158 grain magnums ONLY in 340 M&P

[SasquatchBigBore]

Hello all, I recently shot my 340 M&P at the range for the first time while testing various brands of 158 grain magnum loads. It was my idea of fun. YMMV.

From what I have read online it seems most would shoot 38's ranging from +P ammo in the 120-158 grain range and the occasional half box of magnums. Is this due mainly because the structural integrity of the firearm would be compromised only shooting magnum loads?

I understand the consensus of the felt recoil being too abusive and/or the almost guaranteed possibility of developing a flinch. I also see many state the firearm for being a "carry a lot, shoot little" tool for mainly backup gun duty.

Of these points I have no contention. My main concern is finding any evidence of it being unsafe to fire a steady diet of ONLY 158 grain factory made magnum ammo. I understand that it is naive to think any firearm capable of shooting such rounds through a lightweight frame is fully capable of handling the abuse simply because it is stamped 357 magnum on the barrel. However, I would like to know if anyone has inquired from the manufacturer that shooting these rounds pose an immenent risk to the user.

TL;DR: Will 158 gr magnums make my 340 M&P catastrophically fail and make me left-handed permanently?

(A thousand apologies if this has been discussed to death)

 

[press-1-for-english]

You can always call S&W customer service and get the answer straight from the horses' mouth.

 

[wheelyfun66]

With ammo and component prices what they are... your bank account may run dry before the Scandium frame decides it has had all it can take?!

I would think that with a very steady diet of magnums through a 340 M&P, it may develop wear here and there... but catastrophic failure seems unlikely, to me (though, I'm no engineer, ha!)

 

[murphydog]

With ammo and component prices what they are... your bank account may run dry before the Scandium frame decides it has had all it can take?!

I would think that with a very steady diet of magnums through a 340 M&P, it may develop wear here and there... but catastrophic failure seems unlikely, to me (though, I'm no engineer, ha!)

Welcome!

I agree with the above post. My guess is the S & W engineers designed the frame and cylinder to last several thousand rounds of full power .357 loads. Hardly anyone will push those theoretical limits.

As you noted, the main reason for most users promoting .38 +P or lighter .357s is not so much mechanical issues than the perceived need for less than full power, the ability for quick follow up shots...and major discomfort.

 

[colt_saa]

Welcome to the Forum

My 340 has gone through 5+ cases of full magnum Remington 158 JHPs so far

Probably a little over half of it shot by me with the remaining being shot by associates who wanted to try it or qualify with it

After running out of the 158 stockpile it has had an additional thousand or so full magnums from other manufacturers in various projectile weights over the many years that I have owned and carried it

 

[chief38]

I have personally never carried a J frame loaded with Magnums. Wether or not the accelerated wear is a factor, I do not like the slower follow up shots, the excessive muzzle flash and recoil, and last but not least, most of the advantages of a .357 magnum are not realized out of a 1 7/8" barrel.

I carried Buffalo Bore 38 special +P 158 grain SWCHP-GC which out of a Chief's Special with a 1.875 bbl. will do 1,025 fps (personally chronographed many times). IMHO, that is as good or better than a 158 grain magnum will do out of the same bbl. without all the recoil, noice and muzzle flash.

 

[ChiefTJS]

I fired exactly 5 magnums through my 340 M&P and I can pretty much guarantee that will be the extent of its magnum career. I'm a wimp and use it as a .38spl or 9mm (second cylinder) only. Still absolutely love the gun though.

 

[mike campbell]

I suspect you and the one other person who shoots 158 magnums in their M&P340 will have to get together and share tales. I very much doubt any manufacturer will offer any real info about "catastrophic" failure of their product.

Personally, I don't shoot 158 magnums out of my Python, much less my 340. It's always been my understanding that the 125HP was king when the LEO's carried .357's. My EDC load for the 340 is the Remington 125 Golden Saber @ 1150 fps.

I end every 50-round, 38 special practice session by firing one cylinder full of 125HP magnums loaded to match my factory carry load. Those last 5 always go into the same fist-sized group the 38spls made at 30 feet.

Occasionally, I do OK with a second cylinder of magnums. After that, I'd have....uh....issues. So I don't bother. Don't want any bad memories.

 

[just plain joe]

Wish I could speak as to specific round counts in this answer, but I can't. In December 2004 I purchased a 340PD. I carried this as an off-duty weapon until November 2018. I qualified with this weapon twice a year. I fired less than twenty-five rounds of 125 grain jacketed hollow point Federal .357 Magnums through the revolver. All of the remainder of ammunition used for practice and qualification was Speer 135 grain jacketed hollow point .38 Special +P. My agency supplied and specified this for off-duty/back-up weapons.

In November 2018 I discovered a crack in the frame directly beneath the forcing cone. I contacted Smith & Wesson. It was shipped back to them on their dime. Shortly thereafter, they notified me that they would be replacing my revolver and did so.

I mention all this to illustrate that your can experience failures with anything that is man-made, be it a firearm, motor vehicle, or the computer that you are utilizing to read this forum.

Personally, I would have no problem utilizing 158 grain jacketed hollow point .357 Magnum ammunition in my 340 PD. I don't, because aside from being difficult to control in a combat situation, it is painful.

YMMV

JPJ

 

[CajunBass]

Heck, I think 158 grain 38 P+ kick hard enough in a 642-2. I can't imagine shooting a 340 with 357 magnum ammo.

 

[Brian Parrish]

How long?

Wish I could speak as to specific round counts in this answer, but I can't. In December 2004 I purchased a 340PD. I carried this as an off-duty weapon until November 2018. I qualified with this weapon twice a year. I fired less than twenty-five rounds of 125 grain jacketed hollow point Federal .357 Magnums through the revolver. All of the remainder of ammunition used for practice and qualification was Speer 135 grain jacketed hollow point .38 Special +P. My agency supplied and specified this for off-duty/back-up weapons.

In November 2018 I discovered a crack in the frame directly beneath the forcing cone. I contacted Smith & Wesson. It was shipped back to them on their dime. Shortly thereafter, they notified me that they would be replacing my revolver and did so.

I mention all this to illustrate that your can experience failures with anything that is man-made, be it a firearm, motor vehicle, or the computer that you are utilizing to read this forum.

Personally, I would have no problem utilizing 158 grain jacketed hollow point .357 Magnum ammunition in my 340 PD. I don't, because aside from being difficult to control in a combat situation, it is painful.

YMMV

JPJ

Is it possible the crack was there for a while before you found it? I am hearing of people who continue to shoot their cracked airweights, sometimes using Loctite.

Kind Regards JPJ!
BrianD

 

[chief38]

When people look at ballistic charts, they sometimes forget that the .357 magnums are normally tested from 6" to 10" barrels! Most Company's list their 357 magnum velocities of a 158 grain bullets from a 6" barrel at 1,240 fps. However, when shot from a 1 7/8" barrel, usually will drop below 1,000 fps!!!! The 357 Magnum was never designed for a 2" barreled gun!

The Buffalo Bore +P, 38 special 158 grain LSWCHP-GC actually does 1,025 fps out of that same 1 7/8" barrel. I am not just quoting printed spec's here, I have chronographed this many times. Hence, if you are using a 2" Chief's Special you are actually better off with the BB 38 Spl. +P loading IF USING 158 grain bullets.

Not only will you save your revolver from excessive wear and tear, but you will actually lessen recoil, muzzle flash while increasing the speed of follow up shots and accuracy.

Your gun, your life, your choice.

 

[Breakaway500]

Colin Chapman (founder of Lotus cars) once stated any car that is capable of driving one lap after the finish line is too heavy.

That being said..if I were to feed a handgun .357 magnums,I would not trust a 340 to be alive at the end of the 24hrs of Lemans (Or my hands for that matter) I would use a model 27 for that purpose.

 

[stansdds]

I have avoided the aluminum and scandium lightweight revolvers, but I do have an all-stainless J-frame. It's pretty stout with full power 357 ammo, stout enough that I now load it with 38 Special +P. I don't think I'd want to shoot any full power 357 ammo in one of the lightweight J-frames.

 

[.455_Hunter]

When people look at ballistic charts, they sometimes forget that the .357 magnums are normally tested from 6" to 10" barrels! Most Company's list their 357 magnum velocities of a 158 grain bullets from a 6" barrel at 1,240 fps. However, when shot from a 1 7/8" barrel, usually will drop below 1,000 fps!!!! The 357 Magnum was never designed for a 2" barreled gun!

The Buffalo Bore +P, 38 special 158 grain LSWCHP-GC actually does 1,025 fps out of that same 1 7/8" barrel. I am not just quoting printed spec's here, I have chronographed this many times. Hence, if you are using a 2" Chief's Special you are actually better off with the BB 38 Spl. +P loading IF USING 158 grain bullets.

Since at least the late 80's, most companies list .357 Mag ballistics from a 4" vented test barrel. I agree that in earlier decades the test barrels were less realistic.

 

[Brian Parrish]

Just Raises Another ?

When people look at ballistic charts, they sometimes forget that the .357 magnums are normally tested from 6" to 10" barrels! Most Company's list their 357 magnum velocities of a 158 grain bullets from a 6" barrel at 1,240 fps. However, when shot from a 1 7/8" barrel, usually will drop below 1,000 fps!!!! The 357 Magnum was never designed for a 2" barreled gun!

The Buffalo Bore +P, 38 special 158 grain LSWCHP-GC actually does 1,025 fps out of that same 1 7/8" barrel. I am not just quoting printed spec's here, I have chronographed this many times. Hence, if you are using a 2" Chief's Special you are actually better off with the BB 38 Spl. +P loading IF USING 158 grain bullets.

Not only will you save your revolver from excessive wear and tear, but you will actually lessen recoil, muzzle flash while increasing the speed of follow up shots and accuracy.

Your gun, your life, your choice.

I can see what you are saying, and now the question is, How many of dem Buffalo Bores can we shoot?

 

[chief38]

I can see what you are saying, and now the question is, How many of dem Buffalo Bores can we shoot?

First of all they are still a handful in a J Frame - even though they are .38 specials and not Magnums. Secondly, the cost for a box of 20 rounds is up there! Thirdly, even though they are +P .38 specials, they still pack a hell of a punch and although they aren't Magnums, they too will accelerate wear to some extent, so I'd not shoot them on any regular basis.

The sole purpose of these rounds (as I see it) are for self defense only so after the initial familiarity with them, I would dedicate the remainder as self defense only loads. Maybe shoot a cylinder full once a year just to keep up with their characteristics.

 

[THE PILGRIM]

Have shot a few 357s in my J Frames.
But I usually carry 38 + P in my Js.
If I Felt the need to go 357 in the J, would probably go with the 649.

 

[BLUEDOT37]

Most Company's list their 357 magnum velocities of a 158 grain bullets from a 6" barrel at 1,240 fps.
However, when shot from a 1 7/8" barrel, usually will drop below 1,000 fps!!!!
The 357 Magnum was never designed for a 2" barreled gun!

The Buffalo Bore +P, 38 special 158 grain LSWCHP-GC actually does 1,025 fps out of that same 1 7/8" barrel.
Hence, if you are using a 2" Chief's Special you are actually better off with the BB 38 Spl. +P loading IF USING 158 grain bullets.

Hopefully you're not trying to say that a max (+P) 38 Spcl load is faster than a max 357 MAG load using the same bullet (i.e. 158gr LSWC-HP-GC)?

Was the 38 Spcl "designed" for 2" barrels? No, neither was the 357 but that doesn't mean that makes it slower.

Lead bullets are faster, in any given barrel, than a jacketed bullet if loaded the same.

Buffalo Bore doesn't have a 357 loaded with the same 158gr LSWC-HP-GC bullet that I see.

The closest I see is the 158JHP which is a Tactical Low Flash load (translated not a max 357 load) that reaches 1015fps from a 1-7/8 bbl.

A lead bullet would likely gain 75-100fps.

There's no question that 357s loaded with slow magnum powder give vicious muzzle blasts but max loads with slow powder still give higher velocity than max loads with faster powder, even in short barrels.

I don't have a problem with people wanting to use 38 Spcl +Ps in their 357 but don't imply 38s are faster than 357s because if you do it's not an apples to apples comparison.

.

 

[just plain joe]

Brian D:

It's possible the crack could have been there for a while, but unlikely. When I clean my revolvers I pay particular attention to the cylinder face/forcing cone areas due to carbon buildup. I like to think that I would have been observant enough.

If memory serves me, S & W experienced a problem with the scandium frames. Others may know more though.

As for continued firing of the weapon with a cracked frame, that flies in the face of common sense.