Headspace gauge question

[problemchild]

Im shooting a POF semi-auto 308. I was at a reloading shop yesterday and the guy there said my reloads would benefit from using a head-space gauge. He told me to shoot 10 rounds and measure the head-space and avg the 10 rounds. Then he said I should set my sizing die +/- .001 of the average. Can this be done with a semi-auto or do I need to full length size with small base every time to fit my tight chamber?

I have been reloading handgun for 30 years but precision rifles seem to be a whole new learning curve.

One last question I have the hornady comparator. Can I just buy a .40 head-space bushing for .308 and insert it into the hornady comparator or do I need the whole head-space gauge kit? The comparator base looks the same as the head-space base.

This is from Midway website making me think all I need is the head-space bushing.

"This gage measures from the case-head to the datum line on the case shoulder, allowing proper resizing for a precise fit with your chamber. Bushings fit the comparator body and attach to calipers with a thumb screw. Can be used on bottleneck cases from 17 caliber through belted magnums."

[RaymondMillbrae]

Get the RCBS PRECISION MIC. (Click on the link).

Look around and you can find one for around $40.00 to $45.00.

People will recommend other mics, but this one is ultimately the better buy.

In Christ: Raymond

[freakshow10mm]

Im shooting a POF semi-auto 308. I was at a reloading shop yesterday and the guy there said my reloads would benefit from using a head-space gauge. He told me to shoot 10 rounds and measure the head-space and avg the 10 rounds. Then he said I should set my sizing die +/- .001 of the average. Can this be done with a semi-auto or do I need to full length size with small base every time to fit my tight chamber?

He is correct in his statements. You can even use 5rds as a baseline, but if you have 10, use 10. Set your sizing die to the headspace and maybe a thou to half a thou as you will get spring back from the brass. Most [competent] commercial ammunition manufacturers use this method for bottleneck cartridges. We size our .223 brass to headspace.

If you FL size your brass you might actually push the shoulder too far back creating headspace issues.

[problemchild]

Thanks.....

So can I use the tools in my 1st post or do I need the tool from the 1st reply post?
Do I measure the chamber or the brass? Which is better in a semi-auto AR10 style rifle?

[freakshow10mm]

I think you just get the tool and bushing. My employee has one and that's the one we used to set and check the die.

Either one will work. You will have to make a chamber cast to measure the chamber. I would use the brass, as it is a negative print of your chamber, minus a bit for when the brass cools. Bit easier to work with.

[FLIGHT762]

The answer to your question is yes, the comparator body will work with the .400 headspace gauge for .308 Winchester. Measure your fired 10 cases(be sure to deprime the cases first,without resizing you'll get a more accurate reading) and adjust your resizing die to bump the shoulder back to less than .005". Your brass will last longer.

[ar15barrels]

Im shooting a POF semi-auto 308. I was at a reloading shop yesterday and the guy there said my reloads would benefit from using a head-space gauge. He told me to shoot 10 rounds and measure the head-space and avg the 10 rounds. Then he said I should set my sizing die +/- .001 of the average. Can this be done with a semi-auto or do I need to full length size with small base every time to fit my tight chamber?

You can full-length size to a specific headspace length.
This will benefit the brass by not pushing the shoulder back more than you actually need to.
Since you are full length sizing, the ammo will not have any chambering problems in a semi-auto.

I actually full-length size all my precision bolt gun brass, but only 0.001" more than it needs to chamber.

[problemchild]

Thanks everyone.......

I ordered the gauge from Midway.

What does Hornady Match 308 Factory rounds use for headspace? Hornady shoot really well in my rifle. Will proper headspace make the reloads more accurate?

[Innovative]

problemchild .......

Your brass will last longer when it's resized accurately. Unlike the Hornady Comparator, our new Digital Headspace Gauge doesn't require a collection of bushings. It's much easier to get consistent readings, and it doesn't need any special tools to operate.

Digital Headspace Gauge

Raymond ........

Unlike the RCBS Precision Mic, our Digital Headspace Gauge works on ALL different calibers.

- Innovative

[problemchild]

That gauge is very nice looking. Wish I would have seen that before I ordered the other.

So guys......

I got my gauge.

10 Federal measure on avg. 1.6164
10 hornady measure on avg. 1.6174

What should I size my brass to?

[RaymondMillbrae]

Do NOT split the measurement difference.

Go by your smallest measurement.

In Christ: Raymond

[ar15barrels]

10 Federal measure on avg. 1.6164
10 hornady measure on avg. 1.6174

What should I size my brass to?

1.615