timing barrel

[DaveTooley]

Something whacky is going on. My reply to Donovan doesn't show the body of the message so I'll cut and paste here and see what happens.

Donovan
Interesting rig. Couple of questions

I assume as you rotate the barreled action you're shooting groups and you see changes on the target. When you see changes meaning the best and worse group size based on orientation. Have you ever tried tuning the rifle again? If so what were the results? How consistent were the results?

 

[dmoran]

@DaveTooley
Have used both "in tune loads" and "out of tuned" loads, and while I do believe each position could be tuned more optimally (have done that), the best optimal position(s) still appear to have advantages to both accuracy and POI placement.
From my testing, clocking the bores "high" to 12-o'clock, appear to produce advantages from POA to POI placement (which should yield small tracking and elevation gains to the sights/scope) and less stringing effects for out of tune loads (or a load going out of tune).

 

[DaveTooley]

The

@DaveTooley
Have used both "in tune loads" and "out of tuned" loads, and while I do believe each position could be tuned more optimally, the best optimal position(s) still had advantages to both accuracy and POI placement.
From my testing, clocking the bores "high" to 12-o'clock, appear to produce advantages from POA to POI placement, which should yield small tracking and elevation gains to the sights/scope, and less stringing effects for out of tune loads.

Then your barrels are chambered with the bore aligned in two places in the chamber area and the muzzles allowed to run wild. That would make sense with an out of balance load. The way I chamber the barrel is balanced with a consistent load regardless of orientation.

 

[clowdis]

If I index a barrel, and I don't always, I put it between centers in the lathe and place a dial indicator in the middle of the barrel. Then I rotate it slowly by hand to find the the low point of the warp, and every barrel I've done this way shows a little bit of warp, every one. I'll then mark this as being the top of the barrel and install it this way. It just seems to be easier doing it this way than trying to find it in the bore. Most barrels will be warped .003 to .004 TIR but I have seen barrels warped as much as .012.

 

[Dusty Stevens]

If I index a barrel, and I don't always, I put it between centers in the lathe and place a dial indicator in the middle of the barrel. Then I rotate it slowly by hand to find the the low point of the warp, and every barrel I've done this way shows a little bit of warp, every one. I'll then mark this as being the top of the barrel and install it this way. It just seems to be easier doing it this way than trying to find it in the bore. Most barrels will be warped .003 to .004 TIR but I have seen barrels warped as much as .012.

You can tighten your tailstock and change that

 

[Alex Wheeler]

When a barrel is indicated at the breach end there will be runout at the muzzle end in the lathe. The bullet only knows the bore of the barrel and the barrel ALWAYS points at the target no matter how it was chambered. I have no doubt the variations in the bore have some effect of the harmonic pattern of that barrel. But this topic is often looked at the wrong way. An indexed barrel is not pointing up in the sky at 12 oclock like it was indexed in the lathe, its pointing at the target same as every other barrel. What you have actually done is index the barrel so that first section of the bore and chamber have no horizontal deviation relative to the bore's hypothetical centerline. Thats just one way that guys index barrels, probably the most common.

 

[butchlambert]

@DaveTooley
Have used both "in tune loads" and "out of tuned" loads, and while I do believe each position could be tuned more optimally (have done that), the best optimal position(s) still appear to have advantages to both accuracy and POI placement.
From my testing, clocking the bores "high" to 12-o'clock, appear to produce advantages from POA to POI placement (which should yield small tracking and elevation gains to the sights/scope) and less stringing effects for out of tune loads (or a load going out of tune).

Whatever the method we choose, whatever makes you warm and fuzzy will allow you to shoot better.

 

[clowdis]

You can tighten your tailstock and change that

No, it's not the tailstock. Try it sometime.

 

[HillbillyLongRifle]

I dial my barrels in at Throat and muzzle also. I dont see the reason behind letting the muzzle end flop all over. I drill and bore chamber end and never have more than .0002-.0003 runout from throat all the way back to web. All barrels shoot very well this way.

 

[Danny1788]

I normally rough in with a range rode then only dial in the breech end and 2.7” in front of that. Time the muzzle to 12 o’clock. This means I’m reaming the chamber strait into the throat if I dialed it in correctly and the muzzle means nothing to me for bullet engagement into the rifling. I use piloted core drills to rough out my chambers so the reamers don’t have to cut so much.

I am going to try two different methods soon and see if it really has any effect on my normal method. I do see one common thing said If dialing in the throat and muzzle most everyone drills and prebores to line up the section being chambered. That makes sense to me. Because the breech end of the bore probably has runout and by drilling and boring you eliminate that issue.

 

[tobnpr]

I don't buy any of it.
Barrel harmonics- whip of the muzzle end- will have the bore "pointing" at different points in space depending on MANY variables that change with bullet/powder/load.

Far as I'm concerned, go to all that extra effort for naught, that "12:00" position is likely to end up pointing left/ right anyway.

Alot of time/money for voodoo..

Flame away
The barrel's muzzle is not static in space as the bullet travels down the bore.

 

[Dusty Stevens]

Get a method, plan it out, then figure out how to test it. Ill give you a clue though- if you make a cut on your lathe then check the runout, all youre checking is your machine’s accuracy. You can set up a part in a 4 jaw 1/2” off center and when you cut it then you have the best runout your machine can do. So cutting a chamber then shoving a dial indicator in there isnt really checking your work

 

[Alex Wheeler]

Theres really no need to assume or theorize anything. You can chamber barrels in different ways, critic the throats, test them on target, and pay close attention to how consistently your barrels perform. Its like most things, pay really close attention to every detail you can find and see if you can spot a difference. And I am not recommending any method to anyone other than to look for things you didn't even know were there, and pay close attention to details.

 

[DaveTooley]

Theres really no need to assume or theorize anything. You can chamber barrels in different ways, critic the throats, test them on target, and pay close attention to how consistently your barrels perform. Its like most things, pay really close attention to every detail you can find and see if you can spot a difference. And I am not recommending any method to anyone other than to look for things you didn't even know were there, and pay close attention to details.

Well said. I tell would be pipe fitters I can teach you 80% of what I know. To learn the other 20% either you have the senses and curiosity of an artist or you don't.

 

[clowdis]

Well said. I tell would be pipe fitters I can teach you 80% of what I know. To learn the other 20% either you have the senses and curiosity of an artist or you don't.

Truer words have never been spoken! I have a young fella here that I have been teaching for a while. He can grasp the machining part very well but the "why" seems to escape him sometimes.

 

[Boatschool02]

Time one at 12. Test. Set it back and time at 3. Test. Set it back and time at 6. Test.
Measure the group size, shape and POI shift at 100 yards indoor... until then you're just stating how you wish the test would play out.
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What is inconsequential to you, may not be so to others.
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I don't comment much, but I do find it dissapointing when people attempt to belittle the pursuit of excellence. Its easy to see why some of the great voices in this industry just stop contributing or feel compelled to do so in cryptic phrases. Why not, instead, make a community wide effort to welcome and encourage new ideas and follow-on testing? Why not put all your experience into helping devise better tests? Maybe instead of "advanced gunsmithing" we should call it: "Help me improve my next test" or "Share your test results here."
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Pity that its so hard to distinguish hard earned test results from closed minded opinion... and what makes anyone want to share such test results (be they positive or negative) just to be mocked? This sounds more like "the world is flat" self congratulation than rigorous, repeatable, falsifiable, evidence-based collaboration.
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It speaks volumes to me that @Alex Wheeler is saying dig deeper & look closer, while other heavily entrenched (often not only engineers or machinists but competitors) voices are declaring the case closed.
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Absence of evidence isn't evidence of absence.

@dmoran had the right idea above. Bravo, Sir. Thank you for sharing.

 

[jrm850]

Always an Interesting topic... I time them but only because i set up with two points indicated near the breech, and snug the cathead lightly to control the muzzle wherever it ends up. In my mind this setup leaves the reamer axis as tangent as possible to any bend there may or may not be. (the muzzle has always been "out" at least a couple thousandths in my case) My thought process is that the bullet will engrave with perfect axial alignment this way. Then I check my reloads which are out by way more than anything I may have gained and laugh at myself. Oh well, I'm not on a production schedule and I can honestly say that I've never been laying on the firing line second guessing whether I should have indexed the barrel.

 

[tobnpr]

don't comment much, but I do find it dissapointing when people attempt to belittle the pursuit of excellence

I don't see where anyone, including moi, responded in that manner.
We have these discussions exactly because there cannot be purely empirical evidence because rifle barrels are literally like fingerprints- from the alloy composition to contours, from length to harmonics.

Anyone who took Probability and Statistics 101 knows you cannot have more than one variable change, and that's impossible in this discipline. I find that to be pretty interesting in itself...

In this instance, I simply said I'm dubious of the concept and explained why. This is to invite discussion, and have others tell me why they disagree.

Prices charged to customers are a direct function of the labor time invested. If I don't believe the customer will benefit from the possibly incremental gain at the target as relates to the cost, i make that clear and let the customer decide.

I'm probably one of the few that still chamber more between centers (well, along with McMillan, Kelblys, and maybe one other guy) than through the headstock.

Time is money, and if I'm not confident any extra time spent on a barrel is going to show at the target I generally don't do it, and the cost of the work reflects that. Not every shooter is a benchrest competitor demanding that level of precision. Just because more time is spent "in the pursuit of excellence", doesn't necessarily mean it translates to the target.

 

[butchlambert]

I don't see where anyone, including moi, responded in that manner.
We have these discussions exactly because there cannot be purely empirical evidence because rifle barrels are literally like fingerprints- from the alloy composition to contours, from length to harmonics.

Anyone who took Probability and Statistics 101 knows you cannot have more than one variable change, and that's impossible in this discipline. I find that to be pretty interesting in itself...

In this instance, I simply said I'm dubious of the concept and explained why. This is to invite discussion, and have others tell me why they disagree.

Prices charged to customers are a direct function of the labor time invested. If I don't believe the customer will benefit from the possibly incremental gain at the target as relates to the cost, i make that clear and let the customer decide.

I'm probably one of the few that still chamber more between centers (well, along with McMillan, Kelblys, and maybe one other guy) than through the headstock.

Time is money, and if I'm not confident any extra time spent on a barrel is going to show at the target I generally don't do it, and the cost of the work reflects that. Not every shooter is a benchrest competitor demanding that level of precision. Just because more time is spent "in the pursuit of excellence", doesn't necessarily mean it translates to the target.

Shilen chambers between centers.

 

[Dusty Stevens]

Shilen chambers between centers.

So does douglas. And they do a metric ton of em just like shilen