What Would Cause This?

[Hannibal]

Apparently, unpiloted reamers in CNC machines that are not correctly set-up are the 'norm' for these outfits.

The 'tacti-cool' crowd would probably never notice as they're rolling around on the ground and worried more about looking like an 'operator' than hitting anything they point their rifle toward.

Guess that shows a bias on my part. Sorry. I've seen one too many of these idiots on the public range.

Good luck in your quest for a properly chambered barrel. Makes me wonder what the bore diameter, twist rate and crown looks like on these things . . . .

[country gent]

The only way to know what you have is to indicate both ends of the barrel in to alighnment. Look a an accuracy gunsmiths lathe and it has a 4 jaw on the headstock spindle and a spider on the back. this allows for both ends to be indicated in and supported. thus the bore is concentric and straight when the stub is cut threaded and reamed. A lot wont take the time to do this. A lot run a reamer float and expect this to correct everything.

[Hannibal]

The only way to know what you have is to indicate both ends of the barrel in to alighnment. Look a an accuracy gunsmiths lathe and it has a 4 jaw on the headstock spindle and a spider on the back. this allows for both ends to be indicated in and supported. thus the bore is concentric and straight when the stub is cut threaded and reamed. A lot wont take the time to do this. A lot run a reamer float and expect this to correct everything.

I know a bit about your background, and I do not wish to direct any disrespect toward you in any way. But I do not understand your reply. Would you be kind enough to indulge my question/questions?

I hope so.

In both photographs provided by the OP, it appears that the throat is cut extremely non-concentric to the barrel bore evidenced by the land reaching all the way to the case neck area on one side, and the land absence for several, apparently 10s of thousandths on the opposite side. I do not see how this could be possible with even a poorly-fitting piloted reamer, either live or fixed pilot, unless the alignment was so poor that the pilot broke off and thus the reamer followed the mis-alignment as best it was able to. Thus my conclusion that both chambers were cut by production chamber reamers, in a CNC mill that was not correctly centered and resulting in the off-center chamber/throat.

Please correct me if I am wrong, but a floating reamer holder will have negligible effect on the throat area cut with a piloted reamer, and mostly aids in reducing an oversized chamber in the area closest to the bolt/breech, caused by axial or angular misalignment between the tail stock and the barrel bore as aligned in the lathe headstock, correct? Again, leaving me to conclude that the chamber was cut with an un-piloted reamer in an incorrectly centered CNC mill.

If the alignment was so poor that the pilot broke off the reamer, then obviously it would be hard to guess how the reamer would cut, apart from it will follow whatever path imparts the lest resistance from the barrel bore and the induced angle of the reamer. (?) This is possible, but seems unlikely from a production-based manufacturer.

Perhaps all I'm doing is re-stating what you have observed with more words. (?)

Just trying to make sure my personal understanding is correct. Again, no disrespect meant in any way.

Thank you in advance for your time.

[Moleman-]

Makes you wonder how often this happens and how well they shoot?

[Hannibal]

Makes you wonder how often this happens and how well they shoot?

I don't know how they shoot, but I have returned a few following a bore scope inspection.

I'm pretty sure the answer is something other than 'sub-MOA all day long if I do my part'.

[KLR]

Makes you wonder how often this happens and how well they shoot?

I wondered the same thing myself. It was almost worth it to me to try it, then run a throating reamer in and try it again. Almost.

I'm pretty sure the answer is something other than 'sub-MOA all day long if I do my part'.

LMBO. Or sub-MOA after subtracting that "called" flyer 3" away...

[Hannibal]

LMBO. Or sub-MOA after subtracting that "called" flyer 3" away...

'I know, right? '

If you want to experiment, just a throating reamer won't do you any good. What you'll have to do is set the entire barrel back, cut the chamber area concentric with a boring bar on a lathe, and then re-cut the chamber with a finish reamer.

Sweet. Now you've got a concentric chamber.

But how's the bore, groove and crown lookin'?

A janky barrel is often just that. I've been down the path you're lookin'. Walk it if you must. I had to see for myself.

[KLR]

'I know, right? '

If you want to experiment, just a throating reamer won't do you any good. What you'll have to do is set the entire barrel back, cut the chamber area concentric with a boring bar on a lathe, and then re-cut the chamber with a finish reamer.

Sweet. Now you've got a concentric chamber.

But how's the bore, groove and crown lookin'?

A janky barrel is often just that. I've been down the path you're lookin'. Walk it if you must. I had to see for myself.

My thinking was the throating reamer would be used so that a bullet would seat out at a normal length and not get jammed in to one side of the bore. I know it would make a big sloppy throat.

Bore and grooves looked good. Crown had a few slight burrs.

I came to my senses and I fixed this barrel with a USPS prepaid trip back to the vendor.

[Hannibal]

My thinking was the throating reamer would be used so that a bullet would seat out at a normal length and not get jammed in to one side of the bore. I know it would make a big sloppy throat.

Bore and grooves looked good. Crown had a few slight burrs.

I came to my senses and I fixed this barrel with a USPS prepaid trip back to the vendor.

I'd say you made the best decision. Like I said earlier, I hope you eventually find a decent one. Too bad you don't have a 'Lyman Bore Cam' or something. Chamber casts are cool, but they're certainly more labor intensive and time consuming.

But there is nothing wrong with that method. You have provided photographic evidence that it works. Well done!

Also, if you are going to truly evaluate a bore, you need to cast a soft lead slug, lube the bore lightly, and force this chamber slug into the bore. This involves hammers and brass or steel rod if you are confident in your skills and is NOT for the 'faint of heart'. What you are 'feeling' for is tight or loose spots within the bore. You have to push the slug to and fro in the bore, feeling for abnormalities. It takes a bit of experience to know what feels 'even' and what does not.

But unless you're interested in precision shooting and minimizing copper fouling, then this stuff is of less importance. I've been hangin' around on a benchrest forum and things are 'different' over there. Easy to forget.

Anyhow, best of luck to you Sir!

Again, I hope you get a 'long' straw instead of a 'short' one next time.

[john.k]

Lots of makers hammer forge the entire barrel and chamber in one operation,sim the military,so the lot is concentric within the limits the mandrell is made to..................Hammer forging machines cost 6 figure amounts,so you cant expect to pay $50 and get a product made on tooling of that standard....more than likely the buttoned rifling twist is wobbly too,but you cant see that.

[KLR]

I'd say you made the best decision. Like I said earlier, I hope you eventually find a decent one. Too bad you don't have a 'Lyman Bore Cam' or something. Chamber casts are cool, but they're certainly more labor intensive and time consuming.

But there is nothing wrong with that method. You have provided photographic evidence that it works. Well done!

Also, if you are going to truly evaluate a bore, you need to cast a soft lead slug, lube the bore lightly, and force this chamber slug into the bore. This involves hammers and brass or steel rod if you are confident in your skills and is NOT for the 'faint of heart'. What you are 'feeling' for is tight or loose spots within the bore. You have to push the slug to and fro in the bore, feeling for abnormalities. It takes a bit of experience to know what feels 'even' and what does not.

But unless you're interested in precision shooting and minimizing copper fouling, then this stuff is of less importance. I've been hangin' around on a benchrest forum and things are 'different' over there. Easy to forget.

Anyhow, best of luck to you Sir!

Again, I hope you get a 'long' straw instead of a 'short' one next time.

Thanks for the encouragement. And advice for evaluating a barrel. I've pushed a pellet through an air rifle barrel checking for tight and loose spots, but hadn't considered doing that with a firearm barrel.

[country gent]

I was referring to a new barrels set up and initial chambering when its a blank and the reasons for getting a barrel like this on a new rifle. Reamer floats do good correcting radial runout but nat as much on the longitudinal. A lot of the reamers used in industry are either very loose pilots or in piloted to aid production oil flow and tool life. A single point cut chamber is only as accurate as the barrels set up. Chip load can become an issue also when reaming. A lot of the tooling used in the factory rifles is ground in house and may have some differences from what we get.

[Hannibal]

I was referring to a new barrels set up and initial chambering when its a blank and the reasons for getting a barrel like this on a new rifle. Reamer floats do good correcting radial runout but nat as much on the longitudinal. A lot of the reamers used in industry are either very loose pilots or in piloted to aid production oil flow and tool life. A single point cut chamber is only as accurate as the barrels set up. Chip load can become an issue also when reaming. A lot of the tooling used in the factory rifles is ground in house and may have some differences from what we get.

Gotcha. Thank you.

[uscra112]

I was referring to a new barrels set up and initial chambering when its a blank and the reasons for getting a barrel like this on a new rifle. Reamer floats do good correcting radial runout but nat as much on the longitudinal. A lot of the reamers used in industry are either very loose pilots or in piloted to aid production oil flow and tool life. A single point cut chamber is only as accurate as the barrels set up. Chip load can become an issue also when reaming. A lot of the tooling used in the factory rifles is ground in house and may have some differences from what we get.

^^^^ This ^^^^

For some years Thompson Center shipped .357 Maximum barrels that were chambered off center. I'm morally certain they were using a .357 Max PISTOL reamer, which has a pilot per SAAMI specification of .346", not the .350" that a rifle barrel requires. Careless? Cheap? (A proper rifle reamer wasn't a catalog item back then.) Ignorant? The truth is lost to history now.

[nekshot]

I wonder what you would see with all the surplus brandnew barrels the parts shop stores have for sale cheap?!!!

[Hannibal]

I wonder what you would see with all the surplus brandnew barrels the parts shop stores have for sale cheap?!!!

A WHOLE lot of problems.

[KLR]

Ok, I gave up on the "Tacticool" barrels and bought a sensible Howa Mini bolt action in 6.5 Grendel. I've read that this model is also sold as the Weatherby Vanguard with "guaranteed SUB-MOA accuracy."

So here's it's chamber cast:

[Texas by God]

Amazing. What the heck- I'd shoot it and see if it makes the accuracy guarantee. If so I wouldn't spend another second worrying about it. There's voodoo in the air with you and barrels lately......

Sent from my SAMSUNG-SM-G930A using Tapatalk

[Moleman-]

Makes you wonder if this is going to be the new "norm" we can expect from manufacturers.

[Nobade]

I see that stuff daily. It's been the norm for many years. I'm glad of it myself, it's job security!