586 out of spec

[586]

hey guys i'm new here
i got a 6" 586 no dash last year and had to send it back to S&W for the hammer nose bushing issue. i have been learning a lot about revolvers since then and noticed that alot of the tolerances are out of spec. can you help me understand this ? the b/c gap is .007 when the cylinder is pushed all the way foreword and .015 when all the way back. wouldn't that be .008 endshake ? i need endshake bearings but that would push the cylinder all the way back and i would have a constant b/c gap of .015. that meens i would have to set the barrel back and recut the forcing cone to have a b/c gap between .004 and .008.
am i right ?
also the headspace is .004 with primerless winchester brass when the cylinder is held back.

 

[Dragon88]

If those truly are your BC measurements, that is a lot of endshake, and a large BC gap. Does the cylinder seem to travel forward and backward a lot when you move it with your fingers? You would not want to correct that much endshake with bushings, you will end up with a .014~.015 permanent BC gap, and that is out of spec even for the factory these days. Double check your measurements, and then call S&W.

Oh and welcome to the forum.

 

[chief38]

586:

Welcome to the Forum!

I think you have it backwards............

When you have the B/C gap of .015" that should be in the FORWARD position, and when the cylinder is pushed REARWARD then your gap widens to .007". Is that what you are trying to say?

If this is correct, then you have an end shake problem here. I like a B/C gap of between .004" - .006" with minimal end shake. A B/C gap of only .015" will quickly bind up from lead deposits, and a gap of much more than .007" will allow too much gas loss resulting in velocity drop and lead spitting.

This is not that big a deal to repair, but since you stated that he revolver just came back from S&W I would return it to them and let them repair the problem.

Just a note here.......... there will always be some TINY amount of end shake, because if there were none at all, the cylinder would not operate freely when it gets dirty. A tight gun is nice, but too tight creates operating problems.

Chief38

 

[lebomm]

chief38
How is .015" WIDENED to .007"?

Larry

 

[son-of-a-gun]

From a S&W Revolver Inspection Guide:

Barrel-to-cylinder gap: The ideal B/C gap is .006". A close gap will cause the cylinder to drag when fouled from shooting residue. A wide gap will loose muzzle velocity and may spit particles. The normal usable range is from .004~.010"

Hold the cylinder to the rear and insert the thickest gap gauge that will fit between the cylinder face and the rear of the barrel (with friction). This will be the B/C gap.

Cylinder endshake: This test will measure the front to back free travel of the cylinder. It is a good indicator of wear from shooting. Anything over .002" is considered excessive.

Hold the cylinder forward and insert the thickest gap gauge that will fit between the cylinder face and the rear of the barrel with minimal friction. Subtract the measurement from the B/C gap. This will be the cylinder endshake.

 

[586]

i checked the measurements more times than i can remember and they are the same every time. b/c is .015 and endshake is .008. I just looked under the top strap and can see minor flame cutting also

should the s&w cover the repair

 

[bgrafsr]

S&W will not cover the b/c gap repair. The flame cutting is no big deal, once it goes so far it stops and will go no deeper.
If you do have the .015" gap, then the barrel needs to be set back, although you could shoot it as is. Myself, I would set the barrel back and have done so on several Smith's that I did not like the b/c gap on.

 

[586]

is this big of a b/c gap unheard of or somthing ? you guys sound like your in disbelief

 

[son-of-a-gun]

is this big of a b/c gap unheard of or somthing ? you guys sound like your in disbelief

I just bought a model 19 that measures .009. It also has some forcing cone erosion and endshake of .005.

I fixed the endshake by shimming, but I plan to send the gun in to S&W to make the other adjustments.

How does your forcing cone look?

If it looks like the mouth of a volcano, then you also have some erosion.

 

[chief38]

586 & lebomm:

You are correct! Must have had "too much Jack" before reading your post.......... and mis-read the .015 as .0015. I apologize for the mistake.

The bottom line here is you do have too much end shake, as the optimal B/C gap is around .004" - .006".

Chief38

 

[586]

So what i need to do is put in some endshake bearings, set the barrel back, and recut the forcing cone.
The forcing cone is not eroded but i would have to recut it anyway when i set the barrel back.

I would like to do this work myself. Do you have any advice ?I'm starting a machining class at the begining of the year. I'll ask them if I can do this in their shop once i get comfortable using the equipment.

thanks everyone

 

[Mack]

Water under the bridge but you should have had S&W do this when you sent you gun in for the mod. Shipping handguns is very expensive. Endshake repair is done with shims not bearings and setting the barrel back is a job for an experienced gunsmith or even better the factory. You need special tools to do this without risk of ruining the gun.

 

[586]

Yeah, I know I should have had them do it when it was there but I wasn't aware that anything was wrong. Power Custom calls them endshake bearings, I know they are realy shims. The reason I want to do the work myself is because I hope to be an experienced gunsmith. I'm still learning and it's better to learn on my guns than to screw someone elses up. All I need is a barrel vice, L-frame action wrench, and some time on a lathe.

 

[VM]

I'm kinda surprised S&W didn't tell you that you had other issues while it was in their possession??
I agree with others, let a professional do the work.

Yeah, I know I should have had them do it when it was there but I wasn't aware that anything was wrong. Power Custom calls them endshake bearings, I know they are realy shims. The reason I want to do the work myself is because I hope to be an experienced gunsmith. I'm still learning and it's better to learn on my guns than to screw someone elses up. All I need is a barrel vice, L-frame action wrench, and some time on a lathe.

 

[Maximumbob54]

It sounds like someone was shooting a LOT of hot 125's or even some heavy for caliber loads from that gun. I bet the recoil shield has brass stamps the whole way around it.

It sounds like you may be over simplifying the various repairs a bit. Chucking something in a lathe and turning it is not quite as simple as it sounds and I'm no expert at it. I only learned a few years ago that if you don't use a bushing on your drill bit, even if you use a decent drill press the bit will still flex and box some and not cut as true of a hole as you want. And cutters for the grades of steel aren't cheap.

I honestly hope you already know all this and can just dismiss my post.

 

[Lenny_D]

I have over 30 years as a Toolmaker but have not worked on handguns more than just drilling and tapping and regular maintance. It would seem to me that you would have to determine the pitch of the barrel thread and remove enough stock from the shoulder where the barrel shoulder meets the frame. The pitch of the thread would determine how much material needs to be removed because you would need one whole revolution so that the sites would align properly at the 12:00 o'clock position. Then remove material from the forcing cone to give you what you want for your correct B/C gap. I believe they sell a cutter and arbor that will fit through your barrel and the forcing cone can be "back faced" after the cutter is attached. That ensures your forcing cone is perpendicular to your barrel. Chucking the barrel in the lathe shouldn't be that difficult. You would need a 4 jaw chuck with protective jaws. Just indicate the straight diameter (OD.) of the forcing cone or if there is a straight diameter before or after the thread of the barrel and make sure the face of the barrel that engages the frame is running true. I think that would work. If a gunsmith is a member of this forum maybe he can offer how he would set it up?

 

[586]

It sounds like someone was shooting a LOT of hot 125's or even some heavy for caliber loads from that gun. I bet the recoil shield has brass stamps the whole way around it.

It sounds like you may be over simplifying the various repairs a bit. Chucking something in a lathe and turning it is not quite as simple as it sounds and I'm no expert at it. I only learned a few years ago that if you don't use a bushing on your drill bit, even if you use a decent drill press the bit will still flex and box some and not cut as true of a hole as you want. And cutters for the grades of steel aren't cheap.

I honestly hope you already know all this and can just dismiss my post.

Ha, You hit that nail dead nuts ! It does have stamps all the way around.
... I'm not trying to simplify anything. I know there is a lot of work involved and I have absolutely no machineing experience but that's why I'm going to take the class. Maybe I'm planning too far ahead but I want to learn everything I can.

 

[bgrafsr]

Ha, You hit that nail dead nuts ! It does have stamps all the way around.
... I'm not trying to simplify anything. I know there is a lot of work involved and I have absolutely no machineing experience but that's why I'm going to take the class. Maybe I'm planning too far ahead but I want to learn everything I can.

I have nylon barrel blocks for the different S&W barrels, and I use them when setting up a barrel in the 4 jaw chuck on my lathe, and get zero runout doing it that way. I have set several barrels back one turn to correct the b/c gap that way. I also have the forcing cone cutter set from Brownell's too. I have had to shorten an ejector rod once in a while too, and when I did, I re-knurled the end of the rod and tapered the hole in the end so it would fit correctly with the taper on the locking bolt.

Barrel threads for S&W are 36 TPI, by the way.

 

[586]

did you buy the nylon barrel blocks or mold them ?

 

[bgrafsr]

did you buy the nylon barrel blocks or mold them ?

I bought them, but it has been so long ago, that I don't remember where I got them from. I also got a frame wrench from the same place too. Sorry, I can't help you.
Bill