Uneven forcing cone erosion

[stillhere]

I have a pretty new 629 PC with an 8 3/8 barrel. The gun now has just about 1000 rounds through it, none of which are jacketed. Very few of those rounds were even true magnum. Most are more Special velocity.

After the first few hundred rounds, I noticed the beginning of some forcing cone erosion. I know this is not unusual. However, that erosion is not concentric; it is mostly at the 12 o'clock position (closest to the top strap). The inside edge of the forcing cone elsewhere still has a sharp edge, showing no real signs of wear.

Frankly, the leading has been just terrible. I handload for my other revolvers (686 and a New Vaquero 45 Colt) and I've not seen this problem before.

My Vaquero has thousands of rounds of my handloads through it. It shows some rounding of the inside edge of the forcing cone, but it looks ok to me. My 686 still has a pretty sharp edge on the inside of the forcing cone and it likewise has thousands of cast handloads through it.

I know Smith will gladly take it back and I'm tempted to send it back but I wanted to solicit some feedback as to what the cause might be.
Is it possible this could be normal phenomenon that will stabilize, kind of like the case with top strap cutting, or is there a true alignment problem here?

Thanks.

 

[garbler]

Without seeing your barrel I cannot be certain but I am certain of the fact that it's more than just a good chance that the factory never machined a concentric cone , i.e., rifling terminates at various depths. I once gauged about ten new revolvers at a friends store and found absolutely no consistency in depth or taper degrees. It's like these guys barrel a frame, check the gap and ship it. Often with uneven rough forcing cones you'll find uneven cylinder gap problems on new guns where barrels weren't faced off true which would/could explain the cone . Fact is shooting jacketed bullets many revolvers do pretty well -- good cone bad cone which may explain many things. Found the same on the imported budget clones also -- but I expected this.

 

[stillhere]

The cone appeared concentric before the wear set in but I don't have the tools necessary to prove it.

But now it's pretty obvious the wear happening only in one area, and it's getting worse.

 

[butchkent]

It may be the angle of the photograph, but it appears to me that the rifling needs to be recut. The barrel face erosion, which is the only variation I can identify, could be the result of cylinder gap issues. When looking at the cylinder gap, does it appear to be even across the area of the barrel?also, has the leading always been a problem? If not, have you changed components, etc?

 

[stillhere]

It may be the angle of the photograph, but it appears to me that the rifling needs to be recut. The barrel face erosion, which is the only variation I can identify, could be the result of cylinder gap issues. When looking at the cylinder gap, does it appear to be even across the area of the barrel?also, has the leading always been a problem? If not, have you changed components, etc?

What is it about the rifling that looks off to you? When I compare it to my 29-3, it looks almost exactly the same, and that gun has no such problem. On both guns, the rifling is cut at right angles and looks consistent and cleanly cut from from one land or groove to the next.

I also don't see any obvious problems with the cylinder gap. I don't have feeler gauges but it looks consistent and squarely cut.

I'm not sure about the leading over time. I generally have not shot the gun more than 20 or 30 rounds at a time, and I failed to make any notes regarding any abnormal leading. I've used two types of commercial cast bullets (Missouri and Slash K).

No matter the components, there is clear evidence that the forcing cone is being eroded unevenly, with considerably more at the top (nearest the strap) whereas the rest really shows no erosion at all. That certainly seems wrong, regardless of the components I'm using.

Furthermore, I'm seeing a some top strap cutting much sooner that I would have expected. Nearly all of the loads have been low pressure, using cast bullets. I'm less worried about that because I know that such cutting is mostly inevitable. Just seems premature, however.

 

[BLUEDOT37]

The abrupt cut end angle on the rifling looks par for the course on one's I've bought lately, which is why I bought Brownell's Chamfer Kit. Doesn't seem conducive to smooth bullet engagement.

Like garber said, the FC doesn't look to have any/much taper to it, in the picture. And the roughness to it is, also unfortunately, commonly seen. Just another example that confirms my position that the Performance Center doesn't do any hand fitting, & is essentially the same workmanship as regular production, IMO.

stillhere: Just curious, can you insert the mouth of a sized .44 case into the FC opening?

What weight bullets have you been shooting in it? Powder type?

Sorry, I don't have anything else to offer on the erosion question.

.

 

[Nemo288]

I would guess the cylinder throats are not true to the bore.
They would appear to be too high and are blasting the barrel face.
This is also going to cause leading and inaccuracy.
Send it back and hope you get the right 'smith.
I did with my 696-1 and extraction issues. It's now perfect.
Some here evidently have not.
Let us know what happens.

Here's what even barrel erosion looks like.
Gun is a Dan Wesson 7445 with a couple of pounds of W680 thru it, 30 some grains at a time under various 44 bullets.
The alignment is perfect. The gun is accurate.
I never really shot that much lead thru it.
Barrel gap is .002"

 

[stillhere]

stillhere: Just curious, can you insert the mouth of a sized .44 case into the FC opening?

Yes, a sized case will go in about 1/16 of an inch.

What weight bullets have you been shooting in it? Powder type?

The first couple hundred were 244 swc hard cast, the next few hundred were 200 rnfp hard cast.
For powders, there was 2400, a little h110, and mostly 800x and some Power Pistol. All, except the h110 were substantially downloaded.

Looks like I'm going to contact the factory. After so few rounds, I don't expect erosion like that, especially in one spot.



.[/QUOTE]

 

[MJFlores]

Well, here goes... Sending it back should be a last resort as what I see in your photo is par for the course and not all that bad actually...for a modern day factory S&W. It could very likely come back in much worse shape and with a misaligned barrel. Honestly, I can't see lead bullets wearing your barrel or cone so what you're seeing has probably been there all along. We often notice things in our guns quite a while after purchasing. You mentioned leading but how is the accuracy? These days with new Smiths, I think it's a wise decision to keep it away from them if the barrel is on straight and it shoots accurately. If it were mine, and it shot accurately I'd adjust loads to deal with the leading, change powder to lessen flame cutting, and then have fun trying to shoot the barrel out of the gun! Down the road when it needs a new barrel you can send it to a competent shop and have a new barrel properly fitted, and anything else done to it while you're at it. If you were to call Smith, they could very well give you issues regarding hand loading and blame the entire issue on you! I say that because they did that to me with another issue, and said "they guarantee their guns to function properly with factory ammo only", which is nonsense but whatever.

 

[stillhere]

No, it wasn't like that before. I know enough to know what to look for in revolvers. And that's something in particular that I pay close attention to with my other revolvers as well. Those ones all show typical (which is to 'uniform') wear....unlike this one. And they don't lead, either. Also, they all have far more rounds through them.

If it comes back in "much worse shape", then I'll send it back until they get it right.

My last gun was a 686 PC and it took them three tries before they got it right, and now it's perfect. They paid for the shipping every time. It would have only taken once, had they not made some pretty boneheaded mistakes on the initial repair. But, I do commend them for willingly taking it back and getting it right.

How's accuracy? It's very good for the first few shots, until the leading kills accuracy. After 10 or 15 shots, we're talking minute-of-barn-door.

There's nothing acceptable about that, and in this case, it has nothing to do with the powders, bullets, crimps or anything else. It leads at pretty much the same rate, regardless of whether I'm using softer alloys, hardball, light crimp, no crimp, or heavy crimp. Powders don't change anything, either.

I agree about sending it back being the last resort but I fail to see how an oval forcing cone is normal. And that's just not something I'm willing to spend my own money on fixing.

 

[BLUEDOT37]

Yes, a sized case will go in about 1/16 of an inch.

I asked because they seem to cut them wider (& rougher) than is ideal, which is the way my 627PC was also. Your's sounds similar.

.

How's accuracy? It's very good for the first few shots, until the leading kills accuracy. After 10 or 15 shots, we're talking minute-of-barn-door.

There's nothing acceptable about that, and in this case, it has nothing to do with the powders, bullets, crimps or anything else. It leads at pretty much the same rate, regardless of whether I'm using softer alloys, hardball, light crimp, no crimp, or heavy crimp. Powders don't change anything, either.

Where is it leading at? Just past the FC?

I gave up on trying to get my 686+ to shoot lead bullets. Unless they were barely moving they'd start leading just past the FC. A few of my other guns will lead if I use fast or moderate powders but if I use a slow powder (2400), at the same speed or a little faster, they're fine.

That said, I'm using up the last of my cast lead bullets & changing to coated or plated bullets. For the few dollars more they're a lot less hassle, loading & shooting.

Let us know what S&W says if you send it back.

.

 

[rwsmith]

I think that was miscut.....

1000 rounds of medium loads with lead bullets wouldn't cause that. I don't think it was right to start with.

The FC should taper into the rifling. That looks like a STEP with a sharp edge. I'd get an opinion from S&W about that.

 

[stillhere]

I asked because they seem to cut them wider (& rougher) than is ideal, which is the way my 627PC was also. Your's sounds similar.

Where is it leading at? Just past the FC?


I gave up on trying to get my 686+ to shoot lead bullets. Unless they were barely moving they'd start leading just past the FC. A few of my other guns will lead if I use fast or moderate powders but if I use a slow powder (2400), at the same speed or a little faster, they're fine.



That said, I'm using up the last of my cast lead bullets & changing to coated or plated bullets. For the few dollars more they're a lot less hassle, loading & shooting.

Let us know what S&W says if you send it back.

It's leading the full length of the barrel.

Interesting about your 686 and lead bullets. My experience was the opposite of yours. I started with jacketed, then moved to heavy plated. There was a lot of copper fouling and so-so groups. I'll never go back to those...in any of my revolvers.

I also have a 686 and I can shoot lead bullets all day without leading, even hot loads, and without gas checks. So long as the bullets are sufficiently soft, properly sized, and well-lubed.

Two patches and the bore is clean.

Anyway, I made contact with Smith and so now I'm just waiting for the holiday weekend to be over so I can hear back on what they want to do.

 

[BLUEDOT37]

My experience was the opposite of yours.

Aren't (some) guns fun trying to figure them out?

.

 

[stillhere]

Aren't (some) guns fun trying to figure them out?

.

Some are. This one caused a lot of heartburn.

 

[Nemo288]

Please let us know what the diagnosis is (if they tell you).
I wanna know if my guess was correct
I probably would have been a gunsmith if I had had any talent.

 

[stillhere]

Please let us know what the diagnosis is (if they tell you).
I wanna know if my guess was correct
I probably would have been a gunsmith if I had had any talent.

I happen to concur with you. However, I don't expect any kind of diagnosis or explanation of the cause of the problem. The last gun I sent in went back a total of three times, and all I got back each time was standard form, with a checkmark next to whatever work they did, and nothing indicating why they did it. But at least they got it right.

No matter; I'll be sure to share whatever they share with me.

 

[jaymoore]

Having several 629-6 with scads of lead projectiles through 'em without trouble (from Laser Cast "super hard" and silly to dead soft swaged lead), my first SWAG would be that the leading over the full length of the bore drama could be due to residual copper deposits. Otherwise it's most likely a lube failure. Many store bought bullets have way too hard a lube. Usually easily cured by a quick tumble lube in a small amount of Lee Liquid Alox.

Or buy the coated bullets. I likes those mighty well, but since I have lots of the "old school" bullets about, it'll be a while before transitioning altogether.

Another thought: Undersized throats. Driven hard enough, accuracy will often be ok until the rifling is filled with deposits.

As for the uneven outer edge wear of the forcing cone, I'd look at the barrel cylinder gap first. May be uneven, being looser at the top. Very first N frame I owned, way back in the '80s, had the same drama, plus the cylinder face wasn't square to it's rotational axis so would crash the back end of the barrel on one chamber. A fine introduction to big bore S&Ws!

If the frame isn't bored for the barrel correctly and is a bit high to the chambers' centerline, I suppose could lead to similar, but I would expect terrible accuracy from the "git go". Doesn't seem to be the case here.

Erosion will happen fairly quickly with a steady diet of H110 or similar, regardless.

 

[stillhere]

Having several 629-6 with scads of lead projectiles through 'em without trouble (from Laser Cast "super hard" and silly to dead soft swaged lead), my first SWAG would be that the leading over the full length of the bore drama could be due to residual copper deposits. Otherwise it's most likely a lube failure. Many store bought bullets have way too hard a lube. Usually easily cured by a quick tumble lube in a small amount of Lee Liquid Alox.


Or buy the coated bullets. I likes those mighty well, but since I have lots of the "old school" bullets about, it'll be a while before transitioning altogether.

Another thought: Undersized throats. Driven hard enough, accuracy will often be ok until the rifling is filled with deposits.

As for the uneven outer edge wear of the forcing cone, I'd look at the barrel cylinder gap first. May be uneven, being looser at the top. Very first N frame I owned, way back in the '80s, had the same drama, plus the cylinder face wasn't square to it's rotational axis so would crash the back end of the barrel on one chamber. A fine introduction to big bore S&Ws!

If the frame isn't bored for the barrel correctly and is a bit high to the chambers' centerline, I suppose could lead to similar, but I would expect terrible accuracy from the "git go". Doesn't seem to be the case here.

Erosion will happen fairly quickly with a steady diet of H110 or similar, regardless.

It's not copper. I've not fired a single jacketed or plated bullet though the gun. I make sure the bore is squeaky clean after shooting. Accuracy is acceptable at first, but not great. Then it becomes terrible.

If there is a problem with the gap or alignment, it's going to need to go back to Smith no matter what. As to a lube failure, I'm not experiencing these problems using this same ammo with my 29-3, which also has an 8 3/8 in barrel. The forcing cone looks new and it has way more rounds of all kinds through it.

By the way, it's the inner edge of the cone, not the outer edge.

Also, of the approximately 700-800 loads through this gun, a handful were h110, another 75 or so were 2400 and the remainder were midrange loads using either 800x or Power Pistol.

 

[M29since14]

S&W can't be concerned with handloads and issues resulting from them so don't mention it, but they should be willing to check for alignment and poor accuracy. The wear I see there tells me the gun needs to go back to Springfield, and, as others have already said, just hope it lands on the bench of someone who gives a hoot. Good luck!