headspace on fired .308 shorter than SAAMI specs

[FASTDM]

I am new to reloading so please bear with me.

I'm reloading once fired FGMM 168gr. Using RCBS everything. Precision comp dies, MIC, etc.

These rounds are for a Savage110FP chambered in .308 and were fired out of the same stick.

When I measured my average headspace for the first lot of 100. I came up (-0.004) shorter than SAAMI standards. That was from a 5 rnd random pull. So, I MIC'd another 4 sets of 5 and came up with the same average. The RCBS instructions only mention headspace that measures within SAAMI standards.

I understand that Savage's tend to have tight chambers and that's usually a good thing.

So my question is:
What does this mean in the grand scheme of things for my reloading process and are there any specific steps that I need to take to ensure that my rounds are safe and accurate?

Semper Fi

 

[JeffinTX]

Re: headspace on fired .308 shorter than SAAMI specs

Headspace of the cartridge is measured from a datum line on the shoulder to the base of the cartridge. So, if you're loading that .308 for only that one rifle, its not an issue. Measure and record that headspace and size the dies down to reduce that headspace 0.002-.003" for full length sizing. Now, it may be an issue should you have another .308 rifle and its headspace is more than .005 longer than this rifle, the brass will stretch and fail sooner because of that. BTW, the headspace dimensions has nothing to do with the ogive or COAL. That is about bullet seating and the amount of jump the bullet will take to the lands.

 

[BCP]

Re: headspace on fired .308 shorter than SAAMI specs

Are you running them through a full length die?

 

[jdgray]

Re: headspace on fired .308 shorter than SAAMI specs

If factory ammo chambers freely in your Savage, then the headspace is set correctly. If it chambers with a stiff bolt, you may be a little short. Handloading for accuracy, and good brass life, you should run only a few thousands of headspace.

 

[targaflorio]

Re: headspace on fired .308 shorter than SAAMI specs

I assume you mean you measured the headspace of the fired cases with your RCBS Precision Mic? It helps if you are specific.

My custom Remington 700 measures -.002" on fired Winchester brass.
How hard are you twisting the Mic? Should be just enough to feel resistance.
When you say .004" below saami, you mean below the zero on the Mic?
That is a tight chamber (old reamer maybe).

When you size the cases, be sure to take your headspace back relative to the fired brass measurement. I.e., -.004" -.002" for .006" set back. or jump right into neck sizing only and leave the shoulders alone until they are hard to chamber.

Of course, I'd not start with federal brass. If you are new to handloading, buy some new win brass or shoot black hills or SWAmmo factory and load that. Federal is more finicky than Winchester.

 

[FASTDM]

Re: headspace on fired .308 shorter than SAAMI specs

Thanks for all the info.

Semper Fi,

 

[TexIndian]

Re: headspace on fired .308 shorter than SAAMI specs

Sometimes what the 'standard' is and what I see in my brass (or my tools) are different, just like your numbers. I have a Redding Comparator (or whatever they call it nowadays, pic below) that comes with a special sample case you use to zero the dial indicator to the SAAMI minimum headspace. Then you measure your brass in relation to that 'minimum'. All unfired brass I ever tested shows to be under that minimum. Most fired brass shows to be over the minimum, but I have had some that showed zero or a minus number. It might be just a variance in the tool or it might be how we set up or use the tool. But as long as you stay consistent and size your brass according to the same numbers from the same tool, it doesn't really matter what the numbers themselves are.