Having slugged multiple S&W .38spl/.357 and 9x19 (just one on an M940). I cannot detect a difference with a Globaltronics (German made) caliper. Having slugged one Taurus 605 and one 905, I cannot detect a difference. I guess it makes sense since 9x19 revolvers are niche guns. Does anyone KNOW if Ruger uses the same dimentions/part (or if the S&Ws Taurii or Charters use the same (.38spl) dimentions and ot parts?

__________________
Certified Curmudgeon

Sorry, don't know the answer to your question, but I'm curious how you measured the S&W slugs that have 5 grooves?

__________________
I'd like to agree with you BUT

Odd numbers of lands and grooves makes measurement more "interesting" shall we say. First off, I am comparing a group of 5 land barrels to each other, the cross measure in each of five places (center land to center opposing groove) is an accurate average between the land and groove measure. If five are same that makes life easier. If they are the same between six barrels then I am convinced the same barrel (or at least the same dimentions to cut really really similar barrels) are being used. I can also measure other points on the slug to insure that they are identical (of course I would have to eyeball to find an approximate, or experiment with differently sized bullets to find the true land or groove dimensions.)

__________________
Certified Curmudgeon

Since all the manufacturers you mentioned adhere to SAAMI standards, I would expect that they have the same nominal groove diameters. There will of course be slight differences due to manufacturing tolerances. In checking the SAAMI website, I was surprised to find that 9x19, .38 Special, and .357 Magnum all have the same nominal groove diameter, 0.355 inches.

I'm also interested in how you measured groove diameter from 5 groove S&W slugs.

If you look at older specifications for barrel dimensions, there are differences in specs between manufacturers for .38/.357. 9mm tended to be less different, but there was always some overlap between maximum and minimum groove diameter between the calibers.

S&W barrel spcs used to be 0.356-/0.358 groove diameter for .38/.357, 0.354-0.356 for 9mm.

Colt used two different standards with the Official Police & Python using what amounted to 9mm groove diameters. The rest being closer to S&W, but not exactly the same.

Calipers aren't the best tool for this measurement, too much room for operator error. It's why they developed micrometers.

BTW, why don't you email Ruger with this question?

Oldish German dial caliper, supposedly accurate to 1/1000 inch ( yes, west german and sae not metric). Mike probably better, but being oldish I have a fondness for oldish stuff.

__________________
Certified Curmudgeon

I have heard Colts (I guess some not all) were "tighter". I am guessing that with the large number of semi autos sold S&W used SAAMI specs for them. But with the 940s short production span and nitche status, maybe they just roll stamped white 640 barrels "9mm". At least the ONE I have is identical (although it could just be a "loose-er" one).

__________________
Certified Curmudgeon

Using my dial caliper i had the pointer just about exactly halfway between .357 and .356 reading center of land to center of opposing groove. This is of course neither the land dim or the groove dim, but the average of both. Lucky for me it was consistant over multiple land-groove pairs on multiple slugs. I take it to mean barrels are absolutly identical. If I needed to know the land dim I would try a .355 sized bullet, see what kind of marks are made, over 15 years I have a collection of bullets, and could likley find the exact dims with a few passes.

__________________
Certified Curmudgeon

A caliper is not designed for the fine measurements you are trying to obtain. You'll get an approximate figure. A good micrometer will provide you with a more accurate ( and repeatable ) figure.

I've found Colt revolvers generally have slightly tighter bores than Smith & Wessons, but often Colt chamber throats are larger than Smith & Wessons. With some of my Colts, I can slip a .359" cast bullet into a chamber throat; don't think I've ever been able to do this with any S&W revolver. Many S&Ws won't accept a .358" bullet, but a .357" will usually fit any of them. None of my guns, Colt or S&W, are newer models, so maybe that makes a difference.

It's a lot of trouble to use two different sized bullets, so I use .358" in everything; not a perfect fit, but close enough for decent cast bullet accuracy.

I was surprised too, enough to look it up. As you say .357 mag, .38 special, 9x19, (.357 sig, .38 auto, .38 super) are nominally .355 grooves and .346 lands (.380 acp is .355/.348). Since all my numbers ended up on the high side (but are the same) I guess my measuring devise is giving me consistently erroneous high numbers.

__________________
Certified Curmudgeon

Not easy to use, but easy to buy different size bullets without even trying.

__________________
Certified Curmudgeon

I had an elderly, very experienced gunsmith slug my barrel and measure the throats of my model 686.

The groove diameter was 0.3565"
And all 6 throats were 0.3572"

So, I use 0.357 bullets... not 0.358"

__________________
I'd like to agree with you BUT

ruger uses the same bbl's for the 38spl/357/9mm in the LCR line of firearms.

They started switching to 1 in 18.75" twist in some of the bbl's in the LCRx line of firearms in the 38spl/357 calibers. Their short bbl'd (1.87") firearms in the LCRx line have a 1 in 16 twist and the 3" bbl'd revolvers have a 1 in 18.75" twist.

Other than that ruger has always used the same bbl's for their 38spl/357/9mm revolvers.

Thank you kindly, sir.

__________________
Certified Curmudgeon

Hmmm. I slug all my guns (except my rimfires) and don't have any 38 Specials or 357 Magnums that slug less than.357". I have 3, 9mm that slug .356", .3565" and .358". FWIW...

As a lifelong machinist/mechanic there are tricks to measure odd shaped slugs, but one I use for barrel slugs on odd number of grooves is slowly spinning the slug as I close the spindle. By feel I can usually get within .0005"-.001"