Page 2 of 3 FirstFirst 123 LastLast
Results 16 to 30 of 41

Thread: Berger bullet failure test

  1. #16
    Join Date
    Feb 2004
    Location
    Nebraska
    Posts
    585
    Henry
    If I understand your post you are saying that the bullets fail at the base.

    If you read this post by Dave Tooley http://www.benchrest.com/forums/show...6&postcount=32

    The one bullet he was able to ascertain where it was failing was at the ogive/body junction.
    So if I understand correctly you and Dave aren't in agreement on where the failure is taking place. Could you clarify that for me since maybe I am just not understanding?

    I am in no way being argumentative, I am hoping to learn something and I greatly respect both your's and Dave's opinion.


    RG or Eric,
    Is there any reason to not use a pure lead core in a target bullet?


    James

  2. #17
    Join Date
    Feb 2003
    Posts
    253
    Quote Originally Posted by Chisolm View Post
    Henry
    If I understand your post you are saying that the bullets fail at the base.

    If you read this post by Dave Tooley http://www.benchrest.com/forums/show...6&postcount=32

    The one bullet he was able to ascertain where it was failing was at the ogive/body junction.
    So if I understand correctly you and Dave aren't in agreement on where the failure is taking place. Could you clarify that for me since maybe I am just not understanding?

    I am in no way being argumentative, I am hoping to learn something and I greatly respect both your's and Dave's opinion.


    RG or Eric,
    Is there any reason to not use a pure lead core in a target bullet?


    James
    Yes, especially with the relatively fast twist rates (as compared to traditional benchrest) required for stabilization, by the bullets in question, core "stripping" (slippage between the jacket and core) as the bullet begins to rotate [down the barrel] is more likely with "pure lead" cores (see Rifle Accuracy Facts, by Harold Vaughn) . In all of my experience, short of specific barrels, which cause failures, alloyed cores make superior bullets - that is, where superior equates to precision.

    Based upon empirical evidence, individual barrels are as big an issue as jackets: I have seen and had customers "report" from both sides of the coin - yes, with barrels from the same manufacturer, and varying chamberings, featuring the same twist rate(s), but with completely opposite results!
    It appears the barrels featuring odd land/groove counts tend to be less destructive - especially in combination with 5R type rifling profiles.

    My pal, Tom, has two barrels from one very good maker, purchased at the same time,then, chambered with my 6/250 Ackley Imp. reamer - at the same session, using the SAME components, one barrel destroys EVERY BERGER, Sierra and BIB bullet before the chronograph records 2900 FPS (the bullets "vaporize" before reaching the 100 Yd. berm), while the other barrel has yet to produce a SINGLE failure of any of these bullets and MVs in excess of 3100 FPS, which should also equate to considerably MORE pressure. "Go figgure"! Oh, that offender barrel shoots the Lapua 105 Gr. Scenar bullets quite well . . .

    Last spring, Bill Niemi provided Tom and I with 100 sample 105 Gr. bullets, made with "thick" jackets - Bill was not at liberty name the source - he asked us to run those bullets through the "bullet wrecker" tube and report back. Tom shot the entire 100 without a single failure - and at 3100+ FPS no less! In order to make certain that the bullets weren't "going into the same hole", each shot was fired at a serarate "aiming "bull" - the distance was 200 yards . . and, once the rig was zeroed, the bullets performed quite pleasingly. Having followed this thread, I'm hoping that Bill obtained the jackets from Berger/J4, and they will eventually be made available to the custom bullet trade.

    Then, this winter, an individual called - he was interested in trying my 108 Gr. FB for 600 Yd. and possibly some 1K work - since his platform featured a 1:7" twist barrel, I tried to talk him out of using/testing the BIB 108 - his formula is known to produce failure (I don't like hearing that the 108s will be shot through a 1:8" twist, which is 12% faster than necessary!)! But, the gentleman would settle for nothing less than, "seeing for myself ". So, off went a few of the FB 108s - he called back and ordered MORE - the bullets had proved excellent at 1K! Following my standard lecture, he stated that he was going to now chamber a 1:8: twist barrel [of the same make, as he had one on hand] and "laugh all the way to the podium" . . . but when we last spoke, the new 8" twist tube was destroying a fair percentage of the SAME bullets which had worked so well via the 7" twist!

    What do I KNOW for Certain about bullet failures? NOTHING IS ABSOLUTE. The variable set is large and dynamic. I do believe that, with the thicker jackets, Eric and Berger Bullets are onto a probable cure. If you're only slightly carzy, cut a bullet wrecking barrel back from it's current 28+" length, to 24": the friction reduction is [sometimes] obvious! Good shootin'! RG
    Last edited by R. G. Robinett; 02-10-2008 at 05:13 PM.

  3. #18
    Join Date
    Feb 2003
    Location
    NE Louisiana
    Posts
    58

    Dave's test

    Chisolm,

    You understood correctly. I believe the bullet jacket that fails due to overheating, fails at the base of the bearing surface. That would be near the base of a flat base bullet and near the base of the bearing boat tail junction of a boat tail bullet.

    Several months ago, Dave and I discussed running a test to determine where, along the length of the bullet the molten lead was being ejected after the bullet leaves the barrel. Without going into detail, I believe it is impossible for the lead to be ejected out of the hollow point at the front of the bullet. (If you think differently, consider the decelleration of the bullet due to air drag compared to the centrifugal acceleration that the molten lead must overcome to reach the hollow point.)

    I suggested to Dave that if he could find a worn out 30" long 6mm barrel in 12in. twist then shooting hot loads with flat base long range bullets, for example 116 or 121 grain Bibs might give the answer. The 12" twist would not stabalize the bullets then all one would have to do is shoot through a 20 yard target until a failed bullet went through sideways. This would also indicate that heating is the primary cause of failure, not twist.

    Dave sent a scan of a target where he fired a bullet through a piece of 1/2" or 3/4" piece of plywood turned at 45 degrees. The idea was the plywood turned at 45 degrees would cause the bullet to tumble.

    I agree that the plywood would likely cause the bullet to tumble but if that is the test you are refering to then I can't accept the results. First it did not appear to me that the molten lead was being ejected from a definate point. Second one has to consider the impact of a bullet at about 3000 f/s on a piece of plywood and what effect that will have on the bullet. That is not an acceptable way to test the effect we are looking for, in my opinion.

  4. #19
    Join Date
    Jan 2004
    Location
    hou tx
    Posts
    31
    ok from what you are saying this is a frictional issue with a direct correlation between bullet jacket thickness and barrel. what is being tried is thickening of the jacket to impart more tensile strength to the jacket. adding or changing core mix ratios by the addition of antimony for harding, is obviously not the solution, as it imparts very little temperature increase to the mix. i was thinking more along the lines of additional tin, or zinc in the mix thus making the core harder but also raising the melt temp to closer to 795 degrees. i have also noted that the barrels being used are in the 30" range. could this be an issue that can be solved by shortening the barrel length to reduce the time of frictional heating? bore diameter can also be increased by 0.0005 this should reduce friction all by itself, while a softer jacket material will still upset enough the maintain accuracy. i do realize that palma shooters are using undersized bores to increase velocity and bullet seal, but they are not seeing the same issues with the larger projectiles, core volume adds it own help to the problem. berger has a good product line without changing its manufacturing processes or materials. from what i have been seeing discussed as the bore diameter goes down frictional resistance increases with the j-4 jackets. if this is correct then the use of cut barrels should give the same results as button rifled barrels. it may also be nothing more than the manufacturing tolerances when on the small side could be attributing to the failures. all failures could be attributed to the jackets being on the low side or the thickness spec, then pressure cut by the bore. if this is the case a major redesign of the jackets would be unnecessary. it could be solved by moving the jacket thickness tolerances up 0.001 to 0.002. if it turns out to be a cut rifling issue, which it mite, then changing a wining design will just be chasing your tail, as there are many completive button rifled barrels out there. i don't think that berger should produce a produce that is a do all end all. i don't think it should be required to work in every barrel that is manufactured out there. another thing to look at is what is the differences between the mass jacket ratios for other bullets that are not have this problem and the ones that are. once you know what the differences are it should point to the answer to this problem.

  5. #20
    Join Date
    Feb 2004
    Location
    Nebraska
    Posts
    585
    RG and Henry
    Thank you both both for your great responses.

    Henry in the question of lead being forced out the tip would it be possible for the centrifugal forces to cause the lead to displace the antimony and force it out of the tip? I don't know I just know you can accomplish some weird stuff with a centrifuge.
    As far as do I think that happens, I am on the side of I don't have a clue what happens and am glad people like you guys share your knowledge.

    James

  6. #21
    Join Date
    Feb 2003
    Location
    NE Louisiana
    Posts
    58
    I believe the problem is overheating of the jacket and melting of the core is a result of overheating the jacket, as stated above.

    The length of the barrel is very likely a big factor but the jacket thickness at the base of the bearing surface is the biggest factor, I believe.

    Here is a simple example of frictional heating:

    Say one has a cube of copper 0.55"x0.55"x0.55" sitting on a flat steel plate 28 inches long. A pressure of 35000 psi is applied to the top of the cube, thus force between the copper and steel is 10,587.5 pounds force. Say the coefficient of friction between the copper and steel is 0.3, thus if one tried to move the cube horizontally, the force required after the cube began moving would be 3176.25 lbf.

    IF the cube were moved 28" then frictional heat would be 3176.25*28/12 ft-lbf or 7411.25 ft-lbf or 9.5 BTU. Thus, the longer the cube is pushed, the more frictional heat is generated which would flow into the cube, the steel plate and the atmosphere.

    The coefficient of friction between a bullet and a rifle bore is likely much less than 0.30 because the bore is generally coated with nitrocellulose residue. Through tests I have found that nitrocellulose residue is a great lubricant and many bullets that fragment after being fired out of a dry bore will survive after the bore is fouled.

    To reduce bullet failure, the primary concern is increasing the bullet jacket thickness, especially at the base of the bearing surface. That has two effects: If one increases the jacket thickness from 0.020" to 0.025" at the base of the bearing surface, then there is approximately 25% more jacket material to heat up at the hottest part of the jacket. That means the jacket will not be heated as much because there is simply more jacket to heat up. Thus the jacket is stronger because it is cooler and in addition it is further strengthened by the additional thickness.

    It appears that making the core of the bullet pure lead has a small advantage in keeping the jacket cooler. The specific heat of lead is higher than antimony and it is likely that the thermal conductivity of pure lead is greater than lead/antimony. Thus the a pure lead core would help slightly in keeping the jacket cooler. In the case of a boat tail bullet, using pure lead would move more of the mass of the core into the boat tail where it can not contribute to dynamic core pressure in the bearing area and thus that would also aid in keeping the jacket cooler. Yet another advantage of pure lead is that it has a higher melting temperature than lead/antimony.

    I say a small advantage for pure lead because the specific heat of copper and the thermal conductivity of copper are both substantially greater than lead or antimony. The thermal conductivity of copper is about 19 times greater than the thermal conductivity of pure lead (that is from memory so it is not intended to be an exact ratio).

    So again, I believe the primary consideration is increasing the thickness of the jacket in the right places. The jacket is the strength of the bullet and if it is kept relatively cool, the core will not melt whether it is pure lead or lead/antimony.

    Eric's comments on the blown primers with the thicker jackets are interesting. Here is the only thing I can think of at the moment: When the primer fires and the propellant begins to burn and drive the bullet into the lead of the rifling, it might be that the thinner jacket deflects inward more than the thicker jacket and is not engraved as deeply, initally, as the heaver jacket is engraved. That would likely result in a higher engraving force for the heavier jacket thus allowing initial pressure to build sooner. That of course is speculation.

  7. #22
    Join Date
    May 2006
    Posts
    216
    There has been a lot of information in the last several posts. Instead of discussing specific statements I will share with you my thoughts and knowledge on the general topic which will touch on many of the items dicussed.

    The goal is to achieve the higest level of precision while reducing the the number of bullets that fail, it is not to make the toughest bullet. Using alloys that are similar but have more antimony does lower the melting point of lead so this is not better. Alloys including other items like tin are not tested in precision shooting and will require much proving before I'd use these alloys in Bergers.

    We did learn long ago that increaing the jacket thickness by 50% (which is much more than we increased the thickness for this test) does not significantly increase the strength of the copper in these thicknesses. Maybe a length of copper that is 12" thick would be much stronger if you made it 18" thick but we are dealing with .001 so this is not the case. The one thing that making the jacket thicker does is it moves the core further away from the source of the heat (friction between the rifling and the bearing surface).

    We spent a lot of money and time working with folks at MIT who modeled the stresses that occur when a bullet is moving through the barrel. The result was that while a bullet is solid the greatest stress occurs on the jacket in the area of the ogive near and including the bearing surface (front of the bullet but not the tip).

    Once the characteristics of lead as a liquid were used the greatest stress moved to the rear of the bullet and the forces realized by the jacket was tremendously higher than the forces realized by the jacket when the lead was solid. I know this is modeling (not real world testing) and I am not sure exactly what this tells us but it cost us a great deal to learn this so I'd like to believe it is significant

    I suggest that once the core becomes plastic (not solid) the bullet will fail to some degree. The location of where this bullet will begin to tear apart is frankly not important. I accept that the suggestion of shooting bullets in a twist that is too slow will allow for us to see where that particular bullet starts to tear appart but I will suggest that a bullet that is tumbling is realizing extreme forces similar to those realized by shooting point forward through a board.

    My point here is that both testing methods are flawed because neither duplicates what a bullet experiences in typical flight. The only way to see for sure where a bullet begins to tear apart in typical flight is with the high speed video which is horribly expensive and can only record inches of the bullets flight path. (This technology is available for about $350,000 from a vendor we spent a lot of time talking to at the SHOT Show.

    Focussing on where the bullet starts to tear apart is like trying to analyse where would be the best place to stick your finger if a dam sprung a leak. Instead the focus should be directed to the only area of the bullet that matters in this situation and that is where the heat is realized because this is what creates the condition that tears the bullet apart.

    I believe strongly that heat is what makes a bullet fail. I also believe strongly that heat may produce poor accuracy (fliers). I further believe that there are many ways to manage heat since heat in this case is the direct result of friction.

    Anyone who is looking at the burning powder or the friction realized by the air is wasting their time and efforts. The greatest source of heat on a bullet is the friction at the point where the rifling engages the bearing surface.

    I will agree that the heat may be greatest (in this area) toward the rear of the bearing surface (although this is speculation on my part). I will also share that I strongly believe that the heat is the highest on the bullet at the muzzle.

    Anything that can be done to address this heat is a step in the right direction. Land configuration, bore diameter, groove diameter, barrel surface finished, the characteristics of the copper, lubricant on the bullet, lubricant applied to the barrel, inclusions, metal stresses, carbon or copper fouling, cleaning practices and solvents used, lead angle and roughness (from reamers that are not sharp), load pressures and the resulting velocity, barrel length, barrel blocks instead of action blocks on BR rail guns and finally the bullets (jacket thickness, bearing surface length, OD, lead hardness, bullet straightness). All of these things (and probably a few others I didn't think of) influence the heat realized by the bullet.

    As a bullet maker I can only influence my product. I can apply solutions to the bullet that either reduce friction or increase the bullets ability to absorb (withstand may be a better word) heat while protecting the core (and overall structure of the bullet) so that the bullet hits where you aimed it. Because this is important I will continue to pursue this course and our next step is the introduction of a full line of THICK jacketed bullets.

    Frankly, there are many shooters who won't need these thick jacketed bullets because they manage or address the other causes of heat. For those who either want to push the limits of their equipment or for those who just don't want to worry about it (and likely take no specific steps to address heat) they will now have an option.

    Someone will find a way to make these thicker jacketed bullets fail. I will admit that I don't know how hard I will work to solve that issue since it is likely that this person is pushing the extremes even farther than is safe or reasonable. I will, however, solve our part of this issue so that I don't have to hear the "J4s are too thin" statement ever again.

    Regards,
    Eric

  8. #23
    Join Date
    May 2006
    Posts
    216
    Two more quick statements:

    1. I agree with Henry's description of how the heat moves through copper of different thicknesses (mass). I have been talking from the point of view that the thicker jacket insulates the lead core from the heat. It is more likely that the thicker jacket reacts to the heat as Henry describes which results in preventing the core from realizing tempurates high enough to melt. You might say that we are saying the same thing differently but I feel clarity is key to applying successful solutions.

    2. The jackets that Randy mentioned that were aquired through Bill Niemi were J4 jackets. They were 25 cal jackets that were sized down to 6mm. The 25 cal jacket is made with .032 base thickness material. Standard 6mm J4 jackets are made with .027 base thickness material.

    Using 25 cal jackets to make 6mm jackets will produce a 6mm jacket that is thicker than regular 6mm jackets. This solved the failure issue in this case. The THICK jackets that we produced for our test were made with the same base thickness material that is use in our standard 6.5mm jackets. The portion of the jacket that is thicker is in specific locations up the side wall.

    Regards,
    Eric
    Last edited by Eric Stecker; 02-09-2008 at 04:23 PM. Reason: Clarification

  9. #24
    Join Date
    Jan 2008
    Location
    Seattle, Washington - USA
    Posts
    9

    Coated bullets

    I was really surprised by the failures of the molied bullets as it's been a very successful solution to one of your competitors bullets that was blowing up on me. Since I started coating (maybe 500 rounds ago) I haven't had a single failure. I know this isn't what this test is all about, just related. I hope you can do a little test of some sort, on it's own with appropriate methods and controls. Like doing the moly test 1st before the barrels are scorched. Coating bullets and and handling them is undesireable, but effective in my application and experience. And technically, I use Danzac.

  10. #25
    Join Date
    May 2006
    Posts
    216
    Kabang,

    I believe strongly that dry lubricant on the bullets does help with the bullet failure situation. I also believe strongly that these lubricants help maintain precision for longer periods during a particular shooting session. Walt, Eunice (while she was alive) and I have shot nothing but moly coated bullets since moly was introduced.

    Shooting moly during this particular test was not meant to prove or disprove anything about moly. The barrels had been thoroughly abused with many rounds shot very rapidly with minimal cleaning. I did not believe that moly by itself at the end of this particular type of shooting was going to prevent failures.

    The funny thing about testing is that it is always better to guess and prove with a test than it is to guess and have nothing to back it up. Many folks guessed that the Patriots were going to win the Super Bowl. They played the game for a reason and we shot moly after this test out of curiosity.

    A thorough testing of coating and its influences on bullet failures will require many barrels and tightly controlled processes. Several barrels would be required to confirm truly consistent and repeatable result. It is possible to do this but would be more than most are capable of doing.

    Looking at the fact that moly does reduce velocity because of reduced pressures I am compelled to believe than this reduced pressure comes from reduced friction. Anything that reduces friction helps reduce or eliminate bullet failures.

    For the record I talk more about moly because it is what I have used. I am sure that danzac, boron or any other true lubricant bullet coating will influence bullet failure by reducing friction. I have no proof of any of this but it makes sense to me.

    Regards,
    Eric

  11. #26
    Join Date
    Feb 2003
    Location
    NE Louisiana
    Posts
    58
    [QUOTE=Eric Stecker;384773]T
    The location of where this bullet will begin to tear apart is frankly not important.

    The above statement, by Eric, is selfdefeating in the goal to design a better match bullet. The point at which the bullet fails is extremely important and can confirm what is causing the bullet failure or give one a clue as to what the cause of failure is.

    The point of failure, for a bullet failing due to an overheated jacket, will be found to be at or very near the base of the bearing surface and that is the area the jacket must be made thicker. That heating is the result of jacket to bore friction, partially from static forces of forcing the bullet through a bore in which it will not freely fit. But the primary frictional forces are due to dynamic core pressure which increases from near zero at the top of the lead core to approximately 35,000 psi, at maximum chamber pressure, at the base of the bearing surface. You might not understand the concept but the folks at MIT who did work for you will understand that concept. Henry

    I accept that the suggestion of shooting bullets in a twist that is too slow will allow for us to see where that particular bullet starts to tear appart but I will suggest that a bullet that is tumbling is realizing extreme forces similar to those realized by shooting point forward through a board. (Eric)


    Your comments in the paragraph above are not correct. The primary stress producing force on the bullet as it exits the muzzle of the rifle from a maximum charge of a long range match load is the base pressure which induces core pressure and resulting tensile stress in the jacket.

    The next significant stress producing force is centrifugal force resulting from the high rotational speed of the bullet imparted by the 8" to 9" twist rifling used in the tests described above. Shooting a 121 grain 6mm Bib bullet out of a 12" twist will not introduce additional significant stresses in the bullet. The reason is that the tumbling rate of the bullet is extremely slow compared to the rotational speed imparted by the rifling. Since centrifugal force varies with the square of the rotational speed, the centrifugal forces resulting from the bullet tumbling would be vanishingly small. Henry

    (all comments below by Henry)

    Core melting: If one analyzes the heat required to melt the entire core of a Berger 6.5 mm, 140 grain VLD bullet (a one sample core weight of 99.29 grains) then one will realize that only part of the core melts when the jacket gets too hot. It is not possible to melt the entire core when the bullet is fired normally with an acceptable load.

    The above statement is not that significant but just a point of information. What is important though is that if any part of the core melts then the jacket has likely gotten too hot and will be more likely to fail.

    Copper has one of the highest coefficients of thermal conductivity of all pure metals (only silver and gold have higher values), about 11 times greater than pure lead. But in order to melt part of the lead core in only 1.5 miliseconds the temperture drop across the jacket is very large (heat flow = conductivity coefficient X temperature difference X area). The inside surface of the jacket must be much greater than the melting temperature of the core in order for the high heat transfer rate to take place. That means that when part of the core melts, the exterior surface of the jacket is likely as hot as 1000F or higher. That weakens the jacket and increases the likelhood of jacket failure.

    One does not want to insulate the core from heat flow but wants to send as much heat flow to the core as possible without getting the jacket too hot. That is why using pure lead will help. Pure lead likely has a higher heat transfer coefficient than lead/antimony or lead/tin.

    Coefficient of thermal conductance is the heat flow a material will pass through a unit thickness, through a normal unit area for one unit of temperature difference.

    The coefficient of thermal conductance of pure copper is:
    11.3 times greater than pure lead
    18.8 times greater than pure antimony
    5.9 times greater than pure tin

    Heat capacity is the amount of heat required to heat a unit mass of material one unit degree of temperature:

    The heat capacity of pure copper is:
    3 times greater than pure lead
    1.9 times greater than pure antimony
    1.7 times greater than pure tin

    Heat capacity, like thermal conductance, is very important in transient heat transfer (Heat flow to a bullet as it travels down a barrel of a rifle is an extreme case of transient heat flow.). In the example of copper and lead it means that the temperature of one pound of copper will heat up 1/3 rd. the temperture rise of one pound of lead when absorbing the same amount of heat.

    The above values are for pure materials but in the final analysis, in comparing pure lead to lead/antimony, the thermal conductivity of lead/antimony must be known.

    However, I believe the most importan improvement that can be made in match bullet jackets is to increase the jacket thickness where the the jacket gets hottest over the greatest time period. A thicker jacket will absorb more heat and it will provide a larger channel area to conduct heat to other parts of the jacket.

    It might be true that the hottest point on the bullet jacket occurs while the bullet is forced into the rifling lead. But keep that in perspective: 1) the area of engagement of the rifling lead is small and 2) the time period of engagement is only about 1% of the bullet travel time in the barrel.

    You might not understand it but again, your friends at MIT will, after the jacket engages the rifling lead, the area of highest friction and jacket heating due to friction is at the rear of the bearing area and that remains true for approximately 99% of the bullet's travel through the barrel.

    Henry
    Last edited by HBC; 02-10-2008 at 10:13 AM.

  12. #27
    Join Date
    Sep 2003
    Posts
    357

    great to see ya back online henry

    is it possible to calculate the reduction of friction by reduction of duration or barrel length?i have noticed that most reported falures have come out of 29-30 inch barrels,if the bullet destroying barrels were shortend by 1 inch at a time to the point of not destroying,would that produce a valid result with your theory of jacket heating ? tim in tx

  13. #28
    Join Date
    May 2006
    Posts
    216
    Henry,

    I do not wish to engage you in a pissing match since you are obviously much stronger in mechanical engineering knowledge. Your theoretical (based on facts you know along with few others) analysis cannot be disputed directly by me. I have read your entire post and it seems that you have reached the same solution that we have so I am not sure what is the goal of your post.

    Is there really a reason to debate the significance of one method of determining the result over another. You are assuming that the point where the jacket tears apart is also the point where the cause of the tear occurs. Having seen Dave Tooley testing where he marks the bullet with a sharpie it has been proven that the jacket tears in random places around the bullet not in relation to any given point in the barrel.

    This being true (and proven) it is reasonable that the location of the tearing of the jacket is not directly connected to the true root cause which is heat caused by friction between the rifling and the bearing surface. Dave Tooley's testing on this subject was a significant discovery because it allowed us to shift our focus from the result to the cause. It seems to me that looking at the result now is the same as trying to figure out how a drunk driver got into an accident by looking at the site of the crash. In this example the drink is what caused the crash and the solution to preventing the crash is found there not at the crash site.

    Your following statement:

    "It might be true that the hottest point on the bullet jacket occurs while the bullet is forced into the rifling lead. But keep that in perspective: 1) the area of engagement of the rifling lead is small and 2) the time period of engagement is only about 1% of the bullet travel time in the barrel."

    This statement tells me that you have not been internalizing my information but have actually been focusing on how you can dispute it. I have said many times that the greatest source of heat is the friction between the rifling and the bearing surface. This has been proven (beyond all doubt) in high speed thermal images.

    I mentioned lead angle along with a long list of items that should be a part of a shooters understand of all of the things that MAY influence the friction realized between the rifling and the bearing surface. These statement are focused on providing shooters ways to manage friction which is the solution rather than being meant to focus on the result.

    Henry, just because I cannot quote the coefficient of thermal conductance of pure copper or because I do not have the years of training in mechanical engineering does not mean that I cannot understand or analyze facts presented in a way that leads to a solution. Your shots at my intellect are again focused on your means to dispute our findings rather that to embrace our solution.

    Our solution has been proven to work. We will be implementing our solution in a full line of THICK bullets. I am confident that this solution will solve the problem. Your vast experience and understanding of mechanical engineering had not provided you with a solution that was found to be successful and in fact you are the one who was originally pushing the "lead too high in the ogive causes failures" theory which has been proven to be false.

    I will suggest that you offer your opinions as "your OPINIONS" and that you not provide such strong support of them until they are proven. Many people read these posts and you sound like an expert. I am not saying that you are not knowledgeable but some of your statements do not jive with facts proven in real world testing.

    Believe me when I say that I respect your knowledge. I am listening to your comments and I am internalizing the role they play in the solution. Please do not be so prideful in your opinions that you cannot accept that someone like me who "doesn't understand" may in fact be capable of finding and implementing the solution.

    Regards,
    Eric

  14. #29
    Join Date
    Jan 2005
    Location
    North Georgia
    Posts
    145

    bullet blowup

    Eric:

    Just my $.02: (1) I am very glad that you and Berger Bullets continue this open forum to the benefit of competitive shooters on such a "hot" topic; (2) It is great to see Henry Childs back posting on this board as his reputation is top shelf; (3) Randy's imput is invaluable (4) I would also love to see Bryan Litz (sp) and Charles Ellertson engaged in this thread as well.

    I have blown up four bullets in my competitive shooting, all at Hawks Ridge on the same relay. I was shooting a 300 WSM with N560 pushing 187 BIBs out of a 12 twist. I blew up 3 on my sighters and one during a record light gun string (5 shots). The shots on paper were nicely formed in about a 5" group.

    That evening I loaded the same brass with the same lot of bullets -- but with a somewhat compressed charge of H-1000. On the next day, I experienced no blowups and I won my relay with somewhere around a 5" group.

    Of course, an additional variable on this occasion was that the H-1000 load was considerably under the fps of the N560 load. I never really figured it out as I have shot a lot of N560 before and after the blowups, with the same barrel and lot of bullets with no problems.

    FWIW, I have noticed that I can actually "feel" the difference in barrel heat after a string with N560 as compared to H-1000, H4831SC, H4350 etc., and I can also feel the difference in barrel heat when shooting moly vs. naked bullets. I suspect that one is related to the double base powder and the other is a coefficent of friction issue.

    Keep up the good work as this is a very educational thread.

    Jim
    Last edited by Law Dawg; 02-10-2008 at 03:51 PM.

  15. #30
    Join Date
    Feb 2003
    Posts
    1,483

    Hats off,,

    ,, and a standing ovation for Eric Stecker!

    Sincerely,

    Gene Beggs

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •