I purchased an alpha wolf barrel in 357Sig for my shield 40 to see how it would function while shooting 357Sig rounds out of it. I found out yesterday that when I loaded my magazine with 357 Sig speer gold dot(53918) I obtained a jam because it failed to eject the spent case before trying to feed a new round. I know I would not be able to carry this setup for self defense since it is not reliable although it has been 100% reliable in the original configuation with the 40S&W barrel.

Did it extract the casing from the chamber? Or did the casing extract and fail to eject?

You put the correct ammunition into the magazine that corresponded to the new barrel.

You had a problem with that 1st round firing...

You have since decided there is no chance this new format will be reliable...

Good luck!

Cheers!

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Sit Reloader Sentiret

Could be the lighter much faster 357sig is over running the ablity for the pistol to function with the 357sig. You might find the same issue with shooting underwood 135gr or 155grm in the 40sw barrel , I had a buddy some years ago that tried a 155gr underwood load that in my 4" pistol I carry managed 1321fps in a kahr tp40 and was my standard carry load but in his 1/2" shoorter barrel P4 it would not cycle .

Since the mags and cartridge rims on the .40/.357 Sig are the same my only guess would be powder charge.

My 5" .40 M&P runs flawlessly with either caliber 5" barrel AND with the comped 6" .357 Sig barrel.

It sounds like an "Under-recoil", the slide isn't traveling back all the way before starting forward again.

1: It could be that the lighter bullet of the .357 Sig isn't generating enough recoil energy.

2: It could be the ammunition you selected is somewhat under powered. If you reloaded it you may want to bump up your charge weight 1-2 tenths of a grain until the slide recoils fully.

3: You may try replacing the recoil spring with one of a couple pounds less weight tan the spring in the gun for .40 S&W.

An example from my own experience. Several years ago I bought a new condition Walther P-1, the aluminum framed civilian version of the German military P-38. When I took it out first time the gun would under-recoil with a 124 grain bullet and a full book charge of Unique. The gun would not recoil far enough for the slide to lock open on the last round, a classic under-recoil. There is no problem with the bullet weight, or Unique in 9mm Parabellum! Since changing recoil springs in the P-1 is not a practical solution the only thing to do was increase the powder charge. I had to increase the load in .1 grain increments from the book load of 5.7 grains as I recall, all the way to 6.2 grains before there was adequate recoil energy to get the slide all the way to allow the slide stop to lock the slide open! Chronographed muzzle velocity was still within normal range for the cartridge and bullet weight, so there were no concerns with pressure!

There are three solutions for you, take your pick. I would start with the recoil spring or changing ammunition.

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Gunsmithing since 1961

Slide may be traveling back correctly But at a faster pace and mags may not be up to the task . You can buy wolf +5% mag springs . Heavy recoil springs are limited and costlier .

I never found the fasintaion of the 357sig when a 150gr or 155gr 40sw from underwood or buffalo bore simply covers anything the 357sig could ever do . Buy a box of these hotter loads and see if your 40sw barrel will even cycle them or the faster 135gr that will exceed 1400fps from a 4" barrel . Heck none of these hotter handgun cartridges are garOteed one shot man stoppers .

Groo here
Try shooting one handed..
I have seen to many shooters who use that "Thumb High " hold ride the slide and throw the gun out of time.
This will cause all sorts of problems.
Due to this I will NEVER use a thumb high hold on ANY gun not modified for it.
PS I have a Shield with a Remsport 357sig barrel.
It shoots very well...

Bigpoppa, was a solution found? I just ordered myself a barrel and then found this post. Hope I don't have the same issue.

Thanks,

Rosewood

I have shot top end loads in my shield and I get "pregnant" cases (bulged). I emailed S&W and they said it was within spec. I think it is partially unsupported (like the old Glock 40s) so I am hesitant to shoot hot loads (even factory) from the Shield. I own multiple S&W 40s and this is the only one to ever have this issue. I am hoping the 357 sig barrel will be better supported and figured it would be worth a try. Yeah, I know, I could have bought a new 40 barrel, but thought I would try the sig just because.

Rosewood

I shoot 40 S&W, 357 SIG & 9mm out of my M&P 40s without any problems... That's an M& P 1.0 4.25" PC C.O.R.E., a FS 1.O with a 4.25" & a (2.0) 5.0" slide and a 1.0 Compact 3.6".

Everything has worked reliably (as long as there is the correct barrel, ammo and magazine, of course!) using the standard S&W factory RSAs.

This is with 98+% of the ammo being my reloads, which can run from mild (i.e., 357 SIG 125gr @ 1,200 fps) to WILD! (But not quite as wild as the Underwood or Buffalo Bore stuff...)

Just my personal experience...

Cheers!

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Sit Reloader Sentiret

I have been eyeballing a 357 sig barrel for my 5" M&P. I am getting 1430 FPS with a 124 XTP in my P229 with a 3.9" barrel (using Longshot powder). Bet I would hit over 1500FPS in a 5". I am getting 1180 FPS with 180gr XTP in the 5" 40 barrel using Longshot, sucker is getting into 10mm territory. No pressure signs either.

Rosewood

MY 40sw's are full size s&w and I use a heavier 20lb recoil spring . One pistol is a 12 year old 4.25 model that originally had 16lb recoil spring ! My other is a 5" 2.0 PC model and nether bulge brass . But lite recoil springs and hot load do not work well and chambers lacking support just compound the problem . Early 40sw glocks were far worse for chamber fit .

I run some 135gr 40sw underwood loads just to try and velocity was 1438fps in the s&w 4.25" but never cared for the lite bullet when compared to the Gold Dot from underwood . Thats one ammo I have taken a couple deer with over the years when they showed up under my climbing stand some 20 feet below . The gold dot bullets performed very well and both pass thru with 16 to 17" of tissue damage . I practice ammo is home rolled ammo mostly coated swc 155gr FN Xtreme and a near max of longshot and mid 1200fps .But there will be a day I 'm probably change to slightly milder 165gr hst for personal defense

I have M&P 357Sig Compact 1.0.
Bought S&W 9mm & 40 S&W barrels.
Never had a problem. One failure to eject when daughter "limp wristed" it.