Cylinder Throats

[e rex]

Has anyone had the throats opened up on their 686 to accommodate lead bullets without leading? If so, who did it and what was the price?
I'm not good with a micrometer but my throats and bore appear to each be .357. I've sized .357, .358 and .359, used different alloys and powders and still get lead in the first inch or so of the barrel. I clean it with a chore boy pad on a brush but wish I didn't have to.

 

[Schwing]

Before you do this, slug your barrel instead of using a micrometer and verify that it is a problem. How is your accuracy? If accuracy is good, it could be that your alloys are simply TOO hard.

 

[murf]

what bullet weight and velocity?

murf

 

[ljnowell]

Don't be surprised if the barrel is restricted where it screws into the frame also.

 

[murf]

see if a .357" dia bullet will fit down the throats. if so, try the .358" one. it's a better way to determine throat diameter.

murf

 

[GBExpat]

see if a .357" dia bullet will fit down the throats. if so, try the .358" one. it's a better way to determine throat diameter.

murf

This ... IMO, should be your 1st step. BTW, do not trust the box labels, carefully measure the bullets that you will be using.

 

[anothernewb]

^ did that with my GP100. .357 bullet passess through the throats with a little push. Lead pushed through comes out with much more force, and is nice and shiny!

OP, I've debated reaming mine out too. Still on the fence, as plated rounds and soft lead wadcutters seem to run just fine and the cost is pretty nominal.

 

[slickracer]

I shoot a stock 686-6 with .358" and have no problems with leading. What bullets and powder are you using?

 

[e rex]

I have used Hornady swaged and straight wheel weight a 50-50 mix of linotype and pure lead. 2400 powder, Unique, HP-38. 358477, 358665, and 358155 with checks(these aren't bad) .
feet per second is from around 800 to 1250 from my 4" barrel. Perhaps a rough forcing cone? Maybe thread choke at the frame? I'm not smart enough to know.

As far as accuracy.........at 73 and harder to concentrate on the front sight it's seems pretty good for me pulling the trigger.

 

[LUCKYDAWG13]

pm sent

 

[Driftwood Johnson]

Howdy

Good luck slugging the bore on a Smith and Wesson. They usually have five grooves in the barrel. Much easier to get a good measurement when the grooves are on opposite sides of the barrel. Pretty difficult to get an accurate measurement on a slug without some fancy equipment when there is a groove on one side of the barrel and a land on the other side. I have slugged a lot of barrels, trust me on this. With an odd number of grooves, the best you can do is measure the slug from high spot to low spot, then try to get a height measurement of the imprint of the groove above the imprint of the land. Pretty inexact.

Just for fun, I just ran a slug down the bore of my 686. As I expected, it shows five grooves.

Don't rely on the internal measuring points on a standard caliper to measure a small diameter hole. There is an inherent error created by the tiny flats on the points. Not very good at getting an accurate measurement of a 357 hole.

As stated, the easiest thing to do is run a bullet into the chamber throats. The ideal bullet will just hang up in the throat, and will be easily pushed out with light pressure from a pencil. If it falls through , it is too small, and can lead to leading. I have never had any problems with .358 bullets in any 38 Special/357 Mag revolver.

 

[e rex]

Thanks a lot for the information. Would anyone have contact information for cylinderthroat.net besides Facebook?

 

[Confederate]

I don't think I'd ever rethroat any of my guns, as it would queer your accuracy with jacketed ammo. Better to size down your bullets than your throats in my view. That said, I have leading problems regardless of what I do. I've been told that running a patch with Breakfree CLP on it down the barrel every 5th or 6th shot helps. Others say hard chroming the bore also works because it deposits the chrome into the pores of the steel itself. And finally, you might try using Semichrome, Flitz or Mother's Metal Polish on one of those .45cal swabs and using it to polish your bore to a mirror brightness (use one size up from your caliber to ensure a snug fit). And if you use a brush, use a .45cal stainless steel brush (dry) toget as much out as you can, then use a good lead solvent to clean the rest out (note: there is no good lead solvent).

One more thing. Try shooting some jacketed magnum ammo after your last lead shot.

°°°

 

[Sam1911]

I don't think I'd ever rethroat any of my guns, as it would queer your accuracy with jacketed ammo.

What? No,no. I've done this myself and there is no loss of accuracy. If anything, the opposite. (In my case it was .44, not .38, but the point is the same.)

Better to size down your bullets than your throats in my view.

How does that make sense? You push bullets through a smaller aperture (the throat) and then have them "rattle down" the oversize bore? How would that be conducive to good accuracy?

You want to set up a situation where the bullet is a very tight fit in the throat, and the throat should be a half-a-hair (like 0.0005"-0.001", max.)over the groove diameter of the barrel. And use a bullet that's the same diameter as the throat, or as close as possible.

Squeezing the bullet down to below groove diameter certainly would be a very obvious reason for why you "have leading problems regardless" of what you do! Of course you would! Check those throats and fix the problem if it exists.

 

[Airman Basic]

Thanks a lot for the information. Would anyone have contact information for cylinderthroat.net besides Facebook?

Think it's
Cylinderhone.net on Facebook. But I've always gotten prompt responses and quick work from them. Worth trying the other remedies in this thread first, though.
My problem with cylinder throats is inconsistency rather than wrong sizes. That problem seems to be with Ruger more than S&W. Different processes, I guess. Haven't come upon a Smith that needed help in that regard. Ha, my cataract surgery helped me more than cylinder honing, and can't get Blue Cross to recognize my gunsmith anyway.

 

[joneb]

I have a S&W 696 with tight throats .429" it runs .429-.430" just fine at 12-14 BHN.
http://www.practicalmachinist.com/vb/gunsmithing/measuring-5-groove-slugs-189215/
If I were to have the throats reamed it would be to uniform them rather than enlarged em.

 

[murf]

when is the last time you cleaned (deleaded) your forcing cone. with that much lead in the first inch of the barrel, you probably have a ton of it on the forcing cone.

murf

 

[e rex]

Murf, looking close and paying attention the forcing cone doesn't seem to catch much lead. It seems to start on the leading edge of the rifling.
Rough spot on the rifling? thread pinch?
Rex

 

[murf]

curing a leading problem can be frustrating at times.

as ljnowell said, you could have a barrel restriction. slug the barrel and feel for the restriction. fire lap or taylor throat the barrel.

the forcing cone could be cut wrong. have it recut.

as schwing said, your bullet alloy could be too hard. soften it.

or, you may have a gun that just does not like lead bullets without a gas check. i have a 44 special blackhawk with this problem. until i solve it, i shoot jacketed and gas check bullets in it.

luck,

murf

 

[fecmech]

I have used Hornady swaged

I recently bought a box of the SWC's for the .38/.357 and I get throat lead in all my guns with .38 level loads. Checked the bullets and discovered the diameter at the base was .354 and did not get to .357 until halfway up the bearing surface! Sure recipe for leading! Gave Hornady a call but they didn't seem too concerned about it, I thought they'd replace them. I'll just chalk it up to experience, dump them in my pot and cast some good bullets out of them.

 

[Catpop]

I had same problem. I opened my blackhawk throats up about .001 with an adjustable reamer and have never looked back. Leading disappeared and accuracy improved. Reamer cost was about $35 I think I remember.
Note: I do not shoot jacketed bullets, only lead.
Catpop

 

[Jim K]

You say you have tried different alloys, but they all could be too soft. Barrel leading at handgun velocities is often the result of too soft bullets and/or the wrong lube. If you are loading very hot, you might have to use gas checks.

Jim

 

[Vern Humphrey]

First of all, are your throats uniform? Throats are easier to measure than the bore -- and more critical.

Then check for a constriction near the breech end of your barrel -- S&W uses a crush fit nowadays for barrels, which often results in that part of the barrel being slightly constricted. This can sometimes be dealt with by fire lapping (shooting bullets coated with an abrasive -- you can buy kits over the internet.)

Next, check bullet hardness -- too hard a bullet will often not upset, and will allow gas to escape around it, resulting in gas cutting of the bullet.

 

[Confederate]

What? No,no. I've [rethroated my chambers] myself and there is no loss of accuracy. If anything, the opposite. (In my case it was .44, not .38, but the point is the same.)

This is true if tolerances are in spec. If not, the bullets aren't adequately stabilized and they enter the forcing cone just a little skewed, and it affects accuracy; not dramatically in most cases, but significantly. If the chambers have no throats (as did two Taurus 66s) I ordered in the 80s, you'll have zero accuracy. But most decent revolvers will be fine...but not perfect. On production guns it's common to be a little off on some chambers, but dead on with others. Some competition shooters will isolate a chamber that's unusually off, but for plinking, casual shooting or defense, it's not usually not an issue.

How does that make sense? You push bullets through a smaller aperture (the throat) and then have them "rattle down" the oversize bore? How would that be conducive to good accuracy?

It wouldn't. One hopes to have the forcing cone and throats about the same dimensions, and it's adhering to these tolerances that often distinguishes the really good guns from the not-so-good ones. The first S&W 686s were designed with the goal of being as accurate as Colt Pythons, and they were (and probably still are). And the company did this by narrowing the tolerances on forcing cone-dimensions, barrel/cylinder gap, barrel diameter, headspace and, of course, throat dimensions. For shooters who want ultimate accuracy with jacketed rounds, the throats should be at .357, the same as the barrel diameter.

You want to set up a situation where the bullet is a very tight fit in the throat, and the throat should be a half-a-hair (like 0.0005"-0.001", max.) over the groove diameter of the barrel. And use a bullet that's the same diameter as the throat, or as close as possible.

Yep. You can take 6-7 125gr JHP bullets and drop one into each chamber. If they stick, that's a good sign. Wadcutters are a bit larger and are more forgiving of sloppy tolerances. But yes, if the throats are undersized, that also is a problem.

Squeezing the bullet down to below groove diameter certainly would be a very obvious reason for why you "have leading problems regardless" of what you do! Of course you would! Check those throats and fix the problem if it exists.

Well, I have...and I also have more than one 357. They all lead to some extent and Hoppe's #9 isn't very effective at removing it. I've tried various lead removers -- foul, odorous concoctions that should be used with a mask and rubber gloves -- all with limited success. The Louis Lead Remover is okay, but on the expensive side. Also, it's common for new guns in particular to have leading problems until the lands and grooves get polished in.

°°°