Case Trimming a 308, should I? if so, most suitable tool?

[CodeBasher]

I'm fairly new to reloading and have been reloading 308 Lapua brass thinking I had all bases covered.

I now find after about three firings that the cases have lengthened to 2.010" and rounds are starting to become difficult to lock in the chamber. The neck length is correct as my pre-sized little hand held neck trimmer doesn't skim any metal so the extra length is obviously in the case.

So do I....

a) Do a full length resize using that particular die in my kit?

b) Buy trimming apparatus and trim off the extra length and see if that does the trick. If so what is a suitably economical piece of kit.

This far I've gone for reasonable quality gear buying mostly RCBS products recomended to me by the guys at the QRA Q-Store. I've only come across this revelation today so it's late next week before I see Michael and Jenny again.


PS: I'm using 46gns 2208 => 155gn Dwyers.

[Aubrey]

Giraud trimmer is the best.
http://www.giraudtool.com/prod02.htm

[Matt P]

Wilson best there is.

[johnk]

First & foremost, the recommened maximum case length of the .308 before it prudently should be trimmed is 2.015" & the trim to length is 2.005". That assumes that you have a standard commercial chamber of the tightest SAAMI specification, but many are more generous. Therefore, it is highly unlikely that the case length per se is the cause of your difficulty. However, at some time in the not too distant future you will need to gain access to case trimming apparatus, so talk to Mike about the costs & benefits of available options.

These following suggestions are based on the impression I've come by from your post that you are using a set of Redding competition dies.

About any die you will use to size necks has the potential to distort the case which comes from a standard (compared to a neck turn benchrest type) chamber, particularly if not appropriately lubricated. It can draw the neck forward (in the case of the button on a standard die) or down towards the base, perhaps even changing the shoulder (in the instance of just about any other die). Mechanical advantage on most presses conceals just how much effort is applied to cases during preparation.

If cases will chamber readily again after firing, but becomes difficult to do so after being prepared for reloading, then the chambering difficulty is a consequence of something that you have done during your loading process. You might work through that with Mike. If they are stiff to rechamber after having been fired & let cool down, then you could try partially sizing the body with your full length die (body die?), but only enough to permit the case to rechamber with barely detectable effort. Sizing cases down to the full capability of a die in a commercial chamber will be excessive & only lead to more chambering difficulties, a very good risk of premature case separation - and a liklihood of not achieving the accuracy potential of your gear. What you want is a case that chambers OK but is still as close as possible to the dimensions of your chamber.

What you need to do is run the die into the press so that there is quite a distance between the bottom of the die & the top of the shell holder when the press is at the maximum up position - enough so that the die barely starts to touch the fired case. Don't set the lock ring down for the moment. Lubricate a case (if you don't have any yet, Mike sells Redding Imperial die wax, to mine, the best around), run it in, wipe it clean & try to chamber. Continue to increment the die in by small fractions of a turn, bugger all in fact, repeating the process each time with a different case until you can chamber without any difficulty. Then the tricky bit. Set the lock ring so you can run the die in to exactly the same position that you've arrived at and no further in the press with the lock ring tightened down, then run a handful of cases through to check that it's still working OK. You might like to make index marks on the die & the press with a fine felt tip pen to verify the alignment. Even .001" more constriction of the case, particularly the shoulder can be detrimental, so really make sure that you get this precisely right - and there speaks the voice of costly experience!

John

[Brad Y]

Should you trim? YES!

Im going through that issue at the moment in a 22BR. I didnt trim to length and actually have my case necks being crimped onto the bullet causing pressure issues. If I had not of been using mag primers with a thick cup then I think I may have been in more trouble. The pressure produced with the case neck crimped onto the bullet must be enormous and its had me puzzled all weekend.

Now ive trimmed to length and havent lost an eye or damaged my rifle, Im going out tomorrow to see if that will fix my problem.

[CodeBasher]

I'd say you nailed my issue John. Though I'm using imperial dry neck lube I can tell there's a lot of extrusion going on when I'm withdrawing the round back down from the neck die. As you mentioned they are also tight to load but always very easy to extract once the round has fired.

It all makes sense now.

Thanks for the heads up chaps... The full length die will stay in it's case for now.