Forcing cone erosion?

[hulkster]

hello all, new member here looking for some advice. I have a 686 plus that has maybe 500 or so rounds through it. When cleaning it I have noticed what looks like forcing cone erosion around the top inside of the cone. I am new to firearms, this is my first, so I have no idea if this is normal wear or not. Thanks for any input.

going to try to post a pic hope it shows up.

http://smith-wessonforum.com/attachment.php?attachmentid=661183&stc=1&d=1704126420

 

[toad67]

Looks like lead build up to me.

 

[USBP SW]

It appears to have some erosion and some flame cutting. Perhaps it's the angle of the photo but the erosion appears only at the top of the barrel extension, the erosion I have observed was always uniform around the entire inside edge of the barrel extension.

 

[jcelect]

Erosion

This is barrel erosion on model 53 barrels!

jcelect

 

[John Patrick]

Looks like lead build up to me.

Me too.

OP, is that material proud of the barrel extension, as in protruding? (Which would indicate build up.)

Or is it material missing from the barrel extension? (Which would indicate cutting.)

Can’t be certain from your photo.

 

[hulkster]

Me too.

OP, is that material proud of the barrel extension, as in protruding? (Which would indicate build up.)

Or is it material missing from the barrel extension? (Which would indicate cutting.)

Can’t be certain from your photo.

It looks to me like the material is missing

 

[Hair Trigger]

Looks like lead build up to me.

Same here. The other 2/3 of the edge is sharp. Erosion is generally circumferential. Looks like you could scrape that off with a pocketknife. There is a bit of flame cutting under the top strap, but it's inconsequential and expected of a gun that's had a few hundred rounds through it.

Edit: After looking at an enlarged image, even the "cutting" looks more like a spray of lead. The inside of the FC is too clean and new-looking to be erosion or wear. Looks like the cylinder and barrel are minimally out of alignment (chamber higher than barrel), causing the lead to accumulate at the top, almost like shaving.

 

[steelslaver]

I have to wonder just how square the barrel shank is. Interesting that it is mostly located at the top. IF it is erosion, some powders are more apt to cause erosion than others. Slower powders loaded to give max velocity will accelerate it.

Maybe in another 5000 round it will be enough actually effect something.

Think of it this way if your buying factory ammo, 500 round probably cost about $350 or so and 5000 rounds about $3500. I do not know what a gun smith charges to remove the barrel, set it back one turn, face the shank back off and redo the forcing cone, but it only takes me a few hours. That gets you all brand new surfaces and only removes .0273 of barrel length.

My model 53 looked just like the one above. Now it looks brand new.

If you reload use faster powders and back off the velocity some. You can still fire full blown fire breathing loads, but what is the need for lots of them. If your into something like knocking over metal silhouettes and then bigger heavier bullets don't need as much speed.

 

[hulkster]

Me too.

OP, is that material proud of the barrel extension, as in protruding? (Which would indicate build up.)

Or is it material missing from the barrel extension? (Which would indicate cutting.)

Can’t be certain from your photo.

sorry I'm not a very good photographer maybe these photos are better

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[S&W Fan]

This is the forcing cone of my 1978ish 66-1. I bought it showing very little signs of use, more like it rode in a holster or perhaps a glove box/nightstand. Very little flame cutting too. I've only put 6 rounds of 158gr jhp .357 through it as just don't enjoy shooting magnums that much any more, probably 150 .38s in the 8ish months I've owned it.

 

[HorizontalMike]

Resurfacing Forcing Cone

...<snip>.....

Think of it this way if your buying factory ammo, 500 round probably cost about $350 or so and 5000 rounds about $3500. I do not know what a gun smith charges to remove the barrel, set it back one turn, face the shank back off and redo the forcing cone, but it only takes me a few hours. That gets you all brand new surfaces and only removes .0273 of barrel length.

My model 53 looked just like the one above. Now it looks brand new.
....<snip>....

Yep, I had a second hand 686ND barrel shortened for $295 back in late 2018. I went from a 0.009in gap down to just 0.003in and WOW, what a difference! The image is with new Gap and after 50rd. Happy camper here.

BTW, I kept my bought new 686ND in original at 0.005in gap.

 

[Nightowl]

Flame cutting or lead buildup, either way, it should not look like that! It sure appears to be a chamber/barrel misalignment.

 

[steelslaver]

If the face of the barrel was out of square so that the gap was wider at the top than the bottom. more gas would flow out the top and cause more erosion.

Any timing or lock up issues can cause side to side misalignment between barrel and cylinder, but they can not cause vertical misalignment. Plus, as the face of the cylinder pivots on the yoke tube where it begins any misalignment of the yoke tube will case problems at rear of cylinder NOT the face, and any side to side movement in yoke at its pivot will cause lateral movement not vertical. Unless the yoke tube to pivot distance is incorrect or the barrel is incorrectly located in the frame the vertical centering must be correct. I guess it is also possible one or more chambers could be located outside of their correct radius.

Therefore my first suspicion is an out of square face on barrel and the erosion there being accelerated by hot loads of slow powder, my second one or more chambers being off their radius on cylinder. But if you fired 500 rounds of max loads of something like H110 you would have some erosion even with perfect alignment it would just be more uniform.