Brass bulge...how much is too much?

[Texashogman]

What weight buffer? "Full house" and suppressed, you are suposed to run the 8 oz buffer
5 ps comes with the gun, and 3 oz is for light loads

It's a radial delayed blowback system so I would try a heavier buffer if you arent already

[The_Shadow]

The barrel support seems to have a bunch of unsupported area above the case web...it may be the nature of the bolt locking lug area with the Banshee and barrels.
I remember Mudrush (of SwampFox ammo) mentioning that the longer barrels of the pistols caused case bulges because the recoil cycle was happening while pressures were still high.
What about the Banshee, it is said to be a "Delayed Blow Back" system.  I would check into stronger spring pressure at lock up to see if that would improve brass conditions with added dwell time.

That being said you may not want to reused those brass loaded to the upper end of performance.
You may see a case separation if they are reused with high end reloads.

Looking over the resized cases, they seem to be getting worked down to a good size, but they may also get work hardened fairly quickly.  As such the brass may have interior cracks or become brittle where they could do a case head separation, which might leave the upper section of the casing inside the chamber.  Something to be mindful of!

If you want a different solution, try cutting down some 6.8SPC brass to load as the web is thicker, you may need to adjust the powder charge but it may provide more reusable brass life.

[Mike D]

A random selection of reload and factory ammo with Banshee Bulging at the base:



Some are swollen to the point that they cannot be resized. Others run through the dies fine.

Here are some resized and bulge-busted:



Close-up:



I'm setting aside once-fired Starline brass with Banshee Bulge, and if they resize fine I'll reload them and see what happens with the brass. Multi-loaded mixed brass with bulging goes in the trash.

Any input?

Wow!


Sent from my iPhone using Tapatalk Pro

[Muskrat]

Thanks everyone!

I'm using the 8oz buffer even though most of my loads don't meet the power factor to "require" it.

I'm not at all sure that the swelling is due to premature bolt movement...I think there's just that much unsupported chamber where the bolt face covers the base of the cartridge. Bolt movement may play a part, however. While not pictured, some brass bulges so dramatically that it will not go through a sizing die.

As you can see from the pictures, some of those pieces of brass have been reloaded a LOT. They go in the garbage if they get a visible swell...most of them are A-USA, which probably should have gone in the garbage while new. S&B brass is holding up remarkably well, btw.

I'll see what happens with new Starline brass and resizing, and look into the 6.8SPC brass as an option. The Banshee is nothing but a range toy for me, so if I get a case head separation it's just going to mean the premature end of a shooting session. I mean, I keep it handy around the house, but then it's loaded with something other than reloaded range ammo...

[Texashogman]

Have you checked the length of the brass? The bulged brass pics look like the mouth of the case might be rolled in, indicating that the brass might be too long or the chamber too short--- or ot could just be an optical illusion.

Have you contacted the manu regarding the issue? They would probably tell. You not to run reloads though if you brought it up

[Muskrat]

Brass is not too long, but that's a good idea.

CMMG is aware of the issue and, when asked, will provide a boiler plate response to the effect of "we're aware of the issue....switch to different ammo...swelling is safe but we recommend avoiding ammo that swells...etc.." They have nothing to say about reloading ammo that's been shot through a Banshee, which makes sense.

Basically the Banshee swells brass (sometimes dramatically) with hot loads, period. Common sense says that some of that brass gets thrown away, but then some of it is probably ok for range loads...I'm trying to find that line.

I will say this for the Banshee: it runs flawlessly. It has eaten every single load I can find to feed it without a single hick-up, and it has proven a lot more accurate than I expected it to be. In fact, to date I think it's more reliable than my Glock 20. No doubt some of that reliability has to do with the unsupported rear portion of the chamber, so pick your poison.

I'm happy with that trade-off, but I'm really disappointed that I had to figure it out on my own. Nothing in the box from CMMG...NOT A SINGLE MENTION of it from any of the dozens of gun reviews done on the 10mm Banshee, and I know for a fact that they were getting visible bulging with the ammo they were using. I've written comments to some of the reviews...they get deleted. Goes to show what those reviews are really worth...

[DDRiller]

If you have any way to cut a case that was run through the bulge buster in half length wise it would be interesting to see the thinning area.  I've only been reloading a little over 50 years but I would not use those cases again.

[The_Shadow]

Here is a look at the sectioned 40S&W case that had a smile line

Once the brass is "SMILED" it will not iron out because the brass has started to shear...


The "SMILED" brass was run thru the Pass-thru-die system but it does not remove or repair the shearing...look close at the left side of this casing.


Same brass different view...This isn't the best picture, but the brass is shiny from resizing above and below the smile, but the smile is still visible. This chambered just fine before sectioning. This is the piece of brass in the picture above.


Thanks to Yondering who originally posted these pictures of the smiled brass over at GT!

[Muskrat]

The difference between a smile and a bulge seems to be the sharpness of the stress line...no?

Looking at my brass under 20x magnification I cannot see any shearing or cutting in any of the stress areas, FWIW.

What's the best way to cut a piece of brass in half...I haven't figured that one out yet.

[The_Shadow]

The shear is more on the molecular level where the stretching will not return to the original shape.  As you try to reshape it the area around the line moves but the line remains.
I have taken a badly smiled brass that actual had the primer pocket enlarged as the primer was also blown out from a commercial ammo test.  I passed it through the pass through die, while it did fit the case gauge and actually tighten the primer pocket some and I reloaded it just to test its reuse, long story shot it re-smiled and the primer fell out after that test...

I didn't cut the one pictured but I have used a Dremel to cut some and a sander to clean up the cut...

[Graybeard]

The difference between a smile and a bulge seems to be the sharpness of the stress line...no?

Looking at my brass under 20x magnification I cannot see any shearing or cutting in any of the stress areas, FWIW.

What's the best way to cut a piece of brass in half...I haven't figured that one out yet.

Dremel makes a non ferrous metal cutting wheel. They're bigger than the ferrous metal wheels. Clamp the dremel to a table and hold the brass with needle nose vice grips. Pass the brass under the cutting wheel like an inverted table saw. It may not be the best way, but that's my solution. Make sure the rotation at the point of contact is away from you.

[sqlbullet]

Clamp the brass in the jaws of a jig for you Bridgeport mill.  Make passes with a 1/2" end mill until you reach the desired depth. 

[Muskrat]

Bulged and resized brass:

[Muskrat]

Here's a Underwood brass, severely bulged, next to a new piece of Starline brass:



I passed it through a Lee full length carbide resizer...it was so bulged that a ring of nickel got stripped off the outside of the case!



Next I bulge-busted it:



And finally I cut it in half:



I am not seeing ANY tearing or molecular damage, even with such an extreme bulge. I'm not planning on resizing any brass that's so bulged, but it would appear that less bulged brass is probably fine for range loads. Maybe?

If there's any other way to inspect brass for internal damage, I'm all ears.

[sqlbullet]

Bulged is usually not a problem, even if the bulge is large.  Cold working the brass makes it stronger.

Smiled is usually a problem.  The smile line is where the brass started to separate, tear or crack. Even if you mechanically move the brass back, it will not become one uniform piece again.