Pressure signs at low velocity on 30 Nosler

[sbruni]

Have a new build in 30 Nosler and am scratching my head as to why I'm getting pressure signs at around 75 grains H1000 with the 215 Berger at only 2700 fps. Bolt is stiff. Primers are flat. It's loaded 30/1000 off the LANs at an OAL of 3.548. There should be 4-5/1000 chamber clearance on the neck. Fired cases measure 4/1000 greater than loaded rounds at the neck. A bullet will easily slide into the neck of a fired case with room to spare. Using virgin ADG brass. ADG has had no reports of issues with the brass which shipped more than a year ago. Barrel is a Proof 1:10. Scratching on the brass would seem to indicate that the lock up is in the first 3/4" or so forward of the web. Trying to get my hands on the reamer drawings but my smith thinks it's sammi minimum with tighter neck and 1.5 throat angle. I suspect that it's a bit tighter in the body than Sammi min. Virgin brass is -4/1000 at the web than once fired and -3/1000 from fired and sized.

Any help would be much appreciated... Thanks Scott

 

[Mram10us]

Dumb question, was there any oil left in the chamber? Was it cleaned very well before firing? Have you compared a fired case to a new case for headspace purposes? Or was that what you meant by web measurement?

 

[sbruni]

By web measurement I mean just forward of the case head... About the lowest point that gets sized by a body or FL die. I clean the barrel thuroughly after each range session and finish with cleaning the chamber with a patch around a brush with 4-5 drops of oil on it... A possible issue but would think that would disapate after the first firing or two. Virgin brass is about 3/1000 shorter than fired around the datum

 

[sbruni]

Freebore is .140 w/ 1*-30 throat

 

[sbruni]

Ttt

 

[adam32]

You clean the chamber with a patch and 4-5 drops of oil? So the chamber has oil left in it?

 

[muleystalker]

Everyone I know that has built them and shooting the 215 & 230gr Bergers and getting the higher velocities are running at least a .200 freeborn, thats what I specked out when I had my 30-28 Nosler reamer made.

 

[muleystalker]

Deleted, double post