Curvature in barrels and chambering

[frwillia]

If a gun drill wanders while drilling just how much does it 'wander' and, assuming that it does is that not negated to some degree when they ream the bore? A reamer, being fluted for, say, an inch only cuts really on the bevel on the end but how much flex can the reamer have while it's cutting?

If the reamer streightens the bore because it is long and stiff it acts sort of like a tublar roadgrader. In that case, I'd think it will make the bore bigger than reamer diameter in the reigons where it is correcting. Not a lot, but bigger none the less. I'd think this would show up in the air gaging process and might get the barrel thrown out if it was crooked enough to cause the diameter variations to exceed specs.

So long as the chamber and throat is perpendicular to the bore it really doesn't matter where the bore goes between the throat and the muzzle, within reason, of course. That's why Gordy isn't concerned with the muzzle when he's chambering. He wants the 'high' point to be at 12 o'clock in relation to the action simply because it will give the 1,000 yard shooter a couple of minutes of more elevation. He said that is the only reason to be concerned with that. It's of no concern to us point blank shooters.

It also reduces range related changes in windage, but except in extreme cases, for point blank range varmint hunting and target shooting the variation would be less than the wind, or too much caffine.

I get my coffee, nobody gets hurt.

Fitch

 

[Roger rodbolt]

"In simple terms, the range rod is a long sloppy tool, on which assumptions are made. A 10ths indicator is a precise tool, with a lot less chance for error. i.e. it is more repeatable."

"Gordy has a hypothesis, not a theory. Until it can be quantified through analysis of variance, or some other practical means, I would say he cannot correlate his increased amount of accurate rifles to the assumed angular alignment of the bore to chamber."

"Quote" Ben]


The bushing tolerance, inner and outer, makes any bushed tool "sloppy", however Gordy uses a typical long reach 10ths indicator for the final adjustment before boring and again before reaming. The negates the "sloppy" range rod.

I attended (paid for) Gordy's chambering class/training at his shop in Iowa. The method shown on his video and much discussed here (less some details) is just one component of his approach to building a winning long range rifle. I can't quote him exactly but he said something to the effect "It now takes me four times as long to chamber a barrel as it did 20 years ago and I was building accurate rifles back then." I can testify that Gordy is not a slow worker, actually he is fast, organized and efficient, but because he is extremely diligent in his attention to detail means more shop time.

I've been around the block more then a few times and I've never seen such a thoughtful, common sense approach to accuracy from start to finish as Gordy exhibited. He build guns for consistency, which I believe trumps "repeatability" and with his record of building winning long range rifles I personally think that his method of chamber/crown alignment play a part, maybe small, but a part in his accuracy edge. It up to me or any 'smith to determine what is a good, best or reasonable effort (time $'s) to spend on a given procedure. When I saw his attention to checking new barrel blanks, testing tolerances on custom actions before barrel fitting, etc., it was clear to me that that good or reasonable isn't enough if you are building to the highest standard. Larry

 

[Butch Lambert]

Fitch, If you have as you said an engineering background and know a little about arithmetic, how much under bore size will your bushing be to slide down the barrel. How much clearance is there between the button and measuring rod?
How do you factor that in your equation?
Methinks Mickey is right. Do the best that you can, but spend your time at the range if you really want to be a good shooter. I don't think these keyboards have produced a winner yet.
Butch

 

[Dusty Stevens]

I don't know butch- it's come real close.... well, maybe not

so did yall chamber your first barrel yet? sometimes you just gotta do it to see how it works

 

[4Mesh]

I hope that some day I get my hands on one of these super crooked barrels so I can see what all the hubub is about.

If I had to guess, I'd say that taking "care" when doing the job is more important than the method you use. Winning guns have been built with about every method known to man, so condemning or promoting one over all others is tough to do.

If we are all honest with ourselves, we'd probably confess that a good bit of the accuracy in our rifles is put there by the folks that make the parts in them. Oh, we might not win all the time, but to call what match guns do, "bad" is really a stretch. Even when they're not shooting so good, they're still very good.

For the last many decades, the search for accuracy has been a slow process, looking for things so small they're almost not worth discussing. Things like this range rod deal, it may well be an irrefuteable accruacy asset. But, proving that over the other methods is virtually impossible. Gordy makes 1000 yard guns. Well, how do you proove that one 4" gun shoots better than another 4" gun"? They're both pretty darn good guns. So.... If one method works for you, or if you even think that method works for you, then use that method and do the best you can wtih it. If you're like me and think that something is meaningless, then you don't worry about that thing and worry about something else. (not trying to say good setup is meaningless here. Some things people do I disagree wth, and vice versa. It all works.)

I know that when I cannot PROOVE to myself that something I do is helping the situation, I stop doing it. I have done a lot of things to guns in my day and seen them go to the range and not shoot one lick different. I pretty much wait till I do something that makes the gun a lot worse, and then avoid that stuff. It's easy to identify troubles that way. Seeing improvements is a lot tougher to do.

 

[Roger rodbolt]

so did yall chamber your first barrel yet? sometimes you just gotta do it to see how it works

Yaw I cut on a few but don't understand how it works. Maybe you can help.

Why is it that the same run of barrels rifled with the same cutter or mashed with the same button, chambered with the same reamer and shot with the same run of bullets, each loaded for their best-- shoot to a different level of accuracy in the same rifle? Why do the "crooked" bores sometimes out shoot the "straight" bores? Why do the barrel makers say they can't pick a "hummer"? Since some jobs done alike turn out better then others it couldn't be in barrel fitting/setup could it........? My hair is gray and I still don't know these things.

 

[tim in tx]

roger

if the barrels are the same they would shoot the same,so what is different between the barrels,there has to be something different,my guess is the type of curve through the barrel are different even if it is the same run of barrels.i suspect it has an effect on the whip of the barrel, is it an s curve or a bananna curve? or is one straight and the other is curved. tim in tx

 

[Bnhpr]

frwillia,

Let us know how it works for you. Sometimes we get hung up on the process, and it becomes more important than the end result. A common pitfall of an engineer.

I could not get the Gordy's method to work for me, I tried to indicate a repeatable setup, and failed.

Maybe I'm just a poor machinist.

I am certain I can get a chamber in <.0002 tir, with unknown angular alignment.

But then as Jackie told me, what good is that when your brass is out .002"?

And who knows how bad it is angular?

 

[frwillia]

Fitch, If you have as you said an engineering background and know a little about arithmetic, how much under bore size will your bushing be to slide down the barrel. How much clearance is there between the button and measuring rod?
How do you factor that in your equation?

The answer to the first question is I don't know. But, in answer to the second question, I don't think it matters any more than it matters that an indicator tip isn't bore size when one sticks it in the bore. All that's required to zero out the clearance is to be sure the bushing stays against one side of the bore, just like the indicator tip does.

I don't think one needs a set of bushings to get best fit with a Grizzly rod in order for the method to work. One only has to have the bushing roll on one side of the bore.

I do want a set of busings to get best fit for the pilot on the reamer though. The same bushings work on both the Grizzly rod and the reamer so I suppose I could fit the bushing on the rod.

Methinks Mickey is right. Do the best that you can, but spend your time at the range if you really want to be a good shooter. I don't think these keyboards have produced a winner yet.
Butch

Roger that! Lot of wisdom in that and what Mickey wrote.

That said, this excellent forum is allowing discussion that is accelerating my learning process. It says a lot about this forum that a new guy can take a somewhat contraversial approach and have a good productive dialog. That is a very good feature of a forum.

Regardless of the project, I like to get my mind around something before I do it. Thinking it through, trying to understand is allowed, though not always taken advantage of. I realize I probably won't "get it right the first time", but I'd like to get as close as I can.

When I got back to reloading after a 35 year hiatus between when my Dad and I did it, well he did it and i watched and "helped", and now, I bought QuickLoad to be a teaching tool. A lot had changed in that time, and when I did it as a kid, I didn't really understand everything that was going on (Dad probably didn't either but the bullets always came out the other end just fine). I learned a lot before I ever measured the first charge, and was in a position to understand and evaluate my results, so I got up to speed in a very short time. I'm hoping that exercising due diligence with rifle smith metal working (chambering and truing) will have similar dividends.

Fitch

 

[frwillia]

frwillia,

Let us know how it works for you. Sometimes we get hung up on the process, and it becomes more important than the end result. A common pitfall of an engineer.

I resemble that remark.

Fitch

 

[brian roberts]

Now, all ya need......

to do, is to incorporate Gene Beggs' indexing of the barrel, and we can ALL go grounhog shootin'

 

[Pete Wass]

I wonder

How Savage Arms chambers?

 

[sharpshooter]

If you actually seen how they do it at Savage, you'd either laugh out loud, or wonder why it would still make their guns shoot like they do. It is accomplished on a turret drill press. The barrel is clamped vertically and stationary, and the tools turn. Oil is fed from the muzzle. The first tool is a champher, the 2nd is a core drill. The 3rd and 4th are a rougher and finisher reamer. The last tool is a flexi-hone which takes 20 strokes. The chambers come out well, but as far as being straight with the bore, that's another story.