First let me say that I know nothing, but I read and hear lots.

It is my understanding that most factory chambers used to be cut with the barrel rotating and the reamer stationary. This technique would produce a very concentric chamber. Maybe a bit oversized, but very concentric. Over the last few years many manufactures have changed to just the opposite where the barrel is stationary and the reamer rotates. This would produce a nice tight chamber, but chance of producing an off center chamber would be greatly increased.

Now my question. I have a 280 A-Bolt laying around and gathering dust. Just for the hell of it I would like to have it chambered in 280 AI. My smith told me that the chamber is off center. If he were to cut the AI chamber his way (the old way) that the new chamber would end up way oversized. He basically told me he would not do it. Any ideas as to how I can get this thing rechambered and is this a common problem with newer barrels?

Steve

I can't say that I agree with your first paragraph regarding chambering methods. A good straight concentric chamber is the result of proper set-up, a good sharp reamer, and a smith who knows what he's doing. Factories usually lack all three.

How exactly did your gunsmith determine that your 280 chamber was off center?? Regardless, he should be able to put it in a 4-jaw chuck and get everything lined up fairly well. And if worse comes to worst, he should be able to rechamber a 280 to a 280 AI by hand. Very little material is removed with this type of conversion.

However, in order to do it properly you need to make sure he understands that the barrel has to be removed, set back one thread, the chamber re-cut, and then the barrel tenon re-done. Otherwise you'll end up with excessive headspace.

If you are going to rechamber just "for the hell of it" don't forget that those jobs are not cheap, considering barrel removal and replacement and the set up time to get everything straight. There's nothing wrong with the 280 just as it is. Agreed, the 280 AI is one of the better wildcats (I have one) but after you buy dies and fireform the brass you'll wonder if it was worth it.

JMHO

Ray

There is a photograph in one of my ancient gun magazines of a gun company's operation in which a woman was chambering barrels with a drill press.
It was a floor model drill press with a metal garbage can sitting on the base. Inside the garbage can were a number of barrels leaning to one side and she was about to start the reamer in one of the barrels. After seeing that photo I made a point to never own a rifle from that company again and I haven't.

quote:

Originally posted by Cheechako:
Steve

A good straight concentric chamber is the result of proper set-up, a good sharp reamer, and a smith who knows what he's doing. Factories usually lack all three.


Ray

Right, but if you set up properly(concentric) on a barrel with an already off center chamber, wouldn't you be boring a straight hole into a crooked hole? And wouldn't this make the new chamber way out of specs?

WOw Ray,
with factory rifles today being "duds" if they are under MOA, i just can't get what you are sayuing... remingtons, rugers, and savages are known for superb accuracy (yeah yeah, don't want to hear about rugers 20 years ago) ...

in fact, the factory tend to produce within spec chambers, to the tune of hundreds per day, that is close enough to spec to keep them from being sued 3 times a month.

Steve,
Your smith may or may not be correct, but one should setback a thread when doing an AI chamber, to ensure everything is clean
jeffe

quote:

Originally posted by jeffeosso:

Steve,
Your smith may or may not be correct, but one should setback a thread when doing an AI chamber, to ensure everything is clean
jeffe

I had him convert my old Rem 700 30-06 to an AI last summer. He set the barrel back and cut the chamber perfectly. Everything turned out great. When I asked him to do my A-Bolt he was a bit hesitent. He said he needed to see it up close and personal before he would agree to do the work. He did his inspection and advised me against the conversion. He said that there were other smiths around that would do it, but in his opinion it wouldn't be right.

quote:

Right, but if you set up properly(concentric) on a barrel with an already off center chamber, wouldn't you be boring a straight hole into a crooked hole? And wouldn't this make the new chamber way out of specs?

Steve

What I meant was that you set up so that the existing off-center chamber is lined up, not the outside of the barrel. That, plus a reamer will tend to follow an existing hole. So your new chamber should not be any more off-center than the original.

Jeffe

I never meant to imply that all factory barrels and chambers are duds. Some are very good (probably more luck than skill) but some are very bad. Factories simply do not have the time to do things right otherwise they'd have to charge a lot more than most guys would pay.

I know that you've owned custom barrels made by real gunsmiths. There is no comparison with the best of factory jobs. It's the reason custom gunsmiths have backlogs of orders for re-barrel jobs.

JMHO

Ray

Ray,
I can agree with that... though I am a realist, and understand less than 2% of all rifles go see a gunsmith for a rebarrel.. heck, i doubt 1/10 of 1% get rebarreled, though some folks HAVE to have new barrels...

go to your local range and ask every guy there if their gun has been rebarreled.. even the pistol guys... and if its more than 2 in 100, i'll buy the next round of beers

The interesting thing about a bad rifle barrel is most owners never know what the problem is and never do anything about it except sell it. This is a killer for the gun manufacturer's reputation. The rifle with the bad barrel spends it's life being sold from owner to owner never being used but leaving a bad name for the brand where ever it goes. Given such a rifle can last a 100 years one bad rifle can be a black eye for the company 20 times over.
This is a case of manufacturer beware.

Jeffe

I try to avoid bad-mouthing other shooters because we gun owners need all the friends we can get. But I suspect that the guys on this Forum are not your typical public range shooters so I'll say this.

Assuming your 2% number for rebarrels is close to being correct, then

1) The other 98% are probably happy with their 1MOA factory rifle

2) The other 98% probably cannot afford the $400 or more for a good re-barrel

3) The other 98% probably could not tell a good barrel from a bad one

4) All of the above.

I do my own smithing so I can't honestly say how long it takes to get a good smith to make a good barrel. But I doubt if those smiths are sitting around waiting for customers. I do experience the long wait for a barrel blank plus the wait for custom reamers and that tells me that their are a LOT of guys turning to the customs. And once you get one and see how a rifle or pistol can shoot, you'll never go back.

JMHO

Ray

quote:

Originally posted by Cheechako:

Steve

What I meant was that you set up so that the existing off-center chamber is lined up, not the outside of the barrel. .


Ray

How can you line up the existing off center chamber with the reamer if the barrel is going to rotate and the reamer remains stationary. Wouldn't this be physically impossible? If you line up the reamer on a crooked chamber, rotate the barrel 1/2 turn, now you are no longer lined up with the chamber. Wouldn't you be boring a big old cone shaped hole, kinda like rotating your hand drill in a hole to hog it out a bit.

[/QUOTE]How can you line up the existing off center chamber with the reamer if the barrel is going to rotate and the reamer remains stationary. Wouldn't this be physically impossible? If you line up the reamer on a crooked chamber, rotate the barrel 1/2 turn, now you are no longer lined up with the chamber. Wouldn't you be boring a big old cone shaped hole, kinda like rotating your hand drill in a hole to hog it out a bit.[/QUOTE]

Steve, to put it in a nutshell, you set the barrel up in the lathe by indicating off of the bore at both ends. Then when the barrel turns, the bore runs true even if the outside wobbles around it.

quote:

Steve, to put it in a nutshell, you set the barrel up in the lathe by indicating off of the bore at both ends. Then when the barrel turns, the bore runs true even if the outside wobbles around it.

Correct, the bore runs true, but the existing chamber is NOT lined up or parallel with the bore, it was cut crooked or off center with the bore.

If the original chamber was cut crooked to the bore, you're not going to straighten it with an improved chamber. In that case, you can;

A. Enjoy it the way it is.
2. Send it down the road.
D. Rebarrel it.

Your gunsmith was wise to say no thanks. When you work on a messed up piece, your name and reputation becomes permanently attached to it.

Steve,

Before you go worrying too much about it, you might want to get a second qualified opinion. Some gunsmiths will say anything to avoid working on A-Bolts because of the special shaped tooling required to pull the action.

FWIW, I have rebarreled and rechambered 'A LOT' of A Bolts and they are pretty consistent in their quality. You may in fact have an out of whack one, but based on what I've seen with A Bolts over the years, I would question an off center chamber claim without personally eyeballing it or running it in a lathe.

steve - like westpac says get a 2nd opinion - you're in minnesota - take a drive to bloomington & have jim kobe look, you're only out a few hundred dollars worth of gas

Assuming the smith is right, and the factory chamber is not concentric with the bore. Then why wonder how it would be possible to rechamber that barrel?? Why even consider plowing a whole bunch of $$$ into a dud barrel??

If the original chamber is truely off, rebarrel or sell the rifle.

Btw, a lot of factory chambers are hammer forged with the bore these days.

- mike

OK, thanks for the help. My questions have been answered and then some. I will take your advice and get a few more opinions.

quote:

There is a photograph in one of my ancient gun magazines of a gun company's operation in which a woman was chambering barrels with a drill press.
It was a floor model drill press with a metal garbage can sitting on the base. Inside the garbage can were a number of barrels leaning to one side and she was about to start the reamer in one of the barrels. After seeing that photo I made a point to never own a rifle from that company again and I haven't.

This was probably Thompson Center. They used to do it that way. They have come a long way since those days.

It was not TC. It was an old photo of the company that makes a big deal of locking their barrels in with a nut. They have been through several owners since then. I hope they don't use the drill press any more.

Ireload2, Savage makes very accurate rifles the last several years. They are butt ugly, but shoot.
Butch

The drill press incident reminds me of a tour of the Winchester facility on an outdoor tv channel about 4 or 5 years back.

The Model 70 barrel production was impressive until they got down to finish chambering and final headspace. The barrel was torqued up on the action then laid on a table, a rod was inserted into the bore, a pull reamer threaded on, bolt inserted behind it and hooked up to a glorified hand drill, reved up with rod flopping and bolt pushed closed with reamer rotating. Presto, a "precision" chamber according to the narorator.

Remington does their barrels the same way.
Look, it is entirely possible to correct a minor misalignment with a set back and rechamber but the work involved is greater than the fitting of a new barrel. Done correctly, there is no reason the chamber should end up oversized.
I'm not sure spending any money on an A-Bolt is everjustified! Regards, Bill.

quote:

Originally posted by Craftsman:
The drill press incident reminds me of a tour of the Winchester facility on an outdoor tv channel about 4 or 5 years back.

The Model 70 barrel production was impressive until they got down to finish chambering and final headspace. The barrel was torqued up on the action then laid on a table, a rod was inserted into the bore, a pull reamer threaded on, bolt inserted behind it and hooked up to a glorified hand drill, reved up with rod flopping and bolt pushed closed with reamer rotating. Presto, a "precision" chamber according to the narorator.

I always wondered why almost every late winchester classic I have seen has a ring around the firing pin hole on the boltface. Now I know.

quote:

Originally posted by mho:

Btw, a lot of factory chambers are hammer forged with the bore these days.

- mike

Hammer forging is for the rifling and OD.....not the chamber.

The chamber, bore and lug recesses on Sauer 200 series rifles are hammer forged. H&K also offers semi-auto rifles which utilize hammer forged chambers.

Blaser hammer forges their chambers.

- mike

Not saying it ain't so, but I've yet to hear of any of the gun companies advertising or mentioning that their barrels have hammer forged chambers, and I've seen the equipment in action in 2 different facilities.

quote:

Originally posted by triggerguard1:
Not saying it ain't so, but I've yet to hear of any of the gun companies advertising or mentioning that their barrels have hammer forged chambers, and I've seen the equipment in action in 2 different facilities.

Hi Matt
a wise guy onse told me that
Absens of proof, is not the same as proof of absens.

Alot of european companies hammerforge ther barrels to the final outer conture, and fully finished internal with both rifelings, and chamber, only needing treading, or turning and milling for counterhold for the lugs (switch barrel systems).
The manufactor of those hammerforging mashines, is mainly Austrian Steyer.

I guess that eventualy american companies also enter the present, instead of using the tecnology of the last millenium

This from a man who still cutrifle
But also runns unmanned multitasking mashines

Check out H&K's fluted chambers. Kinda hard to cut one of them with a reamer.

Eddie, of late I have run into a couple of references to "fluted" H&K chambers. Any idea what the purpose of these are??? Why does it make sense to "flute" a chamber - or how should I understand this??

- mike

quote:

Originally posted by mho:
Eddie, of late I have run into a couple of references to "fluted" H&K chambers. Any idea what the purpose of these are??? Why does it make sense to "flute" a chamber - or how should I understand this??

- mike

There are minor grooves along the inside walls of the chamber, designed to leak gas down the outside of the case, so it doesnt stick to the chamber, while realoding still under preasure. As it is an gasoperated semi/automatic rifle

Results:
It works werry stabil, and it always destroy your brass

Thanks jørgen, that makes sense.

- mike

quote:

Originally posted by jeffeosso:

go to your local range and ask every guy there if their gun has been rebarreled.. even the pistol guys... and if its more than 2 in 100, i'll buy the next round of beers

Jeffe - I appreciate where you are coming from, but before you make offers like that, you might want to be a little more circumspective about it. That is, you might want to restrict it to PUBLIC ranges.

Our private range has over 1,000 members/shooters. At least 1/8th of them (125) that I know of have had their rifles rebarreled. We have a rimfire match, a benchrest match, a varmint match, etc., every month. Those guys do what they need to do to have a chance to win. So, 48 weekends of the year, at our range you would be buying the beer!!

Now, if you came to our club during the 4 weeks of Sight-in Days every year, when we let the public use the facilities, you'd probably be getting the free beer. But that isn't a balance sheet that I'd think you'd want to explain to der hausfrau, is it?

Point well taken, just suggesting that venues differ,so a guy has to consider his audience.

And gives me an excuse to yank your chain anyway.
,

Best wishes,

AC

quote:

There are minor grooves along the inside walls of the chamber, designed to leak gas down the outside of the case, so it doesnt stick to the chamber, while realoding still under preasure. As it is an gasoperated semi/automatic rifle

Blows holes in the theory that case to chamber-wall grip keeps bolt face load to safe levels.

I have reloaded cases fired in a fluted chamber and they were just fine. The cases I did not like were those fired from an R4 (Galil). These all had a severe dents in the case wall from violent ejection.

quote:

Originally posted by 303Guy:

quote:

There are minor grooves along the inside walls of the chamber, designed to leak gas down the outside of the case, so it doesnt stick to the chamber, while realoding still under preasure. As it is an gasoperated semi/automatic rifle

Blows holes in the theory that case to chamber-wall grip keeps bolt face load to safe levels.

I have reloaded cases fired in a fluted chamber and they were just fine. The cases I did not like were those fired from an R4 (Galil). These all had a severe dents in the case wall from violent ejection.

Who with any basic knowledg about firearms made this theory about case sticking helping to maintain saft bolttrust.
Actualy UK prooftest require an oiled chamber under the tests with 30% overload.

If a weapondesign is so weak, that there would be any risk, or material stress, when a chamber is wet. This design is both POOR AND HASARDUS.

Most boltrifles are designed to withstand boltthrust 3 times higher than a standardloaded and oiled case can deliver

quote:

Originally posted by jørgen:

Who with any basic knowledg about firearms made this theory about case sticking helping to maintain saft bolttrust.

I'm sure someone somewhere uses this line of thinking to justify pushing the envelope beyond the limits. If a person is loading a round so hot as to need the case to grip the chamber to help reduce pressure on the bolt lugs, then they are in over their heads and should seek help. Now!

quote:

Originally posted by Westpac:

quote:

Originally posted by jørgen:

Who with any basic knowledg about firearms made this theory about case sticking helping to maintain saft bolttrust.

I'm sure someone somewhere uses this line of thinking to justify pushing the envelope beyond the limits. If a person is loading a round so hot as to need the case to grip the chamber to help reduce pressure on the bolt lugs, then they are in over their heads and should seek help. Now!

I lube the cartridge with moly based products for maximum bolt thrust. The molybdenum disulfide lubricants have a breakdown ~50,000 psi, and help the case slide back, so it can push on the bolt face harder.


Someone once said that not lubricating a case, so that it will stick to the chamber to reduce bolt thrust is like putting the radiator in front of the bumper to protect the bumper.

But I don't think the fear of pressure in the gun culture has any silliness equals in other fields....maybe women who fear mice.

This could be becuase we read so much written by those with gunsmith folklore backgrounds on what is really engineering calculations.
....Like pressure.

Hi tc

I ame not quite sure about the meening in your post.
But bacicaly one should not rely on casesticking, in firearmsdesign, because you newer know if the sob, by accident puts oil in the chamber while cleaning .

Basicaly the weak point in most boltactions, is the casehead, beeing expanded from the primerpocket, leading to increased presurearea. Starting with the internal case area. Ending up with the entire boltface, as on CRF rifles exposed to casehead floating.

On a std casehead the preasurearea rises from 0.75cm2 to 1.7cm2, when a casehead lets go.
While on a PF rifle like remmington with there original extractor, the casehead is keept more or less intact, for a mutch longer time, resulting in no significant increase in area.
This has nothing to do with casesticking, only casehead design, and boltface rim support.

Your picture ilustrates nicely the beginning and continjuing of casehead floating.

Most bolt design can withstand from 10 to 20 tons of static boltface thrust, while a normal cartridge in std headdia. delivers from 2-3.5ton of thrust. From witch a normal quality brass is capable of carrying from 1-1.5 ton, by sticking to the chamberwall.

It might influence on accuracy and the creation of barrelvibratinos, but hardly on the stress of the lucking design

I think Ackley did an experiment with shooting a partially disassembled lever action where nothing held the action shut but his hand on the lever.

I would not try that with my hand and a lubricated case.