Pre bore the chamber results?

[butchlambert]

I wouldn't say I know little about basic machining practice. I'm a machinist by trade and work for Pierce Engineering. In standard machining practice, you use a drill .010-.015 under the reamer size. I understand that, chambering seems to be some guys prebore and some guys don't. I don't understand why you chose to call me out when I said nothing negative about pre-drill/boring. I am not a chambering expert, and I noted that in my post. I simply said using just the reamer seems to be simpler and works for me. I never said drilling and boring was any less or more precise.

Does Gordy's method straighten the bore?

 

[Spotshooter]

LOL…. Only if you pull on the bore hard enough…

Gordy’s method ensures your chamber is perfectly coaxial with the bore at the end of the barrel you are chambering…. so the bullet goes in perfectly straight…

All barrels have some “rainbow” to the bore in them… Gordy’s method aligns you with the end of the rainbow !!

He Teaches a lot more than that in his class.. knowing how to evaluate a barrel is critical, not to mention how to orient the barrel‘s rainbow so hit is arcing in the right direction.

His class is worth it…

 

[jackieschmidt]

LOL…. Only if you pull on the bore hard enough…

Gordy’s method ensures your chamber is perfectly coaxial with the bore at the end of the barrel you are chambering…. so the bullet goes in perfectly straight…

All barrels have some “rainbow” to the bore in them… Gordy’s method aligns you with the end of the rainbow !!

He Teaches a lot more than that in his class.. knowing how to evaluate a barrel is critical, not to mention how to orient the barrel‘s rainbow so hit is arcing in the right direction.

His class is worth it…

What makes you thing the ID of barrels have he shape of a rainbow?
I find it difficult to believe Gordy told you that. He knows better.

 

[LVLAaron]

Gordy doesn't say that - Spot just means the bore isn't usually straight or aligned perfectly to the OD of the barrel.

 

[SKWERLZ]

Gordy doesn't say that - Spot just means the bore isn't usually straight or aligned perfectly to the OD of the barrel.

Considering long they drill that hole it’s amazing they aren’t far worse.

 

[Jud96]

Does Gordy's method straighten the bore?

I don’t know what you’re talking about?? I never said anything about Gordy’s method or saying that it straightens a barrel. I simply said I prefer using just a finish reamer over Pre-drilling and boring. I’m confused here.

 

[Spotshooter]

Bruce owner of BAT actions refers to what the bore does as a rainbow….

Gordy used to have a sliced up barrel laying on his table where you could see the bore wanders around inside the barrel as it goes down the barrel to demonstrate a bore wanders…

Hey LVLarson - you didn’t happen to live in AZ and Move to Colorado did you ?

 

[jackieschmidt]

Bruce owner of BAT actions refers to what the bore does as a rainbow….

Gordy used to have a sliced up barrel laying on his table where you could see the bore wanders around inside the barrel as it goes down the barrel to demonstrate a bore wanders…

Hey LVLarson - you didn’t happen to live in AZ and Move to Colorado did you ?

Well, as much as I respect Bruce as one of the premier action manufactures, he is wrong.

I have chambered a lot of barrels, and have never seen one with the ID exhibiting a constant curve like a rainbow.

 

[urbanrifleman]

For thirty-some years, I roughed the chamber with a common drill bit. For anything but match rifles, I still do. I check concentricity of the drilled hole before reaming. If it is off, I can bore it. It is seldom off. For target rifles and for short cartridges (2 inch and under), I'll bore. Straight barrels make for easy set up. Crooked barrels are a pain. WH

Drill bits want to follow the hole.

Bruce owner of BAT actions refers to what the bore does as a rainbow….

Gordy used to have a sliced up barrel laying on his table where you could see the bore wanders around inside the barrel as it goes down the barrel to demonstrate a bore wanders…

Hey LVLarson - you didn’t happen to live in AZ and Move to Colorado did you ?

It does. It's a spiral.

 

[Pres100]

Well, as much as I respect Bruce as one of the premier action manufactures, he is wrong.

I have chambered a lot of barrels, and have never seen one with the ID exhibiting a constant curve like a rainbow.

I think it was more of an analogy rather than in the literal sense .... Just a guess.

 

[Alex Wheeler]

I have seen barrels very straight on one end and pretty bad on the other. It would be very hard if not impossible to ACCURATELY measure that was going on in the middle. From what I have been told speaking with the barrel makers I use is, the reason the drill gets kicked off center is because of inconsistency in the steel. Even as little as 1/2 point in hardness can do it. So to say bores are curved in this way or that way is wrong. Since every piece of steel is different They are all all different. It does not seem to matter though.

 

[SKWERLZ]

I think it was more of an analogy rather than in the literal sense .... Just a guess.

This!

 

[butchlambert]

I don’t know what you’re talking about?? I never said anything about Gordy’s method or saying that it straightens a barrel. I simply said I prefer using just a finish reamer over Pre-drilling and boring. I’m confused here.

Sorry, you just quoted Gordy's book. Most of us agree the the bore moves in a random fashion through its length. Not a curve or rainbow. If you just use a reamer that allows the bushing to follow the bore, the back of the reamer will cut a larger body as it is acting as a boring bar. Hopefully you are following "my" reasoning. Now if I indicate both ends with the Deltronic Pins that I have-25 pins in a set for each caliber in .0001" increments. I drill and it allows me to reach in with my 513-504 Mitutoyo indicator. It has a short stiff probe and the body will fit in the drilled hole allowing you to indicate the throat area of a BR or PPC chamber. As mentioned above I indicate a flute of my reamer and move my compound to follow the flute angle. I have several solid carbide short boring bars. Now I taper bore to the indicated throat. Now your reamer will follow a taper bored hole that is coaxial with your throat and your reamer will be cutting with all the flutes. Now your bullet will be centered on the bore. I really don't give a damn which way it travels down the bore nobody but Jesus Christ can make any bore straight. On the muzzle I indicate both ends and cut a crown perpendicular to the bore. On a hunting rifle I recess the crown for protection.
Extra time you ask. If you want to do the best job that you are capable of a few extra minutes is nothing.

 

[Will Henry]

By the way, I have seen exactly one barrel which was visibly straight when set up in the lathe. By visibly straight, I mean there was no apparent runout of the bore when the lathe was running. It is possible to see a couple thou of runout this way. This barrel was no perfectly straight but was very, very, close. After I dialed in the muzzle to cut and crown it, I cut off four inches and checked it again. TIR was .0004; so that bore was offset by 2 tenths at that point, Pretty damn straight. I have seen a few others which were very close but a lot more which were freakin' awful!
Generally, if the drill gets a poor start, it ain't gonna get any better. One maker I visited drilled consistently crooked barrels and employed a barrel straightening press to attempt to straighten them, There was a stack of blanks next to the press and I picked one up and had a look through it. When I asked to see one of the straightened ones, he seemed offended and told me that was straight. It was not even close. The bores on those barrels were corkscrews, and I don't now how you would straighten them.
When I was working in a hydraulics shop, I was tasked with making some cylinders which featured a rod which had a hole drilled up the center (a probe fit inside the rod and signaled the amount of extension). Two of these were 2 1/2 inch rods, 54 inches long, and needed a 9/16 hole 52 inches deep. I took two new drill bits and turned 3/4 inch of the shank to 3/8 inch. I then fitted a 1/2 inch extension, 28 inches long, to the bit and silver soldered it on. The bits and extensions were perfectly straight I set the rod up in the headstock, just like I would a barrel. I bored a hole 9/16 by 3/4 inch deep, the give the drill a good start, and started drilling. I could drill 1/2 inch before pulling out to clear the chip. I took about a half hour to drill 28 inches deep. Then, I flipped the rod around and drilled from the other end. When I broke through, I pushed past the meeting point and there was no apparent offset. The second rod didn't come out as well and there was about .005 of offset. I then welded a plug in one end, to make the holes the proper depth, fitted the pistons, and there they were.
Previous to this, we had always sent these rods to a shop which had a gun drilling machine. This time, he wasn't going to be able to guarantee quick delivery, so I decided to give it a shot. I did them all in house after that. This shows that a common twist drill can do pretty good work, especially if it gets a good start. It's just a lot of work! WH

 

[urbanrifleman]

It does not seem to matter though.

Agreed.

As it is with nearly everything I read on the internets that is given so much importance concerning this topic of barrels and "what makes them shoot" .

 

[swd]

In 20 years I have seen exactly 1 barrel that was like a rainbow. We we’re doing a 50 cal conversion on a lever gun and it was only going to be 16”. We ordered a 33” blank so we could get 2 barrels for not much more then the price of one. When I cut in half on the bandsaw it was visually obvious in a big way. It was a “hey guys you gotta see this!” moment. The middle where I cut it had right at .050” runout! We thought about it for a bit and decided since the ballistics were only around 1300fps to use it just clock the high end at 12:00. It actually worked out very well. I believe it was one of the manufacturers that if a barrel didn’t pass in a smaller caliber they just kept re boring it bigger and bigger. But I don’t know how it passed QC at .500”..

 

[Spotshooter]

Ha - Boy have we wandered off the OP’s topic…

Jud96 - I was joking

Agreed.

As it is with nearly everything I read on the internets that is given so much importance concerning this topic of barrels and "what makes them shoot" .

yep agreed… if anything it will add a slight harmonic / node directional component …

The research group at Lake City outside of KC did some optical bore curvature research on accuracy … so yep..

 

[DSMWerks]

So let me wander a bit more. I've always wondered on the Brownells Chamber sheet about the .708 c'bore depth. Line 4 says A minus C which normally will run about .150" and then add .010" more for a depth of .160". You already have accounted for the .010" in line 2 so why do it again. I'm drawing it up in CAD and now there is .020" gap. I'm programing the .708" c'bore and pre drill and bore the taper a little under size with the same tool.
So do you guys use the .150" difference from the front of the bolt to the lug face knowing the tenon is already short or do you do like Line 4 and go another .010" deep for a .160" c'bore depth?

 

[Jud96]

Jud96 - I was joking

I’m really confused on this thread. I didn’t have any interaction with you or mean to take anything the wrong way. I replied to Butch and I think he misquoted or misunderstood me. I feel caught in the middle of something I’m not trying to butt heads about or really discuss other than I said how I do it and I’m pretty new to it. I didn’t say one way was better than the other.

 

[Dusty Stevens]

So let me wander a bit more. I've always wondered on the Brownells Chamber sheet about the .708 c'bore depth. Line 4 says A minus C which normally will run about .150" and then add .010" more for a depth of .160". You already have accounted for the .010" in line 2 so why do it again. I'm drawing it up in CAD and now there is .020" gap. I'm programing the .708" c'bore and pre drill and bore the taper a little under size with the same tool.
So do you guys use the .150" difference from the front of the bolt to the lug face knowing the tenon is already short or do you do like Line 4 and go another .010" deep for a .160" c'bore depth?

Do you have the action to measure?