Forcing cone and accuracy model 66-2

mark454

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Please help if you can. Over the past year or so, I have noticed that my Model 66-2 is slowly losing accuracy. Having a cloverleaf size group at 25 yards was not uncommon. Now, I am lucky if I can get 2 inches in the same condition. I know 2 inches isn't bad but this gun used to shoot better. This gun has MANY rounds through it (I don't keep accuarte records of that sort of thing but I would guess well over 10K). Most of those rounds have been very light 38 special loads with lead 150-160 grain bullets. The load hasn't changed. I haven't changed (bench rest and other guns prove that in this situation). The gun seems just as tight as my other model 66 example (that shoots much better). I am now wondering about the forcing cone. I doesn't look worn out but is that the best way to check it? Does anyone make a guage of some sort? What angle does S&W use? Is it the same for all models? Has anyone had success with Brownells forcing cone tool?
I am thinking this barrel may need to be turned in a turn but I am was hoping someone here could shed some light with personal experience.
Thanks for the help,
Mark
 
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It would be most unusual if you'd managed to wear your forcing cone enough to cause a noticable lack of accuracy with the loads you've mentioned. Brownells does have the gauges, but the angle of the cone is going to vary depending upon when the piece was made. The original angle was 18 degrees and this changed at sometime to around 11 degrees. An 11 degree cutter can be used to touch up a 18 degree cone if it's not already oversize.

If your 10K round estimate is accurate, a check of range, carryup, yoke alignment, b/c gap, endplay and headspace is in order. I'd do that before deciding that the barrel needs to be set back.

Not to be insulting, but a check of the eyeballs is also indicated.
 
I have never recut a forcing cone (I think the Smith people call it something else), and have had a gunsmith do it only once.

I did have a similar experience some years ago with a 14-3 that suddenly produced larger groups. I asked a friend who has a borescope (actually a tube and manifold scope) to take a look. We discovered a rather heavy build up of some sort of metal fouling in the grooves. Under magnification, the stuff had sort of a purple cast to it.

Never did figure out what it was. A patch soaked with #9 came out clean. Just looking down the bore with the Mk I eyeball, everything appeared shiny, bright, and clean.

I gave the bore a good cleaning with one of the metal eaters (Blue Wonder, I think), and things returned to normal.

I don't cast my own bullets, for reasons of domestic tranquility. But I shoot quite a bit, so I buy a lot of cast/swaged bullets. I try to buy locally, to save freight charges. My guess is that some batch of gun show bullets had something in them that should not have been there.

Perhaps it's something you might want to look at.

Charles
 
Thanks for the input. I don't think it is a bullet quality issue. The same bullet shoots well in my other 38/357's. As for my eyes, no insult taken. My eye doc says they are good and I can shoot just fine with other guns.
Mark
 
Could be it just needs a tube up.

Check and adjust if necessary:
timing
end shake
barrel/cylinder alignment
forcing cone
damage to muzzle
 
IMHO, you have a build-up of lead in the forcing cone and possibly in the cylinder itself. You can get the lead removing kit that uses solvent and brass mesh (i forget the name) or you can get a gunsmith to just recut the forcing cone to the 18 deg version. I have the tools but no longer am a professional gunsmith. The lead in the cylinder can be removed using any of the cleaners that puts lead into a removable solution.

I never could find a good reason for S&W to go to the 11 deg. forcing cone. Without fail every .38 Special or .357 Mag revolver that I recut to 18 deg. shot better after the cut. ....... Big Cholla
 
10K lead bullets is NOTHING to a S&W revolver barrel.
I have a model 14 that has over 100K lead rounds down it, and the bore still shows the original faint tool marks.

It is 99.9% certain that you have a seriously fouled barrel, that can be restored to original performance by getting ALL the lead and copper out of the barrel.

A popular custom barrel maker says over half the "shot out" barrels sent to him just need a thorough cleaning.
 
Without fail every .38 Special or .357 Mag revolver that I recut to 18 deg. shot better after the cut. ....... Big Cholla

Did you have to set the barrel back a turn when you did this?

Thanks again to everyone for all of the advice. I think the gun is clean but because so many here are convinced it is dirty and fouled, I will give it a better cleaning.
Mark
 
mark454: As said; no, it is not required to set the barrel back when recutting the forcing cone. If the face of the breech had to be resurfaced to get it square with the world and the resulting gap with the cylinder face was then larger than acceptable, then the barrel would have to be set back one turn. ........... Big Cholla
 
use lewis lead remover works fine

+1
The Lewis Lead Remover comes with a special tool to clean forcing cones too. I'm not sure that this is your problem but if lead fouling is causing this issue. This tool will get it fixed.

I know this sounds dumb but have you checked to make sure your rear sight leaf is screwed down tight? I've got a M19 that suddenly started to shoot erratically. After several frustrating shooting sessions I finally realized the front screw that holds the rear sight leaf in place had somehow worked loose. Loctited it back in place and the gun shot fine again.
 
From experience, I would say the gun needs a professional cleaning.

Past that, I will bet money you had some vision change over the years and the sights on that particular gun brings out the change more than does another. My vision changed and it required me finding an eye doctor that was an active shooter to make the proper glasses to correct my shooting.
 
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