I have been reading the three volumes of Bryan Litz’s Applied Ballistics and feel like I just discovered a treasure trove of information. I am interested particularly in the effect of “out of roundness” on dispersion at longer shooting distances. Does anyone publish the “tir” (Total Indicated Out-of-Roundness) of their pellets or slugs? This might be an issue with higher twist rates that otherwise might have some advantages…
N/A Slug / Pellet Concentricity
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Imho if a good barrel is concentric, that's how the projectile should be leaving the barrel. Yes/no? My guns all have OST (Original Smooth Twist) barrels in which only the last 4ish inches are rifled. In essence, they "shape" the pellets as they leave the barrel. All 3 are VERY accurate.
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Not exactly. While in the barrel, the projectile follows the form of the barrel (which may help correct a deformed pellet skirt), but when it leaves, it will spin around its center of gravity…. An out-of-round projectile will increase dispersion.
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Nope. Seems like that would be in line with proprietary info to me. I'm likely wrong, not about the nope though.
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I cannot recall where I’ve seen it but there is a video out in the “Inter Webs” showing a devise that someone cobbled together. It has two rollers side by side and a pellet would sit on top between the rollers. As the rollers turned they would spin the pellet and you could inspect the pellet for run-out.
Kenny
Kenny
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I think Kenny is referring to the work of AGN member NoLimits
www.airgunnation.com
Sorting pellets by viewing
Hallo, I live in Germany. Sorry I do not speak English well. Reading works better. That's why I like to read in this forum from time to time. I shoot air rifle and air pistol in .177 caliber for many years. I like to share my experience and knowledge that some European sport and benchrest...
www.airgunnation.com Upvote 0
Yes, this is the way most run-out is measured (using an indicator which measures the change in radius as the object is rotated). Sinclair & Hornady both make run-out gauges, I think.
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To ACCURATLY...measure "every" pellet center would be cost "prohibitive"!
There's two centers that shooting, "any type projectile" have. The projectile center and the barrel center. Add to that, is the projectiles center...ON CENTER ? That is, is that center, "centered", front to back ?
And, a pellet or slug making its way down a barrel...WILL NOT...necessarily "center" itself in the barrel.
A pellet / slug can travel down a barrel either...on-center OR...off-center. The barrel will have little effect in "centering", if the projectile is originally formed "off-center" in the first place.
Now that all said...exactly...WHAT is off center ?
Is it .010" or is it .005", or is it .001...or is it .0001, or even .00001"...off center ?
AND, how much will of that, .00001" pellet center offset from the barrel center, is that going to put the pellet into a spiral, or other oddly shaped flight path.
Mike
There's two centers that shooting, "any type projectile" have. The projectile center and the barrel center. Add to that, is the projectiles center...ON CENTER ? That is, is that center, "centered", front to back ?
And, a pellet or slug making its way down a barrel...WILL NOT...necessarily "center" itself in the barrel.
A pellet / slug can travel down a barrel either...on-center OR...off-center. The barrel will have little effect in "centering", if the projectile is originally formed "off-center" in the first place.
Now that all said...exactly...WHAT is off center ?
Is it .010" or is it .005", or is it .001...or is it .0001, or even .00001"...off center ?
AND, how much will of that, .00001" pellet center offset from the barrel center, is that going to put the pellet into a spiral, or other oddly shaped flight path.
Mike
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Over thinking it I'm thinking 
Precision slugs are for the more neurotic passed threw a sizing die making the O.D. Concentric ... Most casting molds for slugs are made on CNC equipment and have very close TIR specifications for sealing band to bullet body, Lube grooves etc ... Production swagged slugs come out of there forming dies equally accurate in this regard.
If your one who is really looking to get the absolute most out of a pellet or a slug your in with the Bench Rest crowd of shooters who are Very very very obsessed with the finest details in projectiles & barrels etc ...
Good luck on your adventure
Precision slugs are for the more neurotic passed threw a sizing die making the O.D. Concentric ... Most casting molds for slugs are made on CNC equipment and have very close TIR specifications for sealing band to bullet body, Lube grooves etc ... Production swagged slugs come out of there forming dies equally accurate in this regard.
If your one who is really looking to get the absolute most out of a pellet or a slug your in with the Bench Rest crowd of shooters who are Very very very obsessed with the finest details in projectiles & barrels etc ...
Good luck on your adventure
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My current “adventure” is to look at everything in the way of, or perhaps not considered, in configuring a 30 cal slug pcp to become a full- fledged competitor to rim fire rifles in the world of subsonic shooting. This means ¼ MOA @ 100 yds and at least 1/2MOA at 200.Over thinking it I'm thinking
Precision slugs are for the more neurotic passed threw a sizing die making the O.D. Concentric ... Most casting molds for slugs are made on CNC equipment and have very close TIR specifications for sealing band to bullet body, Lube grooves etc ... Production swagged slugs come out of there forming dies equally accurate in this regard.
If your one who is really looking to get the absolute most out of a pellet or a slug your in with the Bench Rest crowd of shooters who are Very very very obsessed with the finest details in projectiles & barrels etc ...
Good luck on your adventure
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so I'm just going to guess that you would want to go with the alteros brand of elr slugs.. assuming that I remember correctly.. what I'm remembering is they advertise the CNC machined slugs.. are they any better than the pressed slugs? I don't know because lead is soft and the Zan, h&n, NSA slugs are like someone else just said, they are precise machine dies..
I don't think there's any point in trying to figure out pellets as they are not going to work as good for what you described..
if you had a small lathe and a dial indicator you could check a few.. problem is lead is soft and easy to deform..
Mark
I don't think there's any point in trying to figure out pellets as they are not going to work as good for what you described..
if you had a small lathe and a dial indicator you could check a few.. problem is lead is soft and easy to deform..
Mark
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Slugs like jsb and h&n are made in a 2 piece body die. Those certainly have the recipe for being out of round just like pellets. I have some knockouts that are horribly out of round.
Slugs made in a single piece body die should be as round as they can get since the dies are turned in one operation.
Altaros should be round as well since the slug itself is turned.
Mike
Slugs made in a single piece body die should be as round as they can get since the dies are turned in one operation.
Altaros should be round as well since the slug itself is turned.
Mike
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I may be splitting hairs here but I imagine a swaged slug (Corbin) to be like a second generation version of a CNC turned slug (Altaros). Altaros seem to claim as much… But, to go back to the original post, why no public numbers on run-out? Berger claims better than 0.0001” and Litz has made comparisons for center fire cartridges and shown the effect on dispersion…
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