Supported or Not Supported...(Terminology?)

[BCB]

I hear this mentioned from time to time…

I sort of understand it as I think it concerns whether the web area of a case has metal under it to completely contact the entire case or not…

Anyone give a better description of this and maybe indicate how to tell one way or the other with a quick glance if that is possible?...

Thanks…BCB

[Nobade]

Well, if you take an empty case and measure where the solid part of the head starts you can mark that point on the outside of the case. Then drop it into the chamber of the barrel you are wondering about you will be able to see if that mark is inside the chamber or not.

Headspace gauges also are normally made to show where that point is. If you have one in the caliber you are interested in, you can use it in the same manner.

The main thing is you want solid steel supporting the very thin walls of the cartridge case to hold it together. If a barrel has been throated too deep or just made wrong, the case will bulge at that point and sometimes blow through. Glocks and maybe some other semi auto pistols are famous for this. Also 1911s that people try to throat for wadcutters when they don't know what they are doing.

-Nobade

[MtGun44]

Are you referring to the 1911 in .38 Super? This is the most common use of this term
that I am aware of. Basically, a normal Colt type barrel in a 1911 has an area at the feed
ramp where the brass case is not fully supported with steel. Aftermarket barrels that
have an integral feed ramp, and require cutting a large slot into the frame, are referred
to as "fully supported barrels" because the integral feed ramp allows a significant change
in the feed ramp and chamber mouth dimensions and allows full support so that the
pressures can be raised a bunch, with the goal of easily making "major caliber" with the
.38 Super. Unsupported chambers with very hot loads and weak brass can have a
nasty "smile" blowout, which can be pretty nasty.

That said, I easily "made major" with an unsupported chamber in my 1911, but had to
avoid Winchester cases. Rem +P, PMC and Midway cases all worked fine and could be
reloaded until the headstamp was battered off the case without problems.

Bill

[Catshooter]

Does this pic help?

http://i379.photobucket.com/albums/oo235/Catshooter45/Items%20for%20sale/IMG_6345_zps8b5a709e.jpg

This shows a sectioned 9mm case in a factory Glock 19 barrel. Notice the thickness of the brass just where the feed ramp touches it.

Although I have no pic of it, the feed ramp of the barrel of my S&W Shorty 45 actually ends right a the beginning of the rim of the case. That is an example of a fully supported case.

Hope this helps.


Cat

[BCB]

Does this pic help?

http://i379.photobucket.com/albums/oo235/Catshooter45/Items%20for%20sale/IMG_6345_zps8b5a709e.jpg

This shows a sectioned 9mm case in a factory Glock 19 barrel. Notice the thickness of the brass just where the feed ramp touches it.

Although I have no pic of it, the feed ramp of the barrel of my S&W Shorty 45 actually ends right a the beginning of the rim of the case. That is an example of a fully supported case.

Hope this helps.


Cat

So, that case is not supported?...

[BCB]

What brought this question on was my buddy got a new Taurus 45 acp. Don’t know the model as I really am not into the semi-handguns, although I do have a Makarov—but, it is just a “beater”…

He asked if I knew anything about a case being supported or not…

Well, that is why I asked the question…

It would seem that the Taurus probably is not supported?...

Thanks…BCB

[MtGun44]

As a general rule, if there is a substantial feed ramp in the bottom of the barrel,
which cuts away any significant part of the cylindrical portion of the chamber
then this area is unsupported. This is not an issue with sane pressures, only when
pushing the cartridge to the extreme limits. This was done in IPSC competition for
a competitive advantage and to meet a measured velocity * wt requirement.

For normal loading, I think pushing the limits is pretty foolish and can hurt yourself
or damage the gun for no good reason. Even in the event of competition, the whole
thing was pretty crazy, and I never pushed my loads to the limit - got hundreds
of loadings. I did become aware that in this application, Win brass was far weaker
than most other brands.

If you stick to normal loading manual loads, this is a non-issue. Especially with unmodified
guns.
Bill

[BD]

Just for the record, using .45acp you can make the current 165 "Power Factor" for IDPA, IPSC or USPSA with any 200 grain boolit going over 825fps, or 230 grainer doing 720 fps. These are not "hot" loads in a .45acp by any means, and any current, unmodified factory .45acp barrel will adequately support the brass at these pressure levels for many loadings. The only factory barrel case support issue I'm aware of was in the early .40 glocks as a result of an over generous feed ramp cut in combination with the higher chamber pressure of the .40 S&W cartridge. I assume this was address in the later versions as I don't find that bulged brass laying around any longer.
BD

[Nobade]

The only issue I am aware of with Taurus 45 ACP pistols is the groove diameter in the barrels. Get him to slug it before he shoots it with boolits. He may be surprised at how big they need to be.

-Nobade

[BCB]

The only issue I am aware of with Taurus 45 ACP pistols is the groove diameter in the barrels. Get him to slug it before he shoots it with boolits. He may be surprised at how big they need to be.

-Nobade

I'll mention it to him, but I suspect he will only be shooting jacketed bullets, and probably not many of those either...

Thank...BCB

[W.R.Buchanan]

A revolver cylinder is an example of a fully supported case.

However, most modern Auto Pistols have unsupported chambers to varying degrees. The place where this is the greatest is at the junction of the feed ramp and the chamber. Usually it is an area about the size of the moon on your smaller fingernails.

This whole thing revolves around the comprimise that has to be made to feed a cartridge into the chamber at a relatively high angle as it is stripped from the magazine. Since the cartridges used are generally pretty short they must be stripped and introduced into the chamber in a very short amount of space. Hence the high angle and thus the feed ramp being pushed further forward.

As far as the bulged brass is concerned that is more about generous chamber dimensions used to facilitate reliable feeding. Most modern Auto Pistols in .40S&W have generous chambers and this coupled with the higher pressures generated by that cartridge leads to cases bulged around the base. However if you insist on running hot reloads in your .40S&W Glock there is a good chance you will experience severly bulged cases and these will have that liitle unsupported area of the case swaged down into the feed ramp area. In really severe cases it will blow the side out of the case.

This is called a "Ka-Boom." Avoid the Ka-Boom! Don't reload .40S&W hot. Stay with nice conservative midrange loads and you'll be fine. If you feel you need to shoot hot loads then go buy factory hot loads.

Here's a pic of a Ka-Boomed case I found at the range once.

9MM run in the same pressure range but the brass is proportionally heavier so it doesn't seem to be a problem with 9MM.

.45 ACP is at a considerably lower pressure range so the bulge doesn't seem to show up much there either.

Randy

[Catshooter]

For an answer to what's supported, WR Buchanan is correct. S&W 3rd generation 45s is another example.

Look and the cut out of the case. See how it tapers? A really poorly supported chamber will have the thinnest portion of the case unsupported. The thicker the brass that is supported, the better the support. When the case is supported all the way out to the rim then obviously then things are set up as strong as they can be.

The brass, under ideal conditions only serves two purposes, to hold the other components together and to seal the chamber under firing. It doesn't do too well at containing the gas pressures generated by firing without help from some steel.

That help?


Cat

[MtGun44]

Old IPSC Major was 180,000 so a 148 gr SWC had to be traveling at
MORE than 1216 fps on the average to be legal. This is right out on
the edge of the .38 Super loading manuals, but with W571/HS7 it
could be safely done in an "unsupported chamber" with most brass,
just not with Win brass. VERY near the edge and not something that
is necessary with the 165K power factor now.

With normal loads this is not usually an issue. Blowing out at the
unsupported are usually involves the failure in a double charge situation.

Bill

[casterofboolits]

I first made "major" in a standard unsupported Colt barrel with the Magma 38S-160-RNBB loaded over BlueDot. I later went to a Saeco 38S-158-SWCBB designed by Wilson in a supported barrel. The load was super accurate and fed like it was on rails. But, I had a hell of a pistol smith That knew what he was doing with a 38 Super 1911.

[nicholst55]

FWIW, Glock redesigned their .40 S&W chambers and barrels in 2005-2006, IIRC. If you have a Gen4 Glock in .40 S&W, it has the newer style chamber that does a better job of supporting the case and minimizes or eliminates the dreaded Glock bulge. My Gen4 G22 does not perceptibly bulge the brass, even with max loads. Then again, it ain't hot here in Yuma yet.

If you're buying and reloading range brass, you have no control over what it was originally fired in. I advise a close examination and a Redding GRX die.