Rockwell hardness on finishes

[ABNAK]

Caveat: please save me the inevitable "You don't need to clean that" when it comes to the bolt tail. I do and will continue to do so. This is a technical question.



Was looking at a company called TR-Enabling and a finish they have called Obsidian. They do a mil-spec BCG in it. It is a nickel-Teflon finish but has a Rockwell hardness of 70 (NP3 has a Rockwell of ~ 50). Now having spoken to Robar a few years ago I found out that using a brass/bronze bore brush to remove the bolt tail carbon deposits on NP3 is a no-go. So is the trusted old green scratchy pads we used in the Army. Have to use a nylon bore brush, and it takes a while to get my NP3 bolt tail spotless using that. My hard chrome bolts, where I can use a brass/bronze bore brush or scratchy pad, clean up really quick.

1) What is the Rockwell hardness of brass or bronze bore brush bristles?

2) I assume you can use a brush with a lesser Rockwell hardness on something with a higher one without removing the finish, right?

I'll bet tom12.7 has a slew of info! (hint hint)

[MegademiC]

Caveat: please save me the inevitable "You don't need to clean that" when it comes to the bolt tail. I do and will continue to do so. This is a technical question.



Was looking at a company called TR-Enabling and a finish they have called Obsidian. They do a mil-spec BCG in it. It is a nickel-Teflon finish but has a Rockwell hardness of 70 (NP3 has a Rockwell of ~ 50). Now having spoken to Robar a few years ago I found out that using a brass/bronze bore brush to remove the bolt tail carbon deposits on NP3 is a no-go. So is the trusted old green scratchy pads we used in the Army. Have to use a nylon bore brush, and it takes a while to get my NP3 bolt tail spotless using that. My hard chrome bolts, where I can use a brass/bronze bore brush or scratchy pad, clean up really quick.

1) What is the Rockwell hardness of brass or bronze bore brush bristles?

2) I assume you can use a brush with a lesser Rockwell hardness on something with a higher one without removing the finish, right?

I'll bet tom12.7 has a slew of info! (hint hint)

The typical copper alloys mentioned are measured using rockwell b scale, and fall in 55 to 90s.

Rockwell c is used for steels and hard materials, it used a different indenting device.

I really doubt brass or copper would do anything to np3, bronze I'm not sure. The metallic brush might take out any ptfe exposed on the surface but I'd imagine the nickel would protect everything else.

You could always try a Mr clean magic eraser.

Edit- is np3 has to be c scale right? A softer material will wear down a harder one over time, it just takes a long time.

[ABNAK]

The typical copper alloys mentioned are measured using rockwell b scale, and fall in 55 to 90s.

Rockwell c is used for steels and hard materials, it used a different indenting device.

I really doubt brass or copper would do anything to np3, bronze I'm not sure. The metallic brush might take out any ptfe exposed on the surface but I'd imagine the nickel would protect everything else.

You could always try a Mr clean magic eraser.

Edit- is np3 has to be c scale right? A softer material will wear down a harder one over time, it just takes a long time.

Hmmm.....off to Google.

[WS6]

I just use a paper towel and g96 clp. My sr25 bolt tail is a mirror. Chrome though. As to that np3 bcg...the locking lugs interface under many psi pressure with steel barrel extension, and the "skids" slide across type iiia ano with impunity...and robar says a copper brush is the devil? One of their claims...is not like the other.

[tom12.7]

Yeah, I sent a pm to the OP.

[ABNAK]

This was a "tech" I spoke to at Robar, not the owner or anything! He just said that using nylon brushes was optimal......but did say nichts on the bore brush or green scratchy pads.

[RetroRevolver77]

I've often times wondered what the long term affects of running say a Nitrided or NicB carrier group in a standard anodized upper. If it wears pre-maturely or not.

[markm]

I scrape the crap outta my bolt tails with a pick or jeweler's screw driver regardless of finish type. Standard bolts often rub to bare metal there on their own anyway.

[WS6]

I've often times wondered what the long term affects of running say a Nitrided or NicB carrier group in a standard anodized upper. If it wears pre-maturely or not.

Based on 3500 or so rounds I have on my setup, no, not really.

[ABNAK]

I had emailed the guys who do the Obsidian, TR-Enabling, with the very question I asked in the OP. Here is their response:

"You can use a brass brush however we would recommend using a standard plastic ap brush".

Not sure what an "ap" brush is. Nonetheless, it appears using a brass brush is not recommended.

tom12.7 likes hard chrome and so do I; you can see the dirt and use anything to get it off there.