles, powders etc. arent perfect we are in the same boat. That does not change the theory one bit.

    So do you think you can get 3000fps out of a .30 cal cast bullet with enough weight, BC, and metplat to be effective on game out to 500y? Also can you do that in a softer expandable alloy all the while keeping excellent shot groups? Also will this loaded round take the abuse of being handled/carried in the field? How about small crimps to be used in tube mags?

    I know target shooters can do a lot better for range an accuracy then I've acomplished. I know that alloys too hard for hunting have higher yield strengths and can be shot farther and much higher pressures.

    But like the OP I use my cast to hunt and if I'm just poking holes in critters and watch them run off what good is it to me?

  14. #34
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    I just got some stellar results from my new (to me) 35 Remington with an RCBS 200g flat point. I cast it from air cooled wheel weights and imagine it would devastate anything it hits.
    The longer I cast, and load and shoot cast ; the longer I hang out here and read stories like this, the more I'm convinced. Jacketed bullets are good for two things. Super fancy whizz bang 5 million fps magnums and (more commonly encountered) people who are too stupid and / or trifling lazy to cast their own.

    I was considering buying some jacketed 35's for my 35 Remington. After shooting this first batch of cast......I spent the money on a few boxes of gas checks. I live in TN and shoot and hunt at ranges less than 200 yards, the majority being under a hundred yards. Name one thing I need a jacketed bullet for?

  15. #35
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    Scouter, I cannot answer your question(s) about shooting anything but paper and/of charging tin cans. I am not a game shooter. I "had" to go hunting with my granddad and dad when "requested" as a student when growing up. Often in pure darkness and in terrible cold. They were showing me the ropes in their minds. Why? So I can be man some day. However, I hated to be around the eventful kitchen later, and still as of today refrain from any kind of culinary duties stemming from way back when. Smells, skinning, shelling, etc. Psychological only, I'm sure, but I leave the area when food is cooking still today. ... felix
    felix

  16. #36
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    Larry - I've only shot the AR carbine @ 100 with cast 3x. I don't trickle, weigh each charge, boolit or select cases. I guessed on the mould selection. Not knocking the RPM theory, I understand gyro effects well. Just saying that a relative newby, someone with a mediocre rifle, not using lino, reasonable skills at casting and shooting can do it, it's not much of a limit. IMHO, the alloy has to allow exit without major damage, after that the gyro action takes over. Basically, two criteria.
    Whatever!

  17. #37
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    Lets say we push the same cast bullet with the same pressure curve (might recall that I measure, record and compare pressure curves in the 3 twists with the same cartridge I'll discuss) to the same velocity with the same imbalances out of 3 barrels with 10, 12 and 14" twists at the same velocity of 2400 fps. All 3 barrels are sub moa capable. Will the accuracy of each barrel with 10 shot groups at 100 yards be the same?

    I think we all know the 10" twist barrel will show very poor accuracy. The 12" twist barrel may show usable accuracy if the imbalances aren't to great. The 14" twist barrel will give very good accuracy. It ist the adverse affects of the centrafugal force on the imbalances of the bullet that causes the inaccuracy during flight (exterior ballistics). The higber the RPM the greater the adverse affect.
    Larry Gibson

  18. #38
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    Quote Originally Posted by goodsteel View Post
    I would like to know more about this.

    I theorize that if I can build a rifle with a perfectly straight barrel, reamed perfectly straight, with perfectly fitting brass, then I can push much faster, and so far, it seems like I am onto something. Perfection is unattainable, but the fewer gross imperfections the simpler the task at the reloading bench, which is where accuracy originates. The key is learning what some of these things, such as 'perfectly fitting brass" for example, truly are.
    When I was trained to make ultra precision bearing assemblies, I learned that "Accuracy starts in the parts" ie. you have to have a precision unit from the ground up. If your barrel is slightly out of straight, and your chamber was reamed slightly crooked, and your boolits are pretty close to being right, and your........fill in the blank, I think that the further you are from perfection, the speed that you can shoot with a soft boolit degrades exponentially. No, it degrades in a linear fashion to about 120-140K rpm.

    It's just like the theory that glass is one of the strongest substances on earth, because it needs a flaw to start a crack. Theoretically, if there are no flaws, then there is no place for a crack to start, and it wont crack, no matter how much pressure you put on it. Sort of....
    I look at HS cast lead boolits in a similar way. I have no proof to back this theory up whatsoever, but I am experimenting, and hoping I can understand what I cannot see. Experimentation, guided by the right person, will help you understand. Lot of meaning to that word.

    I have studied the rifle barrel very closely, and I can see definite flaws in all but the best rifled barrels, and factory barrels and chambers are a joke. It doesn't surprise me that most folks with factory rifles are unable to achieve any better than 1800FPS when they slam their boolits sideways into a warped hole, which sizes the boolit down as it is rolled against the wall of the barrel as it traverses chamber to crown. Some people with factory rifles and even worn-out military rifles can do much better than that, it's all in that understanding thing. If you've learned enough or at least read and listened enough to say the things you say, you should also realize that even a perfect rifle is useless without the knowledge to make it shoot, the same knowledge required to make any rifle shoot.

    Anybody know if I'm on the right track, or am I majoring in the minors here?
    45 2.1, I would value your opinion.
    What track do you WANT be on? Ask questions and maybe the right person will answer them. It is up to you to determine who is right and who is making excuses. Your rifles and skills you can learn both as a riflesmith and a handloader will determine the answer.

    I have one of your builds now, with less than half a thousandth chamber runout and in a caliber that provides the capability to fit brass and boolits with absolute accuracy. But only a fraction of the work is done, the rest is up to me to make it shoot. Someone else may limit-out much sooner with accurate velocity and be limited inherently by twist rate and choices they make at the loading bench, and others may go much farther than I can right now because they understand more than I do about how to make a rifle shoot. Should be interesting.

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  19. #39
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    Considering what the long range black powder cartridge guys are doing with their equipment, I do NOT think it should be all that hard to kill a deer at 2-300 yards with a great .308 rifle. Bullet speed is NOT the real killer, it is accuracy. I have killed a few white tails with guns that would barely keep 3 shots in 4" at 100 yards. These were not up close and personal shots, but out to as far as 200 yards. I have played with many alloys and BHN's from 5-6 to about 45. Pure lead to exotic alloy mixes containing aluminum. HARD bullets act like FMJ's, punching thru without much effect or so it seems. "Soft nose" cast bullets allow a more stream lined shape and act more like a Nosler at impact. Losing the soft nose as the harder base continues thru.

  20. #40
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    I was thinking the composite cast softnose, ALA BruceB, Might be just the ticket to extend the effective killing range of these boolits. I think, as it stands, my .308 MIHEC FP's should kill well out to 200 yards. It is a VERY rare occaision that I have to take a shot past 250. now to open a BIGGER can of worms. Is it possible to have these boolits approach the performance of Nosler Partitions? I know I can drivve the partitions to 2800 fps, so it probably isn't a fair comparison. I will be shooting partitions for elk, until I have a cast load that equals them.
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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