Shoulder bump confusion

[Huntinbouwbow]

Shooting a 6.5 prc. After shooting, i measured the shoulder bump before resizing. I got -.002. I than resized because i only have a FL die. I than measured after and was getting anywhere from .000 to -.001. What did i do wrong?
Brass has been fired 3 times and never had any issues.

Thank you

 

[Benchrest Braxton]

I'm kind of confused by your post.

You are saying your headspace went -0.002" after firing compared to the loaded round? Because thats kinda weird....

but with the headspace decreasing after sizing, that is actually normal if you aren't yet touching the shoulder since the brass flows forward with sizing.

 

[Huntinbouwbow]

I'm kind of confused by your post.

You are saying your headspace went -0.002" after firing compared to the loaded round? Because thats kinda weird....

but with the headspace decreasing after sizing, that is actually normal if you aren't yet touching the shoulder since the brass flows forward with sizing.

No sorry, I have once fired brass that came with the gun. I use that in my gauge and zero it. Than I checked my brass after shoot it and it was -.002. Than I resized it and it went to .000 or -.001.

Hopefully that makes more sense

 

[Benchrest Braxton]

No sorry, I have once fired brass that came with the gun. I use that in my gauge and zero it. Than I checked my brass after shoot it and it was -.002. Than I resized it and it went to .000 or -.001.

Hopefully that makes more sense

was the 1x fired brass that came with your gun sized and ready to load?

it is definitely strange that the headspace increased after firing....

but again, its not unusual for headspace to go down after sizing if the die isn't touching the shoulder when sizing because of the brass flowing forwards, then once it starts making contact with the shoulder it will start going the other way.

 

[1000yards]

Is that a factory or custom chamber?

Sounds like you're saying it shrunk after firing. This can happen with a wide chamber. If the case has to expand outwards in all directions then it will shrink in length. Let us know the width of your unfired, fired, and resized cases.

After that, you're saying it expanded after resizing. What die are you using? Did you lube the inside of the necks? Is the expander clean? I'm not an expert here but I know this can happen if the expander hits too much friction in the neck and pulls the shoulder forward.

 

[ResearchinStuff]

You just need to screw the die down tighter. Fired brass from that gun is the baseline, it can't be - anything. The way your die currently is set it is making the brass get longer, which could be a couple different reasons with a typical full length die, but the solution is always to screw it in more.

 

[Benchrest Braxton]

You just need to screw the die down tighter. Fired brass from that gun is the baseline, it can't be - anything. The way your die currently is set it is making the brass get longer, which could be a couple different reasons with a typical full length die, but the solution is always to screw it in more.

don't screw anything down more until the case is fully formed. depending on pressure this could take 5-6 firings.

don't touch the shoulder until you have to

 

[Thegman]

I'm not completely clear on the issue you're having, but if you're sizing this brass for one rifle only, I'd gradually lower the die until you have a slight crush fit on a piece of brass, and stop there. That matters more than measurements.

 

[wapitibob]

Full length sizing will lengthen the brass if you don't have the die set to compress it (shoulder bump). As mentioned, you don't always need to fl size. And, I wouldn't trust the 1x fired brass to be correct. You can smoke the shoulder of a recent fired case ( light a wax candle and run the case shoulder thru the flame ), chamber it and see if it touches the chamber shoulder. If not, add a piece of scotch tape the base and chamber again. That will tell you where the case shoulder is in relation to your chamber.

 

[wind gypsy]

No sorry, I have once fired brass that came with the gun. I use that in my gauge and zero it. Than I checked my brass after shoot it and it was -.002. Than I resized it and it went to .000 or -.001.

Hopefully that makes more sense

Has the once fired brass been re-sized before measuring?

 

[Huntinbouwbow]

I am sorry if i missed replying to anyone.

The brass that came with the factory Seekins rifle was not resized. I was under the impression that if i kept the same brass it would create consistency with measuring throughout all reloads with my 6.5 PRC. They way i understood shoulder bump was, you take a fired brass and put it in the comparator gauge. than you zero that one out. Than you take the brass you want to resize and it should measure .000 but mine was measuring -.002. I do not have a neck resizing die only so i used my FL resizing die. after that i was getting -.001 and some cases where -.003.

It seems one error is using once fired brass as my control and not using brass from the batch of 3 times fired.

As far as measurements, I will try to measure with my calipers but i do not have any other way to measure my brass at this time.

I hope this helps, and i apologize for confusion. I am trying to explain a problem over the internet that i personally do not understand myself. I did not have this issue when they were 2x fired brass.