Rechambering Problem

rcordis · Jul 2, 2015

Hello all:

This is my first time posting to this forum.

I recently had a customer who brought me a rifle with stainless barrel chambered to 6.5-06. He wanted it rechambered to 264 Win Mag. I rented a live pilot reamer from 4D which they told me had just been sharpened. I dialed in the barrel on my 4 jaw chuck with a grizzly rod to within .0002", used a floating chamber reamer holder and lots of Tap Magic. I followed PTG's recommendation of 120 RPM on the lathe.

The reamer cut very easily and the chamber has a great finish. I put the barrel back on the receiver and hand reamed the last .010" by hand. But, it came out oversize at the breech. Fired brass is within SAAMI spec at the shoulder, but its .007" over maximum just ahead of the belt.

I have chambered dozens of barrels in the last 5 years, but this is the first that I've done with a floating chamber reamer holder. Somebody mentioned to me that feeding the reamer too fast with a floating reamer holder will cause the chamber to be oversize.

Does anybody have any experience with this? I owe this gentleman a new stainless, fluted, PAC-NOR barrel and it's pushing $600.00. I would appreciate anyones advice as I don't want to make this mistake again.

Many thanks.

Rob

300sniper · Jul 2, 2015

How'd the reamer measure? It'd be pretty tough to get an oversize chamber with a truly floating holder.

FredC · Jul 2, 2015

Had you zeroed the tailstock before running? If it was off too far the floating holder may not have had enough float. The floating holder was clean and not worn out?
Was the recess for the belt in the barrel oversize by the same amount? When you finished reaming by hand could something have been rubbing inside the receiver to push the reamer off center?
Just some things I would ask myself so I would not do it again.

ditchdigger · Jul 2, 2015

A "floating reamer holder"? One like a Bald Eagle or one that mounts in the tail stock? In the past 20 years I don't believe I've set the head space by "hand reaming" more than 5 or 6 times.

garyphansen · Jul 2, 2015

Why can't you set the barrel back one thread to save it?

billzweig · Jul 2, 2015

FredC said:
Had you zeroed the tailstock before running? If it was off too far the floating holder may not have had enough float. The floating holder was clean and not worn out?
Was the recess for the belt in the barrel oversize by the same amount? When you finished reaming by hand could something have been rubbing inside the receiver to push the reamer off center?
Just some things I would ask myself so I would not do it again.

With a floating reamer holder the aliment of the tailstock is not that critical and it would take a real offset to run out of range. All other issues you mention, Fred, are worth looking into.
One possibility is that the barrel breech is centred but the barrel it is at a slight angle (not centred at the back of the lathe spindle). Most floating reamers will not correct for angular misalignment. Still, cutting the tenon face a bit should allow a correct re-reaming.

rcordis · Jul 3, 2015

300sniper said:
How'd the reamer measure? It'd be pretty tough to get an oversize chamber with a truly floating holder.

I had already sent the reamer back before I knew the chamber was oversize.

rcordis · Jul 3, 2015

FredC said:
Had you zeroed the tailstock before running? If it was off too far the floating holder may not have had enough float. The floating holder was clean and not worn out?
Was the recess for the belt in the barrel oversize by the same amount? When you finished reaming by hand could something have been rubbing inside the receiver to push the reamer off center?
Just some things I would ask myself so I would not do it again.

Tailstock was checked and was found to be within .0005". The floating holder was brand new and had never been used before. The recess for the belt was barely within spec but measured .546". The front of the chamber is essentially perfect but it just flares out to about .012" over at the belt.

rcordis · Jul 3, 2015

ditchdigger said:
A "floating reamer holder"? One like a Bald Eagle or one that mounts in the tail stock? In the past 20 years I don't believe I've set the head space by "hand reaming" more than 5 or 6 times.

Mounts in the tailstock.

rcordis · Jul 3, 2015

garyphansen said:
Why can't you set the barrel back one thread to save it?

Max diameter spec just ahead of the belt is .5156. Measuring the fired brass, I'd have to cut off about a half an inch to save this thing.

rcordis · Jul 3, 2015

billzweig said:
With a floating reamer holder the aliment of the tailstock is not that critical and it would take a real offset to run out of range. All other issues you mention, Fred, are worth looking into.
One possibility is that the barrel breech is centred but the barrel it is at a slight angle (not centred at the back of the lathe spindle). Most floating reamers will not correct for angular misalignment. Still, cutting the tenon face a bit should allow a correct re-reaming.

Billzweig:

I agree. Geometrically speaking, it looks like the barrel may not have been straight in the spindle. Although how I did that with that long Grizzly rod I don't know. I indicated 2 places about 6 inches apart. I'm baffled.

Jim Kobe · Jul 3, 2015

Finish ream by hand??? never had to do that much to headspace it. Maybe a thou or two at the most. I think you needed to finish it in the lathe; too much chance to have that happen.
Jim

FredC · Jul 3, 2015

After the discussion it is leaving me with a few possibilities. New floating tool defective or misadjusted? Bad sharpening job on the reamer, one flute did all the cutting and packed with chips pushing the tail end of the reamer over? (Pilot held the front more or less centered)
I am not a gun plumber but a production machinist, but I have seen the cutting edges of reamers ground off center too many times. For close tolerance IDs I use boring bars as commercial reamers cause too many problems.

tdmidget · Jul 3, 2015

You will probably never know why. There's a whole flock of reasons why:
1. You're "A production machinist" who rented a tool that you know is rented, sharpened, rented, sharpened, ad infinitum. You didn't measure this thing before you stuck it in someone else's barrel?
2. You sent it back before you measured and found a problem? Lots of luck with that. It' sharpened and on the shelf or out to the next butcher.
3. You did not measure anything until you were at full depth and at the point of no return?
4. You assumed that the reamer holder (that's a whole 'nother chapter) was perfect because it was new? You did not check it for burrs, chips, or other defects before using it, especially on someone else' barrel?
Oh, well

ditchdigger · Jul 3, 2015

Who's "floating reamer holder?" Did the reamer get pushed back and lock-up the 'float' in the holder?

FredC · Jul 3, 2015

tdmidget,
You may have gotten me mixed up with the OP. He said he has done dozens of barrel jobs in the last few years so he may be a beginning gunsmith. I am the production machinist. I used to be a machinest till the spell checker corrected me.
Anyway I have made millions of parts by now and hopefully some of my experience may be helpful here.
FredC

Butch Lambert · Jul 3, 2015

Seen it several times. The old chamber is not concentric to the bore and with your bushing following the bore the rear of the chamber will be oversize. The original chamber job was dialed in differently than the gerdy method. Remember, your flutes will try to follow the old reamed chamber and the bushing is leading it differently . It will work like a flycutter in a mill. The bushing is forcing the flutes to the side and oversizing the rear of the chamber.
I personally do not like the gerdy method of indicating the bore, but after indicating the bore, did you remove your indicating rod an checked for runout of the old chamber at the base? That would have told you something.

tdmidget · Jul 3, 2015

Sorry , Fred, you are correct.
Butch may have it. In any case if you do not measure and test for function on everything you are begging for this kind of problem. An apprentice machinist learns his first week (if not first day) to measure your tools before using as they can be from the wrong bin, marked wrong, ground wrong, whatever but the fault will lie with man who put it in the machine.
If the job was strictly a cartridge change and no problems to solve then the obvious thing to do is put the new chamber where the old one was. Fixing problems that don't exist usually cause a new one.

Maybe tell him you chambered it to .264 rcordis "Improved"

Jwilliams31 · Jul 5, 2015

Butch could you elobrate why you dont like the gordy method for disling in? Thanks

sdean · Jul 7, 2015

Gordy now uses his rods just for initial indicating. When he gets real close he uses a long reach indicator at the throat.

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