Run Out
- Thread starter maka
- Start date
With out typing this my self here is the best I could find to explain:
What is run-out. or as it is more correctly called concentricity. As shooters have become more demanding in their search for accuracy, specialized reloading equipment has come into the market. It is well known that bullet run-out, or concentricity, is a major factor in producing accu-rate ammunition.
In years past, the accepted practice for checking concentricity of a handloaded round was to roll the cartridge across a flat surface, such as glass, and note any wobble at the bullet’s tip. This was a fast way of culling obviously defective cartridges, but will fail to isolate those with less obvious run-out problems. Add to this the fact that run-out problems can be caused by not just an improperly seated bullet, but by the case itself, and the limitations of this approach become unacceptable.
Today, handloaders have several options that are capable of measuring concentricity to .001" or less. Most operate on some variation of the same principle. A loaded cartridge is mounted in the unit, normally supported by a “V” block arrangement at the case head and bullet ogive. The cartridge is rotated slowly, while a dial indicator bears on the area of the cartridge being checked. Any concentricity problems are not only immediately visible, but measurable on the dial indicator.
One of the first commercial models, which is still readily available and quite popular, was the Forster/Bonanza Co-Ax Indicator. Recent entries in the concentricity gauge market include models by Sinclair International, NECO, and RCBS. Some models, such as the NECO Gauge and RCBS Case Master, are capable of not only measuring bullet run-out, but case neck variation, wall thickness and concentricity as well. Given the accuracy obtainable, particularly from many of today’s bolt action rifles, using a concentricity gauge to get the last bit of accuracy out of handloaded ammunition makes perfect sense.
What is run-out. or as it is more correctly called concentricity. As shooters have become more demanding in their search for accuracy, specialized reloading equipment has come into the market. It is well known that bullet run-out, or concentricity, is a major factor in producing accu-rate ammunition.
In years past, the accepted practice for checking concentricity of a handloaded round was to roll the cartridge across a flat surface, such as glass, and note any wobble at the bullet’s tip. This was a fast way of culling obviously defective cartridges, but will fail to isolate those with less obvious run-out problems. Add to this the fact that run-out problems can be caused by not just an improperly seated bullet, but by the case itself, and the limitations of this approach become unacceptable.
Today, handloaders have several options that are capable of measuring concentricity to .001" or less. Most operate on some variation of the same principle. A loaded cartridge is mounted in the unit, normally supported by a “V” block arrangement at the case head and bullet ogive. The cartridge is rotated slowly, while a dial indicator bears on the area of the cartridge being checked. Any concentricity problems are not only immediately visible, but measurable on the dial indicator.
One of the first commercial models, which is still readily available and quite popular, was the Forster/Bonanza Co-Ax Indicator. Recent entries in the concentricity gauge market include models by Sinclair International, NECO, and RCBS. Some models, such as the NECO Gauge and RCBS Case Master, are capable of not only measuring bullet run-out, but case neck variation, wall thickness and concentricity as well. Given the accuracy obtainable, particularly from many of today’s bolt action rifles, using a concentricity gauge to get the last bit of accuracy out of handloaded ammunition makes perfect sense.
Jordan Smith
CGN Ultra frequent flyer
- Location
- Calgary, AB
Runout is essentially when the bullet is seated crooked in the cartridge. Runout is typically measured as the distance between the center axis of the bullet at one extreme to the other (left to right when you spin the bullet in your fingers). For example, if a cartridge has runout of 0.004", then the bullet is 0.002" off center in either direction. You can rough measure runout by rolling the cartridge on a flat surface, and if you can detect any wobble in the bullet, then you have roughly 0.004" or more of runout. If you want to be more precise, you can buy a concentricity gauge.
You can control it by using quality reloading dies, stopping to rotate the cartridge a few times while seating the bullet, by reaming your case necks, and by annealing the necks of your brass.
Here's a picture that illustrates runout on an electronic motor shaft:
You can control it by using quality reloading dies, stopping to rotate the cartridge a few times while seating the bullet, by reaming your case necks, and by annealing the necks of your brass.
Here's a picture that illustrates runout on an electronic motor shaft:
