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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
The Solid Bullet Debate
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<blockquote data-quote="BryanLitz" data-source="post: 289494" data-attributes="member: 7848"><p>I'd like to weigh in on a couple aspects of this discussion regarding the interesting physical contrast between solid and conventional (lead core) bullets.</p><p></p><p>First was the point of inherent accuracy (precision, to be precise). </p><p></p><p>Not considering the rifle, only the projectile, there are a few things that will affect inherent precision. Most notably; the balance of the bullet, and it's alignment. Keeping in mind that both of these components of dispersion are proportional to spin rate, there are several pro's and con's for solids and conventional bullets regarding dispersion.</p><p></p><p>Inherent precision of solids.</p><p>Pros.</p><p>1. No jacket so no worry about jacket run out, which is a potential source of imbalance for conventional bullets.</p><p>2. No imperfections associated with forming the ogive (square and level top to the lead core inside the ogive and meplat irregularities).</p><p>3. Freedom to design the most optimal configuration of bullet diameter and driving bands for minimizing in-bore tilt.</p><p></p><p>Cons.</p><p>1. A solid bullet of equal weight as a conventional bullet requires a faster twist rate. The major components of dispersion related to twist rate are magnified by the faster required twist.</p><p>2. Consistency of material density. I don't know this for sure, but I suspect that a lead core that's swaged would stand to have a more uniform density (and therefor better balance) than the material that's used to make solid bullets. </p><p></p><p>Inherent precision of conventional (lead core) bullets.</p><p>Pros.</p><p>1. Slower twist requirements</p><p>2. Possibly a more consistent density (homogeneous) core.</p><p></p><p>Cons.</p><p>1. Jacket is a possible source of imbalance</p><p>2. Imperfections from swaging procedure (top of core and meplat imperfections)</p><p></p><p>I'm not trying to paint a picture that one type of bullet is better than another, just sharing some thoughts about the considerations regarding inherent precision of the two types of bullets.</p><p></p><p>Like Eric, I have never seen anyone at a rifle match of any kind using solid projectiles. However, I don't think that proves that solid bullets <em>can't</em> be made to achieve high precision; it just means no-one has actually been able to do it <em>yet</em>. Maybe the odds are stacked too much against solid bullet precision, or maybe no-one has tried hard enough yet. Time will tell. I don't think any of the pro's or con's in the list above are decisively in favor of one or the other, just a different and unique set of challenges for each technology.</p><p></p><p>As for ballistic performance (BC) potential...</p><p></p><p>There are also pros and cons.</p><p></p><p>Ballistic performance for solid bullets</p><p>Pros</p><p>1. More freedom to create aggressive shapes that are not possible, or easy to make consistently using swaging (for example, needle sharp points).</p><p>2. Higher achievable max velocity.</p><p></p><p>Cons</p><p>1. Density. In my mind, this is the biggest downside of solid projectiles. To match the conventional (lead core) 'heavyweights', less dense projectiles have to be extremely long, so long that extremely fast twists are required. There is a limit to how fast you can expect a barrel to spin a bullet.</p><p></p><p>Density is very important to the potential ballistic performance of a projectile. The materials that are commonly used for solid bullets (copper, bronze, steel) all have lower density than lead, so they have to make up for it in profiling. </p><p></p><p>If the solid is made with a profile that's 10% lower drag than the conventional bullet, and the solid is 10% lighter, then the two bullets will have essentially the same BC. In this example, the solid has an advantage because it will achieve a higher muzzle velocity (because it's lighter), and having an equal BC, will beat the conventional bullet. </p><p></p><p>The above example is possible, even likely when comparing a low drag solid to a high drag conventional bullet, but when compared to a conventional bullet that's already got a good profile, it will be very hard to make up 10% of drag. Maybe 3 to 5%, but probably not enough to make up for the lower weight of the solid. In this case it's still not clear which is 'better' because the solid will have an advantage in velocity, but with a slightly lower BC. If the solid does come out on top, I wouldn't expect it to be a large advantage.</p><p></p><p>Everything changes if the solid can be made with a material of equal or greater density than lead. In that case, the external ballistic performance definitely would be in favor of the solid.</p><p></p><p>If the bullet and riflesmiths figure out how to make a heavy weight solid (180 grain 7mm, 230 grain .308, or 300 grain .338 for example) shoot consistently, it will likely have an advantage over the conventional bullet in BC due to superior profiling. But if the challenges of stabilizing a super duper long heavy solid are met, then the conventional bullet can just put on some weight, use a faster twist (but still not as fast as the solid requires) and be back in the game. Wildcat bullets come to mind as an extremely heavy line of conventional bullets with demanding twist requirements. I doubt any solid bullet made from material less dense than lead can be made as heavy as the heaviest wildcat bullets and be made to fly consistently with stability.</p><p></p><p>In my mind the ballistic performance comes down to the trade-off between better achievable profiling (in favor of the solids), vs the higher weights (in favor of the conventional bullet).</p><p></p><p>As with the inherent precision issue, I don't think that one or the other will always, necessarily have better ballistic performance. </p><p></p><p>And I really don't believe that 'just because solids haven't been superior to conventional bullets so far means they can't be successful'. I think it's just a matter of someone solving the unique challenges of the technology, optimizing the design, and simply succeeding where others have failed.</p><p></p><p>Even then, when the technology of solid bullets has gone as far as it can, I don't think it can be an all around superior option. As with all things, some performance measures will favor one more than the other, and people will make their individual choices based on their application and circumstances.</p><p></p><p>-Bryan</p></blockquote><p></p>
[QUOTE="BryanLitz, post: 289494, member: 7848"] I'd like to weigh in on a couple aspects of this discussion regarding the interesting physical contrast between solid and conventional (lead core) bullets. First was the point of inherent accuracy (precision, to be precise). Not considering the rifle, only the projectile, there are a few things that will affect inherent precision. Most notably; the balance of the bullet, and it's alignment. Keeping in mind that both of these components of dispersion are proportional to spin rate, there are several pro's and con's for solids and conventional bullets regarding dispersion. Inherent precision of solids. Pros. 1. No jacket so no worry about jacket run out, which is a potential source of imbalance for conventional bullets. 2. No imperfections associated with forming the ogive (square and level top to the lead core inside the ogive and meplat irregularities). 3. Freedom to design the most optimal configuration of bullet diameter and driving bands for minimizing in-bore tilt. Cons. 1. A solid bullet of equal weight as a conventional bullet requires a faster twist rate. The major components of dispersion related to twist rate are magnified by the faster required twist. 2. Consistency of material density. I don't know this for sure, but I suspect that a lead core that's swaged would stand to have a more uniform density (and therefor better balance) than the material that's used to make solid bullets. Inherent precision of conventional (lead core) bullets. Pros. 1. Slower twist requirements 2. Possibly a more consistent density (homogeneous) core. Cons. 1. Jacket is a possible source of imbalance 2. Imperfections from swaging procedure (top of core and meplat imperfections) I'm not trying to paint a picture that one type of bullet is better than another, just sharing some thoughts about the considerations regarding inherent precision of the two types of bullets. Like Eric, I have never seen anyone at a rifle match of any kind using solid projectiles. However, I don't think that proves that solid bullets [i]can't[/i] be made to achieve high precision; it just means no-one has actually been able to do it [i]yet[/i]. Maybe the odds are stacked too much against solid bullet precision, or maybe no-one has tried hard enough yet. Time will tell. I don't think any of the pro's or con's in the list above are decisively in favor of one or the other, just a different and unique set of challenges for each technology. As for ballistic performance (BC) potential... There are also pros and cons. Ballistic performance for solid bullets Pros 1. More freedom to create aggressive shapes that are not possible, or easy to make consistently using swaging (for example, needle sharp points). 2. Higher achievable max velocity. Cons 1. Density. In my mind, this is the biggest downside of solid projectiles. To match the conventional (lead core) 'heavyweights', less dense projectiles have to be extremely long, so long that extremely fast twists are required. There is a limit to how fast you can expect a barrel to spin a bullet. Density is very important to the potential ballistic performance of a projectile. The materials that are commonly used for solid bullets (copper, bronze, steel) all have lower density than lead, so they have to make up for it in profiling. If the solid is made with a profile that's 10% lower drag than the conventional bullet, and the solid is 10% lighter, then the two bullets will have essentially the same BC. In this example, the solid has an advantage because it will achieve a higher muzzle velocity (because it's lighter), and having an equal BC, will beat the conventional bullet. The above example is possible, even likely when comparing a low drag solid to a high drag conventional bullet, but when compared to a conventional bullet that's already got a good profile, it will be very hard to make up 10% of drag. Maybe 3 to 5%, but probably not enough to make up for the lower weight of the solid. In this case it's still not clear which is 'better' because the solid will have an advantage in velocity, but with a slightly lower BC. If the solid does come out on top, I wouldn't expect it to be a large advantage. Everything changes if the solid can be made with a material of equal or greater density than lead. In that case, the external ballistic performance definitely would be in favor of the solid. If the bullet and riflesmiths figure out how to make a heavy weight solid (180 grain 7mm, 230 grain .308, or 300 grain .338 for example) shoot consistently, it will likely have an advantage over the conventional bullet in BC due to superior profiling. But if the challenges of stabilizing a super duper long heavy solid are met, then the conventional bullet can just put on some weight, use a faster twist (but still not as fast as the solid requires) and be back in the game. Wildcat bullets come to mind as an extremely heavy line of conventional bullets with demanding twist requirements. I doubt any solid bullet made from material less dense than lead can be made as heavy as the heaviest wildcat bullets and be made to fly consistently with stability. In my mind the ballistic performance comes down to the trade-off between better achievable profiling (in favor of the solids), vs the higher weights (in favor of the conventional bullet). As with the inherent precision issue, I don't think that one or the other will always, necessarily have better ballistic performance. And I really don't believe that 'just because solids haven't been superior to conventional bullets so far means they can't be successful'. I think it's just a matter of someone solving the unique challenges of the technology, optimizing the design, and simply succeeding where others have failed. Even then, when the technology of solid bullets has gone as far as it can, I don't think it can be an all around superior option. As with all things, some performance measures will favor one more than the other, and people will make their individual choices based on their application and circumstances. -Bryan [/QUOTE]
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