Chamber finish

[Shrek]

After you have finished reaming the chamber what techniques do you use to get just the right finish to grip the brass to limit brass growth and reduce rearward pressure ? Do you cut the chamber slightly short to allow for roughing up the chamber ? What do you think the perfect finish is ?

 

[martin22250]

I don't do nothing to it, just leave it the way the reamer makes it, I do just barely touch some 320 grit paper to the chamber edge.
Dustin

 

[Wirelessguy2005]

I use crocus cloth on my chambers after the finish reamer is done doing its work.

 

[Tim Singleton]

Speaking of finish. What rpm do most of you chamber with? Do you change rpm and feed slower on the last few thousandth?
I have never done anything to the final finish left by the reamer. Don't have any issues with extraction or any other problem. Some turn out a nicer finish than others don't know why maybe difference in one barrel to the next
I only chamber for myself

 

[Wirelessguy2005]

I chamber at 90 rpm, that is the slowest speed my lathe offers.

 

[ab_bentley]

360rpm pre bore and ream, quick 400 followed buy gray scotch brite. When you pre bore the reamer leaves an almost mirror finish.

Adam

 

[Tim Singleton]

I've been pre boring to about .030 under. I could stand to run it faster than I am, I think. Don't really know the speed heavy 10 on the slowest position with my belt
Seems like if I have at least .010 left to ream and can finish from there I get a better result than if only cutting .003 or so.

 

[ab_bentley]

I've been pre boring to about .030 under. I could stand to run it faster than I am, I think. Don't really know the speed heavy 10 on the slowest position with my belt
Seems like if I have at least .010 left to ream and can finish from there I get a better result than if only cutting .003 or so.

Tim, my SB10 is ~360 on large pulley first belt. I have also found .030" on the pre bore to ideal.

Adam

 

[martin22250]

Would some of you guys explain how yuns pre bore, I've been using the reamer for the full depth of the chamber, I only do ppc chambers, would like to extend the reamer life

 

[Tim Singleton]

I rough drill with a 3/8" drill bit. .050 short of shoulder then bore with a boring bar to .400 for a PPC. Then I cut with my reamer

 

[martin22250]

I rough drill with a 3/8" drill bit. .050 short of shoulder then bore with a boring bar to .400 for a PPC. Then I cut with my reamer

Thanks tim I'm going try that next time

 

[ab_bentley]

Thanks tim I'm going try that next time

I measure the distance from the middle of the pilot to the neck shoulder junction, use a drill bit ~.030 undersized, drill the length measured, cut with reamer to shoulder, repeat as needed.

 

[Hal]

Martian

When you bore, set your compound at the same angle as the case your chambering for.

Hal

 

[Danny1788]

I measure the distance from the middle of the pilot to the neck shoulder junction, use a drill bit ~.030 undersized, drill the length measured, cut with reamer to shoulder, repeat as needed.

No boring bar used?

 

[ab_bentley]

No boring bar used?

No, a properly sharpened drill is a slave to the bore. Indicate the bore in right, the drill will follow without walking.

Adam

 

[hoz53]

I have played with as course at 180 grit. I am back to 320 grit. As reamed the chamber is shiney like a mirror. I have never left one like that to see what would happen. So far 320 has given me the least bolt thrust. I should leave one as reamed to test it. I ream at 250 rpm with oil flush. No preboring, I have core drills for the most common cases, If its a shortie like a ppc, reamer all the way, if its long I'll ream until a 1/4" of shoulder is cut, then drill, then finish ream. No runout issues with any method. I am in love with core drills though.

I have been wondering about preboring. So for a short chamber like a 6br you would just use a finishing reamer all the way? How long will your reamer last doing it that way? The main thing Im wondering about preboring--Is the pilot always in the bore? Thanks Again
Hopefully these are things the OP would like to know also

 

[Shrek]

Yes it is the conversation I was looking for. More in fact. Hitting the chamber with 320 is the information I am looking for. How do you apply the 320 paper ? In particular the neck and do you alter the chamber dimensions any.

 

[Danny1788]

I wrap my 320 emery clothe around a pen or wooden dowel and just rough up the chamber I do not stick the emery clothe in the neck. Also I put oil on my emery clothe and leave oil in my chamber as I'm using a flush system.

 

[ridgeway]

Red scotchbrite. Cut a small strip...fold a 1/2 over a pencil point, run inside the chamber and jog at 500-600 rpm. Run back and fourth a couple times and a super nice cross hatch pattern is made.

 

[Danny1788]

like what Alex said if your getting grooves in the chamber, your more than likely rolling a chip over the cutting edge. Not good In my experience. Take your time and practice on a cheap take off barrel. Cut the chamber off and chamber a few ways. I did this as mentioned by someone else when I was first starting and it helped me figure out my routine for chambering a barrel. If you want some cheap old take off barrels I have a few you can have for the price of shipping. Just P.M me

I like the idea of using that center piloted drill bit that Alex had mentioned in a few posts earlier. I'm going to order one and give it a go.

I normally don't prebore or anything. I use a coolant flush system from start to finish with a piloted finish reamer. I cut about .100" the first few reaming's then once I'm about half way I cut it down to .050" (half a turn on my talkstock) With the flush system I found this is were the flutes of my chamber reamers are not loaded up and I retract the reamer and flush off the reamer with the pump. Then go back in, its very fast and affective for my setup. But it took me a few ways of doing it to get to that point.