Headspace Question

[Ryback]

New to reloading. I bought a Redding Instant Indicator to help set my sizing die. Using the brass guage that Redding supplies, I zeroed the indicator. I then ran 50 once fired cases from a Remington 700 (.308) and 50 once fired cases from a Sako TRG 22 through the indicator. All of the Remington 700 brass measured .001-.003 above SAAMI minimum. All of the Sako brass measured .001-.003 below SAAMI minimum.

The Redding instructions provide the following: "to get a true reading of your chamber, use cases that have been minimally resized (or neck sized only) and fired at least 2 or 3 times. The first firing of commercial ammunition and/or new brass may provide a fired case that is not yet fully formed to represent the datum length of your chamber. With the first firing of new ammunition or cases, you may even encounter a minus dial reading. This indicates that your chamber is at or near the SAAMI minimum dimension and that the first firing of the brass has not yet fully formed it to represent your true chamber length."

The instructions provide the typical advice to set a sizing die to bump the shoulder back .002-.003. However, the instructions do not say whether you should do anything differently for brass that reads below the SAAMI minimum or on once fired brass generally.

Given my readings, how would you approach setting a full-length sizing die?

 

[witchhunter]

I have separate dies for every rifle I have. They are adjusted to that rifle's chamber. You do not want to change the adjustment once you get it set. I use the chamber as a gauge to set dies. Adjust it on a case fired in that chamber to just close the bolt easily. Obviously your rifles have different sized chambers, get two sets of dies and mark them for each rifle.

 

[Ryback]

For now, I do not mind adjusting the dies for each rifle. For the Sako brass that measures below SAAMI minimum, should I still bump the shoulder back .002?

 

[johnsta]

For now, I do not mind adjusting the dies for each rifle. For the Sako brass that measures below SAAMI minimum, should I still bump the shoulder back .002?

Someone can correct me if I am wrong, but if brass was resized below SAAMI minimum spec, it should be discarded. Or did you mean to say maximum? How I understand it, below SAAMI minimum spec means that it was oversized and shows signs of excessive headspace (falls below the lowest line on a case gauge). right?

 

[Ryback]

You are correct that it falls below the lowest line on the gauge. However, the brass (federal) has been fired once, and I have not resized yet. Redding provided a brass gauge to zero the indicator. As I understand, the brass gauge should be at SAAMI minimum. As the Redding Indicator is still a comparator, I suppose that the Sako brass reads .001-.003 below zero where zero represents Redding's case gauge.

I am uneasy bumping the shoulder back when the case reads below what is supposed to be SAMMI minimum. At the same time, I assume the case did not shrink during firing.

 

[dauntedfuture]

Don't worry about bumping below SAMMI minimum. It is more likely that your brass is expanding to fill the chamber and springing back a little smaller than the actual chamber dimension. As such this can create the illusion of an under-spec chamber. An under spec length chamber is NOT an issue unless you cant chamber factory ammo if you want too or get sizing dies small enough. Its common to cut a custom die with the same reamer as for the chamber to provide a good match in custom dies / BR guns. What you NEED to worry about is the neck. If the neck is too tight, and you cant get a new bullet into a fired case there is insufficient neck clearance. This will raise pressures and cause erratic velocities until you turn the necks a little. Remington rifles have long throats and big chambers, I suspect the SAKO is more on the small size with dimensions better suited to European brass then US.