625 EDM rifling up close.

[Arlon]

Just for interest I took some close ups of the EDM (actually I think S&W uses ECM) rifling in my S&W 625-8 JM revolver. I can sure understand now how this rifling can have issues "gripping" a cast bullet or maybe any other bullet. I'm surprised that some people seem to have great results shooting these with cast and some don't.

This is the only handgun I own with EDM rifling. I'd love to see how some of the "laser beam" JM models look. I just wonder if the rifling could have anything to do with it the lack of accuracy exhibited my copy? Maybe I need to try to redo the crown, it doesn't look too impressive either..

My only interest is in being able to shoot cast bullets at moderate velocities accurately with this revolver.


Click for the full size version.

 

[Pistolero]

Good pix!

They have a matte finish when you look at them, from the zillions of little sparks that remove the
material.
Not sure if S&W is still making bbls this way. Anybody know if this is still current?
My JM625 has a conventional looking cut barrel.

Bill

 

[Arlon]

If yours has cut rifling or even better EDM rifling it might have something to do with why some of these guns are "laser beams" and others can't hit a pumpkin at 25 yds. Some lead up like crazy and some don't seem to. I do know this is the first and last EDM rifled gun I'll ever own. I have a bunch of old ones that just don't cause me mental anguish. (-:}

The crown even looks like it was cut by the edm machine. Maybe it just got frosted with the finish.. It sure doesn't look like it was cut with a tool. I wish I'd spent the extra $100 for the PC version..

 

[Arlon]

Anyone try the Lyman 454424 in these revolvers? I just wondering if the longer bullet (more bearing surface) might work better with this kind of rifling? I have that mould, I might try some sized to .452 with a little unique and see how they do. It does look like maybe this is going to take some lighter loads to hold the rifling with a cast bullet. I will try light charge heavy bullet in some AR brass and see what happens when I get a few free minutes.

 

[Pistolero]

So far my best groups seem to be with the 452460, a .45 ACP 200 SWC standard target bullet. Several
of my 1911s like it very well, too.

Bill

 

[Arlon]

So far my best groups seem to be with the 452460, a .45 ACP 200 SWC standard target bullet. Several
of my 1911s like it very well, too.

Bill

Have that one. Haven't used it in a few years. I'll give it a try too.

 

[RBHarter]

The 424 worked well in the Colt 1917 but the Smith doesn't like it in ACP . Can't say for the EDM cut .

 

[Bret4207]

Reminds me of a "frosted" barrel like we see in some surplus rifles used with corrosive primers. I'd consider recuting the crown and putting mess of jacketed though it. I don't know if that will help smooth things at all. I never had a lot of luck with stainless that needed fixing.

 

[fiver]

shallow rifling isn't a real big problem.
those ridges on the entrance and no lead in angle though...
I'd try a little tougher alloy and not too big of a diameter.

 

[KeithB]

EDM creates a surface texture that is different than what you get from conventional cutting/material removal processes. There is also a problem of what is called a "recast" layer, where a chemical process re-deposits material back on the surface. Newer EDM machines and process reduce that but lots of things can affect the process and the advice to remove the recast layer and smooth the surface through post-EDM processes is still valid. Smoothing/removing the roughness also improves fatigue strength and prevents microcracking. If I was concerned with an EDM bore the first thing I would try is to simply shoot some jacketed stuff through it to smooth things out a little bit before I did anything else.

 

[Ian]

The crown even looks like it was cut by the edm machine.

That was my first thought when I saw your photo. Weird.

Edm is great for many processes (such as line-boring suppressor cores after they're welded together) but not so good for others.

 

[Arlon]

Actually I think S&W uses ECM not EDM, Similar but about the same. Not exactly sure which process they use.