Curvature in barrels and chambering

C

chino69

New member
The whole discussion around curvature in barrels and proper chambering was very interesting and I learned alot; thanks to all who shared their knowledge. Is this technique something that is relatively new or has it been going on for some time? There is a pretty good article in the new issue of Varmint Hunter by Gordy Gritters that explains the process very well. His exaggerated dwgs. help to visualize what he is describing and it's something that would have never entered my mind. Did one of you guys discover this and pass it on? Has anyone compared the difference between traditional chambering versus Gordy's method and noted the differences?
Chino69
 
Chino

With the risk of sounding like a broken record, the ID's of barrels are not curved,as in the shape of a bannana. They have sudden and abrupt spots that are caused by the Gun Drill walking off at that particular spot.
In fact, I see barrels where there are more than one spot,and the spots might actually run opposite of each other.
Aside from that, Gordy Gridders is an excellent craftsman. He has a method of chambering barrels that he is comfortable with, and the results seem to be good.......jackie
 
Gun Drill walking

jackie schmidt said:
With the risk of sounding like a broken record, the ID's of barrels are not curved,as in the shape of a bannana. They have sudden and abrupt spots that are caused by the Gun Drill walking off at that particular spot.
In fact, I see barrels where there are more than one spot,and the spots might actually run opposite of each other.
Aside from that, Gordy Gridders is an excellent craftsman. He has a method of chambering barrels that he is comfortable with, and the results seem to be good.......jackie
Click to expand...

Jackie,
Thank you for the response. Does Cyro treatment, prior to deep drilling, minimize this walking?
Chino69
 
Among past articles in PRECISION SHOOTING were a few on "barrel Scans". I think the author was Geza Negy.(Someone please correct me if I misspelled his name ).
The barrels sent to a company to have scanned were returned with a graph that showed actual twist, uniformity of twist, bore diameter and straightness. The graph would tell you the most uniform, usable section of the barrel and the ideal spot to locate the muzzle for uniformity.
As Jackie stated the bore is not curved in one big arc, but a series of zig-zags to some extent.
Perhaps someone can post a past "barrel scan" .

Hal
 
Jackie?

With either problem, it would seem the technique of indicating the chamber end of the barrel accurately, is still valid?

Or is it just as well to indicate muzzle and chamber and assume in between is straight?

I've been playing around with these range rods and it is a major pain in the ass to move the spider in attempt to true the throat area, because it is hinging on where the jaws bite on the bbl..

So, what I have been fooling with, is biting the 4 jaw, basically where the throat is, and indicating that in, with this long stylus (thanks to the guy who hooked me up with it) and then, I move the muzzle end in the spider, and dial the breech in. But of course, the throat moved a little, and the whole process started again. Painful.

Maybe I need to just be more patient?

Ben
 
Ben, In the DVD Gordy was getting the first two inches of the bore dead nuts and was not concerned with the muzzle. I had to really adjust my mindset when I finally got the bore straight where the chamber was and the muzzle was running out. In the past I would have both ends running true according to Deltronic pins but the pin wouldn't extend 2 inches into the bore at the breech end. I've not shot the barrel I did a la Gordy but I will sometime today and I'll see how it shoots.

You're right, it is tedious getting the bore running straight for the first two inches. I figured out that you indicate the forward portion by moving the 4-jaw and you move the very end of the breech by using the spider at the muzzle. You just have to keep going back and forth until it's running true. Good luck.
 
Ben

As a Machinist, I can tell you that indicating any thing is a tedious experience. The only thing that makes it less tedious for persons such as Myself, is we have done in thousands of times. It is one of those things that you tend to get a feel for.
The principles are the same, whether you are indicating a barrel or a 40 foot 18,000 pound shaft. With the barrel,you have to be careful and not induce deflection by actually bending the barrel instead of shifting it in the chuck jaws, or other securing devices. It is the same with the 40 foot long shaft.
In the Machinist World, we figure out ways to accomplish this. I have anylized some of the various set-ups that many Gunsmiths use, and I feel safe in saying that they have not.........jackie
 
Adjusting mindset

MColeman said:
Ben, In the DVD Gordy was getting the first two inches of the bore dead nuts and was not concerned with the muzzle. I had to really adjust my mindset when I finally got the bore straight where the chamber was and the muzzle was running out. In the past I would have both ends running true according to Deltronic pins but the pin wouldn't extend 2 inches into the bore at the breech end. I've not shot the barrel I did a la Gordy but I will sometime today and I'll see how it shoots.
Click to expand...

Mickey,
This is the question I was asking, because it appears that some smiths still indicate both ends in as you mentioned. Gordy's method makes sense and now I'll have to buy the Grizzly CD to gain a little more info.
Chino69
 
The problem you are having with the jaws of your chuck inhibiting movement of the barrel when you are attempting to dial it in via the range rod is best solved by using copper wire rings between the barrel and the chuck jaws. I use 1/8" dia copper ground wire to make the rings by winding it around a proper sized piece of round stock like a closed coil spring, splitting them apart with a hacksaw, straightening out the helix in a smooth faced vise and deburring the ends on a belt sander. Slip one over the shank of the barrel and seat the OD of the ring in the grooves of your 4-jaw and start dialing away. The narrow contact area allows easy movement of even the light weight sporter barrels using the spider on the rear of your headstock. Hope this solves your problem.
 
Gordy's method of dialing in a barrel to get the first two inches of the bore straight is somewhat similar to the way an action is dialed in for truing/blueprinting using a Gre'-Tan style action fixture. The first few times I dialed in an action, it took considerably longer than did the machine operations I was dialing it in for. Once I got my mind wrapped around the concept and got past the confusion of having to move the back set of screws in the opposite direction as the front ones, it began to take a lot less time to dial an action in. Same thing is true with using Gordy's method of setting up a barrel - once you've done it a few times, it gets easier & faster.

I also use #9 copper wire around the breech in the 4-jaw, and agree with Riflemeister - it allows the spider to be used to help dial in the breech section without putting bending stress on the barrel.
 
I've watched the video. So, I'm familiar with the Gordy system.

Just wanted some other feedback from people on here, that obviously, do some pretty good machine work.

I do not mind a long tedious indication, since I'm only chambering barrels for myself and close friends, but i just want to make sure the process is the best way forward.

Jackie mentioned some advantages of indicating the ends (he makes a bushing for the muzzle end) The foremost being, that you can set the barrel back up accurately in the lathe. kinda the same concept as turning between centers, where the workpiece can be removed, and replaced accurately every time. With these 6.5x284 bbls I'm doing now, this is important to me.

So, I just wanted to get some opinions from machinists, that work for them.

I apologize, as this has been hashed over a lot....

Ben
 
Ben, No need to apologize so far as I'm concerned. I seldom get my mind wrapped around a new idea or concept the first few times I hear or read it. If I can see it I'm in better shape and that's why I bought the DVD. You can 'splain it to me 'til the cows come home and I may still not fully get it.
 
I use 1/8 inch brass rod in the 4 jaw, indicate at both ends... the muzzle within a thou, the breech as close to a ten thou as I can get... in as close to the throat as I can get...
Barrel%20Fitting%20Set%20Up.JPG
 
I saw one for sale, similar to above, from a high school shop. looked mint, lots of tooling.

It was too far to go pick up, and the guy would not deliver.

Still looking for some good american iron, will continue to use the imitation until then.

Ben
 
Dennis

I haven't seen a little Rockwell lathe in a long time. That one of yours looks to be in great shape.
What size is it??.........jackie
 
Dennis Sorensen said:
I use 1/8 inch brass rod in the 4 jaw, indicate at both ends... the muzzle within a thou, the breech as close to a ten thou as I can get... in as close to the throat as I can get...
Barrel%20Fitting%20Set%20Up.JPG
Click to expand...
You can also buy a piece of copper grounding wire about the same size at almost any lumber and supply.
 
Jay Lynn just picked up another one at auction that was almost like new. He was very lucky. He gave his old one to his son. He does need a good 3 jaw with a L00 backing plate.
Butch
 
It is a great gunsmithing lathe... an old gun smith friend of mine bought it in 1973. I ordered one then and they could not deliver... they stopped making them...

I waited for many years to buy this. I have lots of extras and it has never been abused...

lathe.jpg
 
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