Gauge Pin Question

[jstanton]

I had been researching making the switch to mandrels for setting neck tension, but after watching one of F-Class John's videos about using gauge pins I decided to give those a try. In his video he was reviewing Porter Precision, he gave them a good review, so I ended up ordering some from them. I started with 0.262" gauge pins for my 6.5 Creedmoor and Lapua brass.

So my question is that after I run the gauge pin in the case I noticed that it leaves vertical grooves, like a scratches or stretch marks maybe, on the inside of the neck. I checked the pin to make sure there were no burrs and it was smooth. I am using Imperial Application Media with Dry Neck Lube. Could I be using too much dry neck lube? I dip the case neck in the application media, tap the excess off, run the case up to the pin, let it sit for a few seconds, and then lower it back down.

I also bought pins for my 7mm and 300WM but I am hesitant to try any more of these pins if I am damaging the brass. I used a toothpick to feel the inside of the case and they are definitely score marks in the brass.

Any ideas?

 

[MagnumManiac]

Totally normal, the pin is much harder than brass so it leaves witness marks where you measured. A micrometer on the outside of the neck leaves the same faint witness marks.

Cheers.

 

[CA48]

Try getting some imperial sizing wax on your finger and wiping it off on the inside of the case necks all the way around. It should make things smoother and not mark the brass as bad. Looking at your photos everything looks normal and I understand dry neck lube is easier but I prefer the wax. Something else you might try is not tapping off the excess dry media, a little more might smoothen things up.

 

[Seabeeken]

Perhaps using some scotchbrite on the corners of the gage pin to remove any micro burrs or dull the sharp corners.

 

[bigoldphatboy]

You might have better luck with an actual mandril from Sinclair or 21st century.
They are tapered and align with the case a lot more easily. I do use gauge pins to measure the case after I run a mandril through it to check the actual size after spring back.

 

[Beluebow]

The 21st Century expanders do the same.....it does not affect accuracy best I can tell.

 

[slikmrc]

Try chamfering the inside of the case mouths