Expander Mandrels – what are they & why should you be using them?
We all know that benchrest shooters are fanatical re-loaders and use ‘bushing’ dies to control neck-tension – an important part of the accuracy reloading process.
Many shooters try and emulate the benchresters by also using bushing dies BUT, they miss out one important process – neck-turning. The reason benchresters make effective use of bushing-dies is due to the fact that their case-necks are ‘turned’ to give absolute uniformity.
If you miss out this vital neck-turning step, it’s pointless using bushing dies. You may think your bushing die is helping to achieve consistent neck-tension but, if the brass in the neck varies in thickness slightly – and it does – then when you pass it through the bushing die the ‘hole’ – or inside neck diameter – will obviously vary. Result: inconsistent neck tension – the exact opposite of what you hoped for when you bought that expensive bushing die!
So, if you want to make full use of your bushing die – you MUST neck-turn. But, again, neck-turning is pointless unless you have a ‘tight-neck’ chamber. Increasing the clearance between case-neck and a standard chamber neck by neck-turning will be counter-productive to accuracy. But, all is not lost and this is where the neck mandrels come into play.
Here’s how we use a mandrel. Firstly, remove the expander-ball from your full-length sizing die. With Forster dies you can simply unscrew the little ball. With other makes you may have to grind it down so that it is no longer touching the inside of the neck. Or, the third way – remove the whole de-capping pin/expander assembly and remove the primers with a LEE universal de-priming die or similar.
If you don’t want to grind down the expander-ball, then remove the whole de-capping assembly and de-prime with a LEE de-priming die or other decapper
Now, run all your cases through the die. Then, upsize your brass using your neck-expander mandrel. It doesn’t matter if your brass thickness is a little inconsistent in the neck area – the mandrel will ensure the neck diameter is absolutely the same for every case, thus ensuring consistent neck-tension.
The PGS mandrels come in a range of calibres and sizes in one thou. increments so that you can adjust your neck-tension to the one which gives you best accuracy. It’s usual therefore to buy say three mandrels, each varying by a thou.
The PGS mandrels fit the holder supplied by Brownells or Sinclair (see Spud Reloading Supplies in the UK – www.1967spud.com) which simply screws into your reloading press.
Contact PGS on www.pgsprecision.co.uk