What caused this damage to my M&P R8's firing pin bushing?

[sza]

Lately, I've been putting about 250rds/wk through my M&P R8. The last 500 or so rounds have been 125gr Bear Creek bullets in .357mag cases with 6.5gr 231, using Federal primers. This is a soft shooting, accurate load that I worked up and has shown no pressure signs. It is, however, over Winchester's published load data for lead bullets, which I believe is held low more for velocity's sake than pressure. It's well under even the starting load for a 125gr jacketed bullet.

I was cleaning the gun today and noticed some damage to the firing pin bushing. Here are some photos:

My first reaction was that this was flame cutting from a pierced primer or leakage around the primer. The gun was last cleaned 100 rounds ago, and I didn't notice any damage to the bushing then. I inspected the entire batch of cases I'm using for this load (about 300 cases, on their 6th reload) and did not see any pierced primers, soot around the primers, or other odd damage to the case heads.

Is the damage pictured consistent with flame leakage around the primer? It's interesting to me that the damage is on the outside edge of the bushing, and that there's no visible wear on the firing pin at all. Also, it's hard to see in the photos, but the damage seems entirely limited to the bushing, and hasn't extended into the aluminum frame.

 

[500 Magnum Nut]

Could that be lead splatter? Try cleaning it with a bronze brush. If you want try a small flat stone and lightly polish the breech face won't hurt it either.

 

[WR Moore]

It really wouldn't be flame cutting, but gas pressure cutting from gas leaking around the primer cup.

If you're positive that you didn't see this damage before firing your current loads, you've got the culprit. Could be some loose primer pockets, did you notice any smudging on the base of the cases? You might want to trash that brass and get some new-or use .38 cases for .38 level loads.

I'll go along with some gentle stoning to remove burrs. Possibly some work with a brush/toothpick to see if some of what looks like deposits (smeared lead from the loading process?) will come out of the groove between the bushing and frame. Real gentle work with a dental pick would be a last resort.

 

[sza]

Unfortunately, I can't be sure that it happened between the last cleaning and the most recent 100 rounds. What I can be sure of though, is that none of the cases from the last 300 or so rounds show any signs of anything getting past the primers--I've looked them over about 3 times now.

I've emailed the photos to S&W support, to see what they have to say.

 

[TOM BECKWITH]

Does the slide lock back at the end of each mag? Looks more like slide slamming on the bbl on empty chamber and burr on bbl????

 

[tomcatt51]

The "divots" really look like the gouge you get from an oxy-acetylene torch with a scarfing tip. Makes me think primer leakage. Wouldn't have thought it would blow metal out like that but there it is. You can see how the steel bushing was being cut and the scandium melted.

 

[500 Magnum Nut]

That's what you call a super sized picture!

It looks different to me, as it looks like a build up all around the edge, with a larger deposit on the corner.
Only other possibility is what your seeing, then it's caused by oversized primer pockets. The fix is new brass.

 

[WR Moore]

Does the slide lock back at the end of each mag? Looks more like slide slamming on the bbl on empty chamber and burr on bbl????

The weapon in question is a revolver. Even if it wasn't: there's no firing pin bushing in a M&P auto and that portion of the breech face isn't contacted by any part of the barrel.

 

[TSQUARED]

The photos are inconsistent with a pierced primer. If the primer pierced any damage would be centered around the firing pin area.

 

[Spotteddog]

#3 and #6 IMHO.
Factory, once loaded, or multiple reloading's? It'd only take one piece of bum brass or one poor primer to do it.

 

[HEADKNOCKER]

I'd also note the small bits of "Flowed Primer" in the fireing pin area I would think these would bind the fireing pin up or cause it to stay farward..
Next time the sideplate is removed I'd be takeing that FP out for a deep cleaning or replacement..
Have you scraped at that with a dental pic yet??
Gary

 

[44forever]

Looks like a gouge.

On any of the recent range outings, did you have any symtoms that might indicate some foreign material between the case head and the breach face? Do any of those last 300 cases show damage in a coresponding position on the case head?

You might also check the hand closely for any sign of damage. Any change in alignment or carry up? Last question - when you resize the brass, do all the cases seem to take about the same effort or are a few of them harder to push into the die?

 

[38-44HD45]

I'd echo the acetylene torch analogy. That looks like either a leaky primer (around the pocket, not pierced) or something that was there from the factory, that you just noticed. I'd say more likely the former than the latter. Interesting to me that the melting seems to be about 50-50 on steel and Scandium. Stone it off smooth, check your brass or get some new brass, and it shouldn't be a problem.

 

[Alk8944]

I have seen a lot of these over the years and it is discussed fairly frequently on the forum. It is from a primer that failed at the annulus, not the firing pin impression. Most frequently seems to occur with Remington 1 1/2 primers but it can happen with other brands.

Not a safety issue, just use it and when you have had several others and the bushing is eroded a lot worst than this just send it bach to S&W to have the bushing replaced.

 

[Dan Cash]

Surely seems a lot of strange metal sculpting with these scamdium revolvers.

 

[shawn mccarver]

Does the slide lock back at the end of each mag? Looks more like slide slamming on the bbl on empty chamber and burr on bbl????

The picture is of the breech face of a REVOLVER.

 

[sza]

Wow, lots of feedback. Thanks guys.

#3 and #6 IMHO.
Factory, once loaded, or multiple reloading's? It'd only take one piece of bum brass or one poor primer to do it.

Federal brass with about 6 loads on it. I'm going to scrap the entire batch.

Next time the sideplate is removed I'd be takeing that FP out for a deep cleaning or replacement..
Have you scraped at that with a dental pic yet??

I made an attempt to get in there but felt I was likely doing more harm than good, and that it'd be better to take the pin out to clean it. I haven't had any issues with light strikes or the pin hanging up or anything.

On any of the recent range outings, did you have any symtoms that might indicate some foreign material between the case head and the breach face? Do any of those last 300 cases show damage in a coresponding position on the case head?

You might also check the hand closely for any sign of damage. Any change in alignment or carry up? Last question - when you resize the brass, do all the cases seem to take about the same effort or are a few of them harder to push into the die?

No marks whatsoever on the case heads. They all look like new. Cylinder alignment and carry up are still good. No endshake. There is a small amount of wear on the cylinder stop and the notches in the cylinder, but nothing out of the ordinary for the number of rounds the gun has through it, IMO.

The cases all size with the same amount of effort.

Interesting to me that the melting seems to be about 50-50 on steel and Scandium.

Actually, I don't think it got into the Scandium at all. It's hard to see in the photos, but here's one from tonight that might show it a little better. There appears to be steel ring around the bushing proper, which is where the wear stops. It's easier to see in person because the ring is slightly recessed below the surface of the frame.

I have seen a lot of these over the years and it is discussed fairly frequently on the forum. It is from a primer that failed at the annulus, not the firing pin impression. Most frequently seems to occur with Remington 1 1/2 primers but it can happen with other brands.

This seems to be the consensus, and I agree. Would a slightly crushed primer make it more likely to fail around the edge? I ask because about 1000 rounds ago, I noticed that I had crushed one of the primers slightly. I didn't think anything about it at the time, didn't notice anything odd when firing that batch of ammo, and probably didn't notice the damage to the firing pin bushing until now. The brass has been tumbled and loaded a couple of times since then which is probably why I don't see anything now.

I think from now on rounds like that will go in the reject bin to be disassembled for components.

 

[tomcatt51]

You can see the edge of the bushing. The "ring" around that is from staking the bushing in place. The staking tool makes that "ring". the gouge and melting is right on the bushing/recoil shield juncture, inside the staking "ring". You can see the steel is actually gouged and the scandium is melted. Exactly what a cutting torch or hi temp/pressure gas would do.

 

[sza]

Ahh, I didn't realize that the recessed ring was from staking the bushing in place. Thanks.

 

[WR Moore]

Wow, lots of feedback. Thanks guys.

It's easier to see in person because the ring is slightly recessed below the surface of the frame.

Ah-Ha! A recessed surface could allow the primers to move slightly to the rear when pressurized. Don't know if the rotation of the cylinder would be enough to push the primer back in/wipe any protrusion. This could contribute to leakage/premature wear of primer pockets.

If you do notice primer defects, your idea about pulling them down is probably a good one. Depending upon what the issue is, I sometimes just paint suspect primers with red nail polish and use those rounds for practice use.