Bumping back the shoulder

[rox]

Rox, may I just ask you then - why are you are using this process when you're neck sizing as your cases must clearly have fitted in order to be fired in the first place? Is there another reason for just moving the shoulder back a couple of thou'?

Each time you fire a bottleneck case (without bumping) the shoulder moves forward a little, maybe just 1/2 a thou each time or less, due to gradually reducing springback, work-hardening etc. After 3 firings or so bolt closure can get stiffer as you have to squeeze the case into the chamber.

Bumping alleviates this problem before it develops. You could argue that it also gives a more consistent case volume, while preserving the supposed benefits of improved bore-alignment that result from neck sizing, but these are just my unsubstantiated thoughts.

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[Old Chap]

Rox that was just the answer I was looking for. I didn't mention it earlier because I didn't want to influence people's thoughts but that is exactly what I am getting - tightening bolt closures and subsequently tighter extraction problems. I will try for the bump dies this weekend at the Phoenix.
Thank you.
Phil

[rox]

Rox that was just the answer I was looking for. I didn't mention it earlier because I didn't want to influence people's thoughts but that is exactly what I am getting - tightening bolt closures and subsequently tighter extraction problems. I will try for the bump dies this weekend at the Phoenix.
Thank you.
Phil

Note that the Forster bushings are not 100% interchangable with Redding bushings - I believe you can use Redding bushings, but you will only be able to size at most ~70% of the neck. On the other hand, the Forster bushings are half the price, and apparently are cryo-treated for hardness and low friction.

So far my testing indicates runout is no worse that with the Redding comp bushing dies, so loosing the 'sliding-sleeve' doesn't seem to be as bad as the marketing folks would have us believe.

Setting-up the die to bump just a thou or so is a fiddly process that can require plenty of sucessive refinements. It also depends on having good measuring tools and testing a reasonable sample of brass to account for measuring error and inevitable variations. I found that caliper attachments for measuring case headspace were not sufficiently repeatable, and had to finally splash-out on a case headspace micrometer. I wanted to avoid the expensive RCBS one, but having looked for an alternative for at least two years I gave up the search and took the plunge with the RCBS one. Buying it from Reloading Solutions softened the pain.

I think I bought the die from Hannams. If you want to get one at the Phoenix it is probably worth asking them or your preferred vendor to bring one.

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