Case trimming - thoughts on tooling and technique please

[Dougan]

Good explanation Rox - I'm at the same stage as Magpie, where I'm just starting to need to trim; and was a little confused about the process, and 'bumping' too...

Is there any change to the general advice depending on whether the case is rimmed (e.g .303) with regards to NS, NS and bump, or FL sizing and head space issues?


And a question to Gallery rifle shooters - do you bother trimming your pistol cases for lever action shooting?

[phaedra1106]

This looks really interesting, not seen this one before. Do you know of a UK outlet for these ?

Not that I know of, I bought 3 off eBay US a while back, 308, 223 and 204 Ruger, £30 each or there abouts. I have friends in the US that I get stuff shipped to for collection when we go over or when my friend goes over.

I'm sure Ovenpaa could make these quite easily, there should be a good market for them over here (do I get commission?)

[Magpie]

Hi Rox,
thanks for the tip on shoulder bumping, I had been leaving it alone on the grounds that it came out so it should go back :-) And .001" isn't much work on the brass.

I hear what you say about the window. But the lee only gives you one length so I'm guessing the case will grow more if its got more room to grow - if that makes sense?

Trimming longer or shorter won't 'give it room to grow' (in length). The case mouth should always have 'room to grow' in the chamber, otherwise you would be in the 'crimping the case mouth' danger zone.

If you neck-size then each time you fire a case it will spring-back slightly less as it work-hardens and has less room to grow. Without bumping you might go 3 or 4 loads then it starts to give tight bolt-closure as the headspace dimension gets very close to the chamber size. At that point it becomes necessary to FL size. You can alleviate the work-hardening by annealing periodically. I have never annealed a case myself, but my 6x fired brass is kind of waiting until I have the means to anneal it.

Shoving the shoulder back too far promotes stretching, increasing the case length and thinning the case wall in the body.

You can quite happily just neck size and periodically FL size.
Or you can Neck size and bump, and FL size less frequently (if at all). You'll need a bump die though.
Or you can FL size every time.

The current trend amongst most accuracy nuts is the latter, but you might want to work out by testing for yourself what best meets your needs.

..

Thanks Rox, this is all useful interesting stuff. Do you know why the trend is to FLS? Is it that it leads to better uniformity. I guess they are concerned about case volume? I suppose that each case will grow at its own rate, but a bump die presumably bumps the shoulder back to a fixed position relative to the head? So would this not do effectively the same thing - assuming all cases shoulders go forward by at least the amount you're bumping it back.

[Magpie]

I use a forster 3in1 trimmer.

Not cheap, but they produce nice, cleanly chamfered (in and out) trimmed cases every time in one action.

I lent mine to Russell Simmonds who admits to hating case trimming, he then bought one PDQ

I trim all of my .308 cases the same, so once set up you just leave it.

Hi Maggot,
Another interesting contribution and it does look a nice piece of kit - and its powered smile2
It does however work off the case overall length and I'd be interested in the pros /cons of this approach as to indexing off the shoulder. Interesting that Russell uses this approach.

So many different tools to choose from smile2 !!

[Magpie]

This looks really interesting, not seen this one before. Do you know of a UK outlet for these ?

Not that I know of, I bought 3 off eBay US a while back, 308, 223 and 204 Ruger, £30 each or there abouts. I have friends in the US that I get stuff shipped to for collection when we go over or when my friend goes over.

I'm sure Ovenpaa could make these quite easily, there should be a good market for them over here (do I get commission?)

Hi phaedra1106,

Yes I'm sure that Ovenpass could make one - and make a work of art out of it into the bargain. I did discuss this with him at one time but he seemed a bit sceptical about shoulder indexing ....

[rox]

Do you know why the trend is to FLS? Is it that it leads to better uniformity. I guess they are concerned about case volume?

I assume these, plus allowing cases that would otherwise be fractionally out of true to center themselves on the shoulder. Probably a bit of herd instinct too. It is so unfashionable to neck size these days!

but a bump die presumably bumps the shoulder back to a fixed position relative to the head?

Yes.

So would this not do effectively the same thing - assuming all cases shoulders go forward by at least the amount you're bumping it back.

The same as FL sizing? As far as the shoulder is concerned, yes. The difference with a bump die is that it doesn't touch the case body. They used to be pretty-much only available from custom die makers, but there's a Forster bump die off the shelf that can also size the neck using bushings.

One of the attractions of neck sizing plus bump dies is that it can be done with limited or even no lubing (and consequent de-lubing). On a progressive workflow that can mean just one pass through the press instead of two.

Regarding trimming to an overall length versus relative to the shoulder - as long as you are controlling the position of the shoulder, what's the difference?


..

[phaedra1106]

The CTL is very accurate, all my 308 brass is FLS in the same die so shoulders are consistent.

[Magpie]

Do you know why the trend is to FLS? Is it that it leads to better uniformity. I guess they are concerned about case volume?

I assume these, plus allowing cases that would otherwise be fractionally out of true to center themselves on the shoulder. Probably a bit of herd instinct too. It is so unfashionable to neck size these days!

but a bump die presumably bumps the shoulder back to a fixed position relative to the head?

Yes.

So would this not do effectively the same thing - assuming all cases shoulders go forward by at least the amount you're bumping it back.

The same as FL sizing? As far as the shoulder is concerned, yes. The difference with a bump die is that it doesn't touch the case body. They used to be pretty-much only available from custom die makers, but there's a Forster bump die off the shelf that can also size the neck using bushings.

One of the attractions of neck sizing plus bump dies is that it can be done with limited or even no lubing (and consequent de-lubing). On a progressive workflow that can mean just one pass through the press instead of two.

Regarding trimming to an overall length versus relative to the shoulder - as long as you are controlling the position of the shoulder, what's the difference?


..

I'll second the no lubing, I bought the coated neck bushings to avoid that bit

As regards whats the difference, I don't know but there are two ways of doing it and I'm trying to work out which is the easiest /flexible and most accurate way of going about it .

[Alpha1]

I use a LeWilson trimmer for all the calibers I shoot to trim and to cut the primer pockets. I have used all makes of trimmers over the years the Wilson just works. I like it a lot.

[Blu]

I have been using these dies for about 3-4 years now and I swear by them. A lot less case trimming and case life is a hell of a lot longer especially on calibres such as .303, I have better things to do such as shooting rounds rather than trimming cases all the damn time. I use these dies for all my rifles.

http://www.reloadersnest.com/eq_dies_de ... p?ItemID=1

Blu