I was looking at a new 686 the other day and noticed the rifling looks different from my 686-1, it actually look shallow and less defined. The dealer said S&W actually changed their method of rifling years ago, anyone knows when they made this change?
As a note all my M&Ps barrels still have deeper broached rifling, so I wonder why their semi autos would have the older deeper rifling as opposed to their current revolvers which all seem to have the newer shallower rifling.

About 10 or 15 years ago, Smith changed to EDM to rifle the revolver barrels. This involves using an electric current, with the arcing electicity removing (vaporizing) minute amounts of metal. I don't know why it wasn't done across the board.

Bob

I suspect that the driving factor for the change is COST. With broached rifling a chip fused to the cutter can result in a barrel that is scrap. If you look at all of the profile work required to produce the barrel on the 686 it's rather obvious that is a rather expensive chunk of steel. So, S&W may chose to use the ECM (Electro Conductive Machining) to produce the rifling in the revolvers because it's a more foolproof method for rifling a barrel. It's also possible I'm completely wrong and the only reason the semi's don't have the same method of rifling is simply because the machines are expensive and S&W is accumulating a bit of cash to pay for some more ECM Machines.

Personally I've found the ECM barrels to be exceptionally accurate and the surface finish priduced by this method may provide for a bit more velocity for a given loading when shooting jacketed bullets. Because if you shine a light down the bore you'll see that the ECM barrels are produced with a surface finish that almost looks polished.

With the rifling apparently not as deep or sharp I wonder if it will effect accuracy using lead bullets. I have no doubt that it will stabilize jacketed ammo. The cost cutting explanation makes a lot of sense.

Anyone know the rifling depth; or, the groove diameter and bore diameter for the 325 TR? This talk of shallower rifling is of concern. Called Customer Service at Smith & Wesson. I was curtly told: "We don't have that information...We don't recommend using reloaded ammunition." Have all the people who are now buying shares in S&W forcing this tact? If some are "Christians," why do they not know Jesus' directions to the apostles to sell their cloaks to buy swords?

My experience is that the depth of rifling on handguns is not that critical. Look at some of the 1917 barrels. Not much depth. Yes they were designed for jacket bullets, but many have had a lot of lead fired down them with fine results. A well cast bullet that fit the bore is going to catch and spin in shallow rifling. Maybe something like full blow magnums and softer bullets may have problems.

But, in any case I just looked at both my 325s and 396 my newest revolvers and the rifling seems to be as deep as some of my older guns.

Can't say I've had any adverse experiences with ECM barrels.

And I enjoy posting this little gem from Buffalo Bore.

"You'll notice that new S&W revolvers with short barrels are often shooting faster than older S&W revolvers with longer barrels. The new S&W revolvers are very good and are made with equipment that makes them more consistent and faster than the S&W revolvers of yesteryear."

My 325TR (mfd. Apr-2015) has a .443" bore (using pin gages) & .452" groove (using a telescoping gage).

Of the (8) S&W 45 caliber revolvers & pistols I have the bore on about half measure .443" & the others are .444".

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Waiting for the break of day

I love how everybody jumps on the "because it's cheaper" bandwagon, like that's a bad thing. ECM (Electrochemical Machining / Process explained here: Electrochemical machining - Wikipedia) actually produces more consistent, smoother barrels. No machine marks - in fact when barrel manufacturers first started using this process, the FBI was worried that there would be no unique rifling characteristics transferred to a fired projectile, rendering it unusable for forensic ballistics. Such was not the case.

Looking at the muzzle, guns with ECM rifling are sometimes mistakenly thought to have polygonal rifling because there is a more rounded transition from land to groove. This has little to no affect on accuracy. An Internet tale says that ECM barrels are less accurate with cast bullets - this is highly suspect due to the number of variations that can be present with cast bullets - diameter, lube, hardness. As was said above, matching the bullet diameter to the throat and rifling precludes any complaints about accuracy.

I believe that S&W has been using this process on their production revolvers since 1993. The Performance Center still uses Broach Cut rifling on their revolvers - not because it is any better, but because it is more in keeping with the "hand-built" agenda of the PC.

Adios,

Pizza Bob

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Lots of S&W barrels are ''Hammer Forged''. Specifically those with the

big nuts on the end. These shrouded barrels are used across the whole

revolver inventory. The hammer forged barrels aren't even made by S&W.

They are made by a German company near Atlanta, Ga by Lother Walther.

Ultimate barrel accuracy is achieved thru cut rifling. One groove at a time.

That's the way all Bench Rest rifle barrels are made. Cut rifling is NOT

the cheapest. Just the BEST

Here's a good 2-part article on the different methods of barrel rifling with pros/cons, advantages/disadvantages, etc.

NRA Family | 3 Methods of Barrel Rifling: Pros vs. Cons

NRA Family | Hammer-Forged & Cation Rifling