Supported chambers

[hogan]

What is a supported chamber? I have a new CZ2075 that I will be loading 40S&W.
I have read that with the 40 that the gun should have a supported chamber.
I realize it is a high pressure round and I am guessing why the supported chamber.

So what is a supported chamber and does anybody know if the chamber in my CZ is supported?

 

[LaneP]

"Unsupported" = a barrel chamber that is generously relieved (aka "throated"), in order to minimize feeding hang up and maximize chambering reliability.

Years ago it was generally attributed to Glock, in their zeal to provide an extremely reliable feeding pistol, and most often seemed to center around their model 22 .40 cal offering.

If you look at the pic below, you'll notice the barrel on the left (an OEM Glock G22 barrel from the mid-90's) is much more generously throated, and exposes more of the case wall ahead of the solid web:

The barrel on the right is a Wilson Match replacement barrel for the G22 that is much tighter and more supportive of the case (aka "supported").

The difference between shooting the two is noticeable when examining the fired cases. The barrel with less case support will tend to have larger, swelled cases.

I have not heard of this being an issue with any other maker aside from the early generation Glocks. There is no evidence I've seen that it is of any concern today, considering makers have learned a valuable lesson from that era and have learned to throat barrels such that they function very reliably while still providing the necessary case support.

 

[sourdough44]

As posted, it was more of an issue with early Glocks. I have several Gen III Glocks in 40 and have closely compared chamber support to some H&K's I have. They look just about the same, no significant difference.

You also mention you will be reloading for the 40. In that case you are in control. The 40 can be a high pressure round. Once I get past reliable cycling issues I don't feel the need to get right to a max loading. Yes, for 'woods carry' or self defense I may get to a bit hgher range. Just look towards a medium speed powder with reasonable charges & there should be no problems.

 

[The Blackhawk Kid]

Well, the 40 headspaces on the case mouth like the 38 super. I had to adjust my Full length resizing die down to resize my brass. I also have Wilson barrels in my Glocks. I'm not a fan of the 40 S&W and no longer have one. JMHO

 

[Cholo]

hogan, the .40 S&W is a great caliber, but it has its detractors. I don't care. I think because of the initial Glock problems, other manufactures used tighter chambers. Make sure you keep your case mouths at .420, or even slightly less. While a .45 ACP is forgiving to a point, a .40 S&W isn't. Enjoy!

 

[hogan]

You guys are the greatest. Your input is very much appreciated.

 

[Jimbo357mag]

Those bulges on the side of the cases are sometimes called smilies. There is a push through gizmo for the Lee FCD (factory crimp die) that takes the bulges out.

http://www.midwayusa.com/product/882261/lee-bulge-buster-base-sizing-kit-380-auto-40-s-and-w-45-acp?cm_vc=ProductFinding

 

[WESHOOT2]

I note I've seen generous chambers from most common brands; it's now more about 'the one in hand'.

 

[WESHOOT2]

I've seen, handled, loaded for, shot, and examined a fair number :wink: of 40-chambered guns.
Including all-too-many blowed-up 40 S&W-chambered guns.

 

[Rick Courtright]

Hi,

I don't own a .40 S&W, but have acquired a moderate amount of range brass for it, anticipating the day when a couple of buddies are gonna twist my arm into loading some for them and eventually teaching them to do it themselves. About half of it (500 or so?) has the Glock firing pin mark, and there's a slight bulge above the base, but nothing like the "Glock smile" I've seen in the past, so I figure newer model guns were involved.

I've heard stories going both ways about the wisdom of shooting "Glock fired" brass in other guns that do have better supported chambers. I've only loaded light stuff for these guys in the past and plan to continue that practice. Yay or nay?

Rick C

 

[WESHOOT2]

I say if it resizes properly with a common sizing die it's good to go for 'range'-level ammo. Doesn't matter what chamber it came from....

If you start noting ammo NOT fitting your case gauge, examine that brass batch carefully.


My personal 40 S&W barrel (down to just one) is an EAA 'match' barrel (purchased in the mid-nineties); its chamber is fairly 'tight'. No sins pass it. It's my tightest 40 gauge.

 

[Rick Courtright]

I say if it resizes properly with a common sizing die it's good to go for 'range'-level ammo. Doesn't matter what chamber it came from....

Hi,

Thanks! I'll watch carefully when the time comes to start this next part of my "education!"

Rick C

 

[Beaver Creek]

What is a supported chamber? I have a new CZ2075 that I will be loading 40S&W.
I have read that with the 40 that the gun should have a supported chamber.
I realize it is a high pressure round and I am guessing why the supported chamber.

So what is a supported chamber and does anybody know if the chamber in my CZ is supported?

Check with CZ-USA. So far as I know, every pistol they've made in .40 S&W provides proper support of the case-head.

One thing about "bulge-buster" dies. The only thing that gets corrected is cosmetic. While these types of dies will return the case body to normal appearance, they can't do a thing about the fact that the case has been structurally stressed and weakened in the bulged area in pistols without adequate support of the case-head. Even though the bulge-buster returned it to spec dimensions, if that previously bulged area ends up in the 6 o'clock position again with that previously bulged area directly over the feedramp and unsupported area. Bad things can still occurr.

The simple is to buy pistols that adequately support the case-head. Glock has improved, but not to the point that I'd want to own one in .40 S&W. THis doesn't just apply to the G22, the same condition exists with all of their .40 S&W chambered pistols.

Buy an SR40 and you want have anything to worry about! :wink:

Right on!!! I learned this the hard way when I was a licensed ammo mfg. I was buying .40 cases from an indoor police range. Out of several 100K loads I had reports of 3 blowouts. All were from early Glocks. Fortunately there were no injuries and nor serious gun damage. I recalled all 40's that I possibly could and it took me over a year to conclude exactly what this post indicates. If a shooter was unlucky enough to chamber a previously Glock fired case in exactly the same rotation there was a very good chance of a blow-out. From there a warning label went on every box "RISK OF SERIOUS INJURY - NOT TO BE FIRED IN GLOCKS".

 

[WESHOOT2]

Except I got my once-fired 40 S&W cases fired from Berettas......

 

[WESHOOT2]

And the cop-ammo I manufactured got fired mostly in Glocks.

(They had to make dummy rds for failure drills, because there weren't any ever from my ammo; gotta love it).