Carbide reamer finish / Rainbow

[LVLAaron]

Just an interesting tidbit. Got my first carbide reamer (Alpha Legacy 308) - Did some test cuts and a full chamber today. Really interesting that the finish always has a rainbow in it, it's not just in the photo. I cleaned this one with acetone to remove any oil and the rainbow remained.

 

[Ggmac]

Interesting, next 9 mm I cut I will check . My only carbide is 9mm so I guess I never looked . Was your stainless or 4150 ?

 

[LVLAaron]

416 stainless

 

[shortgrass]

Do you suppose that indicates it's too smooth? "Too smooth"= increased bolt thrust.

 

[LVLAaron]

Do you suppose that indicates it's too smooth? "Too smooth"= increased bolt thrust.

Chamber always gets finished with emery paper after chambering

 

[shortgrass]

Chamber always gets finished with emery paper after chambering

I've always thought that Emory was too course. 320g wet & dry with a squirt of light oil has done it for me for the past 30+yrs. Just a light cross hatch is what I'm looking for. Enough for the cartridge case to 'bite' on when it expands to meet the chamber walls, but not enough to effect extraction. You must cut a lot of A L 308 chambers to buy carbide.

 

[LVLAaron]

I've always thought that Emory was too course. 320g wet & dry with a squirt of light oil has done it for me for the past 30+yrs. Just a light cross hatch is what I'm looking for. Enough for the cartridge case to 'bite' on when it expands to meet the chamber walls, but not enough to effect extraction. You must cut a lot of A L 308 chambers to buy carbide.

I don't, but I wanted to try one of Alpha's legacy reamers. I didn't know they were carbide when I bought it - they dont say it anywhere on the website. After cutting one or two I'd much rather use steel, but the reamer definitely cut a perfect and tight chamber.

edit - I use 320 grit and oil as well

 

[butchlambert]

I've always thought that Emory was too course. 320g wet & dry with a squirt of light oil has done it for me for the past 30+yrs. Just a light cross hatch is what I'm looking for. Enough for the cartridge case to 'bite' on when it expands to meet the chamber walls, but not enough to effect extraction. You must cut a lot of A L 308 chambers to buy carbide.

I have 600 emery, but I use 320 in the chamber

 

[DickE]

I've used green Scotch-brite for many years, goes into throat to clean up that area too. My barrel jobs need very little break-in.

 

[urbanrifleman]

I've used green Scotch-brite for many years, goes into throat to clean up that area too. My barrel jobs need very little break-in.

I use red. Much better than paper.

I made myself a delrin screwdriver to wrap the scotch Brite around.

 

[Carl S]

A wooden dowel with a hacksaw slot
and a piece of grey scotch-brite inserted
does the trick.

 

[gunsandgunsmithing]

I prefer 320 grit paper to put a cross hatch pattern in the chamber. Sometimes I'll follow up lightly with a small ball hone. A chamber can be too slick though.ive seen chambers polished to a really shiny finish. Imo, this is a mistake as it causes more bolt thrust and can contribute to harder bolt lift.

 

[X Count]

It's interesting that we like chambers and barrels that have deliberate textured surface while some applications end up with chrome lined bores and chambers.

 

[SKWERLZ]

It's interesting that we like chambers and barrels that have deliberate textured surface while some applications end up with chrome lined bores and chambers.

Chrome lined barrels are typically a different application where reloading the brass generally isn’t considered.

 

[gunsandgunsmithing]

It's interesting that we like chambers and barrels that have deliberate textured surface while some applications end up with chrome lined bores and chambers.

That chrome isn't the shiny, smooth stuff used on a car bumper, either.

 

[DickE]

3M Scotch Brite Nylon Pads:
7445 - White pad, called Light Duty Cleansing - (1000) 1200-1500 grit
7448 - Light Grey, called Ultra Fine Hand - (600-800) 800 grit.
6448 - Green (?), called Light Duty Hand Pad - (600) 600 grit
7447 - Maroon pad, called General Purpose Hand - (320-400) 320 grit
6444 - Brown pad, called Extra Duty Hand - (280-320) 240 grit
7446 - Dark Grey pad, called Blending Pad (180-220) 150 grit
7440 - Tan pad, called Heavy Duty Hand Pad - (120-150) 60(?)
Blue Scotch-Brite is considered to be about 1000 grit.
(The value inside the parentheses is directly from 3M.)

 

[Will Henry]

The rainbow effect is caused by refraction and I would think it would have to be the result of a faceted surface; even if on a microscopic level. Polishing would likely remove the facets.
I always finish with Scotch Brite. For what that is worth. For a chamber with serious tool marks (I know, I know, chambers shouldn't have toolmarks and usually, they don't) a ball hone is effective. WH

 

[WSnyder]

carbide reamer (Alpha Legacy 308)

Did they supply a reamer print for the reamer? I don't see anywhere that they show prints and I've been unable to find any out there. I'm going to contact them and see if they'll supply a print for a reamer or two.

 

[LVLAaron]

Did they supply a reamer print for the reamer? I don't see anywhere that they show prints and I've been unable to find any out there. I'm going to contact them and see if they'll supply a print for a reamer or two.

I was able to get one for the .308 - I don't think they'll provide the BRA

 

[WSnyder]

I was able to get one for the .308 - I don't think they'll provide the BRA

I’m wanting something other than a BRA. I’ll ask them and see what they say.