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Chamber Finishing

There are a lot of folks here that are way more expert than I however, simple metallurgy tells me that any roughness in the chamber of a harder material when the brass is blown up in it is going to transfer to the brass when extracted, which is something I really like to avoid being pushed into my sizing die.
 
Jesswil61 said:
There are a lot of folks here that are way more expert than I however, simple metallurgy tells me that any roughness in the chamber of a harder material when the brass is blown up in it is going to transfer to the brass when extracted, which is something I really like to avoid being pushed into my sizing die.
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Even my WTC die inserts are a bit cheaper than the bolt on one of my BRMXD actions. I'll take running brass from a 'less than polished' chamber into my dies instead of the case head hammering my bolts. Just puttin' that out there:).
 
"I've had some reamers develop micro chip weld on a flute", 320 grit, Hawkeye at the lathe cures all ills. Thank God for Hawkeye at the lathe!

The notion of running slick tires vs tires with some grip on them does NOT appeal to me.

Grey scotch brite in the bore??? You are living life on the wild side, eh?
 
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Where do you draw the line between rough, smooth, and slick? Will the case always expand to the point where it's surface texture mirrors that of the chamber?

I know someone that used to deliver gun safes with a pickup. He put a piece of smooth 10 gauge sheet metal on the floor of his truck bed because he thought the OE sheet metal was too flimsy to handle the weight of the safes. When you placed a heavy safe on the sheet metal it was very difficult to move the safe into position to strap in down. He removed the smooth metal and installed a sheet of diamond plate and the safes were much easier to move.

Is there a point in a chamber where smoothness increases the friction?
 
I polish chambers for one simple reason. It's expected and the right thing to do for my customers. Smooth, highly polished, cross hatch, blended doesn't really matter. Anything else is secondary. If you're like some and want your used brass to look like virgin, fresh out of the box brass you'll polish chambers. You don't have to do much. I polish at 1500 RPM's w/240 and depending on feel I'll go back and forth 2 to 3 passes. Most of the time I'll go back in with Scotch Brite on a wood dowel just to blend it all together. Just looks better is all.
Rule #1 Don't do anything to make the phone ring.

Brass expands and then contracts in the chamber to allow it to come out. Except for extremes, which for this conversation aren't relevant, chamber finish has nothing to do with extraction. Clearance between the brass and the chamber wall before and after firing are critical for extraction.
 
Edd said:
Where do you draw the line between rough, smooth, and slick? Will the case always expand to the point where it's surface texture mirrors that of the chamber?

I know someone that used to deliver gun safes with a pickup. He put a piece of smooth 10 gauge sheet metal on the floor of his truck bed because he thought the OE sheet metal was too flimsy to handle the weight of the safes. When you placed a heavy safe on the sheet metal it was very difficult to move the safe into position to strap in down. He removed the smooth metal and installed a sheet of diamond plate and the safes were much easier to move.

Is there a point in a chamber where smoothness increases the friction?
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My guess about your friends problem is it's a hardness issue. The smooth plate was soft and sticky so to speak. The diamond plate was harder.
 
Brush Research Manufacturing {Flex Hone} makes some pretty fast and effective chamber polishing devices. I don't use them on every chamber I cut. I find that on some gas guns {M14/M1 Garand} the case will stretch more than it should if the chamber isn't somewhat smooth. Something like .006"-.008" after firing is about right. If I am seeing more than that I polish. Sometimes it will cure a light bolt click on a bolt gun too. These are 400 and 800 grit hones. Not saying they are "better" than a ink pen or broken arrow, ect. Just another option.
Edit: BRM recommends you use their brand honing oil with these things. I don't know what it is made of, but I can say that it will quickly wear out the little stones on these of you don't. It's not expensive. P7080009.JPG
 
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Stan Taylor said:
Here is a gammit of my high dollar burnishing tools.
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We all get this...the sad thing is that there are actually folks out there that will pass on a Douglas barrel now because they expect some high dollar machine.
Mr. Taylor you should have took a picture of a toaster oven and called it a "high frequency pulse magnetic synchronized laser guided CNC demeglinating chamber polisher"...you'd a had 40 orders for new barrels this morning!!!!!
 
msinc said:
Brush Research Manufacturing {Flex Hone} makes some pretty fast and effective chamber polishing devices. I don't use them on every chamber I cut. I find that on some gas guns {M14/M1 Garand} the case will stretch more than it should if the chamber isn't somewhat smooth. Something like .006"-.008" after firing is about right. If I am seeing more than that I polish. Sometimes it will cure a light bolt click on a bolt gun too. These are 400 and 800 grit hones. Not saying they are "better" than a ink pen or broken arrow, ect. Just another option.
Edit: BRM recommends you use their brand honing oil with these things. I don't know what it is made of, but I can say that it will quickly wear out the little stones on these of you don't. It's not expensive. View attachment 1189078
Click to expand...
These are what I referred to as "ball hones) and they do work well.
Regarding bolt thrust and chamber finish:
A typical, rigid, front locking, action will probably deflect about .001" at 50,000psi. I made up a fixture (a split collet chamber) to hold a case and see how much effort it took to deflect a piece of brass by .002". It seemed to take something less than 200 pounds of pressure to deflect the unsupported head by that amount. If this is the case, that is the maximum amount by which a rough chamber will reduce bolt thrust. Now, in a rifle which allows more deflection (a rear locking action, for instance), the effect will be more apparent because, although initial elongation of the brass takes place at relatively low pressures, as the brass reaches it's elastic limit, it is much stronger than that. This is just like pulling on a rubber band; it stretches easily to start but becomes increasingly resistant to stretch as it approaches it's limit.
My conclusion is that in a rigid, front locking, action, chamber finish has little effect on bolt thrust. A transducer could give a more definitive answer, I suppose. A crusher system will not since it measures significant deflection.
If you lube the case in a front locking action, there is little apparent effect. Lube the case in a Lee Enfield and the shoulder will move froward with each firing until the case is impossible to chamber. If the case is dry, the case will stretch ahead of the web and, ultimately, will separate. I have tested this, repeatedly. WH
 
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