Lets discuss the "other" method of barrel chambering. (kind of long)

JerrySharrett

JerrySharrett

Senile Member
There are generally 3 considered processes for threading/chambering rifle barrels .

The oldest process, probably, is the between centers method, what I call the chuck/steadyrest method below. Granted, there have been many barrels chambered using this method, and many Hall of Fame points won by some great shooters using these barrels. Many top benchrest contenders still swear by this method, but it has some limitations not found in the other two major processes.

These processes were developed from the 3 main designs of engine lathes. There are the lathes that have a large spindle bore and a short headstock, this is what can use the spider/chuck method.

Then there is the second lathe configuration, the one with a spindle bore too small to do most barrels but has a sufficiently long bed to allow chambering using the chuck/steadyrest method.

Then there is the third major configuration, where the lathe has a sufficiently large spindle bore but the distance through the headstock is too long to allow using the spider/chuck method. Many gunsmiths use Jets, Nardini's, Mazaks, American, Monarch, Pratt & Whitneys, and such that fit in this box.

Within this third category there have been several processes developed to aid alignment of the outboard end of the barrel that is not being machined at this time. The main two, I would suspect, is to use one of several bushings to support the outboard end, and several unique "gadgets" like spring loaded centers.

Since the drill/bore, drill/taper bore, drill/bore (either method), use no reamer guiding bushing, use a loose pilot bushing or use a snug pilot bushing method has been beat into the ground with no provable answer, lets just skip that discussion here. It is another separate discussion.

IMO, the very best of the above is still the spider/chuck method, if your lathe allows since this process allows dial indicating both ends of the barrel simultaneously. None of the others above allow this direct alignment.
 
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Actually, there is another method. Samantha just wiggles her nose and does a perfect job in nothing flat. I like that one. I wonder if she checks her work?
 
Actually, a skilled hand should be able to chamber a barrel without using any machine at all. The barrel could be held in a vise, and the reamer turned using a bit brace, which like a floating reamer, would compensate for the irregularities of the operator. Of course this would take some practice, but is that not how the counterbore for the breechplug in old timey barrels was cut? As a matter of fact, were not barrels once bored in simple wooden bed and carriage machines, then rifled on wooden rifling rigs. All work was once done by hand. A competent smith would have made his own tooling use forge and file.
 
bingo said:
Actually, a skilled hand should be able to chamber a barrel without using any machine at all. The barrel could be held in a vise, and the reamer turned using a bit brace, which like a floating reamer, would compensate for the irregularities of the operator. Of course this would take some practice, but is that not how the counterbore for the breechplug in old timey barrels was cut? As a matter of fact, were not barrels once bored in simple wooden bed and carriage machines, then rifled on wooden rifling rigs. All work was once done by hand. A competent smith would have made his own tooling use forge and file.
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What you say is true, that is how it was done. That said, the issue of quality is of the essence for precision shooting. Nobody would bring a gun chambered using the wooden lathe approach to a BR match and expect to win.

As has been said in this forum many times (I'm taking the word of the writers, I don't have the personal experience), shooting performances that won championships even 15 years ago wouldn't win today. When I was growing up, hunting, shooting with my dad (late '40's through the 1950's) a rifle that would shoot a 1 MOA 3 shot group was the holy grail of rifles, and there were not a lot of them on shelves from factories, or even some custom makers. They are common today even from the factory at rediculously low prices in todays dollars compared to what the Winchester Model 70 cost back then. My Dad's 1953 Winchester Model 70, which I still have, was a 1-1/2 MOA rifle on a good day. I've made it into a 1 MOA rifle but to be 1/2 MOA it needs a new barrel.

So leaving out making chambers with stones and sharp sticks, I have to agree with Jerry that the large bore short spindle lathe permitting the spider/chuck technique to be used, is as good as it gets. It works for any alignment method, especially the two most common ones, and doesn't suffer from torsional chatter problems that can occurr using the steady rest at the far end of the bed.

Fitch
 
Frwillia, the concept of using a free floating reamer, bears direct relation to the old methods. The moment a mechanic casts the accuracy of the modern machine to the wind, and accepts the inherent accuracy of a tool which follows a different course,he owes a nod to the genius of his predecessors. So essentially, except for the apparently few smiths who chamber strictly using either single point or hard held tooling, most chambering jobs are completed by touch and feel. not at all different from the old ways.
 
frwillia said:
. . . shooting performances that won championships even 15 years ago wouldn't win today. . .
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15 years is not that long ago so I'd have to question that particular number - but, I don't think it has anything to do with lathes or the methods or skills of the operator.

Back in those days we didn't have 1/4 MOA bullets, cases or barrels. Or stocks. Or scopes or rests. Or anything else that todays shooters rely on. Give all of those things to a gunsmith like Gebby or Gipson or Dunlap and they'd shoot little dots too.

JMHO

Ray
 
There is nothing in shooting that does not involve a tradeoff. In fact, there's not very much in manufacturing that doesn't involve a tradeoff. They are just a fact of life. When in comes to chambering, maybe the tradeoffs are in the setup, maybe they are in the bullet delivery, maybe they come in the form of stock alignment or lord only knows what else. Maybe they involve changes in brass prep, or die making, or bullet selection, bullet seating, tool choices, instrument choices, the list is as long as the number of things we know about rifles.

All manufacturing operations involve a mean, and a tolerance. When manufacturing involves a dozen steps, and the guy who does the first operation is lazy and uses the entire tolerance, guess what the 11 poor souls behind him get? Ehhh, between not very much, to nuthin'. Here's where purchasing good stuff comes in. Those parts that you have no control over, had better be either coming from someone you have great trust in, be modifiable, or not need a real close tolerance. Each of these things counts toward the final product tolerance.

Now, when the item being machined and the setup used, involves the amount of geometry a chamber job does, you start to see how discussions like this can take place and have so many folks with different opinions. If this discussion was on , "What's the best way to make a bronze bushing", I think it would come to an end much faster.

Last but not least all of this comes down to your opinion of what is important and what is not. Unfortunately, there is no consensus on that either. About the only thing most would agree on is that the throat should be in the center of the bore. Is one machine or one setup method more or less apt to get that to happen? I'd say each way has a chance (with operator error) to be grossly out of whack. Maybe some methods more than others. My opinions of what is important seem to be a minority opinion at best. Either that or it's the vocal minority that disagrees, and the silent majority that agrees. To me, what angle (every so slight) there is to the chamber, with a stationary bullet, is meaningless. The bullet will BEGIN it's ride from the throat, and that supposed "angle" is already behind it before it starts. Whatever condition in inside the barrel forward of there is out of our control, so no need to loose sleep over that. Get it to engrave right and let'r rip.

With that in mind, I no longer worry about what is happening at the muzzle end of my barrels. I don't remember when was the last time I even bothered with that. Mine go in a bushing, and where it is, it is. The bushing is plastic, it fits tightly (or I make one that does), it's cut ID/OD simultaneously, and it fits in a spindle bore that's pretty darn nice. My "Indicating" is now reduced to running the spindle in jog mode and looking at the thing to see it isn't out a mile. Didn't get a chip in the bushing, or some other crazy thing. Past that, I just don't care. So, Jerry, my lathe setup is the category you mention with the spindle too long to check the other end (without ludicrous work). I know I can easily see .003 with the naked eye (runout) and so if it looks good, I just say "it's good".

If it ain't good, I'll just tell myself that the lathe I use is a hell of a lot nicer than most, so I have some extra "tolerance" to work with! ;) All other things but the barrel are completely within my control (make my own tooling, etc). Does it matter? Well, makers of gun stuff are making pretty nice stuff, so there's not a lot to improve on in many cases. It starts coming back to how much you dot I's and cross T's. With so many doing well on that, chambering is only a very small portion of winning / loosing.
 
Your in-the-headstock bushing, if fitted properly will get you spindle to bore ID concentricity of about 0.0005" and that is close enough to insure the POI is in line with the recoil track. IF, when changing barrels, your POI is within about +/- 2" of the POI of the just removed barrel then that is plenty close.

The part of this thread I was trying to get details expressed for newbies is this bushing-in-the-headstock process.

There are several bushings that need to be made to maintain sufficient accuracy of the finished product.
 
Well, its has been a good education for me Jerry. What I am getting is Its all about the bore, and the orientation of the chamber to the throat as the point from which the rest of the breech end work is accomplished. So If turned between centers what you end up with is true OD surfaces only in relation to the first few thou of the hole on either end, which are likely not in line because the bore itself in not perfect. If you then chuck the barrel up into a steady out over the bed, the angle of the bore will be skewed, and although your indicators will read right on the OD... the ID would be in disagreement. To avoid this situation, the barrel is placed through the headstock into a spider arrangement, and indicated off the bore at a point in the tube corresponding to where you want the throat to be. Because the bore is not true, this may give the out of true appearance to the outboard or muzzle end of the barrel because it is actually not in line with the throat area of the bore as it is turning. Have I got this right? I need a bit of help then understanding what the bushings in the headstock are snugged up with. Is the idea just to give enough support to the barrel in the headstock to keep it roughly centered while maintaining the true bore reading at the business/ chamber end?
 
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bingo said:
. If you then chuck the barrel up into a steady out over the bed, the angle of the bore will be skewed, and although your indicators will read right on the OD... the ID would be in disagreement. To avoid this situation, the barrel is placed through the headstock into a spider arrangement, and indicated off the bore at a point in the tube corresponding to where you want the throat to be. Because the bore is not true, this may give the out of true appearance to the outboard or muzzle end of the barrel because it is actually not in line with the throat area of the bore as it is turning. Have I got this right? I need a bit of help then understanding what the bushings in the headstock are snugged up with. Is the idea just to give enough support to the barrel in the headstock to keep it roughly centered while maintaining the true bore reading at the business/ chamber end?
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Bingo, starting with your steadyrest question, there are at least two steadyrest chambering methods. One method is to put a new center in the breech with a piloted center, then turn the tenon OD (at least partially) and run the steadyrest on that. Some even repeat this process twice. This method may not give you a really good merger of the chamber throat and the barrel bore.

Another method of steadyrest chambering, and better IMO, is to run the breech in the steadyrest and in a spider type sleeve where the OD of the sleeve runs in the steady and it has 4 screws on each end of the bushing to allow indicating the to-be throat area. This method is kind of a pain to dial in but the potential for a better job is available.

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One of the in-the-headstock bushing methods is to start with a bushing on the to be breech end where the bushing OD is a slip fit to the lathe spindle bore and that bushing ID is a snug fit to the as furnished breech OD. (Most common benchrest barrels as furnished have a 1.200" or 1.210" OD) This allows the muzzle to be dialed in with the chuck and its OD turned to fit another bushing,

This new muzzle bushing OD will be a slip for to the spindle bore and its ID to be a snug fit on the just turned place (about 3/4" or so long). The barrel is then turned around to where the breech can be dialed in closely with the chuck. This end is then finished (tenon, cone and chamber).

Another bushing is then used to fit the tenon OD or the tenon threads and the barrel is turned around again. This final operation will include cutting the previously turned portion off and finish the crown.

Intermediate to all of this the barrel must be cut to near the desired finish length. Some smiths even add other steps to the above to improve the finished product.
 
I'm repeating something Dave Tooley told me quite some time ago, so if I get it wrong, don't blame Dave, blame my memory. 15-20 years ago, he use to chamber up some long, thick (1.7") 1,000 barrels on his smaller Nardini, and those had to be done between centers. He'd cut a new center & cut the tenon & thread between centers. Then, he'd set the steady rest up on the threaded part. He always felt he could get a better chamber that way, better than running the steady on the trued blank, or even fresh tenon.

Anybody else had better success setting the steady up on the thread?
 
Jerry, with input like yours, I am piecing the puzzle together bit by bit. The learning curve has been shortened dramatically with knowledge accrued from reading posts on this site. I have completed some builds using the best information I had at the time, but seriously... here, the game moves to a whole different level.
There are a few things about what I was reading that took a bit of time to sink in, which now seem obvious. Still, I have questions, most of which seem to revolve around heat build up, and barrel movement when firing.... the whip of the barrel so to speak, and how these issues are mitigated. Much to think about, much to learn. I know that a lot of guys here have been pondering these issues for a very long time, and working out the answers in sweat and steel.
Thanks for the help.
 
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Charles

I know a couple of very good shooter/smiths who chamber the way you described. They, and their barrels, win a fair share of fake wood trophies. I won't give their names here because they and their methods are sure to be criticised. It's also the way I do mine but no one would put much value on my endorsement.

Spin the blank between centers. Mark a spot near the muzzle end that runs true. (On most good barrels they run true the entire length). Chuck the muzzle end in a four-jaw, chamber end centered, cut and thread the tenon. Transfer the thread to a steady rest and ream the chamber.

Everything is indicated to the nearest 1/2 millionth, of course. The barrel will be shot out and the trophies will be on your wall long before someone tells you that it can't be done that way.:cool:

Ray
 
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Bingo, it is all of those other nagging details that have to run dead true with the chamber that gets in the way. You know, the thread, the shoulder.

I agree with Jerry, if you have a lathe that has a large enough spindle hole, and a short enough headstock, chambering with a chuck and some type of spyder to support the muzzle end is probably the easiest way for the hobbyist to dial a barrel in.

I could set up my EE Monarch to do this, but I insist on doing barrels in my Pratt & Whitney, for reasons of my own.........jackie
 
Yep, the rifles I have done so far have turned out as excellent shooters, and they were done by turning between centers, and chambering in the steady using the piloted floating rougher and finisher. Chambers were cut as pretty as I have ever seen, and turning the tenon, threads, counterbore for the bolt, etc. were done just like any other work I would do on a daily basis, easy peasy. Reading here though, is expanding my horizons on the subject, and of course any job worth doing is worth learning how to do well and with understanding of how each bit is effecting the next bit. Maybe its all for nought but that is a road that will have to be travelled. My sense is that here there are some that have gone the distance.
 
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Thanks Jakcie, I have enjoyed your posts, Guess I will have to get my 13x5 out of mothballs and set up a spider on the spindle. I dont blame you one bit for being attached to
your Pratt & Whitney..... god bless American Iron.
 
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bingo, all the information is good to know, even if you end up considering it what not to do.

Charles, do you mean that Dave was bearing on the uncut tenon, or on threads? You and Ray both mention this, but I'd be surprised if they were bearing on the threads as they chambered. jmho. I suppose it is possible, but I probably wouldn't, and no, before today, I'd never heard of anyone doing that, unless what you meant was to rough the tenon, then bear on it.

I have 4 choices of machines to chamber in, none of which would be considered by many to be ideal for gun work. The Victor has the shortest headstock by a good bit. But it's still not short enough to be able to indicate the muzzle without at least some reaching apparatus, even on a 30" barrel. Two others, while really nicer machines with nice low rpm capability, are simply too big to seriously consider using for barrel work. So, for me it comes down to the smallest lathe and while it does not do a few things the others will, it does a whole lot of stuff they won't.

Tradeoffs, tradeoffs, tradeoffs...

I also wanted to mention about the early posts where it was said about groups from 15 years ago... At least in 1K Br, that was very true, 15 years ago groups and scores would get killed nowadays, and I don't think it's nearly as much because of gunsmithing advancements as it has been in new powders, better bullets, brass and actions. Optics while they do look nicer, did not have huge problems to fix. Nor did barrels. I've seen old barrels rechambered and shoot contemporary groups with new good bullets. Gunsmithing be damned (my own included) I think if you hand everyone some 15 year old bullets, you'll see the groups open back up like they were.
 
jackie schmidt said:
Bingo, it is all of those other nagging details that have to run dead true with the chamber that gets in the way. You know, the thread, the shoulder.

I agree with Jerry, if you have a lathe that has a large enough spindle hole, and a short enough headstock, chambering with a chuck and some type of spyder to support the muzzle end is probably the easiest way for the hobbyist to dial a barrel in.

I could set up my EE Monarch to do this, but I insist on doing barrels in my Pratt & Whitney, for reasons of my own.........jackie
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The two lathes I currently have in the shop are 17 1/2" spindle length, 1.5" and 1 9/16" spindle bore. MY new 2" spindle bore lathe (still arriving...) has been custom shortened to 20" at the factory.

I prefer the thru headstock chuck/spider, or spider/spider method if possible so that I can see where the muzzle is. Barrel blanks usually have to be over 24" for me to work on them and fit up the flushing system attachment at the muzzle though.

For the occasional short barrel (or rechamber job) I have fitted a 'barrel blank extender tube' to the end of the blank being worked on so as it get something out the end of the spindle end to adjust on, as well as attaching the flushing system nozzle. Maybe some guys with an overly long headstock/spindle could try that?

The extender can either be threaded to the end of the barrel blank (if you have enough length to chop the threaded bit off later), or if it is having a muzzlebrake or silencer you can incorporate the same thread.

Alternatively, I did have to make up one 12" long extender tube for a little sako barrel that was secured with 8 little grub screws and a couple of rubber o-rings to provide a seal for the coolant fluid as I didn't want to thread the muzzle on that one. A threaded muzzle is a bit more secure join though......

Good post Jerry....

Cheers, Dean.
 
4Mesh said:
Tradeoffs, tradeoffs, tradeoffs...

I also wanted to mention about the early posts where it was said about groups from 15 years ago... At least in 1K Br, that was very true, 15 years ago groups and scores would get killed nowadays, and I don't think it's nearly as much because of gunsmithing advancements as it has been in new powders, better bullets, brass and actions. Optics while they do look nicer, did not have huge problems to fix. Nor did barrels. I've seen old barrels rechambered and shoot contemporary groups with new good bullets. Gunsmithing be damned (my own included) I think if you hand everyone some 15 year old bullets, you'll see the groups open back up like they were.
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Here's my feelings of the 15 year timeline. I will put my 15 year ago Jef Fowler and Ed Watson bullets up against anything today. Now if you are talking about factory/match I agree that Hornady and Sierra do have better match grade products.

Scopes-The Leupold Competition Series and the March are much better in optic quality and in parallax control than competition scopes of 15 years ago..

Barrels-I'm afraid we may be in for some poorer quality barrel steel for the foreseeable future. It's our fault guys and gals. We let the EPA run most of our critical products industries off-shore. Talk to your legislators about this....today!!

Barrel blank quality-be thankful for what we have available today. Competition has aided this section of product quality.
 
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