3rd Gen. 40 S&W chamber support

[scwv67]

Does the 40xx series pistols have a fully supported, or close it anyway, chamber?

I've never gotten to inspect one closely and was curious since I've recently tripped over posts on other forums where folks claimed 40xx series guns bulged the cases badly.

Internet BS?

 

[robkarrob]

I think that is way over stated. The bulging came from shooting overpowered ammo, like +P. The chambers are fully supported, but S&W makes the chamber slightly oversized, to help with feeding/extraction. That is why some ammo may bulge, but it is a minimal happening, at best. There are very very few mentions of bulging cases on the M&P Pistol Forum.

I have a Shield 40, and carry +P ammo, and shoot some +P,every trip to the range. I have never had a case bulge. Some of the bulging is from poor quality cases.

Bob

 

[scwv67]

Where are you getting +P .40 S&W? It's my understanding there is no SAAMI spec'd +P.

 

[robkarrob]

Sorry, I use CorBon and I get +P in 9mm and 45 ACP. It is not +P in the 40 S&W, but is loaded to +P specs (526 foot pounds energy). Sorry for the misstatement, as I am aware there is no +P in 40. In my mind, because of the higher loaded specs, I think of it as +P.

Bob

 

[ImjinScout]

I load a lot of .40 and where this issue came from is the early glocks, they had had a chamber that was unsupported and it would bulge the brass. I haven't seen any issues with my 3rd gen though. From what I hear is the 4th gen glocks have a more supported chamber.

 

[scwv67]

Thanks for the info.

 

[armorer951]

chamber support

Attached a couple of photos of the chamber on the 3rd generation .40S&W barrel (4053).....hopefully a pretty good illustration of support provided.

CT

 

[Bozz10mm]

I know the 1006 has a fully supported chamber. I have shot some pretty hot ammo from Underwood and haven't noticed any bulged cases. I would think the 4006 is built the same.

 

[scwv67]

Thanks for the pic!

 

[427mach1]

They may have a fully-supported chamber but my 4013TSW still produces bulged cases even with mild loads. I mic'd the chambers and found it was actually out of spec - the inside diameter was larger than SAAMI dimensions. I sent it to S&W, they sent it back with a new barrel. I mic'd the new barrel and it, too, was out of spec. I asked S&W several times if the chamber was supposed to meet SAAMI specs and never could get a straight answer out of them. Their final reply was that the pistol was out of production, they only had a limited supply of barrels, and they were probably all the same dimensions due to the age of the machines used to produce them.

 

[scwv67]

They may have a fully-supported chamber but my 4013TSW still produces bulged cases even with mild loads. I mic'd the chambers and found it was actually out of spec - the inside diameter was larger than SAAMI dimensions. I sent it to S&W, they sent it back with a new barrel. I mic'd the new barrel and it, too, was out of spec. I asked S&W several times if the chamber was supposed to meet SAAMI specs and never could get a straight answer out of them. Their final reply was that the pistol was out of production, they only had a limited supply of barrels, and they were probably all the same dimensions due to the age of the machines used to produce them.

It's my understanding the diameters of chambers on some makes are generously sized to help ensure reliable feeding. Maybe this was the case with 3rd Gen guns? Wonder if the newer M&P's are the same.

 

[Smoke]

and they were probably all the same dimensions due to the age of the machines used to produce them.

That is a (insert unacceptable expletive of choice here) answer. I've worked on Hardinge lathes that were at least 60 years old and they held tolerance perfectly

 

[427mach1]

It's my understanding the diameters of chambers on some makes are generously sized to help ensure reliable feeding. Maybe this was the case with 3rd Gen guns? Wonder if the newer M&P's are the same.

I also checked the chamber in my 9mm M&P and found it to be within spec. Then I checked my Ruger P944 40 cal and it, too, was within spec.

 

[427mach1]

That is a (insert unacceptable expletive of choice here) answer. I've worked on Hardinge lathes that were at least 60 years old and they held tolerance perfectly

I agree. I'm an aerospace engineer with a lot of experience inspecting/accepting wind tunnel models, am familiar with most aspects of the machining/manufacturing processes and I found this explanation "lacking". After the gun was returned, I purchased a spare barrel from Brownells and the chamber on it was large, too. The gun shoots very well, it just makes reloading a little more difficult and probably affects the number of reloads I will be able to get out of the brass.

 

[BLUEDOT37]

4056TSW chambers

They may have a fully-supported chamber but my 4013TSW still produces bulged cases even with mild loads. I mic'd the chambers and found it was actually out of spec - the inside diameter was larger than SAAMI dimensions...

I bought a 4006 (mfd. 1990) & a 4056TSW (mfd. ~1998) last fall at the Wannemacher gun show. I checked the chambers when I got home and, like yours, the 4056's chamber was .008" larger at the breech end than the 4006. The 4006 has .003" taper from the chamber's front/muzzle to the back/breech (.426 to .429") while the 4056 has almost .010" taper (.4275 to .4370"), which is out of SAAMI specs. Both guns feed/shoot fine but the 4056's fired cases are noticeably expanded, but I wouldn't quit call them bulged & they feel normal when I resize them. Apparently S&W had an issue with some of these. What year was your gun made?

.

 

[427mach1]

Bluedot, My 4013 serial number is very close to your 4056 -approximately MSE0300, built November of 1996; an early production date. Yours is probably more likely a 1997 production. I don't have the dimensions in front of me but your chamber dimensions sound very similar to what I found.