lets talk excess pressure

[Old Man Now]

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[Old Man Now]

For some reason the whole link is not highlighted - but any case it's for the RCBS Precision Mic.
https://www.wideners.com/itemview.cfm?dir=210|211|619

But check around for pricing.

[huntandjeep]

So I got to thinking last night about the 7mm. When I finished off the original 20 rounds the previous owner worked up I never had a tight bolt lift after firing those rounds. Since I never checked them with a case gauge just set up the die and went. Is it possible that I never set the die up correct and im creating a headspace issue which is causing the tight bolt and not the powder charge ?

[wsmnut]

If they were incorrectly sized you would possibly have issues closing the bolt.  You have issues opening the bolt due to over pressure.
Those cases plump when they cook.  If you over pressure them they get tight.
Reduce the charge and work up slowly.
Good Luck.

[300rum]

He probably used new brass? or sized/trimmed correctly. 

Yes, you will find signs of overpressure much sooner in a cartridge that hasn't been sized correctly even with a lower powder charge.  For instance, you could use new brass that is within tolerance and have no signs of over pressure then use the same powder charge in a cartridge with a case that is incorrectly sized/trimmed and have signs of over pressure.  You need to size/trim and then work up a load.   

So I got to thinking last night about the 7mm. When I finished off the original 20 rounds the previous owner worked up I never had a tight bolt lift after firing those rounds. Since I never checked them with a case gauge just set up the die and went. Is it possible that I never set the die up correct and im creating a headspace issue which is causing the tight bolt and not the powder charge ?

[2labs]

Yur welcome!

[huntandjeep]

If they were incorrectly sized you would possibly have issues closing the bolt.  You have issues opening the bolt due to over pressure.
Those cases plump when they cook.  If you over pressure them they get tight.
Reduce the charge and work up slowly.
Good Luck.

The bolt was a little tight to close.

[huntandjeep]

He probably used new brass? or sized/trimmed correctly. 

Yes, you will find signs of overpressure much sooner in a cartridge that hasn't been sized correctly even with a lower powder charge.  For instance, you could use new brass that is within tolerance and have no signs of over pressure then use the same powder charge in a cartridge with a case that is incorrectly sized/trimmed and have signs of over pressure.  You need to size/trim and then work up a load.   

So I got to thinking last night about the 7mm. When I finished off the original 20 rounds the previous owner worked up I never had a tight bolt lift after firing those rounds. Since I never checked them with a case gauge just set up the die and went. Is it possible that I never set the die up correct and im creating a headspace issue which is causing the tight bolt and not the powder charge ?

Ordered a case gauge set and trimmer today. Was just thinking out loud

[huntandjeep]

Should I just be bump sizing then? I understand full length sizing returns them to Saami spec ,but I don't need to do that every time correct. Just when using new brass before there fired in my chamber. These will never go in somebody else's rifle

[jasnt]

Should I just be bump sizing then? I understand full length sizing returns them to Saami spec ,but I don't need to do that every time correct. Just when using new brass before there fired in my chamber. These will never go in somebody else's rifle

that would be up to you and your rifle.  Like I said earlier I only neck size no bumping at all. But for those that like the lighting fast cycle and don't mind the slightly shorter brass life normally bump the shoulder back about .002" 

 

[huntandjeep]

While waiting for my trimmer and case gouges  to show up I threw the calipers on my 7mm brass. The 5 that caused the tight bolt measure 2.527 - 2.519 - 2.514 - 2.527 & 2.526 these have been fired twice.  Than I randomly pulled 5 of the original load that have been shot once and loaded twice . They measured 2.510 - 2.505 - 2.510 - 2.503 & 2.521. So I need to trim these all back to 2.490 correct? As soon as the case gauges show up I will throw up those measurements.

[2labs]

It's the datum of the shoulder causing the firm bolt not the neck lenght most likely.

[huntandjeep]

It's the datum of the shoulder causing the firm bolt not the neck lenght most likely.

That's what the previous owner that built the rifle is thinking also. Case gauges should be here tomorrow.

[2labs]

I'm out...Elvis has left the building!

[huntandjeep]

Case gauges showed up today and I measured the 5 fired cases from the 7mm. They measured 2.129 , 2.129 , 2.128 , 2.127 & 2.125. Then I measured 5 of the previously loaded rounds that I pulled the bullets and powder from. They were 2.121 , 2.123 , 2.123 , 2.121 & 2.124.
Am I sizing them correctly?