Smoked bullet aka sharpie Ogive help?

[DeltaRogerVictor]

Trying to determine bullet seating depth for a new rifle, and I am having a bit of some self doubt.
Rifle is a GA Hospitaller in 6.5creedmoor, this is my first rifle of this quality. When I am trying to determine bullet seating depth I am getting rifling stripes on the bullet all the way down to about .030 inches off the case mouth. When I use a hornady/Stoney point gauge with a wooden dowel inserted from the muzzle and tap and feel back and forth it feels like the actual rifling is quite a bit farther out. Are the stripes the result of a tight throat (google only yielded results on possible cause of a tight throat from quitting smoking...) or is it possible that the rifling really begins that close to case? Factory rifles have not prepared me for this as the chambers have been so long that I was limited by my magazine dimension.
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[MtnCreek]

I'd skip the dowel from the muzzle and just use the tool with the rifle held upright (muzzle toward sky). Very, very light pressure when pushing the bullet up. Get several measurement, discard the outliers and find an average of the rest. Seat a test rd at -0.010 or 0.015 and see if it marks the bullet up (insert test cart by hand and keep in mind the ejector may cause marks on one side of bullet when removing from chamber).

 

[spife7980]

Let the rifle tell you

 

[DeltaRogerVictor]

Thanks guys, I'll try the method described in the video.

 

[DeltaRogerVictor]

After speaking with a man at Defiance machine, Norm I think was his name. I removed my firing pin assembly using a piece of high strength small diameter cord looped around my boot and pulled tight against the ridges on the bottom of the firing pin (I.e. Boot lace field disassembly) spinning the bolt body off while holding tension on the spring. Using a 5/64" roll pin punch, this is where Norm came in, he says that is the size they use, I drove out the ejector pin. I had not done this before and Norm mentioned that if you failed to capture the ejector when the punch was removed it almost certainly would fly across your shop. After getting everything situated I grabbed some test brass and Berger 130 ar hybrids and went to work. Final measurement was 2.194", interestingly the Stoney point came in at 2.206 averaged out over 8 tries. Which I didn't think was that bad, being I used the hornady modified case, rather than order a 5/16-36 tap to make my own out of fired and neck sized brass. This method works well with a competition seater die that is micrometer adjustable, and it will be my go to from now on.