Runout of loaded rounds
- Thread starter Nathan
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jetinteriorguy
New member
Not sure if my method is correct, but I use my comparator to find the approximate spot where the ogive would meet the bore. Then this where I measure my runout, not the very tip of the bullet. I guess my thinking is this is where the cant of the bullet would have the most affect, not so much the tip since it doesn’t contact the bore at all.
@ OP I have never really been able to find any verified testing to show that runouts matter. I am interested to see if Nick or Bart can come up with anything
I do know that on my 1 MOA gas gun rounds that a runout of .005 does not seem to matter at all. On my bolt guns I try to keep it between .001 - .003, that's just what I end up with. I load both gas and bolt the same way but in my gas guns the brass gets beat up a lot more.
@ jetinteriorguy - I like that idea. I have never really paid any attention where I place the indicator tip but from now on I will
I do know that on my 1 MOA gas gun rounds that a runout of .005 does not seem to matter at all. On my bolt guns I try to keep it between .001 - .003, that's just what I end up with. I load both gas and bolt the same way but in my gas guns the brass gets beat up a lot more.
@ jetinteriorguy - I like that idea. I have never really paid any attention where I place the indicator tip but from now on I will
jetinteriorguy
New member
It’s interesting what your saying about it’s affect in gas guns. I’ve always questioned if the action is so violent on loading how much that would affect the runout and it’s affect on accuracy. I suppose I could load some dummies and run them through one of my rifles and measure the before and after affects. Hmmm, looks like something to do today since it’s raining out and my setup is already good for .223 right now anyway. I’ll report back, or just start a new thread.
jetinteriorguy
New member
Ok, I conducted a highly scientific tightly controlled experiment. I loaded ten dummies of a current bulk 62gr bullet I’ve been shooting lately. I measured runout and wrote it on each case with a Sharpie. I then loaded them in a mag and cycled them through one of my AR’s by pulling the bolt all the way back and dropping it to simulate a normal cycle of stripping the round and chambering it. I then measured the runout again and there was virtually no affect at all on runout, nothing changed by cycling them through the rifle. I. Actually a little surprised, but very pleased at this result. This is in LC brass that has had the necks turned, is first sized with a Redding body die, then neck sized with a Lee Collet die. All but one round were .001” or less and one of them was at .002”, which is very typical of my method. This ammo in my rifle is a good solid MOA or under shooter. If I shoot five round groups well under 1 MOA, but as is typical with a 20 round group it will grow to 1 MOA.
What dies are you currently using? I started using a universal decapping die and sizing die with decapping rod and expander ball removed. This does more for minimizing runout than anything else I tried.
I have the Hornady tool, so measuring at the tip isn't an option. However, I rarely use it anymore since I started decapping in a separate process. If I have an out of round case mouth I'll seperate those for processing another time. I also never check concentricity on virgin brass, once it's fire formed to my chamber that's when I start taking measurements.
I'm sorry if some of this is redundant, but I don't know your complete process.
I have the Hornady tool, so measuring at the tip isn't an option. However, I rarely use it anymore since I started decapping in a separate process. If I have an out of round case mouth I'll seperate those for processing another time. I also never check concentricity on virgin brass, once it's fire formed to my chamber that's when I start taking measurements.
I'm sorry if some of this is redundant, but I don't know your complete process.
I have never checked my runout. I have seen arguments on both sides of the fence. Imho it may make a very small difference in competition shooting, however it is irrelevant for my purposes.
For me the important factors are these
Matched headstamp, preferably the same lot
Finding a powder charge weight with a low es/SD
Tuning bullet seating node/depth.
Took my budget hunting rifle from 1.5moa down to 0.75moa at 100yds.
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Nathan,
You should be able to get the runout down by several means. First, using the Lyman M die to put a small step in the case mouth for the bullet to sit upright in while you start it into the seating die will help a lot. Second, without doing that, I consistently get numbers in the sub-0.001" runout range with turned necks in the .308 Win using the Redding Competition Seater Die. Many folks report similar results from the Forster Bench Rest and Ultra Micrometer Seater Dies, both of which are less expensive and can be used with compressed loads, which the Redding cannot, but which can require a custom seater stem from Forster for some bullet shapes.
A.A. Abbatiello wrote up an experiment in the 1960s for The American Rifleman (TAR) that is reprinted in the NRA book Handloading, edited by Wm. C. Davis, page pp 86 (his illustrations) and 87 (text). He took samples from 42 lots of M72 30-06 National Match Ammunition (used the M1 Type FMJ match bullet) and measured the magnitude and direction of bullet tilt. His measuring method was similar to the Forster and Hornady types, with head and bullet nose supported (see my illustration of what the same runout looks like with different measuring setups below, with Abbatiello's being the first type shown). He found 0.008" of total indicated runout (0.004" of bullet tip-tilt off the cartridge axis) produced a 1 moa increase in group size.
With that bullet, tilt greater than about 0.0045" caused no additional dispersion, as entering the bore straightened tilt greater than that. He showed that orienting the high sides of random amounts of tilt at the same location around the clock in the chamber cuts that dispersion in half (in other words, it throws the bullets in the same direction consistently). He offers a theoretical calculation that agreed well with his result.
Abbatiello also references F. W. Mann's 1907 record of his experiments, The Bullet's Flight from Powder to Target, a study of multiple firings that mentions the importance of the bullet's CG running true to the spiral path around the mean trajectory line for accuracy.
Abbatiello also references an experiment showing the same effect done by George L. Jacobson at Frankford Arsenal and published in TAR in the January 1960 issue that appears on page 20.
Another source is the late Harold R. Vaughn's book, Rifle Accuracy Facts, which has a bullet cant test on page 133 showing the dispersion. Note that Vaughn's result is smaller than Abbatiello's. This is because he uses a shorter bullet for which an equal amount of tilt moves the CG off-center less than was the case with the M1 Type bullets loaded in the ammunition Abbatiello tested. Vaughn is an interesting authority because he was Head Aeroballistician at Sandia National Laboratories and well as having some good Boone and Crocket rankings, so he was both a ballistic scientist and a hunter with practical experience.
The bottom line is, the bullet choice, as well as the degree of tilt, determine how much dispersion effect you get.
You should be able to get the runout down by several means. First, using the Lyman M die to put a small step in the case mouth for the bullet to sit upright in while you start it into the seating die will help a lot. Second, without doing that, I consistently get numbers in the sub-0.001" runout range with turned necks in the .308 Win using the Redding Competition Seater Die. Many folks report similar results from the Forster Bench Rest and Ultra Micrometer Seater Dies, both of which are less expensive and can be used with compressed loads, which the Redding cannot, but which can require a custom seater stem from Forster for some bullet shapes.
hounddawg said:
A.A. Abbatiello wrote up an experiment in the 1960s for The American Rifleman (TAR) that is reprinted in the NRA book Handloading, edited by Wm. C. Davis, page pp 86 (his illustrations) and 87 (text). He took samples from 42 lots of M72 30-06 National Match Ammunition (used the M1 Type FMJ match bullet) and measured the magnitude and direction of bullet tilt. His measuring method was similar to the Forster and Hornady types, with head and bullet nose supported (see my illustration of what the same runout looks like with different measuring setups below, with Abbatiello's being the first type shown). He found 0.008" of total indicated runout (0.004" of bullet tip-tilt off the cartridge axis) produced a 1 moa increase in group size.
With that bullet, tilt greater than about 0.0045" caused no additional dispersion, as entering the bore straightened tilt greater than that. He showed that orienting the high sides of random amounts of tilt at the same location around the clock in the chamber cuts that dispersion in half (in other words, it throws the bullets in the same direction consistently). He offers a theoretical calculation that agreed well with his result.
Abbatiello also references F. W. Mann's 1907 record of his experiments, The Bullet's Flight from Powder to Target, a study of multiple firings that mentions the importance of the bullet's CG running true to the spiral path around the mean trajectory line for accuracy.
Abbatiello also references an experiment showing the same effect done by George L. Jacobson at Frankford Arsenal and published in TAR in the January 1960 issue that appears on page 20.
Another source is the late Harold R. Vaughn's book, Rifle Accuracy Facts, which has a bullet cant test on page 133 showing the dispersion. Note that Vaughn's result is smaller than Abbatiello's. This is because he uses a shorter bullet for which an equal amount of tilt moves the CG off-center less than was the case with the M1 Type bullets loaded in the ammunition Abbatiello tested. Vaughn is an interesting authority because he was Head Aeroballistician at Sandia National Laboratories and well as having some good Boone and Crocket rankings, so he was both a ballistic scientist and a hunter with practical experience.
The bottom line is, the bullet choice, as well as the degree of tilt, determine how much dispersion effect you get.
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Nathan,
Listen to Unclenick, I used his method and my runnout is less that 1 thousandth,
If you watch Erik Cortina on you tube he doesn’t care about runnout but again he is using a bench rest rifle.
I like my ammo being concentric. I only check 1 out of every 10 rds or so to make sure its not way off.
But the two dies Unclenick has mentioned drastically improved runnout for me in 30-06.
Listen to Unclenick, I used his method and my runnout is less that 1 thousandth,
If you watch Erik Cortina on you tube he doesn’t care about runnout but again he is using a bench rest rifle.
I like my ammo being concentric. I only check 1 out of every 10 rds or so to make sure its not way off.
But the two dies Unclenick has mentioned drastically improved runnout for me in 30-06.
None of the commercial runout gauges position the rimless bottleneck cartridge to the gauge like it is in barrel chambers when fired.
When fired, rimless bottleneck cartridge shoulders center in the chamber shoulder. The only part of the case body that touches the chamber is where the pressure ring is near the extractor groove.
When the first batch of Palma rifle 308 Winchester ammo was loaded with Sierra's new 155 grain HPMK bullets and 45.3 grains of IMR4895, 600 yard test groups were 3 inches maximum. Charge weights had a 3 tenths grain spread, bullet tip maximum runout was 3.5 thousandths.
When fired, rimless bottleneck cartridge shoulders center in the chamber shoulder. The only part of the case body that touches the chamber is where the pressure ring is near the extractor groove.
When the first batch of Palma rifle 308 Winchester ammo was loaded with Sierra's new 155 grain HPMK bullets and 45.3 grains of IMR4895, 600 yard test groups were 3 inches maximum. Charge weights had a 3 tenths grain spread, bullet tip maximum runout was 3.5 thousandths.
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Bart,
I was under the understanding that the concentricity gauge is just what is it just checks the concentricity.
If its crooked its crooked, Im assuming it wouldn’t matter how its position in the chamber if the rd is crooked before it started.
Are you saying that the runnout doesn’t really matter? and that if the bullet has some runnout that the barrel itself corrects it?
I was under the understanding that the concentricity gauge is just what is it just checks the concentricity.
If its crooked its crooked, Im assuming it wouldn’t matter how its position in the chamber if the rd is crooked before it started.
Are you saying that the runnout doesn’t really matter? and that if the bullet has some runnout that the barrel itself corrects it?
Yes, bullets straighten up a little bit when fired. If the runout high point is marked then oriented the same direction when chambered, it helps a lot
I've used a 33 caliber bullet puller in the press to hold live 30 caliber ammo case neck then push the case body to bend the case neck enough to get it straight.
I've used a 33 caliber bullet puller in the press to hold live 30 caliber ammo case neck then push the case body to bend the case neck enough to get it straight.
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Bart,
That’s interesting, My Horandy concentricity tool claims it has the ability to reduce runnout, it has a screw, that pushes the bullet to help correct runnout. I tested and you can reduce it , but it really messes with your neck tension and didnt help my groups at all, in fact in some cases it made it worse, between 2 and 3 thousandths
I spent alot of extra time and effort with concentricity, and what I came to the conclusion was expanderballs in FL resizing can affect it.
A simple experiment I ran was just using a Lee Collet die and sized the neck and seated the bullet. I then Checked the Concentricity was less that 1 thousandths. I took the same brass casing from same lot and ran it thru my lee fls die on my lee breech loader press and runnout was worse.
I Knew then that resizing, not bullet seating was increasing the runout.
Did it make a difference in a 70 yearold M1 barrel not really.
Will
That’s interesting, My Horandy concentricity tool claims it has the ability to reduce runnout, it has a screw, that pushes the bullet to help correct runnout. I tested and you can reduce it , but it really messes with your neck tension and didnt help my groups at all, in fact in some cases it made it worse, between 2 and 3 thousandths
I spent alot of extra time and effort with concentricity, and what I came to the conclusion was expanderballs in FL resizing can affect it.
A simple experiment I ran was just using a Lee Collet die and sized the neck and seated the bullet. I then Checked the Concentricity was less that 1 thousandths. I took the same brass casing from same lot and ran it thru my lee fls die on my lee breech loader press and runnout was worse.
I Knew then that resizing, not bullet seating was increasing the runout.
Did it make a difference in a 70 yearold M1 barrel not really.
Will
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stagpanther
New member
Sorry to intrude late on this thread, but one thing I don't see mentioned is the influence (if there is one, I could be imagining this) of freebore length relative to the bullet's bearing surface length on "straightening out" the bullet.
jetinteriorguy
New member
Yup, this has been my experience as well. I removed the straightening screw and never looked back. Using a full length Redding body die and full length sizing my brass, coupled with a Lee Collet neck die will typically yield runout of .001” or less approximately 90% of the time. When I first started using this method I would measure every round, now I trust it enough for consistency I don’t even bother checking anymore. This is using brass with the necks turned and all trimmed to the same length. I take my measurements right at the point where the ogive starts. I find this point by putting a loaded round in the Hornady tool, I the adjust the gauge to make contact where the bullet meets the case. I then move the gauge along the bullet until you see the needle start to move indicating the start of the ogive. This is where I lock it down.
I have found the exact distance off the lands does not matter for me per say. I start no less than 0.020 off the lands, or max magazines length. Then I start pushing back in 0.003 increments. As I push back the groups vary. They will start open, get smaller, get smaller, get smaller, even out, open up, open up, open up. Then start the cycle over. So there are several points in the harmonics where it will work well. I took a load that was shooting 1.5in down to a 0.70in at 100yds with my budget 30-06 doing it.
Heres a video from eric cortina that explains it a little betterhttps://m.youtube.com/watch?v=oRXlCG9YZbQ