929 - firing pin bushing erosion

[ktm400]

I have severe erosion of the firing pin bushing - see attached.

I'm sending it back to S&W later this week for repair. I have approx. 5,000 rounds through this gun. Any feedback as to what causes this and how to prevent this would be appreciated.

Load: Federal 9 mm brass, Fed Primer, 3.4 gr N320, 147 gr BLUE (.357) bullet > PF = 133

ACTION: APEX @ 4.5#, competition firing pin - not that it matters but also APEX install front and rear sights.

Edited July 6, 2015 by ktm400

[revoman]

Where are the pictures

[DougCarden]

That is surprising.....that is not a light load where the primer wouldnt seal....I would like to see a picture as well.

DougC

[ktm400]

Prego - I reedited to add photo

[Dogged]

Check the center of some of the primers shot out of the gun to see if the they have been blackened and pierced by a damaged firing pin.

[Toolguy]

It's hard to tell from that picture, but it looks like the bushing may have been heat treated too hard and little bits are breaking out of the surface. I haven't seen that one before.

Edited July 6, 2015 by Toolguy

[ktm400]

Primers not pierced but blackened around perimeter of primer

[bountyhunter]

Primers not pierced but blackened around perimeter of primer

Looks like might be some kind of flame erosion if the gas is somehow blowing by the primer seal?

I have never seen that either.

[JohnRodriguez]

looks like my 2 38 supers, and my open super is way worse than yours. It also have a whole lot more rounds trough it too.. I never sent my guns in, the powder burns a little quicker and enough escapes to pit the bushings before the pocket swells up to seal of the primer. I do have several spare bushing, but I have never changed it.

[Forrest Halley]

Looks like magnum primers through a .40...

[ktm400]

See image of brass

[Forrest Halley]

Yes that is exactly what magnum primers in my 40 looked like

[Gregg K]

Hmmm. The Federal brass was your magic ticket for no sticking but could have other problems. I have around 15K through mine with no problems but that was all with Starline brass. I'll have to go dig up some Federals and see if there is any measurable difference in primer pockets.

[pskys2]

Are you using range brass or brass that has been fired in an Open Major gun? If so the brass can actually expand due to the pressures to the point the primers aren't sealing well. Even to the point of being loose in the pockets.

[PatJones]

Looks like gas is leaking out around your primer causing the erosion to your gun. I would stop using those handloads.

[pjk]

Picture looks consistant with erosion caused by leakage around the primer.

I had a similar problem with my super. My brass was exrememley tired and I suspect the primer pockets were not as tight as they should have been. Thinking about it now the brass I was using had been in constant use for about 8 years and probably reload over 50 times.

Fixed mine OK. Kept the same load, fitted a new bush and went to new brass. All good now.

PK

[Gregg K]

I wonder if your sticky cylinder is holding your brass some and not allowing it to set back against the recoil shield and firing pin bushing. When they set back they seal off. Here is a close up picture of one of my fired rounds and you can see the imprint of the firing pin bushing in the brass. The cartridge needs to be free to set back against the recoil shield and firing pin bushing.

[snertley]

Short answer is your brass is wore out. A few years ago I had the same problem with my 610's. I finally figured out that after reloading my .40 brass about 4-7 times it was wore out. I was getting flame cutting on my firing pin bushing. Not every one did it but it only took a couple to cut the crap out of my bushing. Think of it as a 36,000psi plasma torch. Now I use the brass 2-3x then haul it to the recyclers and collect a small check.

[9146gt]

My 929 with the stock firing pin functions 100% with mixed brass, yet somtimes pierces WIN primers but not Federal.

Tom

[10mmdave]

here's a link back to a post about this same issue in autos, I added my experiance and photo's,

my bushing looks a lot like the pjk pic.

I stopped using fed mag primers and up until I switched to an 8 shot I didn't see any more erosion on my 610,

or the 9mm auto for that matter.

Been shooting the same brass for more loadings than I can remember, primer change cured my ill's.

Good luck with the fix, maybe someday I'll send the 610 in for the replacement,

corse it's not like I shoot it anymore

http://www.brianenos.com/forums/index.php?showtopic=146365#entry1642766

[ktm400]

Gregg,

That's an interesting theory and I may flex hone my cylinder when I get it back from S&W. I have about 2k Starline 9 mm brass and would love to use it.

My sticking issues where solved after switching from Starline and to Federal brass but perhaps I discovered another problem. Probably should have flex honed from the get go.

[Gregg K]

Warren's solution of wrapping some Scotch-brite around a .22 brush on a Dremel has worked good for me on cleaning up Ti cylinders. I actually used my 1/3 HP Foredom flex drive to run the brush with the Scotch-brite to slick up the chambers a little. Dremels are for the kids

[Shadowrider]

Short answer is your brass is wore out. A few years ago I had the same problem with my 610's. I finally figured out that after reloading my .40 brass about 4-7 times it was wore out. I was getting flame cutting on my firing pin bushing. Not every one did it but it only took a couple to cut the crap out of my bushing. Think of it as a 36,000psi plasma torch. Now I use the brass 2-3x then haul it to the recyclers and collect a small check.

Sounds possible. I wonder if a trip through a case pro would help? I know I've shot some of my .38SC brass at least 5x and I'm not having any issues at all. Running Federal primers and 132-133 PF just like the O/P. I suspect it's this problem or the cylinder needing polished as suggested. Bubber has told me he's shot brass so much the flash hole eroded out so I'm really curious to hear what's causing this.

[seanc]

I have 1k pieces of federal range pickup brass. Unkown how many times it was shot before I got it but I have loaded it more than 10 times and have not seen any do what your brass is showing.

Federal SPP and titegroup is what I have been using, my primers are completely flattened when shot in my 929 and if you didn't know better you would assume I was WAY over pressure. The same ammo through an auto looks completely normal.

My running theory on flat 929 primers is that under ignition the cartridge has some free run then smashes into the blast shield, primer then pulls out slightly then smashes. I see this with flimsy to thin moonclips and the .040's and a .042 dave made for me, its all the same.

I'd say the brass is suspect.

[PatJones]

I have concerns about your powder selection. It is pretty quick for a 147 in 9mm.

I found some loading data here:

http://www.lapua.com/en/products/reloading/vihtavuori-reloading-data/relodata/6/34

The only 147 grain bullet listed with N320 is the HP/XTP. While your load is less than the maximum listed, you are not shooting a XTP. All the other heavy bullet loads show powders slower than N320. I suspect if you move to a slower powder your problems would disappear.