Bushing sizes
- Thread starter nmkid
- Start date
Measure the neck over a loaded bullet after you have turned the neck down to desired thicknesss.
Keep in mind the neck clearance to your actual chamber (.002" to .005" depending on you cartridge and aplication). Now subtrack .002" from that number and this is your recomended bushing size.
You can adjust the bushing size for more or less neck tension. You may want to get two or three sizes of
bushings, varing in size .001" to set you neck tension to your liking.
Good shooting
Keep in mind the neck clearance to your actual chamber (.002" to .005" depending on you cartridge and aplication). Now subtrack .002" from that number and this is your recomended bushing size.
You can adjust the bushing size for more or less neck tension. You may want to get two or three sizes of
bushings, varing in size .001" to set you neck tension to your liking.
Good shooting
It depends...
For bushing size then you want to turn the necks and then load up a dummy round and measure the diameter to find the appropriate bushing size.
If you are neck turning to provide clearance for a tight neck chamber then you may want to understand the neck diameter before you neck turn so you understand how much is needed to be removed for proper neck clearance. Measure unturned neck diameter of dummy cartridge, subtract enough for your neck clearance desired for proper fit in chamber, turn necks to appropriate thickness, and finally measure final neck diameter of dummy cartridge. Then select bushing for proper neck tension.
Cheers,
Toby
For bushing size then you want to turn the necks and then load up a dummy round and measure the diameter to find the appropriate bushing size.
If you are neck turning to provide clearance for a tight neck chamber then you may want to understand the neck diameter before you neck turn so you understand how much is needed to be removed for proper neck clearance. Measure unturned neck diameter of dummy cartridge, subtract enough for your neck clearance desired for proper fit in chamber, turn necks to appropriate thickness, and finally measure final neck diameter of dummy cartridge. Then select bushing for proper neck tension.
Cheers,
Toby
bigedp51
The following two postings were brought to you by the "Society for the Encouragement of Reading the Dies Instructions. 
Forster
Bushing Selection Algorithm
[(case neck wall thickness x 2) + bullet diameter] –0.002†= correct bushing size (number on bushing)
Micrometer or Dial Caliper:
Measure the outside neck diameter of several loaded cartridges. Ideally, this
measurement should not vary more than 0.001â€. Use the
smallest diameter in the formula below:
cartridge case outside neck diameter –0.002†= correct bushing size (number on bushing)
NOTICE
For increased bullet grip/greater press fit, subtract 0.003†instead of
0.002†in the formulas above.
If using moly coated bullets, the neck bushing may need to be up to
0.003†smaller to maintain adequate bullet tension.
http://www.forsterproducts.com/client_images/catalog19938/pages/files/Bushing_Bump_Neck_Sizing_Die_Instructions.pdf
Forster
Bushing Selection Algorithm
[(case neck wall thickness x 2) + bullet diameter] –0.002†= correct bushing size (number on bushing)
Micrometer or Dial Caliper:
Measure the outside neck diameter of several loaded cartridges. Ideally, this
measurement should not vary more than 0.001â€. Use the
smallest diameter in the formula below:
cartridge case outside neck diameter –0.002†= correct bushing size (number on bushing)
NOTICE
For increased bullet grip/greater press fit, subtract 0.003†instead of
0.002†in the formulas above.
If using moly coated bullets, the neck bushing may need to be up to
0.003†smaller to maintain adequate bullet tension.
http://www.forsterproducts.com/client_images/catalog19938/pages/files/Bushing_Bump_Neck_Sizing_Die_Instructions.pdf
bigedp51
Redding Tech Line & Tips (FAQs)
Bushing Selection
There has been some confusion regarding the correct diameter bushing that should be used with Redding Bushing Style Sizing Dies. The most common misconception is that the bushing diameter is determined by the neck diameter of fired cases or the neck diameter of the chamber that the reloaded ammunition will be fired in. The bushing diameter is related to the chamber neck diameter, but only indirectly, in that the loaded cartridges must have adequate clearance at the neck to allow the bullet to be released properly upon firing.*
The easiest way to determine the proper diameter bushing is to measure the neck diameter of several loaded or dummy cartridges with an accurate micrometer. (These dummy cartridges can be loaded with your old set of dies or a borrowed set.) Then, simply subtract 0.001" from the cartridge that had the smallest average measurement. This will allow for a slight amount of spring back and create a proper press fit for the bullet.
Another method of determining bushing size, is to measure the neck wall thickness of the cartridge cases with a ball type or tubing micrometer. Double this measurement and add the bullet diameter to calculate the neck diameter of a loaded cartridge. As above, subtract 0.001" from this figure to determine bushing size. This method is the least desirable of the two, as a ball micrometer is fairly expensive and more difficult to read consistently than a conventional micrometer.
If you're starting with new cases, the neck wall thickness can be determined as above with a ball micrometer, or you can seat boat-tail bullets in a few cases and measure their neck diameter. Generally, the neck diameter of new cases is small enough to hold a bullet without sizing. As a last resort, you can measure the neck wall thickness of the cases with a caliper. Be aware that you may not select the correct bushing on the first try when using a caliper to measure neck wall thickness, due to the reduced measuring accuracy of the caliper.
The above methods of determining bushing size require that the cases being sized have a fairly uniform neck wall thickness or have been neck turned. If the neck wall thickness varies more than 0.002", it may be necessary to use a bushing a couple of thousandths smaller than your calculations indicate, and then use a size button in the die to determine the final inside neck diameter.
After loading your first few cartridges, it's a good idea to test the grip that the case neck is exerting on the bullet. The simplest method to perform this test is to press the tip of the loaded cartridge against the edge of your reloading bench with moderate pressure. The bullet should not be seated deeper in the case if you have sized at least one caliber of the case neck. If the bullet is seated deeper in the case, switch to the next smaller size bushing and start again.
It has come to our attention through customer calls and our own use of the bushing style sizing dies that in certain instances, a given neck sizing bushing will produce a case neck diameter that can be several thousandths of an inch smaller than the actual diameter of the bushing. This idiosyncrasy occurs when the neck diameter of the fired case is a great deal larger than the diameter of the neck sizing bushing, such as occurs when factory chambers are on the large side of the tolerance range and the brass is on the thin side. Typically, we have not noticed any problems until the case neck is reduced more than 0.008-0.010".
Solutions include, increasing bushing diameter to compensate and/or the use of a size button. Reducing the neck diameter in two smaller steps by using an intermediate diameter bushing will also help. More concentric necks will also result using this method, as the case necks are stressed less during sizing. Don't forget to properly chamfer the inside and outside of the case mouths and apply a light coating of lubricant to the case necks before sizing.
To determine bushing range for standard calibers see "Bushing Range Chart"
If you have any further questions, please feel free to call our technical support line.
* We recommend that the neck diameter of the largest loaded cartridges measure at least 0.002-0.003" smaller than fired cases measured at the same location. This ensures that there is a clearance of at least 0.001-0.0015" all around the neck of the loaded cartridge. This clearance allows the case neck to expand and safely release the bullet upon firing.
http://www.redding-reloading.com/tech-line-a-tips-faqs/140-bushing-selection
Bushing Selection
There has been some confusion regarding the correct diameter bushing that should be used with Redding Bushing Style Sizing Dies. The most common misconception is that the bushing diameter is determined by the neck diameter of fired cases or the neck diameter of the chamber that the reloaded ammunition will be fired in. The bushing diameter is related to the chamber neck diameter, but only indirectly, in that the loaded cartridges must have adequate clearance at the neck to allow the bullet to be released properly upon firing.*
The easiest way to determine the proper diameter bushing is to measure the neck diameter of several loaded or dummy cartridges with an accurate micrometer. (These dummy cartridges can be loaded with your old set of dies or a borrowed set.) Then, simply subtract 0.001" from the cartridge that had the smallest average measurement. This will allow for a slight amount of spring back and create a proper press fit for the bullet.
Another method of determining bushing size, is to measure the neck wall thickness of the cartridge cases with a ball type or tubing micrometer. Double this measurement and add the bullet diameter to calculate the neck diameter of a loaded cartridge. As above, subtract 0.001" from this figure to determine bushing size. This method is the least desirable of the two, as a ball micrometer is fairly expensive and more difficult to read consistently than a conventional micrometer.
If you're starting with new cases, the neck wall thickness can be determined as above with a ball micrometer, or you can seat boat-tail bullets in a few cases and measure their neck diameter. Generally, the neck diameter of new cases is small enough to hold a bullet without sizing. As a last resort, you can measure the neck wall thickness of the cases with a caliper. Be aware that you may not select the correct bushing on the first try when using a caliper to measure neck wall thickness, due to the reduced measuring accuracy of the caliper.
The above methods of determining bushing size require that the cases being sized have a fairly uniform neck wall thickness or have been neck turned. If the neck wall thickness varies more than 0.002", it may be necessary to use a bushing a couple of thousandths smaller than your calculations indicate, and then use a size button in the die to determine the final inside neck diameter.
After loading your first few cartridges, it's a good idea to test the grip that the case neck is exerting on the bullet. The simplest method to perform this test is to press the tip of the loaded cartridge against the edge of your reloading bench with moderate pressure. The bullet should not be seated deeper in the case if you have sized at least one caliber of the case neck. If the bullet is seated deeper in the case, switch to the next smaller size bushing and start again.
It has come to our attention through customer calls and our own use of the bushing style sizing dies that in certain instances, a given neck sizing bushing will produce a case neck diameter that can be several thousandths of an inch smaller than the actual diameter of the bushing. This idiosyncrasy occurs when the neck diameter of the fired case is a great deal larger than the diameter of the neck sizing bushing, such as occurs when factory chambers are on the large side of the tolerance range and the brass is on the thin side. Typically, we have not noticed any problems until the case neck is reduced more than 0.008-0.010".
Solutions include, increasing bushing diameter to compensate and/or the use of a size button. Reducing the neck diameter in two smaller steps by using an intermediate diameter bushing will also help. More concentric necks will also result using this method, as the case necks are stressed less during sizing. Don't forget to properly chamfer the inside and outside of the case mouths and apply a light coating of lubricant to the case necks before sizing.
To determine bushing range for standard calibers see "Bushing Range Chart"
If you have any further questions, please feel free to call our technical support line.
* We recommend that the neck diameter of the largest loaded cartridges measure at least 0.002-0.003" smaller than fired cases measured at the same location. This ensures that there is a clearance of at least 0.001-0.0015" all around the neck of the loaded cartridge. This clearance allows the case neck to expand and safely release the bullet upon firing.
http://www.redding-reloading.com/tech-line-a-tips-faqs/140-bushing-selection
I've ended up with a set of bushings as no matter how well I plan, the reality is slightly different. Regards JCS
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