Case trimming - thoughts on tooling and technique please

[Magpie]

Hi Folks,

I’ve been reloading for a little while now and I want to revisit the subject of case trimming and would like some opinions of the various options available. I should say that I currently have one of the basic lee trimmers and it kind of does the job but not to the degree of flexibility I’d like. You basically have to FLS to use it since its indexed to the case head.

My primary goal is to make consistent, accurate rounds. I’m also a bit lazy so I’d rather have powered assistance if that is consistent with my primary goal. Also the poor old fingers struggle a bit with purely manual tools.

Now this is where I have to put on the fire retardant under pants

It seems to me that there are two key measurements to do with case length and they are both relative to the shoulder.
a. The shoulder to mouth measurement is important to make sure you don’t crimp the bullet on chambering and the round will actually chamber.
b. Then there is the headspace, which is related to the head to shoulder measurement. Too long and it won’t chamber and too short and there is a lot of slack at the head end.
Once we’ve gone to all the trouble of fire forming, it seems to me that more of the energy of the charge would go into ejecting the bullet if it wasn’t expended in making the case fit the chamber again. So I’m looking to do as little work on sizing the case as possible; which should also improve case life.
For cases fired in my chamber. I’m only intending to bump the neck and trim if required. The Wilson case gauge gives an easy visual indication of over length (either end) cases. The only work of every case will be neck sizing.

OK, all that said, dare I ask for people’s case trimming tools / techniques and why you do what you do? As I said before I’d prefer powered solutions but my pocket isn’t deep enough for a Giraud (although they do look really nice).
Specifically any experience of a WFT (Little crow gunworks) or the Possum hollow Kwik case trimmer or their ilk would be interesting.
I’d also like to hear any opinions on why trimming wrt to case shoulder might not be a good idea.

Thoughts please ?

[phaedra1106]

For the 308 I have a very accurate and clean cutting CTS case trimmer, similar but better than a WFT or Possum Hollow http://www.calguns.net/calgunforum/show ... p?t=587361

For the other calibres a simple Lee trimmer and an electric drill followed by the usual chamfer/deburr on a Hornady Case Prep Trio http://www.hornady.com/store/Lock-N-Load-Case-Prep-Trio

[rox]

OK, all that said, dare I ask for people’s case trimming tools / techniques and why you do what you do?

I started with the Lee trimmer, flirted with a Gracey, gave away an RCBS 'lathe' type, nearly bought a WTF, and now use a Dillon.

I had the Lee mounted on a slow speed drill press, with the cutter in the chuck so it was easier to change the case in and out of the lock stud. It was pretty painful (figuratively and literally) getting through any reasonable number of cases. I expected the Gracey to solve the problem, but it was still very slow work that resulted in sore fingers. The Dillon integrates the trimmer with a full length die (you can use it on a single stage press or a progressive). Since it trims as it sizes, trimming takes no additional time whatsoever. The cut is very clean and it leaves no burr. Since most case growth occurs during FL sizing it is, to my mind, the appropriate time to trim. My personal opinion is that achieving identical case lengths is not an important accuracy factor so I have historically trimmed only when necessary, and my more 'mature' brass (say, 6 times fired) has probably been trimmed once, with neck size and shoulder bump accounting for most of the loading cycles and leading to very little case length growth. One drawback of the Dillon trimmer is that the FL die has a very tight neck, so I’m having dies made with more sensible dimensions.

I don't quite follow why you say "you basically have to FLS" to use the Lee trimmer. It will cut the case to a fixed overall length regardless of whether the case has been FL sized, neck sized, bumped or not sized at all.

..

[Magpie]

yes the lee will cut it to a fixed length, but it takes no account of where the shoulder is. So it might be the right length, but it may not chamber.

If you FLS first then everything should be in the right place and right length. Maybe I'm making heavy weather of this?

[Magpie]

For the 308 I have a very accurate and clean cutting CTS case trimmer, similar but better than a WFT or Possum Hollow http://www.calguns.net/calgunforum/show ... p?t=587361

For the other calibres a simple Lee trimmer and an electric drill followed by the usual chamfer/deburr on a Hornady Case Prep Trio http://www.hornady.com/store/Lock-N-Load-Case-Prep-Trio

Hi phaefra1106,
This looks really interesting, not seen this one before. Do you know of a UK outlet for these ?

[waterford103]

No -- you're spot on , FLS first with a tight die then trim to length and chamfer .I also ,as you know , trim the flash hole internally using a Sinclair flash hole equaliser.

I use a battery drill to drive the Lee case trimmer and do the flash hole ,trim to length and chamfer in one operation .

:goodjob: :goodjob: :goodjob: :goodjob: :goodjob:

[rox]

yes the lee will cut it to a fixed length, but it takes no account of where the shoulder is. So it might be the right length, but it may not chamber.

If you FLS first then everything should be in the right place and right length. Maybe I'm making heavy weather of this?

What is "the right length" ? In the case of .308 you have a 20 thou window, according to the SAMMI spec. The specs allow for worst-case combinations to be safe (e.g. max length case with min length head->shoulder). If you have trimmed the case it is likely to be at the low end of the length window, so you effectively have even more safety margin. But yes, the shoulder dimension and case length must be within spec to ensure safety from risk of the chamber constricting the neck causing high pressure.

You need to control the shoulder position for best results, whether it is by bumping when neck sizing or by full length sizing. Common practice to size brass for use in the same rifle is to move the shoulder 0.001" or 0.002" shorter than the fired or chamber dimension. If you do this and neck size you should experience very little case length growth, and therefore little need to trim at all. If you want to get the shoulder position spot on a case mic is an almost essential tool. You can measure with a comparator, but it is very diffiult to get very precise repeatable measurements of shoulder position in this way.

..

[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?

[rox]

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.

..

[Maggot]

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.