velocity of .38+p from a 2" .38 vs from a 2" .357

[Eric_A]

Hi Everyone,

Does anyone have chrono info that shows the difference in the velocity of the same round from a j-frame snub .38 and a j-frame snub .357?

More specifically, I am planning on purchasing a S&W 342pd or 340pd. I'm wondering if I would lose any velocity in the 340pd w/a .38+p compared to in a 342pd.

Has anyone with these two guns or similar j-frame snubs (.38 and .357) chronographed the same round out of both?

I found a post on TFL by Gearhead Jim back in 12/02 where he said he lost 100fps in his 340 compared to a 640 (do they make the 640 in .38? I thought it was a .357) with the same .38 rounds from the same box.

Gearhead Jim, If you're here have you had the chance to see if this happens with other rounds?

Thanks

 

[Delmar]

Don't have figures for you-sorry, but my reloading manual tells me to lean towards faster burning powder for snubbies.

 

[Tamara]

My 640 is a .38 Spl.

 

[Dot_mdb]

The 640 has been made as both a .357 and a .38.

Bill

 

[Tamara]

Indeed.

Perhaps I should have phrased it: "My 640, since it is a 'no-dash' model made before 1995, is a .38 Spl."

 

[tbeb]

Why don't you just buy a S&W Model 642 which is rated for +P ammunition? It has an internal hammer and empty weighs 15 ounces.

The S&W Model 340PD weighs 12 ozs. I, for one, would not buy an airweight .357 magnum like that.

The little bit of velocity loss with a .38 special cartridge fired from a .357 magnum revolver is not going to matter that much in a self defense senario. If you like the 340 that much then go for it.

 

[E357]

All things considered they should be the same velocity-wise. But each revolver is an enigma unto itself so you can't estimate your results on a different gun (when everything is so similar).

Elliot

 

[Jim March]

Supposedly, the longer 357 chambers reduce velocity a wee bit. From the various ammo chrono tests I've seen, I'd bet good money the average reduction is no more than 20fps if that. I strongly suspect that picking a 357 with a .002" or .003" gap will net you more speed than the same gun in 38 and the more typical .005"/.006" (or worse) gap.

Yet another reason to play with the checkout procedure .

 

[WebHobbit]

Jim when you are dealing with the rather iffy expansion of a .38 snub round that 20 FPS may be VERY important. I say if you plan to carry .38's than you should buy a .38 (a nice tight one, I'll agree).

 

[Jim March]

Well...yes, you're right, the extra speed might be useful.

But: first, I advocate 3" barrels over 2" in J-class/SP101s. Except for pocket carry, which I think these are too big for, the extra inch doesn't hamper concealment. And that solves the velocity problem (with the right ammo!).

Second, even in 2" barrels, the new breed of "tactical light" 357s bridge the gap between 38+P and 357 and are worth considering.

 

[RON in PA]

Re: The 640

640 with no dash, 1990-1995 approx. ,
.38 special +P

640-1, 1995 to current, .357 mag, has beefed-up frame

640-2, cataloged 1998 only, 38 special +P, same beefed-up frame as 640-1, but with shorter, unshrouded barrel.

 

[Eric_A]

Thanks for the replies everyone.

Tbeb, I like the 642 and am also considering it, but this will be used primarily as a second gun while on duty, mostly on the ankle, and I want as little weight as possible.

My intention is to use .38p+ ammo and therefore I was pretty much decided on the 342pd.

But then I began to entertain the thought of the 340pd for the extra strength of the scandium in the frame with a slight price increase.

I don't really feel at this time that using the .357 rounds for practice and qualification is a likely scenario, having spoken to a couple of people about how brutal the .357 rounds supposedly are.

I realize that .38p+ is also high in recoil in this light gun, but I haven't ever been very recoil sensitive (within reason).

So, figuring in the possiblity of a dual round gun I was considering the 340pd, as long as it wouldn't come with a penalty in significant velocity loss with the 38+p that I plan on carrying. 20fps seems acceptable, but 100fps that I had read about in the previously mentioned instance would seem to be too much loss...and in that case I would abandon the 340pd idea.

Thanks for your replies.

 

[Jim March]

No way in HECK is it 100fps. Not in just the difference 'tween 357 and 38. Something like that would just jump out from the stats.

20 sounds about right although again, that's smaller than the velocity diff you'll get with different gaps.

 

[Quantrill]

20 fps is probably not even as much as normal variation from shot to shot. If you have to worry about it, just get a bigger gun. Correct Shot placement has far more to do with your survival than 20 fps. Quantrill