Our Expanding Die is a unique Reloading Die designed to work with high-quality Gage Pins, it consists of a die body, collet, and collet nut. It is primarily used for precisely expanding necks on cartridge cases to achieve a desired neck tension over the projectile.
The information below is a general list of information about the system, including some pointers on size selection.
The main advantage of Gage Pins is their durability as well as the vast selection of sizes/diameters/tolerances, allowing you to choose sizes outside of the tolerances and sizes available from commercially manufactured expanding mandrels.
Gage Pins are used to measure the size of a bored hole. They come in a variety of sizes and classes. We provide class ZZ Gage Pins that are sized .0005″ apart and are accurate to .0002″. The pins we source are made from a Carbon Chrome Alloy Steel (grade 52100 bearing quality steel) and heat treated to a 60-62 Rockwell C hardness. We choose this class as a good balance between availability, and size selection. Despite the hardness and polish, some form of lube will be required; graphite or a lanolin based wax manufactured for use with reloading supplies is recommended. Petroleum based products will kill powder and primers.
The die body is available in the “short” version for cartridge cases up to 2.1″ in length such as 308 Win., and the “long” version which is for cartridge cases over 2.1″ in length. We also offer a few other sizes to accommodate special, wider, or longer cases. The standard long or short die body with collet nut is not caliber specific. An extra die body without the collet nut can be purchased if desired. This die system can be used on cases as short as the 6BR through the Remington Ultra Mag, and even larger with some of our larger die bodies. With careful setup the “long” version may be used for the .338 Lapua case. This system uses precision collets that are commonly used to hold milling cutters and drills securely into the spindle in the machining industry. The die body is parkerized for corrosion resistance.
You generally need one collet per caliber but some sizes will work for multiple calibers. The common collet size ranges are:
4-5mm – .157” to .197” – (.17, .20)
5-6mm – .197″ to .236″ – (.223)
6-7mm – .236″ to .276″ – (.25, 6mm, 6.5mm)
7-8mm – .276” to .315″ – (7mm, .308)
8-9mm – .315” to .354” – (.338, .35)
9-10mm – .354” to .394” – (.375, 9mm)
The Mandrel pins are made from 2” long, precision hardened steel pin gauges. One end of the pin will be tapered and polished. These are available in .0005″ increments, and can be purchased in either “PLUS” (+.0002″/-.0000) or “MINUS” (-.0002″/+.0000) tolerance. Most customers start with pins that are around .001″ to .003″ under the bullet diameter to achieve their desired neck tension.
This .001-.003 dimension varies depending on bore size, larger calibers require a little more tension than small calibers. The results you get will be unique due to brass composition and hardness, as well as dwell time on the mandrel. For this reason you will need to start with a baseline, and adjust what size pin you are using to achieve your desired result.
Die body split lock rings are available if needed.
For shipping policy, please refer to our shipping and returns page.
For International customers-“The website will typically over charge for international shipping. You will only be charged actual shipping cost + $10. Any amount exceeding that amount will be refunded once your order ships and a final cost is determined.”
Should you have any further questions please don’t hesitate to shoot us an e-mail, or give us a call during regular business hours.