FIXED !! Firing pin hole outward flaring into primer

[KWhorenet]

Morning all,

More of a heads up to anyone seeing the same symptoms. Didn't see it anywhere through searching & not trying to tell people how to suck eggs if this is common knowledge. It's new to me.

As the title says, I've found a firing pin hole (in the bolt face) outwardly flaring on one side of this old Tikka M55 I'm working on.

Thought I'd start a thread for others to benefit instead of burying in my Tikka thread.

Story goes:
- I noticed an odd looking ring impression part way around a fired primer. Didn't really look like cratering to me.

primer damaged flared firing pin hole.jpg (27.63 KiB) Viewed 7158 times

- Chambered then removed another round and inspected the primer and see the same ring impressed into the primer !

Unfired primer damaged flared firing pin hole.jpg (26.39 KiB) Viewed 7158 times

- Inspected the bolt face and sure enough there is an area on one side of the firing pin hole that has outwardly flared very slightly with no burs (I don't have a depth mic to measure it) but my calibrated eyes and feel suggests ~5 thou. It is enough to contact the primer when the bolt is locked down and to impart a ring into it as the bolt is rotated down and back upwards with out firing it.

- It doesn't seem to be cutting/scoring into the primer but more a smooth pressed ring even when the bolt is rotated as there is no sharp edge to it.

Here is a good example pic for now of someone else's that I borrowed that more clearly shows the type of failure mode I'm talking about (will take pics later)

example pic only showing firing pin outwardly flaring

Mini%2014%20FiringPinHole%20a.JPG (3.13 KiB) Viewed 7166 times

Needless to say I'm not impressed and have done some researching for cause and remedies for a flared firing pin hole.

Speculated most likely cause: Dry firing
Plausible cause: Bent or misaligned firing pin striking against the hole wall driving material up and outwards, but I'm just brain storming here.


Possible corrective action:
Mill/blend/grind to smooth down JUST the flared material and avoid burring into the hole or taking material off the rest of the bolt face so as to not weaken it nor change head-spacing.

Anyway, I will fix with advice or have it done while getting the barrel re-crowned.

Cheers,

Richo

[Chronos]

Have never seen or heard of it myself.

Given that it's using up all the headspace enough to imprint on the primer Id just have your gunsmith throw the bolt in the lathe and face it off, check the firing pin for damage and check the clearance. I guess if the firing pin itself was soft it could over time become burred and that may cause it to flare the edges of the hole. Some good pics of the bolt might help.

Are you sure it's not metal from a pierced primer stuck in there?


Chronos

[KWhorenet]

It is definitely bolt face metal on one side of the firing pin hole flaring up. It is smooth but raised. Very hard to see but I can feel it with my nail and fine dental pick I use for feeling burrs and scoring etc. Tried to take a pic with my crappy phone camera but it wont show clearly enough. It isn't raised much and the surface is too shiny for me to get a defined clear pic.

Just uploading a couple of the primer damage that if opened up a bit bigger should show the result.

[Mich]

That's a new one friend.

I've never heard of this happening but an excess of dry firing seems the most likely culprit as you've suggested yourself.

What is the condition of the bolt spring? I wonder if someone has replaced it with an excessively powerful one leading to the problem?

[Seconds]

Hmm, I was going to say plenty of rifles have hundreds or more dry-fires to their name without problem.

Replacement spring is a theory though....

I wonder if you can find the factory spring tension and measure the current one to compare.

[Aster]

Completely off topic but what are those pink tipped bullets?

[Tonit]

Disc of find sand paper on the flat end of a metal rod? A few spins might take care of it without effecting the bolt face.

[Jack V]

Does it look like the firing pin hole has been bushed ? Just dremmel it down smooth as long as you stay at the centre it will be fine .

[KWhorenet]

Well I cut short my accountant visit as all I could think about was this process and more research

As has been mentioned the spring strength may be in question. There is no way I will know unless I do a compression test knowing the standard.
- In some other instances I've read people were adding stronger springs in an attempt to limit primers blowing back and bursting out into the primer hole by compressing the firing pin spring ??? Most common I've read so far were in self loaders.

Have read all sorts of other theories causing similar symptoms but the most interesting discussions I read about were to do with 'Cratering' that seems mostly blamed on too higher pressures or too soft primers but interestingly the topic of bolt manufacturers chamfering the firing pin hole and over sized holes came up allot. I can imagine if the hole or chamfer was too large allowing primer to flow into gap around the firing pin tip; especially if and compounded by soft primer and or over pressures to boot. Makes practical sense to me.


Didn't have any fine flat rub stone tools and deleted the idea of using the Dremel with tin flex shaft attachment on low speed... too afraid so thought back 20 years to <1 thou tolerance hand tool making even though do I love my man toy Dremel 4000

did the job as it wasn't all the way round I had to focus on a thin lip... PITA !!

Tikka M55 firing pin hole blend - shaved a kebab stick in 800 grit.jpg (7.87 KiB) Viewed 7096 times

clear high area almost blended out enough

Tikka M55 firing pin hole blending high area.jpg (21.38 KiB) Viewed 7096 times

I did take an hour for what could have taken 5 mins if I wasn't afraid of fcuking it up.

tested with light and mini straight edge. flat. no scalloping. fine enough with inner edge lightly de burred only

Tikka M55 firing pin hole blended.jpg (23.3 KiB) Viewed 7096 times

After removing the high without going over board there's no more contact to primer when closing or opening the bolt. Yeh !!

[KWhorenet]

Completely off topic but what are those pink tipped bullets?

17 Rem loaded with 23.5gr AR2208 + Hornady metrosecksual 20gr V-Max.

I have no idea what the primers are but will be on the phone asking tonight.

[Warrigul]

As has been mentioned the spring strength may be in question. There is no way I will know unless I do a compression test knowing the standard.
- In some other instances I've read people were adding stronger springs in an attempt to limit primers blowing back and bursting out into the primer hole by compressing the firing pin spring ??? Most common I've read so far were in self loaders.

Good result.

Back when we were converting our Omarks to .223 with new barrels and boltheads it was found some of the firing pins were a smaller diameter than later models and cratering and primers blowing down the bolt were common issues. Some people fitted heavier springs but this really was only a patchup, the proper fix was the right firing pin or a bushed bolthead or new bolthead. I used heavier primers but ended up getting a better fitting firing pin.

FWIW I always change the firing pin spring every two thousand rounds, the old one is always shorter.

You can dry fire a centerfire all day and do no damage.

[KWhorenet]

Does it look like the firing pin hole has been bushed ? Just dremmel it down smooth as long as you stay at the centre it will be fine .

I cant say for certain but it doesn't look to have been. I guess the polishing and pounding it would receive may hide any fitment/mating line but after light 800 grit I saw nothing to suggest it has. I did read about bushings for out of tolerance firing pin holes.

I've learnt allot today, well touched on allot at so far zero expense.

As suggested I will look into the spring too. Not going to shelve it till then but keep a close eye on it.

Calling the previous owner who bought it from his close family friend just to ask for maintenance/symptom info. I really hope they had it most of its 31 year life.

[bigfellascott]

So what was the problem of it having a slightly flared surface?

[KWhorenet]

So what was the problem of it having a slightly flared surface?

Cant say for all but in this case it was a high enough fine edge to press into the primer surface as seen in the fired primer pic and if I chambered a round but then unloaded it the rotation of the bolt face left a fairly deep sharp half moons into the primer in other pic above.

It may have never caused a rupture but I wasn't keen on living with it.

I originally only thought it was one side but it must have been both as the pic does show one deep and one faint half ring. I blended all around but one side was high.

[bigfellascott]

The first pic looks like a little bit of cratering to me (hard to tell for sure with the pic), nothing I'd be worried about (got a few that do it and haven't ever caused issues) and if I was real concerned I'd go a harder primer.

[Jack V]

Could be a manufacturing fault .

[bigfellascott]

Are you primers seated correctly, stand the cases up and see if they rock from side to side, if so you might want to cut the primer pockets slightly deeper to help get em seated deeper.

[KWhorenet]

The first pic looks like a little bit of cratering to me (hard to tell for sure with the pic), nothing I'd be worried about (got a few that do it and haven't ever caused issues) and if I was real concerned I'd go a harder primer.

There is a pic up top of an Un fired primer with cuts in it after I unloaded. I tried it with 4 random rounds and all got the same.

The pics are rubbish I know. Phone camera in poor light. Up close in hand and it looks worse.

The fired one has the same cuts outside the pin hit and you are probably right in that there is some cratering also.

You guys will know more about this than me but cratering may be from soft primer flowing into the worn pin hole.
I can't rule out over pressure either as I don't know if the loads were built up or plucked from ADI data.
With age/use and the amount of material I see pushed up and out, I'd think the hole dia would be enlarged also.
- Yet to measure it.

[KWhorenet]

Could be a manufacturing fault .

Edit: looking back at the 2nd bolt face pic it looks like a ring that could mean bushing but that is the edge of the high area shined up after blending is almost done.

"manufacturing fault" What are your thoughts on it; hole/pin alignment? bolt material? firing pin/spring assy ?



Scott,
Good call but I checked all rounds with a straight edge over the flat areas of the heads with a light and saw a clear gap. None of the 50 I checked are close to protruding.

After all of this there is no more cutting or contacting with the primers by the bolt face. Put marker on and chambered and un chambered with no contact so as of now I'm not too worried but will check up on the spring, pin hole dimensions, firing pin straightness and wear also.

[Gregg]

I did take an hour for what could have taken 5 mins if I wasn't afraid of fcuking it up.

We've all spent that time

[KWhorenet]

Removed firing pin assy from the bolt for a clean and look-see and all good. Just used taped up pliers to remove. Refitting isn't so easy.
To depress the shroud I used a scrap piece of wood with hole that the firing pin assy could slide in while stopping the shroud. Chiselled out a slot for the firing pin side tab to slide into and stop it rotating. Pushed down on bolt compressing the spring till it's little locking lug was seated, rotated the bolt, re cocked it by hand and voila

wood tool to replace firing pin assy in bolt 2.jpg (22.5 KiB) Viewed 6648 times

wood tool to replace firing pin assy in bolt.jpg (24.74 KiB) Viewed 6648 times

[bigfellascott]

Sound the same procedure as the Howso mate

[Jack V]

That's looks like the Sako bolt strip system . Howa is the same.

[Chronos]

That's looks like the Sako bolt strip system . Howa is the same.

Probably because the Howa is a copy of the old Sako

Also similar to the Mauser, infact Mauser even provided a rivet in the buttstock as a bolt stripping tool.

Chronos

[effex]

Also similar to the Mauser, infact Mauser even provided a rivet in the buttstock as a bolt stripping tool.

What's the advantage of the bolts which are so hard/impossible to cock/decock by hand?

Some like the Ruger I think you can relatively easily do each way by hand, others you need a bolt tool. Why make it that hard?

[Chronos]

Also similar to the Mauser, infact Mauser even provided a rivet in the buttstock as a bolt stripping tool.

What's the advantage of the bolts which are so hard/impossible to cock/decock by hand?

Some like the Ruger I think you can relatively easily do each way by hand, others you need a bolt tool. Why make it that hard?

Im sure a heavier spring will reduce lock time making the rifle less prone to human error but other than that I'm not sure.

I like the rikka T3 system, turn the bolt shroud and remove it. Insert a tool and turn the firing pin to decock. Then you just remove the bolt handle and tge firing pin just slides out.

Chronos

[KWhorenet]

Cut the piece of wood with the hole+slot down to a 2"x2", it is quite easy to de cock and disassemble/reassemble.

As far as 'easing the spring' when not I use; is it really necessary?
Will leaving the spring compressed actually reduce it's ability to push in my lifetime?

[Jack V]

How is it similar to a Mauser ? Mauser thread off and Sako type systems just turn and pop out . Similar in you compress a spring maybe ?

[Jack V]

Cut the piece of wood with the hole+slot down to a 2"x2", it is quite easy to de cock and disassemble/reassemble.

As far as 'easing the spring' when not I use; is it really necessary?
Will leaving the spring compressed actually reduce it's ability to push in my lifetime?

A real quality heat treated spring will last even cocked but I have seen a parker hale have ignition problems because it's spring had weakened after being left cocked for many years. The problem is did it have a weak spring to start with you can't tell . So my advice is why take the risk if you can decock the bolt it may help in the long run. If you can't decock easily then leave the bolt in the gun and decock in the action .

[Warrigul]

That's looks like the Sako bolt strip system . Howa is the same.

Probably because the Howa is a copy of the old Sako

Also similar to the Mauser, infact Mauser even provided a rivet in the buttstock as a bolt stripping tool.

Chronos

Ummm,

At the risk of another dummyspit from you, please explain how a howa and Mauser bolt are similar when it comes to disassembly. I mean I have both and it seems totally different to me?

The "brass rivet" in the stock of a K98 is to place the firing pin in after you have done a basic strip so you can take the tension of the spring and strip the remainder off.

Have you actually stripped both types of bolt before?