Home Forums Hunting & Shooting Gunsmithing M77 firing pin issue

I have a Ruger M77 currently chambered in 338-06 that is having misfires due to lite primer strikes. I sent the bolt back to Ruger who says the firing pin is protruding within spec. I have another M77 chambered in 30-06, both are lefty stainless mark 2's.

I swapped the firing pin / bolt shroud assembly thinking it was a short firing pin and to my surprise, after swapping firing pin assemblies, the issues was still present. So with the naked eye, you can see (in person its very obvious, not sure about pics) that the firing pin sticks out further on the 30-06 bolt farther than it does on the 338-06, even though Ruger says its within spec, clearly their specs are off. When I swap firing pin assemblies, there is no change.

My question is, what could be hanging the firing pin up, suggestions on next steps?

Pics:

https://imgur.com/a/EE51kK2

Thanks in advance.

Hit the cocking piece interior and firing pin interface with dry lube and see if it “snaps” harder. Might be dragging on interior and needing polishing.

The protrusion on the bolt on the left is plainly less than that on the right, but is is certainly adequate. In fact, it looks to me like the bolt on the right is borderline excessive.
Striker travel and the amount of spring compression is important. In addition, I have seen a lot of Rugers with three or four dead coils at each end of the spring. If you remove the assembly from the bolt, you can, with a common bathroom scale and some home made accessories, measure the amount of preload on the spring and also measure the strength of the spring in the cocked position. Preload should be around 20 pounds or so.
It is possible that the striker is dragging inside the bolt body and this is easily ascertained by removing the spring and reinserting the springless striker to check for interference. Internet diagnosis is pretty hit and miss and this is the best I can do for you. Good Luck. GD

Chamber may be cut to deep

I thought that too at first but after inspecting brass after multiple firings I dont believe that is the case.

I striped both bolts and they behave the same with just hand pressure, I can swap them and still the same, so one pin is definitely shorter than the other from the face of the pin stop to the tip of the pin. There doesn't appear to be any obstructions, burr's, gunk etc in the body but im going to soak it overnight in brake cleaner and then run a copper brush up there and hit it with the compressor, then lube and reassemble.
I also bought a 24lb spring (factory is 20lb), lets see what all that gets me.

Ive also been working the pin in and out of the firing pin hole on each to see if I feel any differences...not much difference as far as I can tell. Im going to polish the stop, especially around the bevel and see if that helps any. Im half tempted to try to take a few thousandths off the face of the pin stip but I think that my be working bass akwards, I think to adjust those they probably reeam the inside of the bolt body but im just guessing.

Thanks for all the input gents...i'll post up again after I run out and fire it, hopefully this weekend. Got 25 rounds loaded up and ready to go...we'll see.

I would still try a reload with the bullet jammed in the lands to be double sure.

Wouldnt the extractor prevent it from floating forward in the chamber though? It snaps into the bolt face nice and snug...

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Back long ago, dad bought mom a 77 .243 and put a 4x Bushnell Banner on it. She shot a doe with the thing and it got put away until it become my deer rifle as 12 year old. I hate that rifle. At the range it apparently functions fine, but sit with it in a deerstand for a few hours, loaded and ready, and then try to shoot a deer, and it will misfire with a poor primer strike. A new firing pin spring did it no good. It misfired on me three times, including the first attempt at my first buck. In retrospect I have to wonder what was wrong with my father, giving me such a garbage rifle to use. The thing kept me from buying any ruger product until I was well into adulthood. Meanwhile, I still hate the rifle I killed my first deer with.

Heading out in about 30min to go test fire it...i'll report back after.

Ok, well...out of 12 rounds I had two misfires which is better than I had before. Maybe it's a combination of a firing pin protrusion on the short end of the spectrum even though its within spec and a chamber thats on the loose end of the spectrum, i dont know. Ive attached a couple pics, one is a loaded round that was FL sized next to a fired case from today and the other is the two misfires next to some rounds that did fire so you can see the dents in the primers.

I guess I could order a neck sizer and see what that does, if its a loose chamber, that should eliminate that if it still misfires. After that, I guess next step is to have it set back and rechambered, what do you guys think?

https://imgur.com/a/g1GJX3Q

As a side note, I was shooting 58.8 grains of H4350 under a Hornaday 250g RN. I was getting around 1520-1530fps. It was about 32 degrees and snowing. Primers are flattening but the bolt was easy to lift. Probably a little room left if I wanted to go faster.

100% headspace. Hint………

How are you measuring the shoulder set back when sizing?

I just use the instructions lee gives which is to raise the ram and screw the die in until it hits the shell holder, then drop the ram and go another 1/4 turn on the die then set the locking ring. Then I just run the brass through it, prime and and load.

You're the 3rd person to suggest that so I guess i'll need to find a gunsmith since there isn't anyone around here...

Simply neck up to .35 and come back down,to yoeld a positive headspaced false shoulder. Prime 20 cases,less propellant or projectile and enjoy the newly found 100% reliability,as you Test Pop same. Hint………….

Hmm, thats easy enough to test out, thanks Stick....a 338-06 neck sizing die used on cases fired in that chamber would fix it too though right?

INITIAL headspace control on Virgins,is the shot which sets the clock on case life. Hint.

I'm really not a Neck Size Guy and prefer a FL Sizer,who's lock ring is never locked. Once headspace is established,you certainly don't want to fhuqk it up. If you can close your bolt on a piece of brass with no resistance,you should be scared to death. THAT is excessive headspace,but you never know how much. Hint.

Fhuqk gauges(I have them all),drive by feel. Hint.................

Ok, confirmed. I just ran 4 spent cases through with little to resistance. I have some whelen dies, should I back the sizing die out a bit just to open the mouth or run them all the way through? After that I can back the 338-06 sizing die out a bit and just neck down...