Linotype vs pressure curve?

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  • Last Post 18 May 2016
karlrudin posted this 15 May 2016

Through some fundamental reading on lead and its alloys I understand that there is a pressure area where lead alloys compresses to fill in the bore. Obturation. I also believe the equation for this is Brinell x 1440=the pressure at which to obturate. What I can't understand is that I've been seeing load data, including my own, that doesn't come close to the pressure curve compared to the formula. For my instance, I shoot 7-08Rem, using Lyman 160gr bullets of wheel weight, water dropped approximately 15Brinell. My load is 20.0gr of IMR 4198 and Fed 210 primers. According to Lyman manual, the starting load is 23gr which produce 19500lbs of pressure. My main question is how are people including myself, coming up with any accuracy if our pressure curves are so much lower than the obturation. I've seen a trend that the top spots on cast bullet shooting is being done with straight Linotype, but there pressures are to low for obturation. Or is this just another mystery to the “silver stream". Just asking, and any input will be nice. Don't really want to fall into a trend or money of buying Linotype if there isn't much to back it up. I'm happy using wheel weights:)

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358156hp posted this 15 May 2016

You can always “pre-obturate” if desired. Size the bullets slightly over bore size, if it will work with your throating. Obturation won't/can't make the bullet larger than bore size, assuming of course the obturation takes place in the barrel. Obturation could take place in the throat or leade, and would of course then be limited to those dimensions, only to swage back to bore size of course.

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onondaga posted this 15 May 2016

http://www.castbulletassoc.org/view_user.php?id=9851>karlrudin

 It is not a secret how guys shooting Linotype do well. Their bullets fit the individual rifle very well. You don't have to rely on obduration if you bullets fit well. That is old news too.

Unfortunately, because they don't get obduration, the Linotype bullet fit is more critical and usually involves custom molds and custom bullet sizing dies because the fit is exacting to the point that measuring and chamber casting to find bullet size aren't always enough to be competitive. A trial and error method of sizing  for the pefect fit by feel and ink test usually accompanies the measuring and chamber casting. That sweet spot of fit with Linotype is narrower by measurement compared to softer alloys and alloys matched to the load level so they do obdurate. Your bullet fit with Linotype may have be narrower than .0002” to finally get competitive accuracy. Your bullet fit with an alloy matched to the load for obduration is generally a full decimal place broader and a lot easier to find in my experience.

ALSO NOTE: If you are doing well with wheel-weight alloy bullets and then keep  everything the same with your mold, bullet sizing and load, it is very likely you will shoot worse with simply changing to Linotype. You have to pay the extra effort to make Linotype shoot well and getting perfect fit is not easy and very narrow with Linotype.

Gary

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Larry Gibson posted this 15 May 2016

karlrudin wrote: Through some fundamental reading on lead and its alloys I understand that there is a pressure area where lead alloys compresses to fill in the bore. Obturation. As mentioned most cast bullets, especially those used in rifles are sized to be .001+ over the groove diameter of the bore.  You are correct in essence the bullet is swaged down as it egress from the case into/through the throat and into the bore proper.  That occurs in a very short distance, usually less than the length of the bullet if the nose is forward of the leade.  Obturation, in the context of bullets, is generally thought of as the bullet expanding in diameter to fill the groove/bore.  This is most often referred to as “bumping up".  With cast bullet smokeless powder loads obturation is not a correct definition unless one goes by the purest definition of the word which means to “obstruct” or “seal".  Obviously we don't want to “obstruct” the bore but rather to “seal” the bore. This is what is occurring as the bullet, if larger than groove diameter, swages down when transitioning from the throat/free bore past the leade into the bore proper. There is another component at play here also, that being the lube.  Lube, being basically a liquid, is not compressible (basics of hydraulics) so the bullet is further swaged down to ride over the layer of lube in the barrel.  Recent testing has shown recovered .30 caliber bullets swaged down .003 - .005” to and actual muzzle exit diameter of .303 - .305 instead of the expected .308 groove diameter of the barrel.                                                                                                 Thus the bullet is swaged down farther than we used to think.  The alloy has to go some where and close inspection and measurement of recovered bullets shows the bullet to be elongated.  Depending on the alloy's malleable characteristics this may be an even linear expansion of the bullet or it may not.  If not the bullet will become more imbalanced.  I also believe the equation for this is Brinell x 1440=the pressure at which to obturate. What I can't understand is that I've been seeing load data, including my own, that doesn't come close to the pressure curve compared to the formula. That formula is over simplified for use with bullets.  It is based on the static amount of pressure required before the alloy will deform.  Also it appears you are confusing the pressure curve with published peak pressures.  The two are different.  A pressure curve is an illustration of the time and distance the bullet travels before peak pressure is reached and after peak pressure is reached during the time the bullet is traveling down the barrel to muzzle exit.  Bullets do move so with the alloy under discussion and the load used the peak pressure is not reached until the bullet has traveled several inches down the barrel.  The bullet has already been swaged down to fit the bore/groove diameter and lube conditions and is supported by the confines of the bore.    The bullet also is now moving forward when peak pressure is reached and not “static” as in something solid holing it back.  Thus, though the peak pressure may be above the so called limit of the alloy the bullet is moving away from the pressure.  The pressure is not having the same effect on the bullet as it would have if the bullet were not moving away from it.  However, at peak pressure there still can be enough to further cause collapse, sloughing, etc. of the bullet if the peak pressure is high enough because the higher peak pressure or the longer sustained time pressure curve increase the effect inertia has on the bullet, particularly if the bullet has a long nose.I regularly push ternary alloy (Lyman #2) WQ'd cast bullets to 2900 fps at a measured 45 - 48,000 psi and maintain excellent accuracy (moa) across 300 yards.  Those bullets have a BHN of 22 so the formula says the bullet alloy should crap out at 31,700 psi yet they do not.  As I said the formula is an over simplification.For my instance, I shoot 7-08Rem, using Lyman 160gr bullets of wheel weight, water dropped approximately 15Brinell. My load is 20.0gr of IMR 4198 and Fed 210 primers. According to Lyman manual, the starting load is 23gr which produce 19500lbs of pressure. My main question is how are people including myself, coming up with any accuracy if our pressure curves are so much lower than the obturation.As mentioned, in reality, your bullets are “sealing the bore” through the mechanical means of the bullet swaging down to fit the bore/groove diameter.  While that may be considered “obturation” it is not in the sense of your meaning that the alloy “upsets” to cause the obturation.  It's two different things that have the same results.  Your accuracy is good because the fit of the bullet is correct.  Has nothing to do with the peak pressures the formula may erroneously mislead you with. I've seen a trend that the top spots on cast bullet shooting is being done with straight Linotype, but there pressures are to low for obturation. Or is this just another mystery to the “silver stream". Just asking, and any input will be nice. Don't really want to fall into a trend or money of buying Linotype if there isn't much to back it up. I'm happy using wheel weights:)Not a “mystery” at all.  Most of the loads used are very mild pressure wise.  The linotype does indeed perform well at those pressures.  However, extensive test at higher velocities and pressures clearly demonstrates linotype does perform as well as slightly more malleable alloys that have a better balanced proportion of antimony, tin and lead.  One of the primary reasons linotype is used though is because it casts consistently better bullets with less rejects for CBA matches.  Commercially purchased new linotype is also very consistent in it's composition meaning each “batch” is the same.    LMG

Concealment is not cover.........

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karlrudin posted this 15 May 2016

I would like to thank you guys for your great responses. It looks like a got bullet fit working good, my bullets are cast .001-.003 over the bore diameter. I don't get the hydraulic effect from my lube since I'm still using Lee Alox. It's been working good for me as far as no leading etc. On some of the comments of how precise Linotype bullets have to fit the throat/lead. This is above my technology and means at the moment so i will have to rely on my bullets. Thank you for bearing with me since I'm definitely a newbie at casting since I only started in Jan of 2014. Been loading and shooting since childhood though. Looks like I need a lot more time with a mold in my hand to expect things to get better. I do consider myself thankful though to be shooting with y'all.

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Larry Gibson posted this 15 May 2016

The Lee Alox liquefies under the heat and pressure of the bullets passage. That doesn't mean it has to be runny. If the lube coats the bore between the bullet and the barrel to prevent leading then the size of the bullet must be smaller as the lube is between it and the bore surface.

LMG

Concealment is not cover.........

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358156hp posted this 16 May 2016

If you're happy with the results you're getting, there's no reason to change.Please remember that there are different ways to obtain your desired results with cast bullets, or almost anything else for that matter.

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onondaga posted this 16 May 2016

LMG wrote: The Lee Alox liquefies under the heat and pressure of the bullets passage. That doesn't mean it has to be runny. If the lube coats the bore between the bullet and the barrel to prevent leading then the size of the bullet must be smaller as the lube is between it and the bore surface.

LMG My understanding of Lee Liquid Alox is completely different than yours if you are referring to Lee LLA. After LLA dries on bullets, you can melt the lead under it with a torch and the Alox doesn't melt. The bond of LLA to bullets is also very tenacious. The thickness of 2 coats is .0015” on my bullets. I don't make my bullets smaller to compensate.

Your statement that bullets “must be smaller” because room is needed for the lube completely ignores how many shooters like myself that use bullets very oversize and let the barrel size them. My 30-06 bullets, for example are .312” and tumble lubed with 2 coats of LLA. The un-lubed bullet size of .312” is the chamber size with an ink verified slide fit, I don't use a smaller bullet diameter to leave room for the LLA. It is lube, not bullet alloy. My pickup bullets aren't stripped of LLA lube. The lube moves along with the change of the bullet being sized in the barrel. I have no extra room, my bullets are oversize before the lube is applied.

So, I am completely disagreeing with you and can't understand how you rationalize what you have said about room being needed for LLA lube. Lee's marketing and product description and use recommendations say nothing even close to what you are saying. You have made a general statement about the product that is untrue, not logical and is completely unsupported by Lee.

Gary

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Larry Gibson posted this 16 May 2016

Gary   I am not “rationalizing” anything.  My comments are based on observation of the results of actual measurement of recovered cast bullets.  There are 2 threads on this forum covering the recovery of cast bullets and the measurement of them  Goodsteel's post of his and Lar's experiment building a bullet trap and recovering 20+ cast bullets is well documented.  I also post in those threads with pictures of the bullets I recovered which demonstrated the same phenomenon.   Lar's and goodsteel used several different excellent lubes (Lar's does sell them you know) on the bullets at velocities of 2350 ”€œ 2900+ fps.  All of the recovered bullets showed a reduction in diameter from the barrels groove diameter of .003 - .005.  That is results from actual testing.  I was as surprised as most of you are but the results speak for themselves.  

Over the years there have been numerous reports of the same phenomenon.  Recently on CBF a fellow reported recovered bullets from his .44 Magnum revolver were .002 .003 less in diameter than the grove diameter even though they started out .002 over groove diameter.  I have heard others mention the same and years ago after the snow melt I would recover lots of quite undamaged cast bullets.  I noted at the time that the diameters were all usually several thousandths smaller than they should have been but I blew it off also to weather conditions and the snow was doing something to the bullets.  This is not a new phenomenon by any means.  You might want to look at those 2 threads;   http://www.castbulletassoc.org/view_topic.php?id=12512&forum_id=63&highlight=goodsteel>http://www.castbulletassoc.org/viewtopic.php?id=12512&forumid=63&highlight=goodsteel   http://www.castbulletassoc.org/view_topic.php?id=12488&forum_id=78&highlight=goodsteel>http://www.castbulletassoc.org/viewtopic.php?id=12488&forumid=78&highlight=goodsteel   Does this phenomenon occur with all alloys, at all velocity levels and with every lube?  I don't know, probably not.  However, the point is this phenomenon does occur, with regularity and can be easily replicated at any time.  Now if you have solid evidence from any tests you have done(?) I/we would surely be interested in seeing the results.  This phenomenon may or may not always occur with lubed cast bullets but we don't know for sure.  A better understanding of this phenomenon may actually provide correct answers to some other questions that have long plagued cast bullet shooters such the much believed concept that cast bullets strip in micro groove rifling at velocities above 1800+ fps or so.  Only complete testing will give us the correct answer.  Do you have any such test?   You don't have to defend Lee's LLA to me.  I have used it since it was introduced on many thousands of cast bullets.  I have 4+ bottles of it now and still use it.  I also use it as a release agent when bedding actions.  It works excellently and cleans off easily.  You might want to run one of your double dipped .312 bullets through a .308 sizer and see how much of the LLA is still tenaciously clinging to the sides of the drive bands.  That's why Lee says to use 2 coats; one before sizing and one after sizing.  Additionally have you wondered where the LLA buildup at the case mouth after seating the bullet comes from?  Or perhaps where the buildup of LLA in the sizing die or seating dies comes from?  You might try taking a small piece of dried LLA between your thumb and fore finger and apply pressure by rolling it around”¦..you'll soon see how the “hard” dried LLA gets soft and easily smears around to an even coating on your thumb and finger.  Yes, I certainly agree with you that LLA is a good bullet lube as long as it is applied correctly and used correctly.  I have been doing both with LLA for many years on thousands of bullets and have had no problems with it.    Now if a barrel is “fouled” or sometimes called “seasoned” with a layer of lube coating the inside of the barrel doesn't it stand to reason the bullet doesn't lead because it is riding over that layer of lube?  Also if we buy off on the concept that bullet lube also helps seal the bore to prevent leading then the lube must be between the bullet and the inner bore surface, correct?    Now you mention your bullets are “are oversize before the lube is applied” as are the cast bullet most of the rest of us use.  However, I don't see where you tell us the diameter of any undamaged portion of the drive bands after firing on any of those “pickup” bullets?  Perhaps you could post pictures of those “pickup” bullets?  That would be much appreciated.  That you disagree with me is fine and I don't mind at all.  However, I prefer to deal with facts, especially those provided from actual testing.  Certainly more testing is in order......guess I'll start collecting another bundle of newsprint.........   LMG

Thought I'd include a picture of the 5 bullets I recovered.  They were all shot through a .3077 x .3003 bore (Broughton's measurement of their barrel and goodsteel confirmed that measurement when he installed the barrel).  The recovered bullets measure .303 - .305 on the undamaged portion of the drive bands/bearing surface.

 

Concealment is not cover.........

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onondaga posted this 16 May 2016

http://www.castbulletassoc.org/view_user.php?id=7879>LMG

You still leave completely undefended your statement about room being needed for LLA lube. That is all I am disagreeing with you about. Making bullets smaller to leave room for lube is still senseless and not defendable. All that would do in practice is subtract fit and reduce accuracy potential.

Your word avalanche with graphic is not related to our single point disagreement.

Gary

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Larry Gibson posted this 16 May 2016

Gary

You seem to be terribly confused. Where did I ever say or even insinuate anything about “Making bullets smaller to leave room for lube"?

Your assumption is totally incorrect.

LMG

Concealment is not cover.........

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Ken Campbell Iowa posted this 16 May 2016

danged treacherous english language !!

barely beats smoke signals ...

pictures are usually better ... and numbers ...


pass the popcorn, please ...

ken

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joeb33050 posted this 16 May 2016

The first reference to the connection-mathematical-between bullet hardnass, pressure and accuracy was written by W. C. Davis and C. Ed Harris. I don't know where W. C. is; perhaps Ed would weigh in. joe b.

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onondaga posted this 16 May 2016

LMG wrote: The Lee Alox liquefies under the heat and pressure of the bullets passage. That doesn't mean it has to be runny. If the lube coats the bore between the bullet and the barrel to prevent leading then the size of the bullet must be smaller as the lube is between it and the bore surface.

LMG I quoted you directly- about bullets must be smaller, I haven't made an assumption. You not reading yourself accurately is not a valid argument. It only makes your incorrect statement weaker.

Gary

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Larry Gibson posted this 16 May 2016

Gary   Must you continually misconstrue everything.........specifically the quote is referencing what is happening in the bore.  No where did I say I was “making bullets smaller to leave room for the lube".  That is your own erroneous inference. I do not make bullets smaller to make room for the lube and never suggested the OP, you or anyone else do that.  In context to your misconception this is what I actually posted to the OP in answer to the question; “As mentioned most cast bullets, especially those used in rifles are sized to be .001+ over the groove diameter of the bore.  You are correct in essence the bullet is swaged down as it egress from the case into/through the throat and into the bore proper.  That occurs in a very short distance, usually less than the length of the bullet if the nose is forward of the leade. "   My statement regarding “the bullets must be smaller” referenced what was happening to the bullets in the barrel, not what I sized them to before shooting them.   Thus given that let's take a look at what is happening to the bullets before they go into the barrel and after they come out of the barrel by looking at the example I've given in this thread.  The five 30 XCB bullets I pictured above started out life at .3105 as they measured after WQing 48 hours later.  They were GC'd and lubed in a Lyman 450 lubrasizer using Hornaday GC and 2500+ lube.  They were then sized in a Lee .310 sizer as the throat of the 30x60 chamber is .310.  They were then load in 30x60 cases having necks sized to give .002 tension with the bullet in the throat and the ogive just touching the leade.  Given the 22 BHN of the WQ'd bullets they are not sized down by the case necks.   That is about as perfect a “fit” as there can be.  They were fired attaining 2900 fps in the 31” Broughton barrel with a .3077 groove diameter.   The bullets were shot into wet pack newsprint at 300 yards and recovered.    All five recovered bullets diameter measured .303 to .305 on the driving bands, the bearing surface and the still attached GCs.  The bullets came out of the barrel smaller than the groove diameter of the barrels bore.  So.....the bullets were swaged down by the leade entering the bore which we assume should have been to .3077, the groove diameter of the barrel.  But since the recovered bullets were smaller than the land/groove diameter obviously they were being swaged down to less than groove diameter by something else.  That barrel was clean at the start of the test and two foulers were fired prior to the afore mentioned five bullets.   Other than lube what else was there to swage each of the bullets down evenly, smaller than groove/land diameter?  The bullets came out of the barrel smaller in diameter than they went into the barrel so somewhere in the barrel "the bullet must be smaller"......not too hard to understand, is it?   To further clarify this for you I did not size the bullets down for the lube, I sized the bullets to fit the throat perfectly.  Something else sized the bullets down, while they were in the barrel......perhaps you can explain that?  Or perhaps you have tests recovering bullets showing otherwise?   BTW; in the testing that Lars and goodsteel did recovering 20 some bullets fired at 2350 to 2900+ fps out of different cartridges in different rifles with different lubes they found the exact same phenomenon occurred; the recovered bullets were smaller in diameter by the same .003 - .005” than the groove/land diameter of the barrel they were shot out of.    LMG

Concealment is not cover.........

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onondaga posted this 17 May 2016

http://www.castbulletassoc.org/view_user.php?id=7879>LMG

I'll count this as a win for me because you dropped another word avalanche and denied yourself again with backtracking and back peddling.

What you wanted to say, you said so poorly the first time and so convincingly to yourself something that is wrong about bullets. It didn't get past my reading comprehension. You said,  and now try to deny with pack peddling and restating to sound better, “the size of the bullet must be smaller as the lube is between it and the bore surface.” That is  drag and drop quote from you.

You are one down. If you make a “must” statement, it must be as you say or it is wrong. I really wouldn't have cared if your statement wasn't misleading to others that are here to get a good start in the basics of the cast bullet hobby. You indefensibly mislead them even if it was unintended or a typographic error. I think they understand more about bullet size now. You didn't help.

Gary

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Larry Gibson posted this 17 May 2016

Whatever........

Concealment is not cover.........

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joeb33050 posted this 17 May 2016

LMG wrote:   All of the recovered bullets showed a reduction in diameter from the barrels groove diameter of .003 - .005.  That is results from actual testing.  I was as surprised as most of you are but the results speak for themselves.  

Over the years there have been numerous reports of the same phenomenon.  Recently on CBF a fellow reported recovered bullets from his .44 Magnum revolver were .002 .003 less in diameter than the grove diameter even though they started out .002 over groove diameter.  I have heard others mention the same and years ago after the snow melt I would recover lots of quite undamaged cast bullets.  I noted at the time that the diameters were all usually several thousandths smaller than they should have been but I blew it off also to weather conditions and the snow was doing something to the bullets. Does anyone know, or is there a good guess why, the fired bullets are smaller than when loaded? joe b.

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Larry Gibson posted this 17 May 2016

They are swaged down by the throat taper, the groove/bore dimensions and the layer of lube between the bullet and groove/bore.

LMG

Concealment is not cover.........

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gpidaho posted this 17 May 2016

I think I'll try catching some of my powder coated bullets and see if this holds true with them also. Gp

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Larry Gibson posted this 17 May 2016

That would indeed be interesting to see.

LMG

Concealment is not cover.........

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