I am installing a new barrel on a Model 10. I've done this several times with good results. I used piloted hand cutters to cut back .018-.020 from the rear barrel face with the barrel in a vise prior to final installation. Careful checking and measuring results in a BC gap of .005-.007. I dont get lead shaving or spitting, and the accuracy is acceptable- 3" at 15 yds. offhand with 2"-3" barrel.

My question is whether or not I should re-cut the forcing cone to make up for the .018-.020 removed from the rear of the barrel. If so, I would do this prior to installation with a piloted cutter.

If re-cutting is recommended what angle for the cutter?

Re-barreling should include carefully checking barrel/cylinder alignment with a range rod, checking headspace and correcting excessive end shake (if needed), setting the proper B/C gap, and re-cutting the forcing cone if required. A plug gauge is used to determine whether or not the cone needs to be re-profiled, and is at the proper depth.

The forcing cone re cut work will likely depend on whether or not a factory new barrel or used barrel is installed. For me, the most common forcing cone profile is 11°. I use the Revolver Chamfering Tools, and the forcing cone depth gauge from Brownells.

Forcing cone depth gauge shown below

Attached Images

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Ret. LE, FA Instr, S&W Armorer

Thanks for your reply. I know that is the normal process. My question is whether that .020" that I remove from the barrel face is enough to warrant re-cutting the forcing cone. I guess a forcing cone guage is the proper way to measure, but looking at my feeler guage .020" doesn't seem like much. I recall the guages have a minimum and a maximum depth. Does anyone know the depth difference between the two extremes.

You are not experiencing any shaving or lead spitting....

So if you had just bought the gun and shot it as such,,you'd probably not jumped to the conclusion that it 'needed' a forcing cone job done on it.

There's no guarantee that recutting will enhance or improve anything. You would think it would, but again there are no guarantees listed in the instructions with the tools that I've noticed.

If you know what angle the orig bbl was cut at,,you could touch up the cone to that angle and likely cut a much smoother cone than a factory funnel. Likely more precise too.
But again will it make the revolver more accurate at 15 yds?,,I don't know.
Changing it to an 11* or other do anything.??

Personally. I'd leave it as is unless it isn't performing as you want it to.
Then if you want to recut it later on, do so.
But use the correct piloted tools and a go/no-go gauge so you know when to stop.
The process can be done from the muzzle so you don't need to dismount the bbl from the frame.

I'll swim upstream and say that unless your shooting full wadcutters you have nothing to worry about if a range rod works. If your bullet nose has any taper to it and you have some amount of forcing cone those 2 tapers will cause alignment. I would think in most cases a forcing cone that was way big would be more of a problem accuracy wise.

I have never bought a gauge myself. I simply use a soft lead ball driven into a factory barrel and then measure the base of the impression. Then duplicate that diameter using my cutter. To measure one I am working on, I coat the brass taper I made with Prussian blue, stick it in new cone twist and measure marks. You could also use the brass tapered lap that comes with the kit. Mine is a bit more acute so I get a ring in blue right at entrance

There is no magic angle for a muzzle crown or a forcing cone. What matters is if they are smooth and concentric to the bore.

Bench rest rifles often have a 90 degree counterbore at the muzzle. If the counterbore is slightly off center, it won't matter, because the exit of the bore will still be exactly the same all the way around. I have found that any angle from 90 to 45 degrees will be fine if it's centered on the bore. A lot of times the rounded crown on S&W revos is not centered, causing large groups on the target.

The same is pretty much true for forcing cones. They can be anywhere from 5 to 18 degrees. If they are smooth and centered, not too small, not too large, they work fine. A bit too big works better than too small, but best to use the gage. Many factory forcing cones leave something to be desired.

If you have a good forcing cone and muzzle crown and are still getting leading and/or poor groups, check for a constriction in the threaded area of the barrel just in front of the forcing cone. If there is one, the bullet gets swaged down under barrel size and is rattling down the bore the rest of the way. The bullet is not tightly controlled to the end of the barrel and will not be accurately guided.

If your barrel has no constriction, good forcing cone and muzzle crown, (and good rifling - nearly all of them have good rifling unless it has been damaged or worn out), then you will have a match grade barrel that will shoot most loads well, and some very well. If your barrel has one or more of these problems, it will likely be finicky about shooting anything in an acceptable group.

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protocalldesign.com

I have an set of the 11 degree cutters, a big one and a small for 32s and 22s. They are supposed to self center. But I made a piece of brass for each caliber that just slips down the barrel and over the rod that drives the cutter. By having it on rod ahead of cutter it must stay centered.

Brass round stock is fairly cheap, machines easy.

You really want the brass centering guide, because the original FC may be (often is) cut off center.

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protocalldesign.com

As far as I'm concerned those forcing cone gages are way overpriced and unnecessary because you can make your own for next to nothing or just mark your cutter from a barrel known to have the correct depth of forcing cone cut. Those gages are waste of money except for those who think you have to spend lots of money to get good results. None of this stuff is somehow magical.

I try to make the guns I tinker with as good as I can. But, now days you would probably be hard pressed to find one that was not more accurate than I can shoot.

I also suspect that if you first 1/4" of rifling is removed when forming forcing cone you are in good shape. Look at almost any factory barrel. The difference in length that this would occur between a 5 or 11 degree cutter would be real small. Rifling is only .005 deep. and the 6 degree difference in .005 is pretty small.

I have always believed, after being told this by older more intelligent people than myself over the years, that purchasing and utilizing good quality tools designed for a specific purpose was always a lighter burden than defending a wrongful death litigation in court.

I have never had the slightest desire for an extended prison stay.

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Ret. LE, FA Instr, S&W Armorer

While I believe using good quality tools is always good plan. I would like to see it proven in court that a revolver blew up because a forcing cone gauge was not used. I would simply present the court with the variation in say 20 factory S&W forcing cones.
Trust me they vary plenty and that is the factory. A piece of spit lead would be far and away more apt to be the result of mistiming than a forcing cone issue unless the cone was way to small or non existent.

You are just as apt to get sued over the modification of going from 5 to 11.

You would have to be extremely negligent to mess up a forcing cone that badly. I have a lot more things to worry about. A giant meteor strike for instance

PS trust me, I understand liability. When I inspect the bolt up flanges, heads and manways on pressure vessels, columns and exchangers I have far and away more liability and likely hood of serious criminal charges than anyone cutting a forcing cone. I mostly use a small hammer to ping the nuts, larger ones I may have them show me the correct torque on a random amount of studs. I visually look at the nuts and stud ends to verify correct ones, All I can see of the gasket is the edge through the thin gap to check for right color code and centered. I will look at 100s of flanges in a week. If one of those ever lets go when pressurized with super heated hydro carbon it would make a 500 S&W look like a cap gun and they are going to have lots of questions for everyone, especially the guy who has the final one in the blue book, which would be me. On 04/02/2010 a pressure vessel I used to work on repeatedly let go and killed 7 people. Reason had absolutely nothing to do with my or my crews work. It was determined that weld seam let go from hydrogen embitterment because it had got ran above the steels operational limits.. But, everyone that touched that bank of exchanges got grilled about it. Before anybody had a clue just what happened I racked my brain and prayed that I had nothing to do with what had killed 7 people I had worked and laughed with.

I guess the answer is if it ain't broke don't fix it. Since the others I have done shoot to my satisfaction I'll continue the build without recutting forcing cone. Once together if it sucks I can always try recutting then with the barrel in the frame.

Thanks for all the replies.