At what point does runout start to impact group size? I have always pulled anything 3 thousandths or over. I am loading prairie dog rounds for the summer and had 7 rounds that were out of spec, one as much as 6 thousandths. Instead of pulling them I shot them to see what happened and they grouped the same as usual. Are there other variables that make some rifles more susceptible to concentricity issues?
Watching this. I keep all of mine no more than 2.5 out of alignment.
Watching this. I keep all of mine no more than 2.5 out of alignment.
You can watch this thread, but some things haven't changed since the 70's and bullet run-out tests are one of those things. As for accuracy/precision, its all the little things that add up. Variables that make one hell of a good shooting rifle and bullet run-out is always going to be one of those variables. If you want a great read on the subject, search out Rifle (sporting firearms journal) magazine (#58 1978). In that article, benchrest shooter Chet Brown discusses bullet run-out having a direct correlation between accuracy and precision. He proves that the less run-out you have in your loaded ammo, the less flyers and anomalies you will have in the dispersion of your group. Also, this makes a point that if you want to shoot more precisely, you need to make sure your reloading dies are adjusted to minimize TIR. I use run of the mill RCBS full length die sets that you can buy at any LGS and attain sub .002" TIR for all of my loaded ammo. Mathman has ran a lot of guys through the proper way to adjust dies to minimize run-out. There are also concentrictiy gauges and gadgets you can buy that will adjust the loaded round to the desired level of TIR. These tools are great, but I believe that the less you monkey around with pushing the bullet around in the case, the better off you will be with the end product. Learn to set your dies so you don't have to do this.
My only comment is that a lot depends on the rifle. I see loss of accuracy in my benchrest rifle if bullets if bullets are even .001 out of alignment, but in many factory big game rifles it often doesn't matter if they're .005 out.
On the other, a custom barreled big game rifle can "notice" much smaller amounts. Once had a custom 7x57 sporter (which unlike some 7x57s had a throat about as short as the 7mm-08) that I ran some experiments with using factory ammo. Bought three boxes of some Hornady Light Magnum 139-grain loads, then sorted them for run-out. Put those .003 or less in one box, those from .003-.005 in another, and those over .005 in the third box. (As I recall, none ran over .007, but it was a while ago.)
3-shot groups with the <.003 ran around half an inch, the .003-.005s around an inch, and the >.005 into about an inch and a half.
I will weigh in with the historical perspective...
For 40 years, I've been hearing the number of 4 thou (.004") thrown out there as the threshold for runout before it starts to affect groups. About 20 years ago I was shown the source of that figure. A.A. Abatiello wrote an article in Rifleman discussing the work done at Frankford Arsenal by George Jacobsen. In the 1960 article "Gauging Bullet Tilt", Abatiello says the testing showed "tilt" of 2 thou or less was desirable for long range shooting. At 4 thou, the groups stopped growing and he postulated that perhaps the chamber was correcting the eccentricty at that point.
It's worthwhile noting that the testing was done with 30-06, 173gr NM ammo as provided for the National matches. Firing was done out of a Mann Fixture which is basically a bull barrel locked into a concrete fixture. The testing was done with Long Range competition (which in NRA terms is 800, 900 and 1000 yards). But IIRC the Mann testing was done at 300 yards.
Google will turn up transcribed articles (most of which were posted by a "Clark". I suspect he and our own ClarkM are one and the same). But it's worthwhile tracking down the actual article with it's illustrations and bullet plots. There is also a related article by Jacobsen that further expands the discussion.
I will weigh in with the historical perspective...
For 40 years, I've been hearing the number of 4 thou (.004") thrown out there as the threshold for runout before it starts to affect groups. About 20 years ago I was shown the source of that figure. A.A. Abatiello wrote an article in Rifleman discussing the work done at Frankford Arsenal by George Jacobsen. In the 1960 article "Gauging Bullet Tilt", Abatiello says the testing showed "tilt" of 2 thou or less was desirable for long range shooting.
The Philly PD has a rifle team and the guys at Frankford Arsenal supplied us with weapons, ammo and some very good advice. They were always there to offer help and advice.
I had never heard of runout until they brought it up during a conversation and explained it. They even gave my friend a runout gage and dial indicator they made in house. He gave it to me and I still have it and use it. It is set up to measure runout for the 30/06 and 7.62 military rounds.
I remember being told how to correct runout by putting the bullet in a 30 cal. hole in a steel block and using sideways pressure to correct the runout. It worked and I still do it on occasion.
I believe MD knows already, but for those who don't I have done a similar experiment. I sorted/grouped some Lake City Match ammo by runout and got a friend who is a good trigger puller to do the shooting. He used one of his two 308 rifles, I forget which, both of which were known good shooters. I didn't tell him what he was testing, my instructions were to be as consistent as possible and don't worry about what showed on the targets. It was clear that runout mattered.
As Mule Deer suggests, small changes in the BR rifle I owned for a while can make big differences in group size--indeed in temps below about 65 degrees I never could come with any load that wasn't plumb embarrassing.
To answer the OP, in 308 length cases in hunting loads in a reasonably accurate hunting rifle much over .004 generally will see group size increase. For 30-06 length cases over .006-.007 will usually make groups larger.
But I've had exceptions both ways..........
ChrisF,
Thanks for "For 40 years, I've been hearing the number of 4 thou (.004") thrown out there as the threshold for runout before it starts to affect groups. About 20 years ago I was shown the source of that figure. A.A. Abatiello wrote an article in Rifleman discussing the work done at Frankford Arsenal by George Jacobsen. In the 1960 article "Gauging Bullet Tilt", Abatiello says the testing showed "tilt" of 2 thou or less was desirable for long range shooting. At 4 thou, the groups stopped growing and he postulated that perhaps the chamber was correcting the eccentricty at that point."
I have a pretty complete collection of American Riflemans going back to around 1930, and am pretty sure I have that issue. Will look it up.
I am pretty convinced that some of today's "harder" bullets (especially monolithics) tend to straighten out ("correcting the eccentricity") when entering the rifling. However, how much this occurs depends on how well the chamber was cut, as in whether the rifling taper is even all around the throat. Which is why I suspect monolithics tend to shoot more accurately when farther from the lands. But have also seen the same thing with many of today's high-BC lead-core bullets, even in very precise custom chambers.
Not uber scientific but several years ago, I had a rifle I was working with that I could not get to shoot better than MOA. I felt it should have done better as I had bedded it, recut the crown, trigger work, lapped rings etc. I had done complete brass prep as well for this rifle and hand weighed every charge. Long story short, when I corrected the run out (about .007, Dang Expander ball) and had ammo running around .002 or less, groups went to sub .5 MOA. That told me that runout does matter.
As a side note, I don't understand why people try and hold .0001 when chambering a rifle barrel and having their actions blue printed and then feed them with .005 or greater runout ammo. That is like building a Top Fuel Drag car and feeding it pump gas, makes no since to me.
pullit,
I ran into a handloader who claimed to have never checked run-out, and also claimed that all his handloads shot great.
However, I also found out his standard for "shoot great" in a big game rifle is 1-1/2 inch, 3-shot groups at 100 yards. Now, I know 1-1/2 inches will kill most big game, at most ranges, but wouldn't call 1-1/2 inches "great."
Then there are the guys who are very particular about weighing every charge to the gnat's eyelash but have no idea about runout.
Then there are the guys who are very particular about weighing every charge to the gnat's eyelash but have no idea about runout.
I am interested in hearing about rhe die adjusting method. I usually only neck size with Lee Collet dies, and maybe I also need to check runout, then again my game shots are inside 200yds.
.001 - .0015.
No data, just habit for bottleneck cartridges.
Then there are the guys who are very particular about weighing every charge to the gnat's eyelash but have no idea about runout.
I am interested in hearing about rhe die adjusting method. I usually only neck size with Lee Collet dies, and maybe I also need to check runout, then again my game shots are inside 200yds.
Do you mean the collet neck die?
Recap from old thread on collet die adjustment:
Originally Posted by mathman
The first thing I recommend is to ignore the instructions supplied with the die.
The second thing I recommend is to ignore whether or not the press you're using cams over at the top of its stroke.
The die squeezes the neck onto a mandrel, so for a given neck thickness there is a finite limit to how much sizing you can achieve. This die will need adjustment to suit different thicknesses of brass.
Raise the press ram to the top of its stroke. Thread the die into the press until the bottom of the sizing collet (not the die body) just touches the shell holder. Measure the neck OD of a piece of brass.
Run the brass through the die using a full press stroke. It should take no effort since if you're set up as described the die has done no sizing. Turn the die into the press about 1/4 turn. Run the brass in again. You probably won't feel much sizing going on, but give the neck a measurement just to see. If it's still nothing, screw the die in another 1/4th and try again. You'll may start feeling a bit going on as you work the press handle, and if so you'll be able to measure a little sizing taking place.
Rinse and repeat using 1/16th turn in increments for the die. You'll feel increases in the force required for the sizing stroke. Since you're measuring the neck after each pass you'll eventually find two increments where the neck didn't get any smaller. NOW STOP TURNING THE DIE INTO THE PRESS. Remember you're squeezing the brass against a solid steel mandrel which isn't going to give, so even if the press stroke didn't feel like it took very much force the neck is as small as it's going to get.
There's a learning curve to the die, but it isn't hard.
I like to run cases through the die twice, spinning the case about 1/3 turn (rather than the 1/2 turn in the instructions) between passes. This means the parts of the neck that were under the splits in the collet fingers on the first pass will get hit on the second.
Originally Posted by mathman
Correctly executing the set up method I outlined above makes camming over or not a moot point, and it will not even come close to popping the cap. Furthermore since the full press stroke is used every time I don't have to "judge my lean" on the handle.
As a side note, I don't understand why people try and hold .0001 when chambering a rifle barrel and having their actions blue printed and then feed them with .005 or greater runout ammo.
As in my case.......no one ever told them and you do not se much written about it.
I've got RCBS dies that aren't working (no doubt, due to me). Regardless of having the decapping rod tight or loose, or high up in the body, or whatever, I spend hella time correcting runout in finished rounds with a TruAngle tool.
Would it work better for me to try this:
Step 1: Deprime with
Universal Decapping DieStep 2: Size in current RCBS die with decapping/expanding rod removed
Step 3: Expand case mouths with
Universal Case Expanding Die?
Or am I just a small amount of understanding away from making my current dies sing?
FC
Plan 1: Do your steps 1 and 2. Then install the expander and push the necks over the ball to expand them, but not all the way into the die of course. Check the neck runout to see what you've got at this point. Then you'll know if your brass is sized straight.
I would not recommend that Lee die for what you mentioned. If you wish to go the expander die route then get an appropriate Lyman M-die or one of the expander dies from Sinclair or 21st Century.
One of the things mentioned in the Abatiello article is that when they indexed the eccentricity (high point indicated) the same for rounds with high runout, the groups got smaller. Creighton Audette demonstrated similar. Harold Vaughn wasn't able to replicate the results.
If you can't get rid of your runout, try marking the high point and load the rounds into the chamber with the high point in the same place.
Am familiar with the Vaughan and Audette results. Conflicting results are always interesting.
I have tried indexing rounds years ago and did not see where it helped. I found that eliminating or minimizing runout at it source was a better fix for the problem.
Assuming that the chamber is actually concentric to the bore, wouldn't a case have to be neck sized to see any benefit to less than 0.004" of runout? Otherwise, the case is just laying at the bottom of the chamber, out of alignment with the bore.
Assuming that the chamber is actually concentric to the bore, wouldn't a case have to be neck sized to see any benefit to less than 0.004" of runout? Otherwise, the case is just laying at the bottom of the chamber, out of alignment with the bore.
If one has the case sized correctly (even FL sized - so there's just a hint of resistance to bolt closure), won't the cone-like nature of the chamber and cartridge shoulder center the round as the bolt is closed? Or will it still possibly be tilted? Might depend on the nature of the bolt face and feed style.
Rex
Assuming that the chamber is actually concentric to the bore, wouldn't a case have to be neck sized to see any benefit to less than 0.004" of runout? Otherwise, the case is just laying at the bottom of the chamber, out of alignment with the bore.
If one has the case sized correctly (even FL sized - so there's just a hint of resistance to bolt closure), won't the cone-like nature of the chamber and cartridge shoulder center the round as the bolt is closed? Or will it still possibly be tilted? Might depend on the nature of the bolt face and feed style.
Rex
In theory, if the shoulder is not bumped, yes. All ties in with chamber to bore concentricity, bolt face being perpendicular to chamber, and locking lug engagement. All in a perfect world!
Which I believe is why JB stated you see runout having more effect in a blueprinted bench gun. All of those issue should be addressed. Factory rifles, not so much.
Assuming that the chamber is actually concentric to the bore, wouldn't a case have to be neck sized to see any benefit to less than 0.004" of runout? Otherwise, the case is just laying at the bottom of the chamber, out of alignment with the bore.
Consistency is the key, and if they're bananas they're not laying there out of alignment the same way shot to shot.
I like Eric Cortel and think he gives good advise. Having said that, I do believe that chamber/bullet profile/freebore/brass fit to the chamber all pay a part in the final group size ( as well as other factors) I know that I what I saw on my rifle (that I mentioned earlier in this thread) runout did make a difference. Maybe it was because it was a sporter barrel vs a heavy barrel like Eric has, or one of the other factors mentioned or a combo of factors. Either way, I feel that I want to have as true and straight a round as I can. I strive to keep every at zero but my upper limit is .003 (YMMV)
What tool do you use to measure run-out?
Plan 1: Do your steps 1 and 2. Then install the expander and push the necks over the ball to expand them, but not all the way into the die of course. Check the neck runout to see what you've got at this point. Then you'll know if your brass is sized straight.
I do a variation of this as Mule Deer wrote about in Gun Gack 1. I use my universal decapping die and then FL resize with the rod a little loose so it can seek the center. It works great. With something like a 22-250 expanding the neck in a separate step would probably give better results due to the amount of body taper.
Another thing to consider is how much the die is sizing the neck compared to how much sizing the neck actually needs to hold a bullet.
This is a little off topic, but I bought a custom rifle a few years ago that came with a suggested accuracy load that had the bullet jammed .01 into the lands like a bench rest load (this is a hunting rifle but the builder does a lot of bench rest work). Does jamming the lands help at all if you don't reduce the neck tension like they do in their bench rest loads? It would seem from the responses above regarding jump that you would need zero run out if you jammed the lands with a neck that had enough tension to feed from a magazine. I never shot the suggested load because I wanted to use a different bullet, but I was curious if it would work for hunting purposes.
Assuming that the chamber is actually concentric to the bore, wouldn't a case have to be neck sized to see any benefit to less than 0.004" of runout? Otherwise, the case is just laying at the bottom of the chamber, out of alignment with the bore.
A post that is chasing this question down the rabbit hole!
Mr B,
Vaughn reasoned thru the mathematical reasons why he thought indexing should work, then reasoned thru possible reasons why it didn't turn out in his testing. One of the factors he theorized was the ejector tipping the case in the chamber (he used a Remington 721 which is very similar to the Rem 700 mechanically). Audette shot a P64 M70...no ejector to push the case. ...and I'm not sure what the backend lockup of a Mann Fixture looks like, but I thought my surplus Mann barrel was threaded for a Springfield receiver...in which case, no ejector.
There's other things that he chased that are relevant to this discussion such as the tilt in the bolt that the trigger causes (and that he said shimming or sleeving didn't completely correct. And the headspace dim of the cartridge relative to the chamber.
I am very familiar with Vaughan's book, since I purchased a copy shortly after it was published, and have read it several times. He also concluded that his 721 actions bolt lugs and recessed were lapped due to long use!
I read Audette's stuff on indexing quite a while ago, can't remember where.
I've got RCBS dies that aren't working (no doubt, due to me). Regardless of having the decapping rod tight or loose, or high up in the body, or whatever, I spend hella time correcting runout in finished rounds with a TruAngle tool.
Run out is often a product of inconsistent necks (thickness), and the best dies in the world will not rectify that issue. I both turn and ream all my brass after its first firing. Helps a lot.
One of the things mentioned in the Abatiello article is that when they indexed the eccentricity (high point indicated) the same for rounds with high runout, the groups got smaller. Creighton Audette demonstrated similar. Harold Vaughn wasn't able to replicate the results.
If you can't get rid of your runout, try marking the high point and load the rounds into the chamber with the high point in the same place.
Do you zero your sights for the monkeyed up crooked indexed rounds or the straight ones?
Like you, I had an RCBS die that was driving me nuts, switched to Redding type S and now all my dies are type S and life is simple. ( granted, I only load for 3 cartridges)
There will be the one that claims anything above RCBS is a waste of money, whatever, it’s made it easy for me.
I've got RCBS dies that aren't working (no doubt, due to me). Regardless of having the decapping rod tight or loose, or high up in the body, or whatever, I spend hella time correcting runout in finished rounds with a TruAngle tool.
Would it work better for me to try this:
Step 1: Deprime with
Universal Decapping DieStep 2: Size in current RCBS die with decapping/expanding rod removed
Step 3: Expand case mouths with
Universal Case Expanding Die?
Or am I just a small amount of understanding away from making my current dies sing?
FC
I am very familiar with Vaughan's book, since I purchased a copy shortly after it was published, and have read it several times. He also concluded that his 721 actions bolt lugs and recessed were lapped due to long use!
I thoroughly enjoyed (and continue to enjoy) Vaughn’s book! I had probably bought three or four copies after wearing out my first copy and having one or two not come back after lending it out.
Too bad PS is defunct and thus this book is out of print.
Yes, Vaughn found that that his old bolt had the lugs lapped into contact through long use. ...and when he replaced it, he found that the new action had contact on the bottom only...so he recut the bearing surface of the bottom lug to allow the top lug to bear. He mentions that he found the same situation with his three custom bench rest actions.
I remember a well known rimfire benchrest smith described the same situation in front lug rimfires and set out to redesign the walker trigger so that it did not exert an upward force. That was hella controversial and sparked some very heated discussions.
Vaughn’s solution was to cut the bottom lug and bolt face to account for the bolt tilt which showed improvement in both his instrumented testing for wayward forces on the receiver and in his shooting for groups.
What tool do you use to measure run-out?
Concentricity tool and your eyes.
Actually, just using your eyes works for making sure runout isn't any more than .005--which is plenty for most factory big game rifles. Roll the loaded rounds across a smooth, flat surface and if you can't see any "wobble" in the tip of the bullet, runout is normally .005 or less.
My only comment is that a lot depends on the rifle. I see loss of accuracy in my benchrest rifle if bullets if bullets are even .001 out of alignment, but in many factory big game rifles it often doesn't matter if they're .005 out.
On the other, a custom barreled big game rifle can "notice" much smaller amounts. Once had a custom 7x57 sporter (which unlike some 7x57s had a throat about as short as the 7mm-08) that I ran some experiments with using factory ammo. Bought three boxes of some Hornady Light Magnum 139-grain loads, then sorted them for run-out. Put those .003 or less in one box, those from .003-.005 in another, and those over .005 in the third box. (As I recall, none ran over .007, but it was a while ago.)
3-shot groups with the <.003 ran around half an inch, the .003-.005s around an inch, and the >.005 into about an inch and a half.
John, that’s pretty interesting, your results show the effect on group size is more significant than I would have thought.
Are your numbers total indicated runout “TIR” (how far the needle swings in total) or are they numbers for “out of alignment (TIR/2)?
I think most folks talk TIR numbers even when they say “out of alignment” so I’m never sure. But 0.005” out of alignment would be 0.010 TIR which seems pretty excessive to me.
Not JB but I am JW, and on the example I posted earlier in this thread, my example mirrored JB with the less than .003 cutting my group in half with my rifle I was using. The runout I was using were TIR, so we will say 0.000 to 0.003 or less cut my groups and 0.005 to 0.007 opened them up
Might also mention that maybe 20 years ago went on a pronghorn hunt sponsored by a firearms and ammo company, using one of their bolt-action rifles chambered for the In-Cartridge of the moment, and some of their new factory ammo. They sent me the rifle and ammo before the hunt, so I could mount a scope, sight-in, etc., and it would not shoot worth a darn, with some groups 3" or so.
I wondered how this could be, and checked all the usual stuff--screws, scope, bedding, etc. Turned out much of the ammo had a TIR of .010, or even a little more. Contacted the PR guy for the company, and he said it was not actually factory ammo, because they hadn't quite gotten the factory set up for that yet. Instead it was handloaded by one of the ammo-company guys.
By sorting the ammo to those rounds with no more than .005 TIR, the rifle shot 3-shot groups of 1.5 to 2", and I managed to kill a buck at around 200 yards. After the hunt I took the rifle home (and eventually bought it) and played with it some more, tweaking the bedding and handloads. It never would shoot groups consistently under about 1.5", with any load, so eventually had it rebarreled, which fixed that part of the problem....
Thanks for the clarification. I recently bought a rcbs casemaster and checked some of my loaded ammo and was really surprised to find I was doing a pretty good job. LCD stuff at/under 0.001 and my bulk AR stuff mostly under 0.003 with std RCBS FL dies.
I recently bought “top grade ammo” by the late Glen Zediker and will be setting up the std dies to reduce runout.
Almost 20 years ago I started hand loading and the first stuff I loaded in 35whelen shot terribly. I rolled a cartridge across a mirror and could see a significant amount of wobble. I figured that wasn’t good and replaced the hornady FL die with a Redding FL sizing die and some of my load development “groups” (3 shot - I didn’t know any better) went into the 0.3’s. I don’t know how much runout it takes to see a wobble on a mirror but it was a lot!