Fireforming and resizing

[cajun]

No, just the first firing. But for a brand new case to stretch .009 in a SAAMI chamber is quite a bit on the initial firing.

Try a belted mag. I've seen .015

 

[DoneNOut]

Try a belted mag. I've seen .015

and that is kinda short! LOL

 

[Teri Anne]

We know that fireforming works for getting the best performance out of your cases.

But if you full length resize, you end up putting the case back to saami spec.

Doesn't that mess up the desired effect of fireforming?

I personally do a full length with neck resize every time. But that's just me. It's all good.

I tried neck resizing many years ago and found that the accuracy of that particular rifle dropped off with neck resizing only. Went back to full length and never looked back. Use whatever method that gives you the best accuracy out of a particular rifle. I have found that cases trimmed to an exact length, regardless of the case manufacturer shoot more accurately than untrimmed cases.

 

[Mike Matteson]

I mean, there's limits to what is defining of consistency in hand-loading and depending what you theories you subscribe to, can be quite tedious. Sometimes for not much gain.

You were kind of right in assuming that a FL resizing is SAAMI. This is because most chambers are SAAMI, and you're fireforming to the chamber. So yes, but because SAAMI is fairly loose tolerances (relative) and because of variations in machine tools and manufacturing, you're setting your FL die to bump back the shoulder just enough to close the bolt reliably while keeping it as close to its fire formed size. That's what most people mean who know anything about this mean by .002 bump.

The neck sizing however is meh. If you use a mandrel die, maybe a bushing die you can add setting neck tension into the same step. I don't have all day to mess around loading ammo, so I try to get in and out. A lot of guys here are retired and have no problem doing extra steps. The Lee collet dies can work good too.

Even then, if it's your second firing…the case will continue to change…that's when annealing comes in…
So it would be more like:
-FL resize virgin brass
-Fire form
-FL resize/bump
-Neck tension

Go shoot

-Anneal
-FL/bump
-Neck

I petty much go along with you have said. I use bushing dies. Found that I have been able to set neck tension in the sizing operation (No Mandrel). Now I haven't study the spring back or changing of the I.D. O.D, after the case is sized over a few days. There is some other things I do. New case that never been fired. 1. I cut to length, because of the different in case lengths by as much as .007" 2. I cut for neck thickness in 2 set ups. I don't cut the materials all in one pass. Generally I figured that a new case the inside of the neck is even and no irregulars or uneveness. So a mandrel isn't needed to push the irregulars to the outside of the neck in the sizing operation. It deletes any irregulars in thickness inside and out. One less step in the long run, after cutting the neck for thickness. I also feel that not cutting the necks for thickness doesn't totally stop the uneveness of the neck which inturns effects the opening of the neck, in more than one way releaseing the bullet going down the tube. There is a rebound in the case as it's being fired. Whether the bullet has totally left the neck area is up for debate. That portion of the case neck that sits in the chamber uncut for thickness how is it setting? The neck uneven sitting on which side of the chamber? It probable can be figured out, but that's above my pay grade. Some cases I am having to, or advise to anneal during the size reduction in the neck, because there so many step in getting there.
Again an interesting debate.

 

[Straight Shooter]

I checked my rifles with a borescope and saw they all have about .030" from the case mouth to the chamber wall. I stopped trimming after that discovery. I will, more than likely, blow the primer pockets before they reach that growth.

Ditto

 

[406ANGLER]

I Full Length size every time for consistency, and also use Redding competition shellholders to get .002" shoulder bump if needed.

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