January 16, 2022Grip on Bullet — Many Factors, Not Just Bushing Size. Many novice hand-loaders believe that neck tension is determined by neck bushing size. There are many factors that can affect the grip of your bullet and how it releases from the case neck. This article will explain neck tension and “case grip”. This is an important article. It is worth reading twice. Variations in the force required for a bullet to be released can have a significant impact on accuracy and ES/SD. It is important to understand how the grip of a bullet can be altered by many factors. Grip on Bullets is a Complex Phenomenon
Although we can control neck tension with tighter or looser bushings (with smaller and larger Inside Diameters), this is only one factor. Understanding the many factors that can increase or decrease resistance to bullet release is important. Consider the overall brass-onbullet “grip” rather than just the bushing size (or even the internal neck diameter in nonbushing full-length dies). These factors can have an impact on bullet grip. Neck-wall thickness.
2. The amount of bullet bearing surface (shank), in the neck.
3. Surface condition of neck (residual Carbon can act as a Lubricant; ultrasonic Cleaning makes necks “grabby”.
4. Length of neck (e.g. 6mmBR neck vs. 6mm Dasher).
5. Whether the bullets are coated with anti-friction.
6. The brass’s springiness (which is related with work-hardening, firings, etc.
7. The bullet jacket material.
8. The bullet’s outside diameter and whether it has a pressure-ridge.
9. The time between firing and bullet seating can vary. Necks can become stiffer over time.
10. How often is brass annealed?
11. Size of neck (e.g. You can only size half of the neck.
12. Bushing’s interior diameter or neck section of nonbushing die. You can alter the seating depth and bullet “grip” may change. It can also change if your cases are ultrasonically cleaned. John Whidden, 5-time U.S. National Long-Range Champion, says: “Our tests have shown that the condition of necks, including whether they are lubricated or not and whether there is carbon inside or not, squeaky-clean or not, all matter more than the bushing size. A brand new or ultrasonically cleaned neck makes for a very strong seating force. “In our Shooters Forum, a reader asked: “How much neck tension should i use?” A Forum discussion ensued in which a reader asked: “How much neck tension should I use?” These numbers are the difference between the case-neck OD (after sizing) and the neck OD for a loaded round with the bullet in place. These numbers are also known as the “tension numbers”, which are.001?, and.002? respectively. etc.) While these are useful starting points, neck tension can be quite complex. The actual “grip” of a bullet depends on many factors, including neck-OD reductions during sizing. Understanding all these factors will help you maintain consistent neck tension over multiple reloadings.
This is a simple experiment you can try. With.150, place a boat-tail bullet in the neck. a shank in the neck. With an impact hammer, remove the bullet. Next, take another bullet and place it with.300? You will need to place the bullet in a different sized case with the same bushing size and nominal tension. It is important to note that the bullets with a deeper seated are gripped more difficult.
I’ve also found that thinner necks, especially those used by many PPC shooters require more sizing to provide equivalent “grip”. Do your own experiment. Place a bullet in a case with a.008 tolerance. Now reduce the neckwall thickness to.003?. Compare that to a case with 0.014? Neckwall thickness and sized down to.0015?. The bullet may pull out more easily in thin necks than in thicker necks. However, if you consider only bushing size, you might need tighter bushings to keep the bullets gripping the ground. I think the guys using.0015 are more accurate. The guys using.003 may have a greater sense of tension on no-turn brass than the guys using.005. A better definition of neck tension
We tend to describe neck tension using the bushing size as a quick shortcut. If a man says “I run.002 necktension”, it usually means that he uses a die/bushing to size the necks.002. A loaded round is smaller than a unloaded one. We know a little bit about his post-sizing neck O.D., but do we really know how much force it takes to get his bullets out? Perhaps not. Maybe not. An.001 tension is actually more common than an.001. A thick neck may provide more grip on a deep-seated bullet than a.003? reduction. A neck with a thin wall that holds a bullet with very little bearing surface will result in a reduction. We can measure and verify bushing ID. Because it is easy to measure and verify, we use bushing size to denote neck tension. These factors should not be ignored if you want consistent neck tension to ensure accuracy. We want to find the optimal neck tension for accuracy and maintain that grip-on-bullet throughout time. To do this, you must look at not only your bushing size but also how your brass has changed over time (work-hardened), and whether any other variables (such the amount of carbon in your neck) have changed. The optimal neck tension must be determined experimentally. To find the optimal neck tension, you will need to test it empirically with your bullets and brass. You may also need to adjust the nominal tension setting (i.e. As your brass work-hardens, you may need to adjust the bushing size. The bushing size does not tell us everything about the neck’s “holding power” or the energy required to release a bullet. True bullet grip is a more complex phenomenon. It is affected by many factors, some of them very difficult to quantify. Similar Posts
