Gunsmithing Barrel timing questions

mattsnuked

mattsnuked

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Nov 5, 2007
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#1
There has been some discussion locally about barrel timing and cold bore shot results. What do most gunsmiths time their barrels at, 0 degrees, 180, etc? If the barrel is say timed at 30 degrees would this explain why the cold bore shots are always right? Does it even matter or is the cold bore shot more of the result of a cold shooter?

Interested in knowing your thoughts.

Thanks.
 
#4
Re: Barrel timing questions

I've always thought cold bore shots had more to do with cold shooter than anything else. The more and more I learn the more I realize how much I don't know.

I've been looking into things like barrel whip, how barrel/action torque can add/degrade accuracy, rigidity, ect.

So if I wanted to rebarrel my rifle and clock the barrel to 12 O'Clock how do I know which side is 12 and which is 6? On the back of the barrel where the lettering? is there a clocking/timing mark on the barrel I'm missing?

Sorry for adding more questions Matt!
 
#5
Re: Barrel timing questions

From the center of the bore there is usually a higher spot on the OD of the barrel, whether this has to deal with the barrel actually being slightly bent or the outer diameter being off from the center of the bore I'm unsure. Probably one or the other or a little both I would only guess.

Since you have that barrel all lined up in your guy's lathe take a look and see what it's like.
 
#6
Re: Barrel timing questions

The timing has to do with the curvature of the barrel if Im not mistaken. And I believe most like to put the top of the curve at 12:00, so the muzzle end and the chamber end are lower than the middle of the barrel. I could be wrong though. This is also assuming that the barrel has any runout in it to begin with.
 
#10
Re: Barrel timing questions

We usta time the bbl on Sako Finnfire's. Way the extractor was designed, you could cone the bbl face and "time" the bbl 360 degrees. It took Lapua Midas L and a rock steady rest to tell the difference, but you could tell the difference in 45 degrees. In a threaded CF bbl I think it would be LOTS of trouble. krw
 
#12
Re: Barrel timing questions

It's obvious you guys are just guessing at what barrel timing is. There are a couple that is close but no cigar. The short story is that I have yet to see a BORE that is laser stright, when you are barreling an action you want the curvature of the BORE to arch up, in short allowing you to use less of your scope elevation. How you determine this is another thread entirly.

P.S. the barrel OD doesn't run with the ID if that makes since to you.
 
#13
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triple 6</div><div class="ubbcode-body">It's obvious you guys are just guessing at what barrel timing is. There are a couple that is close but no cigar. The short story is that I have yet to see a BORE that is laser stright, when you are barreling an action you want the curvature of the BORE to arch up, in short allowing you to use less of your scope elevation. How you determine this is another thread entirly.

P.S. the barrel OD doesn't run with the ID if that makes since to you. </div></div>

Yep, and I'm glad this guy knows what he's doing.

He recently barreled one for me, and it's done just right......perfection.
 
#14
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triple 6</div><div class="ubbcode-body">It's obvious you guys are just guessing at what barrel timing is. There are a couple that is close but no cigar. The short story is that I have yet to see a BORE that is laser stright, when you are barreling an action you want the curvature of the BORE to arch up, in short allowing you to use less of your scope elevation. How you determine this is another thread entirly.

P.S. the barrel OD doesn't run with the ID if that makes since to you. </div></div>

So what is the outcome if this is not done correctly and it is off, do you just lose elevation or is there more to it??? That's what I want to know.
 
#15
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mattsnuked</div><div class="ubbcode-body">would this explain why the cold bore shots are always right? Does it even matter or is the cold bore shot more of the result of a cold shooter?
</div></div>

In courses, I have noticed that cold bore effect is clearly reduced if trainees are told to do about 10 dry fires before actual first shot.
(true) error left, if there should be any, will be corrected by adjusting point of aim since shooter know hes personal rifle.
 
#16
Re: Barrel timing questions

Well imagine an arch if one end is stationary say your chamber end and the other end (muzzle) was left to rotate and stop where ever the barrel just happened to stop when threaded on the action. If the arch was going to the say the left the bullet would impact to the left. This is noticed more and more as the distance to the target increases. By timing the barrel to where the arch is up it reduces you having to dial windage on your scope on a no wind day, and also reduces the amount of elevation needed to get to target, but that number is flexable according to how much arch is in the barrel. Also please don't confuse this with bore diameter. A manufacturer can build a barrel with a .0001 bore tolerance and still have a arched bore.
 
#17
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triple 6</div><div class="ubbcode-body">It's obvious you guys are just guessing at what barrel timing is. There are a couple that is close but no cigar. The short story is that I have yet to see a BORE that is laser stright, when you are barreling an action you want the curvature of the BORE to arch up, in short allowing you to use less of your scope elevation. How you determine this is another thread entirly.

P.S. the barrel OD doesn't run with the ID if that makes since to you. </div></div>

What he said. for the most part


Edited.
I believe that once you zero the rifle it matters very very little. I dont know how to do the math but you have a scope 20" or so behind the muzzle. The muzzle is shooting the bullet at a certain point at 100 yards lets say. The scope is pointing at the same spot. At 200 yards I think its only going to be off like 1/10th MOA.
So I think it makes about an inch difference at 1000, after zeroing at 100+


Obviously the straighter the bore, the less there is to worry about.
The more material you remove from a barrel when contouring, the more runout can be induced into it because the barrel will warp as material is removed.

So order big barrels guys
grin.gif



 
#18
Re: Barrel timing questions

To the average hunter shooting deer at say 100-300 yards it wouldn't matter much if you were making body shoots. But lets say you had a barrel with a 24" radius arch and one that had a 36" radius arch, the one with the 24" arch would have less come ups at distance than the 36" barrel provided both were timed at 12 o'clock. I was at one of Sean Littles classes in N.C. I was shooting a rifle that I built and a friend was shooting a stock Remington 5R, both shooting the same load, at 1000yrds I was using 5 moa less and 2.5 moa left windage less than he was. To the normal guy this makes little difference, but who here considers himself a normal shooter?
 
#19
Re: Barrel timing questions

A barrel with timing at 12 or 6 is no different than introducing a canted scope rail into the equation.

Bullets are not curve balls because of bore runout. The bullet will get tossed in the direction of he runout, but it will not curve or arch.

The only arch in a bullets flight is due to gravity and bullet spin(with no wind)

A rifle fired in space, away from gravity, would not arch no matter how much runout a barrel had. It would be shot in the direction of the runout, but its path wouldnt be curved between 10 yards and 100000 yards.

Plus when a rifle fires, the 60,000psi behind the bullet straightens the bore slightly during whip. Like a hose getting high pressure water shot through it, it wants to straighten out. It doesnt completely, but it tries to.

IMO, if you stuck a perfectly straight 12" long, .3000" diameter rod 6" into a .308 bore(with .3002" from land to land), the bullet will travel in the direction that rod is pointing for the most part. It will be flying straight in that direction, and not curving like the bore was.
 
#20
Re: Barrel timing questions

Keith, I'm not sure if were saying the same thing or not. But as an examble of what I'm tring to say, take your pointing finger bend it to have a slight bow in it, palm up, the finger points up, there by putting more "loft" on the bullet as it leaves the bore. Now turn your hand counter clock wise, which way would the bullet travel? I know gravity starts to take hold of the bullet as soon as it leaves the barrel, but I'm not talking about bullets, only how the bore has an affect on it once it leaves the barrel, and the path it will travel as a result of a bore that is not laser stright.

Mark Williams
Old Lodge Armory
 
#21
Re: Barrel timing questions

I think see what youre sayin man, partly anyways. Youre right. Im just trying to go a step further and talk about the bullets path a little I think. I think once sighted in at 100, or wherever, you're good to go and don't have to worry about runout anymore. Not 100% on that though but it makes sense to me.
So actually, I cant see how runout matters at all once sighted in at 100.

My rides here so I have to run off to the shop now but I'll chat more later.
 
#22
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triple 6</div><div class="ubbcode-body">To the average hunter shooting deer at say 100-300 yards it wouldn't matter much if you were making body shoots. But lets say you had a barrel with a 24" radius arch and one that had a 36" radius arch, the one with the 24" arch would have less come ups at distance than the 36" barrel provided both were timed at 12 o'clock. I was at one of Sean Littles classes in N.C. I was shooting a rifle that I built and a friend was shooting a stock Remington 5R, both shooting the same load, at 1000yrds I was using 5 moa less and 2.5 moa left windage less than he was. To the normal guy this makes little difference, but who here considers himself a normal shooter?</div></div>

This isn't making any sense to me, if both rifles are zeroed the same, it won't matter the radius of the runout. It will create a different compensation by the scope, but the second the bullet leaves the bore, it is on a path, and that path is no longer influenced by any bore curvature. I think this is what Keith is getting at. If two rifles are shooting the same bullet at the same velocity, that bullet will require the same amount of windage and elevation no matter where it comes from (ie the bore run out or the scope adjustments). This means if both rifles are zeroed at 100 (bore run out has already been compensated for), then they can't have different come ups or windages....
 
#23
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">Again, I not sure if once you zero at distance, you still have anything to worry about. </div></div>

why does the distance where the zeroing occurs make a difference?
 
#24
Re: Barrel timing questions

A PS gunwriter (Bill Calfee) did an extensive set of testing and multiple articles on indexing barrels. The belief was the barrel being timed so that the bend in it was set at 6 o'clock would produce the best group results.

The test groups did produce POI changes as the barrel was indexed around the clock was the conclusion from the POI testing portion of the experiment.

The group size test groups, when the shooter was aware what clock angle the barrel bend was positioned - 3, 6, 9, or 12 o'clock - produced the best groups when the bend was positioned for 6 o'clock.

The group size test groups, when the shooter was UNaware what clock angle the barrel bend was positioned - 3, 6, 9, or 12 o'clock - produced no consistent group size reduction with the barrel in any one particular clock position.

As stated earlier by someone's post, yes in fact most of us that posted in this thread have no idea what indexing a barrel is all about.
 
#25
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GasLight</div><div class="ubbcode-body"> I think this is what Keith is getting at. If two rifles are shooting the same bullet at the same velocity, that bullet will require the same amount of windage and elevation no matter where it comes from (ie the bore run out or the scope adjustments). This means if both rifles are zeroed at 100 (bore run out has already been compensated for), then they can't have different come ups or windages.... </div></div>

Yes thats what I was saying I believe to be true.

Once the rifle is zero'd at 100, or any distance, I dont see how bore runout matters anymore. Its already been dialed out.
 
#26
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GasLight</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">Again, I not sure if once you zero at distance, you still have anything to worry about. </div></div>

why does the distance where the zeroing occurs make a difference? </div></div>

I just mean zeroing at any distance. Im not saying the distance matters.

The only way I see that runout matters is in scope adjustment. But once sighted in, its sighted in and is traveling along the scopes path.
 
#27
Re: Barrel timing questions

Give me a day and I'll do a graph on the CAD to show what I'm trying to say. I understand what you guys are thinking, and I'm not trying to get in a mud slinging contest. Let me do the graph and then we can see where I'm going.
 
#28
Re: Barrel timing questions

I think you are both right, but what triple 6 is trying to say doesnt matter unless youre scope is lacking in total elevation adjustment.

Think what hes trying to say is two rifles, one clocked at 6 and one at 12, once zeroed will shoot identical, but the 12:00 rifle will have more USABLE elevation still in the scope after zeroing....in a perfect world that is.
 
#29
Re: Barrel timing questions

I say things long-windedly sometimes and might not be too clear.

So the short and sweet answers I believe to be true.....


Most smiths time up at 12 o-clock. This reduces the adjustments you have to make in your scope(for windage). But whether at 12 or 6, it doesnt matter and has the same effect as a canted scope base.


Barrel timing doesnt matter once sighted in down range. Two rifles sighted in at 100, with the exact same bullet/velocity, will hit the same spot at 1000 regardless of barrel runout.
You could time one at 12, and one at 3, they will impact the same at 1000 once sighted in at 100, 200, 500, where ever you want.
 
#30
Re: Barrel timing questions

actually timing it at 12:00 doesn't reduce the amount of adjustment, it just makes the required adjustment favor a longer range shooter. The POI will still be however far off from the mechanical zero of the scope, but with a 12:00 timing it will allow the compensation to take place by dialing the scope 'down', allowing more internal room to come 'up' for longer shots. Enough run out can become a problem in any of the directions depending on the base and scope you are running. A 30 MOA base and a 15MOA runout timed at 12:00 may not allow a 100 yard zero pending the scope's internal adjustments.

Dave
 
#31
Re: Barrel timing questions

Ugh.

Facts:

First one needs to look at how barrels are made. a piece of stock is supported between two bearing cassettes. The stock is rotated at a reasonably high rpm and a long stick equipped with a carbide drill point is crammed in from one side. Oil is driven through this stick to evacuate chips and to help the drill stay straight. (think party favor that you blow into)

Center is center and so long as the drill is ground to the correct geometry it creates a remarkably straight hole. Crazy straight in fact. However few barrel blanks are supported in the middle and this allows for a small percentage of "jump rope" as it rotates. The drill however doesn't care because its cutting along the spindle center.

Everything is bad azz till you turn the machine off. Now the OD of the stock snaps straight again and the hole has a banana in it.

Make sense?

As for timing. The main purpose behind this has little to do with cold bore zeros. It comes into play when a rifle gets to stretch its legs a bit. A barrel with a wiggle in it that isn't clocked in a vertical plane tends to demand a windage correction as distance from shooter/target increases. Clocking to a vertical plane helps mitigate this. It almost surely monkeys with the elevation value a bit but its of no consequence as you need to crank in elevation as you go further out anyway. Your dope masks the "problem" (which doesn't even really exist)

The timing should ALWAYS be with the muzzle "up". Never down. This goes double for bag guns as it encourages the rifle to track a little better. It's caliber sensitive mind you so filter some of what I'm telling you here. A 338 boomer Lapua isn't going to benefit from this nearly the way a dedicated NBRSA gun will chambered in 6ppc shooting 60 grain bullets. The magnum has so much steam your not really going to mitigate the stock acting like a "mosh pit" as it absorbs recoil anyway.

The "supah swag" method that I use to find the TDC (top dead center) position on a barrel's muzzle is to chuck the cylinder portion of the bore in a 3 jaw chuck. I rotate the barrel at low rpm with the crown unsupported. Using a sharpie marker I slowly approach the crown till it makes a mark.

Split the mark in half and you have your "up" clock position. Setup and thread accordingly.

Here's a tip:

Most actions are using either 16 or 18 pitch threads. 16='s .0625/rev. 18="s .0556/rev.

So, say your using a three jaw chuck. Take .0625 and divide by 3. You get .0208 per 120* of index. (cuzz the 3 jaw is a circle split 3 ways right?) rIgHt!!
smile.gif


So, you index your "high" on the barrel with one of these jaws. Just pick one and mark it so you don't forget which one.

Now you thread your tennon and your off a poop load. Say it's one jaw plus a red one short of where you want it.

What to do? Guess? Well that's certainly an option but it sucks. Do some math and it'll go much smoother.

Rotate your receiver(with lug) back to where the base holes time up with the center of the closest jaw. Now measure the gap created with feeler gauges. lets say it's .006".

Your one jaw off plus .006" from being straight up right? We know the pitch between jaws is .0208" so guess what you do next?

You add .006" to .0208" (.0268")

That's how much you peel off the shoulder to get it timed up. You'll need to take off the same amount from the breech face too.

BUT were forgetting something. CRUSH. My threads are perty dern good when I fit a barrel. I'll go so far to say they are bad ass. That being said things still "give" a bit when clamming everything up tight. I try to allow for about .002" of crush. Meaning I'll intentionally stay short about .002" from the mathematical dimension. If it's a fluted barrel I'll keep it even more conservative as they often time up once I install/uninstall the barrel a few times.

Doing it this way takes the guess work out and saves time.

Hope it helps.

C.
 
#32
Re: Barrel timing questions

This is funny stuff coming from this crowd....

We all understand the line of sight and the concept of minutes of angle from a fixed point multiplying exponentially as distance increases when dealing with optics and windage; with forces induced on a bullet's flight by the bullet being physically pushed to the side.....but we can't grasp that the same rule of physics could apply to the direction a projectile is thrown by a bent barrel.

Take a ski jumper for lack of a better example. His ramp is built so it launches him, if he's doing it right, for the most elevation and distance possible. IOW it's timed to 12:00. He goes straight, and up, and in the direction intended. He "groups" his landings somewhere at the bottom of the slope in a landing zone....actual placement dictated by his momentum and areodynamics.

Not at all unlike the physics of a rifle bullet's flight. He is the bullet, the ramp is the barrel, his intended path is the line of sight through an optic, and the landing zone is the target......

Now, hypothetically, if you could defeat gravity on the ramp itself so he wouldn't fall over on his head before actually launching, turn/twist the end of the ramp 90 degrees to 3:00 or 9:00 and launch him from the same upright starting position as he did with the 12:00 ramp. He will NOT follow the same intended path as he did when launched from 12:00. He will veer left or right and gravity will make him fall to the ground left or right of the intended path.....probably in a horrible wreck over the fence a short way from the end of the ramp; but if he wasn't fenced in he would continue to veer left or right; and continue to increase his distance from the intended path as distance from the ramp increases until he is slowed to a stop by the earth.

In the games we play, i.e. long range we certainly can sight in a rifle at 100 yards with a barrel timed something other than 12:00 (or 6:00), and have a blast all day long shooting at 100 yards, no problem. You have an elevation adjustment that put you zero'd there, AND you have a windage adjustment as well.....zero'd.

But, as soon as you want to increase that distance beyond 100 yards per your dope, and on a windless day, you run into a problem. Your dope calls for X elevation for the increased distance. You dial that but you end up needing some windage to account for some mysterious grouping to the left or right. This needed "windage" is because your optic is theoretically aligned to the action, not the business end of the bore, via mounting holes that are theoretically in line with the axis of the action as well. The chamber end of the barrel is also, if properly machined, in line with this action/scope relationship. The varible though is the end of the barrel, the muzzle, which points off in some direction that is not in line with the scope's/action's vertical plane from center...or the intended path of flight, line of sight.

Therefore, when the bullet is launched it is automatically veering in a direction not in line with the line of sight, or the erectors of the scope (which should also be aligned with the axis of the action/chamber)....or with our "zero" set at 100 yards.

As the distance from the muzzle increases the law of radian angles comes in to play, and because the bullet was launched in the skewed direction away from our line of sight it will continue in that direction being influenced only by gravity pulling it to earth; and will continue to increase it's distance from the line of sight until it stops.

It's my belief that some of the "spin drift" crap we read about is simply this not being understood by some people...barrels improperly timed launch the bullet not in the same line as the line of sight/scope mounting actually is.

If you want to test this in real time that you can actually see then take a piece of rigid 1/2" copper tubing 3 or 4 feet long and tweak it "bent", put a decent arch in it. It will represent an exagerated example of a rifle barrel. Stick a spit wad in the chamber end and place the chamber end in a vise or something rigid/fixed, the vise will represent the rifle's action. Turn the bent end up representing a barrel timed at 12:00. Now look through your pretend scope mounted on your hypothetical barrel in a line of sight parallel with the jaws of the vise. Chuck the spit wad through the copper tube with a blast of air from an air hose. It will launch straight out in the same direction as the line of sight, arcing in a trajectory parallel to the line of sight until gravity makes it hit earth and stop.

Now turn the "barrel" to 3:00 and repeat still aiming your eye/line of sight parallel to the vise jaws. The spit wad will launch to the right, arc in a trajectory influenced by the direction of the bore at the muzzle, and increase it's distance from the line of sight exponentially as the distance from the "muzzle" increases.

Turn the "barrel" any way you want but you will NOT get the spit wad to follow the same path as the line of sight unless the "barrel" is turned to 12:00 or 6:00; or you adjust the line of sight by turning the vise to match the impact point.

Simple Physics 101............
 
#33
Re: Barrel timing questions

You are forgetting that the scope is adjustable from the centerline of the action. This is how we can compensate for elevation at distance. The scope is adjustable in an angular fashion. I am sorry but I am un-educated and can't use the proper teminology here. However, what I am saying is that while the bullet may be traveling away from the centerline of the action it matters little, because our scopes can be adjusted to find that straight line, it will match it from here to infinity if there was no such thing as gravity or wind.

Once the bullet is on its path, it is no longer affected by the bore curvature. It travels in a straight line affected only by external forces (wind, gravity, spin-drift, corriolis.. plug your force in here).

By your physics example above, people would have different come ups if they had a 20 moa base vs a flat base, vs a 30 moa base... the same is also true with your skier, once he leave the ramp, his down range trajectory is no longer affected by the ramp...

if you can zero at 100 yards, it will be the same zero as 1000, aside from external factors. The flight of the bullet is not an exponential deviation from the action centerline, it is very linear...
 
#34
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lvcatfish</div><div class="ubbcode-body">I time all of my barrels to 16:47 UTC -7 and factor leap seconds in too. </div></div>

So you mean Coordinated Universal Time
wink.gif
 
#35
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mattsnuked</div><div class="ubbcode-body">From the center of the bore there is usually a higher spot on the OD of the barrel, whether this has to deal with the barrel actually being slightly bent or the outer diameter being off from the center of the bore I'm unsure. Probably one or the other or a little both I would only guess.

Since you have that barrel all lined up in your guy's lathe take a look and see what it's like. </div></div>

We'll check it out Matt, we had planned to put the OD high spot at 12 o'clock. With the bore rod showing 0.0005" of run out I've noticed 0.002" of run out on the OD of the barrel. Gonna have to read over my clocking notes and get ready to do the deed.
 
#36
Re: Barrel timing questions

also, gravity is not an exponetial force, and a fixed value wind would not be either, the reason they appear to be exponential is because the friction between the air molecules and the bullet cause the projectile to lose velocity, allowing as the bullet gets further from the muzzle (source of velocity), increased exposure to those forces per linear distance traveled...
 
#37
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GasLight</div><div class="ubbcode-body">You are forgetting that the scope is adjustable from the centerline of the action. This is how we can compensate for elevation at distance. The scope is adjustable in an angular fashion. I am sorry but I am un-educated and can't use the proper teminology here. However, what I am saying is that while the bullet may be traveling away from the centerline of the action it matters little, because our scopes can be adjusted to find that straight line, it will match it from here to infinity if there was no such thing as gravity or wind.

Once the bullet is on its path, it is no longer affected by the bore curvature. It travels in a straight line affected only by external forces (wind, gravity, spin-drift, corriolis.. plug your force in here).

By your physics example above, people would have different come ups if they had a 20 moa base vs a flat base, vs a 30 moa base... the same is also true with your skier, once he leave the ramp, his down range trajectory is no longer affected by the ramp...

if you can zero at 100 yards, it will be the same zero as 1000, aside from external factors. The flight of the bullet is not an exponential deviation from the action centerline, it is very linear... </div></div>

A lesson in supposition, that.....
 
#38
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tripwire</div><div class="ubbcode-body">
A lesson in supposition, that..... </div></div>

Yeah, I had to google that to know what it meant, like I said I am un-educated, but that doesn't mean I am wrong
wink.gif
 
#40
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triple 6</div><div class="ubbcode-body"><span style="font-weight: bold">Your</span> not wrong, just uneducated. lol, I'm sorry, I couldn't help myself. I'm working on my graph, and I hope it will help. </div></div>

you're... just since we are throwing digs
laugh.gif


I'll be curious to see your graph
 
#41
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triple 6</div><div class="ubbcode-body">It's obvious you guys are just guessing at what barrel timing is. There are a couple that is close but no cigar. The short story is that I have yet to see a BORE that is laser <span style="font-weight: bold">stright</span>, when you are barreling an action you want the curvature of the BORE to arch up, in short allowing you to use less of your scope elevation. How you determine this is another thread <span style="font-weight: bold">entirly</span>.

P.S. the barrel OD doesn't run with the ID if that makes <span style="font-weight: bold">since</span> to you. </div></div>Edumacation? Haha I couldn't resist either. Fire back at will though, no thin skin here. Interesting thread
 
#42
Re: Barrel timing questions

To be honest if I hadn't experianced and seen the difference between two rifles shooting the same load at the same distance, both zeroed at 100yrds I might be hard to convince, but once I did it got me to asking why and how that could be. I've built quite a few rifles and the way I find the "12 o'clock" postion is by using a 4 jaw chuck, run the barrel though the head stock of the lathe much like some of the builders here. Put a Range Rod in the chamber end and run two indicators one next to the barrel and the other close to the end of the Range Rod, indicate the chamber in using the chuck to get the indicator near the chamber running true, we have four bolts at the end of the spindal bore that is adjusted to get the indicator at the end of the Range Rod running true. Once this is done, take the Range Rod out and put it in the muzzle, and put an indicator on it, you will never find one running true as was on the chamber end, thus the bow to the bore. Most of the time you can only get the indicator to touch in one spot, thus the "12 o'clock high Postion".
 
#43
Re: Barrel timing questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: redirt78</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triple 6</div><div class="ubbcode-body">It's obvious you guys are just guessing at what barrel timing is. There are a couple that is close but no cigar. The short story is that I have yet to see a BORE that is laser <span style="font-weight: bold">stright</span>, when you are barreling an action you want the curvature of the BORE to arch up, in short allowing you to use less of your scope elevation. How you determine this is another thread <span style="font-weight: bold">entirly</span>.

P.S. the barrel OD doesn't run with the ID if that makes <span style="font-weight: bold">since</span> to you. </div></div>Edumacation? Haha I couldn't resist either. Fire back at will though, no thin skin here. Interesting thread </div></div>

Good thing spelling isn't a requirement to graduate from my old high school huh? We're just argueing our beliefs here, good thing we're in kuntry were we can do dat huh.
 
#46
Re: Barrel timing questions

This is my contention, I believe strongly that once the bullet leaves the bore, it travels in a very straight line, other than what is caused by the forces, none of which are the bore. If there was no air, the bore runout would cause the bullet to travel in a straight line at some angle away from the muzzle. It would not arc in any way, the only deviation from this straight line is caused in part by gravity and friction with the air, be that in the form of wind or spin drift. Also, a deviation from POA can be caused by the target moving (coriolis) with the earth while the bullet is traveling through the atmosphere...

I also stongly believe that the angle at which the bullet is now traveling away from the centerline can be compensated for at all distances with an angular correction in the scope
 
#47
Re: Barrel timing questions

I should clarify, I can foresee circumstances where the mechanical limitations of a scope could not overcome bore run out, but for most realistic and minor angular influences of the bore, I believe most scopes are capable of compensating for the affects of bore run out.
 
#48
Re: Barrel timing questions

True, these things can be compensated for with most scopes. And I also believe that the bullet travels in a stright line if you take out the effects of wind, gravity etc. But I also strongly believe the run out of the bore to the OD of the barrel has an effect on which way that stright line may be. To compensate for it hitting say 1 inch left at 100 yrds you just dial in some windage, but if you only dial in elevation at say 500 yrds, you will see it start hitting left again, that is if you were in a place where wind and the earths rotation or the spin of the bullet played no effect. That is my story and I'm sticking to it.
 
#50
Re: Barrel timing questions

I will concede this, sorry for the poor drawing:

Since there is a distance between the muzzle and reticle, there will be a very minor angular difference from the bore run out to centerline (angle A) compared to the reticle to eye angle from centerline (angle B). I don't have the mathmatical desire to compute the maximum difference at a 100 yard zero compared to a 1000 yard zero, but I believe this is very negligible.

2h31kax.jpg
 
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