Gene Beggs: muzzle 'clocking'

A

Al Nyhus

"It'll never work!"
Since Gene's threads on tuners opened this subject up, I thought it may be best to start a new thread to keep his 'Tuner' thread on topic.

Both of my .30 cal. BR rifles (30BR VfS and 30 Wolf Pup Hunter Benchrest) have barrels on them that have the bores significantly 'off ' in respect to the muzzles o.d.'s. The bores are straight..just not centered pefectly at the muzzle. One of them is .025 out and the other around .035. When Stan fitted the first one to my 30BR, it just happened to have the 'heavy' part of the muzzle at 6:00. This gun has never shown any sign of horizontal tendencies.

When it came time to fit the second barrel on my WolfpUp, Stan and I kicked it around a bit and decided to index the 'heavy' part of the muzzle at the 6:00 position to try and dampen any horizontal that might happen if the 'heavy' part ended up at 3:00 or 9:00...thinking that maybe that's why the 30BR barrel acted as it did. Once again, no horizontal tendancies.

Both of these barrels are from the same manufacturer and are, to date, the absolute finest performing .30 cal. barrels I've ever had on any of my BR guns, regardless of manufacturer.

Now, does this prove anything? Maybe. Maybe not. Maybe I just got two exceptional barrels. Maybe not. Maybe the 30BR and 30 Wolf Pup aren't the best examples to use here, given the .30's tendancy to hold their tuneup a bit better than the 6PPC. Maybe not.

But is sure is an interesting coincidence, if nothing else. ;)

When Stan recently fitted up the 30BR barrel for my 10.5 lb. RFD actioned rig, I was hoping the muzzle was a bit 'heavy' on one side. ;) But wouldn't you know it...the bore is straight and perfectly concentric to the o.d. of the muzzle. :eek: Such is life. :D

"24 cans of beer in a case. 24 hours in a day. Coincidence? I think not."
-Steven Wright

For consideration..... -Al
 
Barrel Indexing

Good morning Al

Excellent post! Glad to hear your experience with barrel indexing mirrored what I have found.

For as long as I can remember, it has been said that if one finds a competitive barrel in twenty, he is very fortunate, and the hummers come along even more infrequently than that. This really stuck in my mind. At the time, I had no idea why that was the case, but as I became more knowlegeable and especially after studying Vaughn's book, "Rifle Accuracy Facts" I began to understand.

When one purchases twenty fine barrels from a reputable maker and they all check out as perfect as they can be in regards to bore and groove diameter, twist rate uniformity etc. Then he has those barrels installed by a smith that is known far and wide to be one of the best, yet only one or two of those barrels proves to be competitive. Why? I believe the answer is that the inevitable, slight curvature that is present in all barrels was not taken into account when the barrels were installed.

There is no way, with today's technology, that a perfectly straight hole can be drilled through thirty inches of steel. And even if by some chance it happened once in a while, there is little chance that such a barrel would remain perfectly straight after rifling, heat treatment and contouring. So all barrels wind up with some degree of curvature; some more than others, but none are perfect. But this is not detrimental to accuracy if, and it's a big if, the barrel is installed on the receiver with the natural droop at six o'clock.

If only one barrel in twenty proves to be competitive, that sounds suspiciously like the chances of a barrel accidentally being installed in just the right position.


Gene Beggs
 
This ties into tuners in a way that you might not expect. One of the two tuners that I have shot, is as close to the one that Dick Wright shoots (built by Dwight Scott) as we could make it by looking at the picture. Dwight also gave one to my friend Chet Whitebread. He put it on a rimfire bench rifle and in trying various settings, discovered that things really came alive when it was rotated to the 4 o’clock position. (For those who have not seen a tuner of this design, it clamps to the muzzle and supports a threaded rod that can be adjusted in and out, parallel to the bore, usually set up with the rod at 6 o'clock, under the barrel.) After reading Gene's post it occurs to me that a non-concentric tuner might, be positioned to at least partially compensate for a barrel's being fitted with its heavy side (relative to the CL of the bore) somewhere other than 6 (or possibly 12) o'clock. I can see it now, everyone "spin balancing" their barrels between ball bearing centers. Seriously, it would seem that this subject is worth further study and discussion. Way to go Gene.
 
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I did a search ("clock" and "droop"), but could not find the original post.

I've always assumed that the hole wanders through the barrel in a sort of helical swirl, not a single nice curve. That being the case, how do find the "heavy" side of the barrel? You're not saying it is just the muzzle position that is important, are you?
 
Charles:

Stan felt this was a great time for me to put my Quantum Physics background to some sort of Real World use. So, in true 'Forbidden Zone' form, after a quick bow to the East and a hurried scattering of chicken bones stolen/borrowed from Randy Robinett:

We just eyeballed it from the muzzle end.
 
Charles

Gene Beggs said:
James, I made up a faux receiver of aluminum threaded exactly like the action. Once the barrel is partially chambered and tenon threaded, I place the faux receiver in the chuck and indicate it in, then take a light skim cut off the face so it's running true to the lathe bed. Then screw the barrel in and tighten just snug. Place a dial indicator against the muzzle of the barrel and slowly rotate the spindle. You will quickly locate the position of the barrel that wants to be clocked up at six o'clock. Mark this in some way. I wrap a piece of masking tape around the barrel and mark this spot with a pencil.

Now, take the barrel out of the lathe and screw it into the receiver that it will be installed on and tighten it up. If you are lucky, the mark you made will be on the bottom of the barrel in the six o'clock position relative to the receiver. But if you're like I am, the darn thing will probably be somewhere else. :rolleyes: Let's say the mark is at nine o'clock. This will make it necessary to rotate the barrel 90 degrees clockwise to line it up. If the barrel is threaded 1.063 X 18, you will need to remove .0137 from the tenon shoulder. This should then put the mark at six o'clock. Hope this makes sense. I'm gettin' tired; think I'll call it a night.

Gene Beggs
Click to expand...
Genes original post on clocking a barrel.
It can be found in the How a tuner works thread.

James
 
What symptoms would you look for to see if the clocking is not correct?

horizontal dispersion or some stringing away from vertical?

Interesting indeed.

Jerry
 
Gene and Al's discusssion on barrel clocking turned the light bulb on in my head; a minor miracle in itself. I have set barrels back and suddenly found them to shoot much better. As well, I have set back a good shooting barrel only to find it didn't live up to what it did before. I always used an educated guess but never considered actually clocking the barrel as any part of the equation. I think I'll spend some time looking through some barrels. I wonder if there is a correlation between "hummer" barrels and correct clocking first time??

Mike Swartz
 
what if..

what if you turned a barrel a bit out of round so there was a designed heavy side?
 
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What if you got some wheel weight lead tape and stuck it on the bottom of the barrel and then the side of the barrel and then the top of the barrel and saw what effect that had on the performance with the same load.

Seems a dead easy way to test the off centre weight scenario.
 
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