I'm reloading for my Ruger M77 Mark II '06 with an RCBS single-stage press. Because I'm testing some recipes, I'm only loading a dozen or so rounds and using the primer seat on the press. I'm getting some misfires, all but one of which fired after recocking the bolt. All of the primers showed an imprint after the first misfire. I'm assuming I'm seating the primers (Winchester large rifle) a bit too deeply. Right? Anything else I might be doing wrong? Thanks.

Might be related to the firing pin/spring.

I had the same problem years ago on a Savage 110. I had previously taken apart the bolt for cleaning and didn't adjust tension on the spring properly.

The primers MUST be seated to the BOTTOM but, NOT crushed!!!

To me it sounds like it "could" be the gun, but does the gun fire -------------> EVERY TIME <--------------- with factory loads????? If it DOES, look for the following, as these would be the next things i'd look for,

Primer NOT seated to the bottom of the primer pocket (keep the primer pockets and flash hole clean)
Crushed primer from "over seating" (don't force the primer)
The die is seated too low, pushing the shoulder back when you size the case creating too much headspace
Moisture in the cases when you load them (brought in from the cold?? Rained on??)

If the gun doesn't fire every time with factory loads, take the bolt apart and see if grease or dirt has built up around the fireing pin..

Drilling Man

Sounds to me like the primers aren't seated fully.

This is interesting you posted this. I was having the same problem only a couple of months ago with a Savage 110 .30-06. My suspisions were confirmed that it was my firing pin tension rather than my reloading technique. I too had taken my bolt apart previously and the spring/firing pin assembly was loose, causing erratic patterns in ignition. I pulled the bullets of the misfired rounds (16 out of 50) and reloaded to the same specs as before. Not one misfire!! For the record, before I did this, I also tested with some factory rounds and had a few misfires as well, which led me to examine the bolt. I would definately double check the bolt to make sure all parts are snug and in contact as they should be, and that there is no excess buildup of foreign materials.

I was told by several people on here, when I started reloading to not use the primer seat on the press, I dont know if this is true, because following their advice I bought a hand priming tool. I have never used the primer seater on my press, so I cant say if this is your problem, but I know 4 people that reload in my group of friends, and all of them use a hand priming tool, and none of us have had a misfire. Hope this helps.

I had the same problem with a 30-06 and thought maybe the firing pin was sticking so I disassembled and cleaned the bolt and it still did the same thing .It turned out to be faulty primers out of a new brick . I've had them in storage in a dehumidified room for a couple of years so I guess they just went bad ,but as soon as I changed primers the problem went away . Anyone wants some cheap primers .

How deep (below flush w/case head) are you seating them?