Polished brass. Can it be too smooth?

[spclark]

Brass is soft while steel is hard. That’s why chambers work best with a little surface texture, the brass moves into the texture very slightly upon case firing.

Brass can be polished or rough, but if WET the pressures go WAY UP ‘cause fluids don’t compress! (I killed a new SAAB once idling thru a 10” puddle when wake from car ahead came back at me when she suddenly stopped in the middle.)

 

[rammac]

Well now I guess we'll have to listen to a repeat of all the crazy stuff about bolt face forces. Having experience as a competition shooter doesn't qualify anybody as an expert in engineering any more than being a driver would qualify any of us as an automotive engineer.

 

[dkhunt14]

Well now I guess we'll have to listen to a repeat of all the crazy stuff about bolt face forces. Having experience as a competition shooter doesn't qualify anybody as an expert in engineering any more than being a driver would qualify any of us as an automotive engineer.

No, you don't have too, you can not open or read the threads you don't agree with. Matt

 

[LA50SHOOTER]

Well now I guess we'll have to listen to a repeat of all the crazy stuff about bolt face forces. Having experience as a competition shooter doesn't qualify anybody as an expert in engineering any more than being a driver would qualify any of us as an automotive engineer.

One doesn't need to be an "Engineer" to know about bolt thrust or to understand it. - A basic understanding of physics, pressure & mechanical force will do. - And I'd beckon to say that a good number of competition shooters have a decent idea of bolt thrust.

That's my 2 pennies.

 

[alinwa]

I'm still trying to digest the concept of "WHY??? would a person enter into a conversation ABOUT BOLT FACE FORCES..... and then say "now we have to lissen to.....CRAZY stuff.....bolt face forces...blah blahh blahh"

I am sometimes SO confuze......

 

[msinc]

.......And I'd beckon to say that a good number of competition shooters have a decent idea of bolt thrust.

That's my 2 pennies..........

Well, there might be a "good number" that understand it somewhere...but it is apparent there are many that remain clueless. I guess if a decent idea about it means they know what recoil is and have felt it on their shoulder...they could deep down subconsciously know, but still not admit to it.

 

[Dusty Stevens]

I have no idea about bolt thrust past what ive seen first hand- a custom benchrest action line being recalled due to lugs shearing off. I also posted pics on here a few years ago of a model seven short mag that was all mangled up inside from the bolt thrust. Past that all you engineers get to calculating what happens in the other world. Im an electrical engineer so ill stay out and let the more qualified theorize on what could happen

 

[alinwa]

I have no idea about bolt thrust past what ive seen first hand- a custom benchrest action line being recalled due to lugs shearing off. I also posted pics on here a few years ago of a model seven short mag that was all mangled up inside from the bolt thrust. Past that all you engineers get to calculating what happens in the other world. Im an electrical engineer so ill stay out and let the more qualified theorize on what could happen

Yeahhh, WSM's are perty brutal with almost a quarter inch of surface presented to gas pressure..... and factory loads running 70,000psi!

You get a well-fitted case or a guy neck-sizing-only and that's 10,000-15,000 pounds pounding on those lugs


And unseating the barrel joint.

And I build 338 Lapuas to run near 80 Thou........ BIG wrenches

 

[dolek]

Polished brass. Can it be too smooth?
So,whats the answer ?

 

[dcali]

Polished brass. Can it be too smooth?
So,whats the answer ?

Nobody knows. What we know is that friction is somewhat dependent on surface finish of both materials, as well as lube, and probably other things like temperature, pressure, and the instantaneous state of stress in the case.

Weird stuff happens, and friction is very hard to nail down with any certainty. Can a case be too low in friction? Yes. Does polishing brass take it from "it's fine" to "it's no good?". No idea, and it probably depends on other factors.

I'm not even willing to say whether polishing brass increases or decreases friction. I could see that going either way, but I'm no tribologist.

 

[dcali]

And unseating the barrel joint.

This has always bothered me. It's absolutely true that there are thousands of pounds of force pushing the barrel out of the action, which you would think need a strong preload to counteract - which means a very high torque on the barrel. (bigger threads need higher torque to generate the same preload).

So why is it that people get away with lightly torqued switch barrels and the like? You would think this would be problematic. It seems like our barrels are probably gapping ever so slightly with every pull of the trigger. Or not?

Harold Vaughn seemed to push the idea of ramp threads, but that never took off. The American Rifle Company came up with a slick way of providing a substantial preload, but I don't get the sense that shooters appreciate it. Maybe because it just doesn't matter. But it should...

 

[LA50SHOOTER]

Polished brass. Can it be too smooth?
So,whats the answer ?

NO - (as long as it is dry)

 

[urbanrifleman]

Smooth is good. Too clean is bad. Especially inside, ala ultrasonic cleaning. From my experience. Cleaning the cases too well really shows the sintered texture inside the case. Effectively making you case necks look like this.



Which is bad. Brass that has not been drawn smooth seems to always have a sintered surface. I much prefer a bit of carbon inside my cases. Slightly dirty is just fine. Super clean sucks.

 

[dcali]

Smooth is good. Too clean is bad. Especially inside, ala ultrasonic cleaning. From my experience. Cleaning the cases too well really shows the sintered texture inside the case. Effectively making you case necks look like this.

View attachment 1051817

Which is bad. Brass that has not been drawn smooth seems to always have a sintered surface. I much prefer a bit of carbon inside my cases. Slightly dirty is just fine. Super clean sucks.

That's not at all what my brass looks like after ultrasonic cleaning. How are you cleaning brass to get that finish?

 

[urbanrifleman]

That's not at all what my brass looks like after ultrasonic cleaning. How are you cleaning brass to get that finish?

It does on the inside.

 

[dcali]

It does on the inside.

No, it doesn't.

 

[urbanrifleman]

http://bulletin.accurateshooter.com...eaning-case-neck-friction-and-bullet-seating/

If you zoom in in the surface of ultrasonic cleaned necks they look like sandpaper. I am not the first person to discover that.

 

[dcali]

You can definitely see the scratches from neck turning more clealrly (because it's clean), but I don't see a sandpaper or sintered look at all. Just very lightly scratched brass. The surface finish looks just like the outside. Maybe it's the cleaning solution?

 

[urbanrifleman]

You can definitely see the scratches from neck turning more clealrly (because it's clean), but I don't see a sandpaper or sintered look at all. Just very lightly scratched brass. The surface finish looks just like the outside. Maybe it's the cleaning solution?

Probably. I think if you really had some magnification you would see the sintered/600 grit sandpaper look. Of course, it could be the method used. I didn't like ultrasonic cleaning. I have gotten where I am not really crazy about cleaning my good brass at all. Shoots much better slightly dirty. But of course, we all have our own methods!!!

 

[dcali]

I've looked at it with some pretty high magnification (a 10x loupe), because I hear often that you need the carbon. That hasn't been my experience, but I wonder if other factors enhance/mitigate whatever is going on. I tend to use a little neck tension as possible, and I clean with a very mild solution (basically very dilute simple green and a *small* amount of citric acid). I rinse thoroughly in clean water as soon as the cycle is done. I also do not anneal.