I'm about to rechamber a barrel , or two, from 6,5x55 to 6,5-284.
My qustion is:
How do I do this, and still be sure the chamber dimesions are right. Is there a special tool (reamer) thats made for this purpose?
As I can understand the reamer will "live a life on it's own" without any alighnment as long as the pilot dont enter the barrel.
I'd love any tip on this from you experieced gunsmiths, before I try to do this on my own. at least I want to know if there is a special tool for this.
Thanks in advance..

Arild

When rechambering an existing chamber, dial indicate the throat of the barrel to within .0001 inch. Then use a boring bar to bore out the chamber .001 inch larger than the diameter of the new reamer just behind the shoulder to a depth that will allow the pilot to engage.

Dial indicating the bore at the throat depth requires a very long stylus on the indicator. If you dont have such, dial indicate the chamber true.

The reamer will now follow the chamber accurately untill the pilot engages.

I was also wondering about this as I'm getting ready to rechamber a 6.5x55 to 6.5x284. I just now need to find someone with a lathe.

Rad

I'm not a gunsmith. Am I thinking backwards, shouldn't it be .001" smaller?

quote:

Originally posted by Craftsman:
Arild

When rechambering an existing chamber, dial indicate the throat of the barrel to within .0001 inch. Then use a boring bar to bore out the chamber .001 inch larger than the diameter of the new reamer just behind the shoulder to a depth that will allow the pilot to engage.

Dial indicating the bore at the throat depth requires a very long stylus on the indicator. If you dont have such, dial indicate the chamber true.

The reamer will now follow the chamber accurately untill the pilot engages.

quote:

Originally posted by Fjold:
I'm not a gunsmith. Am I thinking backwards, shouldn't it be .001" smaller?

quote:

Originally posted by Craftsman:
Arild

When rechambering an existing chamber, dial indicate the throat of the barrel to within .0001 inch. Then use a boring bar to bore out the chamber .001 inch larger than the diameter of the new reamer just behind the shoulder to a depth that will allow the pilot to engage.

Dial indicating the bore at the throat depth requires a very long stylus on the indicator. If you dont have such, dial indicate the chamber true.

The reamer will now follow the chamber accurately untill the pilot engages.

I'm sure that's what he meant, maybe, but I personally wouldn't recommend bringing it to within .001 of the finished diameter for fear of developing chatter when running the reamer. I would hold it to no closer that .010 myself just to provide enough resistance to produce a smooth cut.

quote:

Originally posted by Craftsman:
Arild

When rechambering an existing chamber, dial indicate the throat of the barrel to within .0001 inch. Then use a boring bar to bore out the chamber .001 inch larger than the diameter of the new reamer just behind the shoulder to a depth that will allow the pilot to engage.

Dial indicating the bore at the throat depth requires a very long stylus on the indicator. If you dont have such, dial indicate the chamber true.

The reamer will now follow the chamber accurately untill the pilot engages.

Sounds right to me, .001" larger than the NEW REAMER JUST BEHUND THE SHOULDER, that way you will be able to get the the new reamer in far enough to engage the pilot, then as you ream deeper, the taper of the new reamer will still be cutting quite a little metal. I've measured and loaded for a few improved rounds and even the straightest-most blown out- have .010" taper from head to shoulder. If you bored to .001 smaller you wouldn't be able to get the reamer in far enough for the pilot to engage.

AHA!!!

Now I'm starting to get the picture!!

Thanks guys! I knew this was the right spot to ask such a problem...

Arild,

Knowing how far off chambers and throats can be on most factory barrels, I usually set up this way when rechambering factory barrels.

First I place the barrel on centers and take a truing cut on the major barrel thread. Just enough to true a spot for my roller bearing steady rest to ride.

Next, with a clean bore and a good back light I will eyeball the chamber, throat and bore while it is spinning to check for out of whack alignment. If there is too much movement then there is little anyone can do to straighten it out without cutting off the threads and starting from scratch.

Depending on how smooth everything appears to be running, and with experience you can tell a lot by simply observing shadows and reflections while the object spins, then I will either true the old chamber using a carbide boring bar, provided the new case is big enough to allow the truing, or, I will simply run the reamer "as is" using a PT&G "Bald Eagle" floating reamer holder.

I haven't had any problems so far holding original alignment using this method. Remember, with a prechambered factory barrel, you are pretty much stuck with what's been cut. The best you can hope for in this situation is not making the alignment problem worse. Good luck.

So, what you say is;

-As long as the old chamber runs true, the new reamer will cut straight as long as it running in a floating reamer-holder?

Or at least as good as it gets..

Not just ANY floating reamer holder, this one:

http://www.midwaynorge.com/apps/eproductpage.exe/showproduct?SaleItemID=542929