Straight Bores?

B

bob3700

Member
Boyd,

I can't tell you how foolish I feel. The rod that I am using to indicate the bore is a range rod and has a taper to it. Am not using the taper portion of the rod to indicate, just the bushing. It seems that I am reading the taper off the rod as I go from one point to another.

Just overlooked the obvious.

Thanks for your reply.


Bob
 
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When you do this, are you leaving the muzzle centered, He does not. He adjusts the outboard spider, (and the chuck) to get the readings that he wants at the chamber end of the barrel. This generally moves the muzzle off center. Once the muzzle is off center, it brings up the issue of clocking the barrel on the action. Some do. Some do not. It would seem to me that if one is shooting at a variety of distances, and making sight adjustments for wind, that clocking would be appropriate.
 
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Boyd,

"It would seem to me that if one is shooting at a variety of distances, and making sight adjustments for wind, that clocking would be appropriate."

Could you explain this statement?

Dave
 
Dave,

I won't speak for Boyd but here is what I believe the jest of the comment is.

When you center the bore/throat using the Gritters method, you are not indicating the muzzle. You just adjust the muzzle to make the breach end run true. Not the muzzle will be pointing off center to the bore line.

When you do that, most will index the bbl to have the max runout of the muzzle vertical. Now when you put your iron sights on the rifle, you are not using up all the windage on the rear sight to get the POI centered on the target.

For long range shooting, this indexing can be important so that you keep max windage adjustments on your rear sight.

Bob
 
It was a little more than that. If would seem to me that having barrel curve oriented at 90 degrees to vertical (worst case) would mean that the line of sight and the line of the bore would be divergent, be at a small angle to each other. With that situation, there would be a horizontal distance between the two that would decrease from the rifle to the distance that it was sighted in for, and then increasingly diverge from that point on, in direct proportion to the additional distance beyond that at which the the rifle is sighted. It would be as if a scoped rifle was sighted in in a canted position but with the turret axes vertical and horizontal. For shooting at one or two distances this would be no particular problem, but when a variety of target distances are involved, and accuracy standards/requirements are high, the result would seem to be undesirable complication. Or I could be wrong. :)
 
Boyd

I understand what you're saying but at some point, usually very quickly, real world conditions over ride theory and geometry. I've shot in some pretty bad blows over the years. One hurricane and I don't remember anyone running out of windage. I understand it's different way to skin a cat and it works but I have never seen a reason to try that method. I never bought into the argument about running out of windage and no matter what we still have to crank on knobs to adjust to the wind conditions we are facing at that point in time.

I had an opportunity to test 10 barrels on one receiver recently. Two different 338 calibers. All chambered through the headstock indicating the throat and the muzzle. Same barrel maker and same lot of steel. While testing these for accuracy it dawned on me that I had and may never get another chance to try this again. While shooting groups I fired one shot from each barrel on a seperate target with no scope adjustment through the whole test session. 9 of them went into 3.3" in a round group, 7 in less than 2.5". The odd barrel printed 4" left and was repeatable. Unfortunatey I didn't have time to investigate that one barrel to see if I could determine why it did that. I would have liked to set it back 1/2 a turn and see if it went right. Come to think of it I might be able to get my hands on that barrel again and try that.

All this is put into perspective from my time shooting 1K comp and what I'm doing now. In 1995 single digit groups were the exception. Now we have 338 sniper rifles shooting factory loaded ammo around .7-.8 MOA @ 1K. Much of what I thought was of the utmost importance has disappeared into the background noise.


Dave
 
Dave Tooley said:
Boyd

I understand what you're saying but at some point, usually very quickly, real world conditions over ride theory and geometry. I've shot in some pretty bad blows over the years. One hurricane and I don't remember anyone running out of windage. I understand it's different way to skin a cat and it works but I have never seen a reason to try that method. I never bought into the argument about running out of windage and no matter what we still have to crank on knobs to adjust to the wind conditions we are facing at that point in time.

I had an opportunity to test 10 barrels on one receiver recently. Two different 338 calibers. All chambered through the headstock indicating the throat and the muzzle. Same barrel maker and same lot of steel. While testing these for accuracy it dawned on me that I had and may never get another chance to try this again. While shooting groups I fired one shot from each barrel on a seperate target with no scope adjustment through the whole test session. 9 of them went into 3.3" in a round group, 7 in less than 2.5". The odd barrel printed 4" left and was repeatable. Unfortunatey I didn't have time to investigate that one barrel to see if I could determine why it did that. I would have liked to set it back 1/2 a turn and see if it went right. Come to think of it I might be able to get my hands on that barrel again and try that.

All this is put into perspective from my time shooting 1K comp and what I'm doing now. In 1995 single digit groups were the exception. Now we have 338 sniper rifles shooting factory loaded ammo around .7-.8 MOA @ 1K. Much of what I thought was of the utmost importance has disappeared into the background noise.


Dave
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Hey Toot, quit trying to bring sanity back to chaos. Don't you know that the rod thing is going to rule the accuracy world??
 
Dave,
Actually, I wasn't talking about the indicating in the muzzle and throat method of setting up a barrel through the headstock. I was referring to the way that Gordy Gritters has demonstrated on his CD.
Two very different ways to successfully skin the same cat. When doing it his way, the barrel is likely to end up at an angle to the CL of the action. What I wrote was intended to only apply to that situation. Heck, with you, Dwight Scott, and Jim Borden doing it the "old fashioned way" I would imagine that it is hard to maintain a respectable reputation, with such sketchy associations. ;)
On a more serious note, I always pay a lot of attention to your posts, and thank you for taking the time to write them.
Boyd
 
Boyd

I was contrasting the way I do it to Gordy's way with some real numbers. There is the occasional wild barrel that points off in different direction but 9 barrels in 3.3", two different calibers. I'm not sure a variation of plus or minus of approx 1.1MOA in impact is critical. Also I have learned a few things about harmonics, moment of inertia and some other large engineering words working with these all aluminum rifles that I think would have to carry over to other disciplines. That's for another thread.

You don't call anymore. ??

Dave
 
Hi Butch

I'm always curious about things. Sometimes it takes me awhile to catch on. Something about making a living restricks how much time I get to test these days. The good news is the basics are still just that and the more I learn the more important they are. Without bullets ( several to choose from), barrels ( plenty of good ones out there) and a concentric chambers (plenty of good smiths these days) subtle things get lost in the shuffle. These days I'm off tweaking things that nobody else would even try. Reamer design, bore dimensions, so many things to examine and so little time.

Dave
 
Dave Tooley said:
Hi Butch

I'm always curious about things. Sometimes it takes me awhile to catch on. Something about making a living restricks how much time I get to test these days. The good news is the basics are still just that and the more I learn the more important they are. Without bullets ( several to choose from), barrels ( plenty of good ones out there) and a concentric chambers (plenty of good smiths these days) subtle things get lost in the shuffle. These days I'm off tweaking things that nobody else would even try. Reamer design, bore dimensions, so many things to examine and so little time.

Dave
Click to expand...
Toot, Summers and I solved some of issues last night (shooting odd twists in new-age barrel designs and such).
 
Dave,
It's great to see you posting. I hope you do a lot more of it. Talked to Jeff last fall about you, I'd though you fell off the face of the earth but he said you were busy making the big bucks.

It's interesting reading what you are seeing at 1K. The army many years ago went to indexing artillery barrels to 6:00. It has to do with accuracy as it related to sustained rate of fire. It just made them more predictable. I always figured that 1K would be far enough to show a difference if there was one.

Kevin Hovis
 
The question that comes to my mind is, Even after indicating rods and bores on both ends, how do you "know for sure" if the bore is straight from end to end, without a slight deviation in the middle, and does it truly make a difference to the group size, or just to it's placement relative to the bolt axis? I am trying to maintain an empty mind on this subject, and others as well.
Regards,
Bob
 
Bob,
I believe all barrels have a deviation from one end to the other. Some are slight and some can be alot. I have chambered a pretty crooked one and it shot very well. I prefer straight barrel bores, but that doesn't seem to be the end all secret to a hummer barrel.
 
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