Pressure with Neck-Sized Brass but not Full Length Sized Brass?

[MSLRHunter]

I have a load for my 280AI that shows no pressure with new or FL sized brass, however that same load with NS brass often shows an ejector mark. Both dies are bushing dies using the same bushing so neck tension should be the same. When FL sizing, the shoulder is set back 0.002". Any ideas what could cause this? Has anyone else experienced this?

[Canadian Bushman]

Id say that your running pretty close to a maximum load. Now that the case isn't absorbing some of that boom by expanding your experiencing some high pressure signs. Have you shot any through a chrono for comparison.

[Joe King]

Put up a pic of the ejector mark. I'm wondering if it's just a shiny spot or if you have some brass extruded into the ejector hole. I it's the latter I'd say your loads are pretty hot for your gun. If the former then you'd be getting a press fit when you chamber a round. How is your extraction? resistance on the bolt lift, hard, no resistance?

[MSLRHunter]

Originally Posted by Joe King

Put up a pic of the ejector mark. I'm wondering if it's just a shiny spot or if you have some brass extruded into the ejector hole. I it's the latter I'd say your loads are pretty hot for your gun. If the former then you'd be getting a press fit when you chamber a round. How is your extraction? resistance on the bolt lift, hard, no resistance?

I'll put up a pic tonight of the mark. It is near max with H4831sc and 168vld, however velocity isn't very high-2815fps. Chambering and extraction are a little snug with the NS brass only.

[Mikecr]

Do you have any REAL pressure signs?

[Bart B]

Right off the bat, I believe case head extruding into holes in the bolt face is a "real" indicator of pressure being too high. Typical cartridge brass starts to extrude at about 65,000 CUP to 70,000 CUP; that's about the same as about 85,000 PSI.

There has to be something different between your dies and techniques to cause that if the components are the same. Probably a dimension someplace. So you've gotta measure everything between the two sets of resized cases from each tool and process as well as the dimensions between the loaded rounds of each. Every detail dimension wise should be checked.

[Mikecr]

He would have every pressure sign known with a 280 at 85kpsi & the subject would be all together different. That's not what's going on, and it doesn't seem to me like a real problem(so far).