300 win mag fired brass issues

[Speed]

I just started to reload my 300 win mag brass and their all coming in under the saami case length spec of 2.610. New brass is at 2.612, my fired brass is around 2.606 to 2.608? It also wont fit my headspace gauge. The base sticks up approx. 062". Ive loaded many rounds of 223, 308, 30-06...never saw this before. I chambered several rounds with primers and they were fine. I must be doing something wrong, so any critiques are welcome. Tia

 

[FLIGHT762]

Belted Magnums "Head Space" off of the belt. You should be setting your F/L Die to move the case shoulders back .002"-.003" shorter than your fired cases, just like the beltless cases you've reloaded before.

What "Headspace gauge" are you using? Are you using a Drop in gauge like a Wilson, Sheridan?

 

[hlee]

Fired brass, as it comes out of your rifle is shorter than the virgin brass that you used to load the rounds?

Does your fired and sized brass fit in your rifle?

 

[m1match]

OP you appear to be referring to case length, which is not the same as headspace. Case length is only important in that you want reloaded cases to be trimmed to a consistent length and your case length shouldn't exceed SAAMI max to be safe in all rifle chambers of that caliber. It sounds like your fired case gauge is a drop in gauge, which does not measure where your case shoulder is, that kind of case gauge is machined to mirror a minimum size chamber to ensure rounds will fit in all chambers of that caliber. A fired case will not fit in a case gauge because it was expanded by firing to fit the size of YOUR chamber. Most drop in case gauges are made to SAAMI minimum so ammo that fits in it will fit in all chambers of that caliber. When you resize your cases you should be bumping your shoulders back like FLIGHT762 said. You need a real headspace gauge like the Hornady headspace gauge to measure where the shoulders of your fired cases are.

And the reason your fired brass was shorter than new brass is firing it expanded it to your chamber so as the case diameter got bigger to fit your chamber, the case length got shorter.

 

[Ankeny]

And the reason your fired brass was shorter than new brass is firing it expanded it to your chamber so as the case diameter got bigger to fit your chamber, the case length got shorter.

Right there is your answer. The hell of it is, depending on where and how much the case expands, you can get a thin spot that might lead to early case separation.

 

[A&8's]

Fired brass will always be shorter than new brass, because it is expanding to the chamber walls. Run it thru a FL die and it'll grow again.

 

[Speed]

Thanks for your responses. Yes, i am using a Hornady drop in case gauge, not a head space gauge. My son keeps calling it a head space gauge and it stuck. I need to pay more attention to those kinds of details. I do have a head space gauge set and should know how to use it correctly, that will be todays mission. I understand the fire-formed part, it just seemed weird that it didn't grow as i expected it too. I'll try running them through the fl die again. I primed and fired several resized cases and they chambered just fine. I had MY brass set aside and my son was given a couple hundred fired cases and mixed them together before he decided to clean all of them. I was a bit worried that those cases were not fire formed by my rifle, so i was just going to resize them all and basically start from scratch again. Thanks again!