Home Forums Hunting & Shooting Gunsmithing Chambering methods

Butch thats what im getting at i think im doing something wrong? i shouldnt have that much runout on the outboard spider side right? Its just a facotry take off barrel im learning on. Im using a long reach indicator and measuring off the bore and lands, i measure at the end of the barrel then run the indicator as far in as i can and dial in at that point.

Chambering a barrel is like voodoo magic to gunsmiths. They all have their little quirks on setting up a barrel. BOTH methods work. You'll find that 'smith's who chamber barrels for short range benchrest prefer to indicate both the muzzle and the throat area in while SUCESSFUL longrange gunsmith indicate the throat area and 2" forward.

We learned it in person at Gordy's basement shop in Kansas City MS. Much research and testing went into choosing a method before I flew Brady out to study directly with Gordy for a week. We use weighted Grizzly rods and a Starrett No. 708A .0001" indicator to reach the throat and 2" farther in. We don't stop dialing until the needle has no perceptible run out. That's the best that can be done.

Not many winning gunsmith publishing their actual methods but I would venture to guess Gordy and Shiraz are not the only ones. That system makes more sense than any other method. The banana bores are real and can be reliably measured and proven. Does it mean that between centers can't work. Certainly not. I would venture the majority of records were set before Gordy ever took up the sport. I also know that to be at the top guys are hand picking the best barrels possible, chambering themselves or having them done and then testing to find the best ones. The rest are sold to varmint hunters. Even using our method I would still do the same if I wanted to compete.

The 708A Starrett has a 13/16" probe. How do you reach 3.5" plus with a 13/16" probe. I do know many of the winning gunsmiths personally. 95% of them do it in the headstock. They indicate both ends. If your barrel is curved in the bore, Gordy's method will not straighten it. A crooked bore is like a spiral. Top guys hand picking barrels is BS and nobody can tell you if a barrel is good until it is shot. Tony Boyer is without a doubt the best BR shooter of all time by a great margin. Tony can shoot a barrel about 25 rounds and he will know if it is good. I hope your shop is not selling sub standard barrels to the public.

How does your method "straighten" a crooked bore?

There's a lot more to shooting beyond SR Benchrest...

This is a tough room tonight. How can you critique the Gordy method if you don't even know what it is as demonstrated by your response? Slow down and reread the whole post. I will try one more time but this is it. If I wanted I can reach about 8" or 9" into a barrel with a 12" long Grizzly rod. I hang a weight on it and use an O-ring lubed up in a drill chuck for it to pivot from. The business end has a fitted bushing on it and rides on the top of the lands held down by the weight. The Starret 708A is located as close to the barrel as possible to read any movement of the Grizzly rod.

I locate the end of the Grizzly rod with a fitted bushing at the throat and then 2" farther in. I go back and forth between those two spots and adjust until there is no perceptible runout for that 2" section. Then the barrel tennon is machined, the chamber single point cut to within .005" to .010" at the shoulder so when the reamer comes in the bushing is supported by the perfectly dialed in throat and 2" farther up the bore. Otherwise it's all for naught as the reamer will just follow the crooked bore leading up to the dialed in section.

Still with me? This gets the chamber and bullet perfectly aligned with that part of the bore. Inspection with the bore scope will now show that the throat and all rifling are of uniform length from the neck.

Dialing both ends at the same time will show rifling starting closer to the neck on one side than the other due to the curve present in every barrel. Even the slightest misalignment shows up with the borescope. In my shop that is cause for reject and the culled barrel is trashed on my dime. No questions asked. That's just me.

I wish I could prove my method shoots better but the truth is it is about impossible prove. As you know, no one can tell for sure how a barrel will shoot until you actually shoot it. We have all tuned up some factory trash that shot way better than it should. I can't explain why they work but the results on paper can't be disputed.

Dialing both ends at the same time, no one can tell if the barrel has any curve to it. Barrels are contoured from the ends so on the outside all looks well. While inside is another story.

When I said hand select they are slugging and visually inspecting the bore. The best ones are then machined up and then test fired. Same as I said earlier. The good ones go to the match and the sub par ones get sold to who ever at a discount. There is no secrets or deception. What does Tony Boyer do with his new barrels that are not up to shooting in competition? Does he melt them down or trash for scrap? Not likely. I'm pretty certain they end up getting sold to somebody.

No one is straightening a bore or a barrel. No one can control the bore inside a barrel so the best we can do is get the bullet into the bore as straight as possible and out of the crown as straight as possible. We also try to start with the best barrel we can find to begin with. Even here on hunting rifles we inspect every barrel before we waste a dime of the customers money machining on it. If the barrel doesn't pass then it is returned to the barrel maker for replacement.

I like precision. I like the best machining possible because it makes me feel good about what we do and I believe people deserve the very best for their money. For a fee I'm sure Gordy will be happy to teach it to you too. Like us, he loves the sport and wants everyone to be as successful as possible.
That's as simple as I can get it.

I have rifles and a race car to build so this will be my last on this subject for awhile.

Shawn

I built a tool similar to what you described. I soldered a pair of balls to a piece of drill rod. One end is held in a starrett center finder, the other rides the bore with a small weight to keep it down on the lands. I also have a 312b that has the 2.75" reach. I can't fine any appreciable difference, but the interapids has less margin of error, yet offers potential side loading the stylus.

I always try to start with my spiders close to zero on the bore on both ends, but from there.....it is what it is per the business end of the bore. I like to single point to get started just because I can't believe that little bushing is gonna work that hard to follow the bore perfectly. I use a floating holder that I built myself. I would love to have a rigid holder.....but I again can't swallow being able to yank it out of the bore 25 times and stay bang on, and my flush system is not yet done.

My system works well enough for me and my measuring tools. I can stay inside 3 tenths on my chamber using my system and sometimes better.

If I could change anything, I would have to try the deal nate dagley built in hopes of cutting my time. I can't do better work with what I have, but I would love to be able to do it faster.

Just wanted to save that little jewel...

Shawn a few years ago Dwight Scott (the smith who actually chambers barrels for Tony Boyer) was working on evaluating barrels prior to chambering and then tracking the barrel on how well it shot. Dwight was working with John Krieger to make improvements in John's barrels. I never did find out what Dwight used to critique a barrel, I do know people who received barrels from Dwight and we're told to save said barrel for national events, Dwight felt they were excellent barrels.

FWIW, if one does the math on a bore out even .050" over the 26" or 28"......you are talking about a bit of deflection that most of us can't chase out in the length of a throat with much luck unless you have a 500 tpi adjustment stud on your spider.

Or I'm just impatient. Or honest.

Shawn,
I know about Gordy's method and I have visited with him extensively. AJ Mag, ask Dwight about his chambering sessions with Tony. Ask him about Tony staying with him and looking over Dwight's shoulder. I think Dwight is as good a BR gunsmith as any person. You might ask him why he doesn't use the Gordy method.
Thank about this Shawn. A crooked bore is not banana shaped. It will be a helix. If the barrel is not straight, how can you indicate 2 points to the same exact axis. You can't. If you have done any machine work, you will know that you can't put a .2371 bushing in a .2371 hole. It would have to be about .2368 to slide in the bore. Also the bushing will require .0003 clearance on the Gordy rod.
Think about this for a little. I will return with more.

Gunsmiths can fuss all day about their methods of chambering a barrel and most of these smiths will turn out good shooting rifles , others will turn out average shooting rifle and every now and then one will turn out a great shooting rifle capable of winning matches. Every body has their way of doing things and some are just better than others. The best way to judge a Gunsmith is to look at his record.

Yes you can...

If your statement were true than how can you dial in the throat area of a barrel and at the same time dial in the muzzle area 20"+ away placing them both in the same plain?

Been doing it for over 34 years as a journeyman toolmaker, but hey you know better.

AJ300mag,
I guess I wasn't clear. I'm saying a barrel with a helix or whatever, you cannot indicate the bore or grooves to the same axis 3.5" apart and it being exactly straight between those 2 points. Is that better?
When I indicate both ends with my Deltronic pins, I am not concerned about what the barrel does between these 2 points and we have no control over it either.

Questions again?

Better...

Thing is, that 2" area between the two points will be closer to zero runout than if you idicate the point of the throat and the point of the muzzle crown, and then check the area forward of the throat. I've seen minor differences in the length of the pin. I understand the concept of trying to keep the bullet aligned with the bore using Gordy's method, yet benchrest smith's will tell you it doesn't matter. As I've said earlier other than in benchrest either method appears to work. I've done benchrest barrels using both methods and haven't seen a difference, I'm not at Tony's level of shooting either.

I think I'll stick with the magic pixie dust...

If I can indicate the throat and taper bore just short of it, It will be coaxial to the throat. Now my reamer will follow the taper bored hole and my reamed hole will be coaxial to my throat. It doesn't matter with my method or Gordy's as we still have no control over the straightness of the rest of the bore. My throat will allow for the bullet to be aligned to the bore. To get your compound at the right angle to taper bore put your reamer in the tailstock and indicate a flute until your compound is parallel with it. I ream with a pusher that I made. I don't want a reamer holder to influence my reamer travel.
Takes a lot of time.

I follow roughly the same process. Pre-drill the chamber and then check the throat area one last time. I bore the chamber (straight) to .01" under the shoulder diameter and then ream with a pusher, no floating holders for me.

Not to mention those indicating rods are not perfectly straight to begin with.

It's all tolerance stacking. or indicator can only read so close, the rod has it tolerance, How much runout in the spindle bearings of the lathe (not talking about your Monarch Butch) all this stuff adds up.
and like I said in my first post is depends.

And old Mosin nagant I'd chamber that with a cordless drill,
A precision rifle. I'm going to indicate with a rod to as best i can while also chasing my tail trying to keep the muzzle close to true.

On a bech rest gun... I'me sending it out for someone better then me to do

And guys if you don't know what Butch is getting at with a helical bore you don't understand deep hole drilling. The holes that are not straight are in a helix and don't just curve off in one direction. it's just like using a really long drive shaft you build torsion and that not only twists the shaft it also compresses and it ends up in a slight helix every time.

I could do the same with a rusty coat hanger. The method is not dependent on straightness or spindle slop of which I have none by the way. The weight holds the slack out. The .0001" indicator has zero movement at the throat and 2" farther is as good as it gets. Helix, banana, garden hose in a pile or a crazy straw with a knot in it. This method gets the bullet into the bore straighter than any other way. Until something better comes along this is the best way. Sorry I can't take credit for it.

Between centers shows up every time in the borescope and that constitutes a cull barrel. Even if they still shoot great I would never know because that barrel would have went in the trash. I refuse to bank shoot bullets into the wall of the barrel just because that's the way it's always been done.

Well you can sell that lathe for a million dollars because there is no machine in the world built that doesn't have run out. Add age and wear and tear and it gets worse.

Believe me you machine has runout you just never looked for it. Or if you feel so confident just show me the factor test report that came with your machine when you bought it.

A Hardinge second op lathe or one of the really nice Leblond's or Monarchs with the million dollar bearing option still have measured and noted run out. On the better machines it's listed in the millionths of an inch but on a standard tool room machine .0001" is not uncommon at the spindle. then add the TIR for everything you mount to the spindle, Magnify the spindle run out because now you are working a few inches away from the spindle face.

Then pull the specs on your indicator and read the accuracy and repeatability spec,
Even an interapid will not repeat to zero. See you trust a tool that you think has no degree of uncertainty.

[quote]I refuse to bank shoot bullets into the wall of the barrel just because that's the way it's always been done./quote]

Yet you refuse to look at the real numbers coming into play on your machine with your equipment and your tools. When was the last time that indicator was calibrated? Straightness of the rod matters to unless you are not rotating it with the barrel then you are potentially scaring up the bore.

All I'm saying is add up your runout and you will see it's not as close as you think

Young man,
You have a lot to learn about machine work. I hope your mind is not closed on this subject.