Maybe a dumb question

Alderman · Aug 30, 2015

I am going to start doing some bullet seating based on info received from the Hornady OAL gauge.
The cases that are modified for use with the gauge will not fit as precisely in the chamber and will likely be shorter to the shoulder.
Should this difference be accounted for or when a round is fired does the brass expand enough to fill the chamber before the bullet begins to move?

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hellrazor · Aug 30, 2015

They will expand to the chamber size. Just make sure the case meets minimum length specs.

jimbires · Aug 30, 2015

I've never used this hornady tool . if it works the way I think it does , yes the shorter brass will make a difference .

I use a piece of brass that has been fired in my rifle . I do not resize it . I push the neck against the edge of my table to make a flat spot . I then sharpie color a bullet . just start to seat the bullet into the brass case . then put this long bullet into the rifle and close the bolt . as you close the bolt you will push the bullet into the case , as the bullet pushes in the flat spot you put in the case neck will scrape the sharpie off . open the bolt and eject carefully so not to push the bullet deeper in the case . look at the sharpie on the bullet if it has not moved measure it . if it has moved push it to the mark in the sharpie and measure it . if it's stuck in the barrel use a cleaning rod to push it out and put the bullet into the case to the sharpie mark and measure it . do this a few times to get a consistent measurement , and this is your max OAL with this bullet . if you switch to a different bullet you need to do this process with that bullet .

Darkhorse · Aug 30, 2015

I have one of those Hornady OAL gages. I used it one time. When I was doing the prep work on my Browning A-bolt .300 Win. I used it to find where the lands started, then I loaded one up about .015 shorter for starters. But when I tried it in the clip it was over .100" too long.
I felt like I was going to panic. I had never heard of a .100" or more jump.
Turns out I let the BOSS do the work and ended up with one of the most accurate rifles I've had the pleasure to own.
I do like "jimbires" does. I think it's the best method.

JohnB · Sep 2, 2015

Alderman

You can drill and tap a case that has been fired in your chamber for use with the Hornady tool. Then you will know that you have an accurate measurement.

You could also measure the difference in the headspace measurement of the modified case and a case that has been fired in your chamber with a bump gauge and adjust the bullet seating depth accordingly.

JohnB