chambering problems

[cramfarm]

I have been putting my own barrels on my x-course rifles and hunting rifles and to my knowledge have never chambered off center, I always use piloted reamers and assumed they would follow the bore perfectly and always have. I picked up a barrel on ebay 28 inches long and chambered in 7br and wanted to chamber it in 284. The barrel had the most interesting case of chamber chatter I have ever seen it probably had 30 serations in the chamber 15 thou deep, It looked like a strange box end wrench. After confering with the reamer maker who thought I could send the 284 reamer in the hole and not suffer any reaccuring chatter so I chose a proper fitting pilot and comenced to chamber the barrel and had no problems with chatter. After putting it on the rifle I looked down the bore with the scope and the chamber is not centered with the bore, one side of the leads are farther out than the other .The only thing I can think of is the chattering chamber went astray and aperently the reamer will follow the old hole with or without a tight fitting pilot. just wanted to let others know so they don't have this problem

 

[tobnpr]

The only thing I can think of is the chattering chamber went astray and aperently the reamer will follow the old hole with or without a tight fitting pilot. just wanted to let others know so they don't have this problem

Exactly. Reamer's a form cutter- it will follow the hole. There'll be enough clearances with the reamer (a few tenths on the pilot itself, as well as the pilot to bore) that it can and will do that. I think the chatter didn't cause the problem- you may have failed to correct an existing problem before you started.

Which is why many of us pre-bore and then skim cut the hole with a boring bar to get the hole precisely concentric. Then, the reamer will follow the hole- and while I still use a properly fitted pilot, I suspect it wouldn't much matter if it were smaller than optimal. Might not even need it...

Did you use a range rod, dial the existing chamber, or something else?
If you dialed the existing chamber, and it wasn't concentric to begin with, it would be problematic.
I would've checked first with a borescope to see if the existing throat/chamber were concentric with the bore- and if it were I would've dialed the chamber. If not, range rod to "start over", and once the bore was properly dialed in, use a boring bar to get the existing chamber true.

Just my opinion...

 

[RandyB]

7 BR base diameter .4703. 284 shoulder diameter .4748 . That poor 284 reamer was wandering around like a drunken sailor before the pilot ever found home. You did not elaborate on your setup but what you wanted to do can be done with a little extra work. Good luck Sir.

 

[DaveTooley]

To get a concentric chamber you have to start with a concentric hole. There are no short cuts.

 

[cramfarm]

In hindsight I should have used or made a range rod and used a boring bar to remove the serrations from the chattering reamer

 

[cramfarm]

Exactly. Reamer's a form cutter- it will follow the hole. There'll be enough clearances with the reamer (a few tenths on the pilot itself, as well as the pilot to bore) that it can and will do that. I think the chatter didn't cause the problem- you may have failed to correct an existing problem before you started.

Which is why many of us pre-bore and then skim cut the hole with a boring bar to get the hole precisely concentric. Then, the reamer will follow the hole- and while I still use a properly fitted pilot, I suspect it wouldn't much matter if it were smaller than optimal. Might not even need it...

Did you use a range rod, dial the existing chamber, or something else?
If you dialed the existing chamber, and it wasn't concentric to begin with, it would be problematic.
I would've checked first with a borescope to see if the existing throat/chamber were concentric with the bore- and if it were I would've dialed the chamber. If not, range rod to "start over", and once the bore was properly dialed in, use a boring bar to get the existing chamber true.

Just my opinion...

I think you are are correct in your assumption of events causing this, live and learn. It also makes me wonder how much influence we truly have when we go to great pains to perfectly true the bore in the headstock when evidently the reamer is going to follow the bore regardless.

 

[Dusty Stevens]

You gotta get a good method to push your reamer. All you need is some bar stock, a good set of pin gages, and a few good chucking reamers to find what works and what doesnt. Everything we do is simple to test if you just stand back and think about it. You can develop methods based off whats acceptable to you

 

[tobnpr]

It also makes me wonder how much influence we truly have when we go to great pains to perfectly true the bore in the headstock when evidently the reamer is going to follow the bore regardless.

Depends on the method, no?
I used to dial the bore at the throat, then just run the reamer in.
Absolutely nothing wrong with that IMO assuming a quality barrel that'll have little to minimal runout down the couple of inches to the breech. If direct dialing, one can easily see whether there's variance of any significance from the throat to the breech. Drilling and boring before chambering removes any runout in that area if needed- but for me, more importantly- it reduces wear on the reamer, esp. the throat area.

If you dialed the original chamber, and it wasn't concentric- your problem started and ended there.
So, you really do have "influence" to correct bore runout in the chamber area- but you need to bore the breech concentric to whatever section of barrel you indicated. Then, the reamer will follow your bored hole- not necessarily the bore itself. Again, JMO...

Borescopes have become so inexpensive that they're really a "must have" now. Too many obsess over immaterial stuff that doesn't manifest at the target- but as I mentioned for me it's invaluable in checking throat concentricty; I do it right after starting, and again after completion.

 

[cramfarm]

Depends on the method, no?
I used to dial the bore at the throat, then just run the reamer in.
Absolutely nothing wrong with that IMO assuming a quality barrel that'll have little to minimal runout down the couple of inches to the breech. If direct dialing, one can easily see whether there's variance of any significance from the throat to the breech. Drilling and boring before chambering removes any runout in that area if needed- but for me, more importantly- it reduces wear on the reamer, esp. the throat area.

If you dialed the original chamber, and it wasn't concentric- your problem started and ended there.
So, you really do have "influence" to correct bore runout in the chamber area- but you need to bore the breech concentric to whatever section of barrel you indicated. Then, the reamer will follow your bored hole- not necessarily the bore itself. Again, JMO...

Borescopes have become so inexpensive that they're really a "must have" now. Too many obsess over immaterial stuff that doesn't manifest at the target- but as I mentioned for me it's invaluable in checking throat concentricty; I do it right after starting, and again after completion.

I agree with all you said when I was refering to going to all the trouble to perfectly indicate the bore I was meaning on a barrel which had never been chambered before and I don't own a range rod and the chamber on my barrel was so chattered ,the high to low chatter marks I think might have been possibly .020 so indicating the chamber was not practical to me. Thanks for all the good responces I should have made a thight fitting bore gauge to indicate off then used a boring bar