300 wm head space gauge

I got my 300wm head space gauge and it is quite different then my other gauges 7mm saum, and 308. I understand because it is belted but do I use it the same way i do the other gauges it is really short. Also my fired cases from my factory savage rifle are 15 thousands longer measured at the datum line then my new brass I only bump them back a couple thousands when i resized them after firing so they are not stretching so much like when they are new. Should I use a fired case from my current rifle which shoots great to get headspace for the new rifle and then just bump my shoulders back when i reload a couple thousands when I reload them.

I would advise against using your old brass as a gauge for your new barrel . If your new barrel has a shorter length and you set it to shoulder you will be stretching your cases ,possibly beyond there limit. Use your headspace gauges Is your new barrel factory or custom?
Gary
Will you have 2 diff rifles when finished, or are you replacing one barrel for another? If your gonna have two rifles in the same cartridge seperate your brass

my 2 cents...Size it with a new case so the shoulder dose not interfere, then set your die to the new chamber.

Why cant i understand this, the saum was easy so was the 308, new brass is only 1 thousands shorter then a fired piece in both of those CBI barrels. Do I use the 300wm gauge like the other gauges even though it is so short just put it in and tighten down new barrel like I did the others then check with tape on the gauge, other rifles will only go to 1 o clock with the tape on, or is this gauge different if how I use it, also if i use a piece of brass from my other rifle wouldnt they now be headspaced the same or I am not understanding something. thanks for any help

You use it exactly like your other gauges even though the magnum gauge is shorter.

Here's why: Since the 300WM headspaces on the belt, the headspace gauge does not need to be very much longer than the distance from the front of the belt to the rear of the gauge.

Put it in, make sure the bolt closes, make sure with a couple of pieces of scotch tape the bolt does not close, and you should be good to go.

Best of luck.

As was mentioned, use the guage just like any other. Set the dies and reload the fired brass just like any other and as you've been doing with minimal bump of the shoulder.

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Originally Posted by Blue Avenger

my 2 cents...Size it with a new case so the shoulder dose not interfere, then set your die to the new chamber.

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This is good advice, make it tighter than what has been suggested. The belted case headspace is much tighter more like .002 maximum. Then as blue said once you fire it necksize or set your die to only bump .002 max on the shoulder you want minimum room for growth with a belted mag.

thanks for the advice, I really appreciate all the help.