21st Century Undersize Expander Mandrels for 30cal Stainless Steel



These undersized expanders are for 30cal. SOLD SEPARATELY. If you wish to build your own set just add to cart each of the ones that you want.

These fit into either of the STD or Tall 21st Century Expander Die Body (purchased separately).  Click here for that

They are in .005″ (half thousandths on an inch) increments and stamped so on each expander.

For example:  The engraved sizes are 0.3040″, 0.3045″, 0.3050″, 0.3055″, 0.3060″, 0.3065″, 0.3070″, 0.3075″, 0.3080″, 0.3085″, 0.3090″

Custom expanders are deemed by manufactuers as non returnable items. 

Stuart’s Tips:
Please note: Like most machined products there are tolerances. What we measure, with good equipment (good micrometers), is in the range of up to 0.0002″ (two ten thousandths of an inch) either side of the actual stamped size. Total variation 4 ten thousandths of an inch. For many people this would be acceptable, but for some others, maybe not. Therefore, we are pointing this out before you purchase!
We have another brand which are much more accurate and precise in actual size. Due to those being Ground to Size (as opposed to machined to size). But, naturally are more expensive too.
As a suggestion, usually at least a couple of sizes will be required anyway. So if you are concerned which to choose first, then maybe start with a size 0.oo1″ less than calibre and try it, then maybe later add another. A size above or a size below as required. Very many people do email and ask us to choose the size for them. We don’t. We wish we could help, but we cannot know this because we can’t know how much actual neck spring-back will occur with YOUR brass.