AFRICA HUNTER QUEST© 

Chapter 15 - THE BONDED-LEAD CORE BULLET 

    D:      Is it possible to start with the simplest potentially balanced generic design? There are so many interrelated factors to consider. I need some relief. 

    GG:   I suspect the balanced designs will be easier to understand because of the concepts you already seem to have mastered.  

    D:      So which one of the remaining three is the easiest to understand? 

    GG:   I think the bonded-lead core bullets are. In cross-section they look exactly like a cup and core bullet. However, the copper alloy jacket is either chemically or electrostatically bonded to the lead alloy core. Why do you suppose that is done? 

    D:      Hmmm. To get rid of the plane of weakness. 

    GG:   Excellent. Bonding the jacket and core allows both to work together to resist deformation. It makes what I believe is the non-issue of jacket-core separation go away.  

    I only tested one bonded lead core bullet, a 30-caliber, 200-grainer fired from my 300 Winchester. Its impact velocity was 2570 fps. It penetrated 23 inches, had a retained weight of 99%, a percent deformation of 53%, and an expansion ratio of 2.18. The recovered bullet had a very obvious egg-shaped mushroom. The bullet apparently began tumbling at 22 inches, within an inch of its penetration termination length. The wound cavity looked like a guppy. 

    The bullet is a flat-base spitzer. The copper alloy jacket extends all the way to the bullet’s tip. There is no exposed lead in the bullet’s profile. Of all the bullets tested with no poly tips, the 200-grainer had the smallest tip diameter. 

    One test result is not enough to establish any trends on which to base firm conclusions. That being said, the 200-grainer produced wound cavity volume and penetration results that I believe are in keeping with its conceptual design. 

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    As you have indicated, the bonding of the jacket to the lead core eliminates the significant plane of weakness inherent in the cup and core’s generic design. I believe eliminating this plane of weakness contributes to likely improving both wound cavity volume and penetration compared to the basic cup and core design. 

    One benefit of the bonding is to reduce the rate at which the mushroom expands. Even though the copper alloy jacket isn’t strong compared to the copper in solid copper bullets, it is strong compared to the lead in the core. The bonding creates a composite material with a net strength greater than the lead alloy’s. This greater composite strength reduces the rate at which the mushroom forms, and thus allows the potential for greater penetration. 

    Although the bonding likely reduces the rate of mushroom formation, it apparently does not limit the maximum mushroom diameter. The 200-grainer had an expansion ratio of 2.18, the largest expansion ratio of all bullets tested. The resultant mushroom size contributed to this 200-grain bonded-lead core bullet achieving the second-highest inferred blood-shot wound cavity of all 11 bullets tested, tied with the much lower impact velocity 35-caliber, 250-grain cup and core bullet. By blood-shot wound cavity volume, I mean all the volume before the ‘tail’ section of the critters I have used to describe the cavity shapes. The only bullet that beat these two in inferred blood-shot wound cavity volume was the .375-caliber, 300-grainer. Among the 30 calibers, the large mushroom diameter of the 200-grainer allowed it to achieve about a 15% greater wound cavity volume than the 240-grain cup and core tipped match bullet, 22% greater than the 220-grain round nose, cup and core bullet, and over 2 times greater than the 165-grain solid copper bullet.  

    D:      Two times?! 

    GG:   Yep. 

    D:      And tied the 35-caliber, 250-grain cup and core contest winner in blood-shot wound cavity volume?! 

    GG:   Yep. Kindly a humdinger. 

    One of the things that may have contributed to this large expansion ratio was that the bonding apparently limited weight loss. I believe this modest weight loss was a contributing factor to this bullet achieving its excellent expansion ratio. Instead of lead being stripped away from the core, it remained to help form an ever-increasing mushroom diameter. Because virtually no weight was stripped away from

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this bullet, I believe that the average mushroom diameter I measured might be the largest or at least close to the largest produced during the bullet’s penetration. I would expect this general trend for bullets of this generic design unless the bullet was subjected to uber impact velocity. In that circumstance, the mushroom measured at the bullet’s termination could conceivably be less than the maximum it achieved along its penetration path.

    D:      Those wound cavity comparisons give me the impression that its performance is obviously one-dimensional, oriented toward producing wound cavity volume at the expense of penetration. How did the 200-grainer compare to the others in penetration? 

    GG:   Outstanding question. As I said, its total penetration was 23 inches. For context, that is only 1 inch shy of the benchmark 300-grainer’s 24 inches. Although its simulated blood-shot wound cavity volume tied the 35-caliber, 250-grainer, its penetration was 9 inches less. Compared to the 30-caliber, 165-grain solid copper bullet, its penetration was almost a full foot less, really not surprising. But compared to the two other 30-caliber cup and core bullets, it penetrated 4 inches greater than the 220-grain round-nose bullet, and 2½ inches greater than the poly-tipped 240-grain match bullet. 

    I believe the bonded-lead core’s generic design both helped and hindered its penetration. In terms of helping penetration, bonding the jacket to the core reduced the rate of the mushroom’s formation, with a slower rate allowing the bullet to penetrate farther before maximum drag on a fully-formed mushroom can occur. The bullet’s initial small meplat, or tip, had no exposed lead beyond its copper jacket. This copper alloy tip encasement also contributed to this relatively slow mushroom formation.  

    In terms of hindering its penetration, the bonding apparently does not limit the actual diameter of the mushroom that forms. Without design features to limit the actual mushroom diameter, the mushroom continues to form, and the ever-increasing drag causes it to penetrate less. 

    There is also no design feature to enhance the prospect of bullet symmetry. This particular bullet had a mushroom with the greatest egg shape. I believe this shape was a major contributor in causing the test bullet to tumble, thus contributing to poorer penetration. The egg shape could have created unbalanced tipping forces in the bullet that contributed to this tendency to tumble. 

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    Finally, the percent deformation was 53%, second highest of all the bullets tested. The frangible 30-caliber, 240-grain match bullet had the most deformation at 59%. I think this deformation magnitude gets at what is going on with the metallurgy of the lead alloy used in this 200-grainer by this particular manufacturer. If the manufacturer chose to make the lead core less malleable, that alteration would likely decrease the both longitudinal deformation and maximum mushroom diameter, thus increasing penetration. 

    D:      So, all this fiddling with the lead core’s metallurgy would be to increase this generic bullet’s penetration at the expense of wound cavity volume? 

    GG:   Potentially. That’s what I would expect. Wouldn’t that be a hoot to play bullet designer and find out? 

    D:      (Rolling his eyes) If you say so. If a poly tip were on this bullet, would it expand faster, thus producing a greater wound cavity volume and reducing its penetration? 

    GG:   (Grinning like a Cheshire cat) Potentially. Again, that is what I would expect. For someone who doesn’t want to be a bullet designer, you seem to be doing a bang-up job. As long as you are into designing stuff, what would scoring the jacket at the nose’s interior every 90 degrees likely achieve? 

    D:      (Glaring) If the jacket was thick enough and strong enough to allow such scoring, a more symmetric mushroom with likely better penetration. 

    You never did definitely say where the 200-grainer finished in the bullet competition. Did it tank? 

    GG:   Finished third behind the cup and core 35-caliber, 250-grainer and 375-caliber, 300-grainer. 

    D:      Was it truly runnin’ with the big dawgs? 

    GG:   Let’s just say it kindly acted like an over-achiever. A lot of fight in that dawg. 

    D:      A 2570 fps impact velocity is more than the 2400 fps limitation for any- angle shot on the shoulder with a cup and core bullet. Are there any shot angle limitations or impact velocity limitations for bonded-lead core bullets? 

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    GG:   For impact velocity, yes. For shot angle, potentially. In the case of shot angle, I would be reluctant to take a shallow-angle rear quartering shot with this bullet because its penetration is slightly less than the arbitrary, 24-inch penetration standard I have selected based on the 300-grainer’s penetration. I would have to have some field experience with this bullet on any broadside shot pass-throughs to have full confidence in it for a shallow-angle rear quartering shot. No problem with any other shot angle as long as the impact velocities fall within the manufacturer’s recommendation of 2000 to 2900 fps.  

    D:      Manufacturer’s recommendation?! The 2000-2900 fps impact velocity range is actually listed as a recommendation on its website? 

    GG:   Yep. No mystery for me having to make judgments based on pictures of deformed bullets.

    That being said, I am skeptical that an impact velocity range that broad encompasses an impact velocity sweet-spot where increasing impact velocity produces both an increase in wound cavity volume and penetration. Regardless, I expect keeping this manufacturer’s 200-grainer within its recommended impact velocity range could likely result in satisfactory performance in terms of a recovered animal. 

    I need to point out that Nathan Foster believes the performance of most bonded-lead core bullets “tends to wane at 2400 fps, with wounds becoming narrower at 2200 fps and below”. That implies the maximum mushroom diameter begins to significantly decrease at about 2400 fps, becoming significantly smaller by 2200 fps.  

    I believe that assessment is indirectly corroborated at least once. The bullet tested by Mann where he obtained actual wound cavity volume data was a bonded-lead core from a different manufacturer. My graphical interpretation of his wound cavity data indicates a fall-off at about 2570 fps. Furthermore, my graphical interpretation of mushroom diameter indicates the diameter appeared to radically decrease at impact velocities less than 2500 fps. That’s within spittin’ distance of 2400 fps. 

    D:      Is the recommended impact velocity range of 2000-2900 fps as indicated by the 200-grainer’s manufacturer applicable for all bullets of this generic design? 

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   GG:   Don’t know, but likely not. I should point out that this manufacturer has a recommended impact velocity range as low as 1900 to 2400 fps for some of its bullets, probably because of different copper and lead alloys, jacket configurations and tip designs. Bonded-lead core bullets from other manufacturers can also be expected to have different jacket and core alloys, jacket configurations, and tip designs that would affect terminal performance. For me, to predict the extent that these design variables could have on the impact range recommended by this one manufacturer would be well beyond a wild-a$$ guess.   

    I do know this: the upper impact velocity is not unlimited as suggested by one manufacturer of bonded-lead core bullets. As I said before, physics and strength of materials say otherwise. That being said, my testing results indicate generic bonded- lead core bullets can offer considerable performance benefits at impact velocities well above the 2400 fps threshold for shoulder shots compared to a traditional, unbonded cup and core generic design. Ample penetration from most shots in conjunction with excellent wound cavity generation at these elevated impact velocities can logically be expected from this generic bullet design. 

    D:      (Smirking) That seems like an overly broad generalization from just one test of one bullet from one manufacturer.  

    GG:   Could be. But I look at it this way. A manufacturer made implied performance claims for its product based on a published quantitative specification. That performance was confirmed to my satisfaction by independent testing conducted within that specification. That’s about as strong as it gets. If one manufacturer is capable of achieving such performance, the odds are good that other manufacturers of this generic bullet design are also capable of such performance. At what impact velocity range, I can’t say. Regardless, actual gel test results furnished by the manufacturers that included wound cavity volumes would be highly beneficial given the potential wide range of alloys and tip designs inherent with this generic design. 

    GG fell silent. Donny couldn’t believe that he was done talking about bonded bullets, given the extensive concepts and explanations involved with the first two generic designs.  

    D:      Is that it? 

    GG:   Yep. What are your takeaways concerning bonded-lead core bullets? 

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    D:      Likely good balance between wound cavity volume and penetration over a reasonably broad range of impact velocities, as indicated by one manufacturer. The upper-bound impact velocity for your 30-caliber test bullet indicated by this one manufacturer is more in keeping with modern high velocity chamberings. Shot angles do not appear to be a major concern, although your comment about shallow-angle rear quartering shots points to a potential limitation, particularly at close range with high impact velocity shots that could reduce penetration because of aggressive mushroom growth.  

    GG:   Excellent appraisal. Is your 270 Winchester a high velocity chambering? 

   Donny eyed the Old Man. “The Geezer thinks he’s slick, droppin’ corn that leads to the bonded-lead core bin. There are two other bins out there, and I’ll just wait to see what’s in ‘em.” 

    D:      Yes.  

    GG:   Any questions about bonded-lead core bullets? 

    “There is absolutely nothing subtle about the man,” thought Donny. “It would be tough to be his son.” 

    D:      Nope. 

    GG:   All righty, then. Time to move on to the battery bullets. 

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