Concerning bolt shroud gap/firing pin lug wear

[stickhunter]

Concerning bolt shroud gap/firing pin lug wear - update post #25 with new firing pin assembly pics

I recently posted in the "Triggers" forum about my Sako AV, but have now found something that's concerning. I'd noticed with this rifle that there appeared to be a gap between the shroud and bolt that I hadn't noticed before.

Here's the gap when the rifle is cocked:



When the rifle is fired, the gap reduces, but is still present:



After firing, the shroud has play and I can push it in with my finger to close the gap:



I took the bolt apart to investigate and found some very concerning wear on the firing pin lug:





The lug has clearly worn considerably, and this reduced width that allows the shroud gap.

I'm hoping this might be repairable by having a gunsmith use TIG to deposit some metal and reshape the lug, or perhaps silver solder a new lug. Any thoughts?

And what could be causing this significant wear? Is it simply lack of lubrication on the lug, or is something else awry?

Your help is greatly appreciated (and needed!)

 

[m995]

Watch auction sites for bolt shroud. Build it up with weld (in water or you will cook the bluing) & file, lack of lube or bad smithing. Check the bore of the bolt for like damage, if it is bad look for a bolt assembly

 

[m995]

The lug is there to hold to bolt together much like the threads on a rem. 700, if it fails while cocked ( or during firing ) the firing pin assembly will launch out the back............ DO NOT FIRE THIS UNTIL FIXED.................. Put up pictures of the bolt face & bolt lugs.

 

[stonecreek]

Ummmm . . . this is something I haven't seen before. It appears that the rifle has be subject to some kind of abuse. Otherwise, it could be a result of deficient metallurgy of that part, but that is a very unlikely cause. This one needs to go to a REAL gunsmith who can look at it in the flesh. Diagnosing the problem through a website may not cut it in this instance.

 

[bloorooster]

Oh Man! How in the world could the lug wear like that under normal use!...almost looks like it was filed away!~Bloorooster

 

[misako50]

Bloo- you may have hit on the answer. When I looked at it, the first thing that came to mind is that someone in the past took the bolt apart and couldn't put it back together. Filing the lug down was their "bubba" answer to making it easier to put back together. And please don't fire it.-Misako

 

[bloorooster]

Misako...I had the same thoughts about the Bubba aspect...Can't say for sure thats what happened here but wow! Well...there are firing pin and bolt parts available for the AV models, or a bit of TIG work from a worthy smith. Good thinkiing on Sticks' part for trouble shooting and asking about it, and hats of to M995 for bringing the hazards to light.

This is why the SCC is such a good place to be!~Bloo

 

[kevinlg]

Stirling,

Wow!!!!! I've never seen such a "thing"!!

It kind of makes our trigger discussion kind of moot. Besides.....why would one need to apply the safety while the bolt is open? Oh, well......

Things that come to mind......abuse/wear.....someone filed it.....mismatched parts.....firing pin assembly disassembled & BADLY reassembled.

Things to check......bolt interior....firing pin protrusion.....bolt lugs and action seats......(I probably missed something, that the guys will catch).

I agree with the guys.......find a GOOD gunsmith.

Once again..........WOW!!!!!!!!

 

[stickhunter]

Well, I think I may have found the smoking gun to this problem. Here are some pictures of the relief raceway in the bolt body:





Notice the shiny sliver at the end? Curiously, this sliver is actually deep enough down the straight raceway to enter the circular raceway, and the distance from it to the front edge of the raceway about matches the width of the remaining firing pin lug. The sliver does not appear to be burr as I can't see/feel any grooves in front or behind it. Pushing a pin head down the raceway is stopped by the sliver, while dragging a pin head from behind the sliver doesn't catch anything and just drops down. So I'd describe the sliver more as a "step" than a burr. Possibly it is a result of the cutter that formed the straight raceway.

The rest of the circular raceway looks normal and dragging a cotton bud didn't show any snags. The only oddity (and it may very well be normal) is a scallop relief on part of the circular raceway that isn't involved during bolt lift/close (as shown in the second picture below):





The rest of the action shows little wear, except for the cocking piece camming surface. I initially thought this was the source of the shavings, but I don't believe that to be the case anymore (and I do note that Sako recommends lube on this surface):



The remaining pictures are of the action and bolt. I don't believe there are any signs of abuse/damage in these pictures:

















As I mentioned, I was doing a lot of testing/adjustment of the trigger, and had probably dry cycled the action a few hundred times before I noticed the grittiness and found the powdered shavings. Initially, I thought all the firing pin lug wear was caused by my actions and lack of lube, but I'm now skeptical given (a) the amount of shavings doesn't look like it would amount to anywhere near the missing lug material and (b) the step leads me to think that bolt assembly is the issue, and I hadn't taken the bolt apart prior to noticing the problem.

My hypothesis is that the "step" is a manufacturing defect, but there was still enough clearance to allow the bolt to be properly reassembled. Either this step contributed to the wear or upon subsequent disassembly/reassembly, someone encountered troubles inserting the shroud because it was hitting the step, and decided to (incredibly stupidly!) reduce the width of the lug so that it was fit the reduce raceway.

For the life of me, I can't imagine anyone filing away this lug, but I also don't see otherwise how such significant wear could have occurred. I now suspect the shavings I saw were simply smoothing out/wearing down the already cut away lug surface.

Thanks for the sound advice to not shoot this rifle. Fortunately, I've never had it at the range, and won't until I've had this issue addressed. I've contacted Sako's Canadian distributor with the pictures and will also try to contact Sako Finland to see if they know anything. I'm concerned that a bolt shroud replacement may not be enough if the source of the problem is the bolt body; that would truly be unfortunate.

 

[stickhunter]

The wear/damage is definitely a surprise to me, and very concerning. No worries on me attempting to fire the rifle --- I've had it for a few months, but never taken it to the range and won't until the problem is addressed. I also found something very interesting in the bolt body that may be related; that post is currently waiting for moderator approval because it contains updated pictures.

Kevin, yes this issue definitely makes all my concerns/questions about the trigger seem moot

BTW I measured the firing pin protrusion at 0.065" --- is that in spec? I don't see any apparent damage on the surfaces that control the firing pin.

 

[L-46]

Wow, i have never seen this, on any gun,
The photos show no signs of rust, wear or abuse
Is this part machined or cast?
But then i have seen a A1 222 with the end of the barrel belted flat with a 10 pound hammer! now that's abuse!
L-46

 

[stonecreek]

But then i have seen a A1 222 with the end of the barrel belted flat with a 10 pound hammer!
L-46

Maybe the perpetrator thought, like a shotgun choke, that would make it shoot tighter!

 

[stickhunter]

Sako distributor response

Stoeger, the Canadian distributor for Sako, got back to me with this response:

Stirling;



I have seen this exactly once before (probably 10 years ago) and the damage was man made. If I remember the story correctly, a gun enthusiast “gunsmith”/machinist was attempting to lap the locking lugs and smooth the bolt travel of a Sako and ruined the cocking piece of the rifle. I don’t know if he got lapping compound where it didn’t belong or didn’t have any lube on the tabs that retain the shroud but the damage was exactly like this. If you bought the gun used in this condition, I’d almost bet money this is the same gun or the firing pin has been switched and this gun sold with the damaged firing pin. The only fix will be to replace the firing pin assembly.

So, as the SCC members have surmised, I'll scratch this up to being the result of someone's poor judgement/execution. I still suspect the step in the raceway is precursor for the efforts to modify the shroud and will take care reassembling when I manage to source a new assembly.

Are L61R firing pin assemblies the same as AV firing pin assemblies?

Much appreciated, everyone, and I hope the pictures were at least interesting, if not a bit disturbing!

 

[misako50]

Stick- Thanks much for the great pictures and the timely delivery. You are fortunate to have Stoeger Canada on your side. I have thoroughly enjoyed the entire saga, albeit at your expense.-Misako-----------As for the question about the assemblies- No, they are not the same but you may be able to interchange the entire assemblies. The firing pin is threaded and slotted for adjustment on the open shrouded L61 Rs.

 

[kevinlg]

Man......this makes my head spin!!! Someone may have been messing with lapping compounds???? Oh...the horror's one can envision!!!

If mine.....I guess the very first thing I would do, is strip the bolt.....find the proper set of headspace guages....and check it.

It's possible that, not only is the bolt damaged, but the receiver lug seats as well!!!

Again.....gotta find that GOOD gunsmith.

 

[stickhunter]

Hi Kevin,

Thanks for the heads up... I've inspected the bolt/receiver very carefully and don't see any further damage/abuse. I have some high resolution close ups that I posted yesterday of the critical action parts, but the message is still waiting moderator approval. The pictures should make things clearer as to what I think the problem is --- probably not lapping compound but rather someone with a file/grinder trying to get the bolt reassembled. That being said, I will have a gunsmith check it over and measure the headspace.

Misako, Stoeger got back to me about a replacement firing pin assembly and, after checking their records and finding my rifle is a 1985 AV, advised that an L61R assembly is the proper replacement:

I need the serial number to confirm the action model. The pre ’91 long action was the L61R, the ’91-’95 long action was the L691. The L691 firing pin will go the L61R but the L61R will not go in the L691.

Stoeger gave me part number S5940160, which I looked up at Brownells and appears to match my assembly --- the Brownells Q&A also suggests the same. I'm still sometimes confused by Sako's multiple model designations...

http://www.brownells.com/rifle-parts/bolt-parts/firing-pins/pin-firing-assy-l61r-prod31125.aspx

 

[gunner620]

stick,you are lucky Brownells has it in stock,hope you can get it to Canada! I was able to get some Sako items from Stoeger Canada shipped to the U.S. but had to have a business with export license get the parts from Stoeger Canada and then ship to me. Your question about firing pin protrusion , (.059-.071) thousands is what was at one time listed in the Sako literature. This replacement firing pin assembly will most likely be pre-set within those tolerences. You will still need a smith to check everything out for safety (bubba is capable of much damage). Good luck and keep us informed how it goes. Jim

 

[bloorooster]

This has been an incredible tread...Tho' it has been quite unfortunate for Stickhunter, to find that the rifle has issues that render it unsafe is terrible...BUT...its a very good experience for all of us, as shooting enthusiasts, to see and understand the possibilities. For one to purchase a rifle, second hand like alot of us do, and not know certain signs to look for , things that don't feel right, and so on...this situation could have been much worse if not questioned and investigated. Likewise, on the other end of this, My grand-dad told me once that "there where only two people that would take the back off of a watch...Watchmaker...and a fool". I guess what I'm trying to say is to be aware of the little things that make guns work...be familiar with the operations and mechanical aspects, as best you can....When you come to a point where something is not right, it wont go back together, or it just dont feel right, stop...take the time to ask someone and someone else may have help, and always have the number of a qualified person to do any work that surpasses ones own prowess and skill...great job guys....Stickhunter I hope the best for you in respect to your task at hand, Good luck!~Bloo

 

[stickhunter]

stick,you are lucky Brownells has it in stock,hope you can get it to Canada! I was able to get some Sako items from Stoeger Canada shipped to the U.S. but had to have a business with export license get the parts from Stoeger Canada and then ship to me. Your question about firing pin protrusion , (.059-.071) thousands is what was at one time listed in the Sako literature. This replacement firing pin assembly will most likely be pre-set within those tolerences. You will still need a smith to check everything out for safety (bubba is capable of much damage). Good luck and keep us informed how it goes. Jim

Hi Jim,

Fortunately, Stoeger Canada had the firing pin assembly in stock and for only $5 more than Brownells, so I've already placed my order. Hopefully it'll arrive in short order and I can get this rifle back on it's feet. The rest of the rifle looks untouched, so hopefully bubba's ignorance was limited... I'll definitely have my local gunsmith look it over, but I'm fairly confident the shroud is the only issue.

BTW Stoeger checked the serial number on this rifle, a Fiberclass AV in 338WM, and dated it to 1985.

 

[misako50]

Stick- Just a quick story---A few years back I bought an L579 firing pin (threaded and slotted) to repair a young ladies Sako HB. I got the bolt apart properly and removed the open shroud and cocking indicator by loosening the tiny set screw in the bottom of the cocking ind.- All was well and good until I reassembled the bolt and replaced it in the rifle. It suddenly sprung back and just missed my head and promptly stuck itself in the wall of my workshop. Funny to me now but could have been bad. Too bad I left good feedback for the POS that sold it on GunBroker to me. The original owner had not loosened the tiny screw that keeps the firing pin set in proper adjustment, causing the threads to be damaged and stripped. Yours may be the kind that does not come apart without much difficulty. Some are set so they can't easily be tampered with. I think you have this under control. Thanks again for sharing this with us.-Misako