Chamber Finishing

[tobnpr]

Nah, wouldn't worry about it.
I use 240, 320, gray scotchbrite...but I honestly don't think it makes a difference.

Above my pay grade, but for the engineers here, "Varmint Al" did a write up on this and found no real increase in bolt thrust from slick chamber walls.

http://www.varmintal.com/a243zold.htm

 

[PWS]

Perhaps it's foolish but my next step after finishing the reaming is to spin up the lathe to top rpm and give it about a minutes worth of cross lapping with 500 grit abrasive paper on a split dowel. I'll work on the breech face and chamber mouth with 240 but figure 500 won't remove tooling marks to leave some "grip" but will knock off any minuscule roughness and certainly won't change dimensions appreciably.

 

[Toolbreaker]

Above my pay grade, but for the engineers here, "Varmint Al" did a write up on this and found no real increase in bolt thrust from slick chamber walls.

http://www.varmintal.com/a243zold.htm

That's the kind of info I was wondering about. Thank you.

 

[Stan Taylor]

That's the kind of info I was wondering about. Thank you.

We'll now I guess that means the rest of us are a bunch of dumb asses.LOL

 

[Dusty Stevens]

 

[INTJ]

Well if we are doing show and tell......

 

[Toolbreaker]

We'll now I guess that means the rest of us are a bunch of dumb asses.LOL

Ha! Stan, considering that I've chambered exactly 4 barrels (1st one with adult supervision), I'm thinking there's not much doubt on who the dumb azz here in the room is . The bolt thrust numbers from Varmint Al's simulations in the link above did surprise me but I do tend to nerd out on the engineering stuff, though.

 

[Stan Taylor]

Ha! Stan, considering that I've chambered exactly 4 barrels (1st one with adult supervision), I'm thinking there's not much doubt on who the dumb azz here in the room is . The bolt thrust numbers from Varmint Al's simulations in the link above did surprise me but I do tend to nerd out on the engineering stuff, though.

Toolbreaker
We all rattle each other on this stuff, no offense at all towards you, we all learn new tricks of the trade off of each other ain't nobody perfect.
P.S. this website is definitely a place to learn new idea's for sure.

 

[Stan Taylor]

View attachment 1188918

Is that what I think it is,out of brass.

 

[338 dude]

Is that what I think it is,out of brass.

Is that brass or a well used greasy piece of wooden dowel

 

[Stan Taylor]

By golly I think your right I couldn't picture Dusty using a high dollar piece of brass.LOL

 

[338 dude]

Who knows now you have me second-guessing myself when I expand the picture the end of the dowel in question seems to have a green tint saying it could possibly be brass

 

[Edd]

Who knows now you have me second-guessing myself when I expand the picture the end of the dowel in question seems to have a green tint saying it could possibly be brass

wood dowel color codes

 

[SBLH10]

I have chambered a quite a few 6ppc barrels polished some and some not. Most barrels where shot 1200 to 1800 rds using less than 60 pieces of brass. All rounds where shot at a very heavy PSI loads.
Never seen any different in having to trim the case or difference in case life.

So what am I really looking for in a polished chamber? I only ask because I really don't know the reason of polishing the chamber if using a nice clean sharp reamer.

Chet

 

[Toolbreaker]

Toolbreaker
We all rattle each other on this stuff, no offense at all towards you, we all learn new tricks of the trade off of each other ain't nobody perfect.
P.S. this website is definitely a place to learn new idea's for sure.

None taken at all, Stan. You're golden . The thing that piqued my curiosity on this was the tools themselves. I've used their through-hole burnishers before and they left an almost mirror finish. Even though they state a 15µm finish, it appeared alot smoother than that from memory. I was thinking that with the finishes I've seen previously, that it wouldn't provide a decent grip on the brass & that bolt thrust would increase substantially. Varmint Al's website seems to disprove that to an extent, though.

 

[DaveTooley]

Once again there are many ways to skin a cat. For me I polish because every reamer cuts differently and changes during the course of it's life. I've had some reamers develop micro chip weld on a flute. That leaves rings on fired beass and makes the phone ring. The bolt thrust argument is BS. It can't be measured only talked about. Temperature sensitive powders affect thrust way more than any chamber finish ever has.

 

[Stan Taylor]

Exactly what Dave said.

 

[SBLH10]

Thanks Dave, Your reply make's very good sense to me.
Chet

 

[DaveTooley]

Something to consider. Case head separation. It's caused by continually stretch the case side walls by thrust applied to the case head. It always happens at the same location regardless of caliber. If chamber finish had even a marginal affect on thrust/stretch that point of seperation would vary but it doesn't.

 

[Dusty Stevens]

Who knows now you have me second-guessing myself when I expand the picture the end of the dowel in question seems to have a green tint saying it could possibly be brass