Reading the quote in the Rifle Magazine thread and saw Mathman share the typo relating to .03 or correctly .003 and MD’s assertion that number being ok for varmint rifles but not benchrest. Made me curious.

My question is - zero runout would of course be the goal but when does runout become a significant problem to accuracy? .003? .005? .009? I’ve got a case master and each set of dies seems to generate its own result. Is this a shared experience?

I don’t know as much as I should about this topic & would enjoy learning more.

Tim

I’ve always heard that a reasonable goal is .002 or less.

RCBS's directions for the Casemaster suggest .005 for big game loads, and .003 for varmint loads--but obviously those are only general guidelines.

Some of it depends on the bullet. I've found some are more sensitive to run-out, generally "softer" bullets, though in my experience that includes the Nosler Partition, due to the open rear end. "Harder" bullets tend to be not as sensitive, especially monolithics, I would guess because they tend to straighten out when entering the rifling.

Thanks, MD! I’ll be down cellar tonight rolling things around. Interesting thought on bullet hardness.

What can the rifle and shooter resolve? A good benchrest rifle can "see" differences that something like a well worn Savage 99 can't.

I had a friend who is good on the trigger shoot some runout sorted Lake City Match ammo through a good Sporter 308. He didn't know what he was testing so he had no bias. The groups clearly went to pot when runout got above 5 thou.

I don't think there is a magical number. Many BR and F-Class champions state they do not measure runout.

if your worried about accuracy and run out on brass used with a good rifle just buy Lapua brass its a lot less work in loading new brass or reloading your brass for accuracy.

^^^^right there^^^^ yes I can easily get my loads down to minus .003....but my lack of skill at the shooting bench pretty much makes it more about confidence in ammo...than results. If I fire a boo-boo, I know it's me, not my ammo. And I seem to fire a lot of boo-boo's.

Not measuring runout is no indication that it doesn't matter.

i shoot in the master division its not that of big of deal except i want people to understand this = > good brass is very important to shoot well . the only thing i do with my new Lapua brass for run out is weigh my new Lapua brass all 500 cases from the same lot number. and put them in piles so this new brass is with 3/10 ths of a grain in each pile . then load and reload same 50 cases over and over i may candle reneal those 50 cases after shooting them every 5 or 6 times ? medium powder loads is easier on brass life too ! i also always volume load so do most of the guys i know , matter fact one friend just won South Dakota 600 yard big shoot last fall 2021 with a 6 BR doing exactly this way with his brass and volume loading.

Thanks all! I appreciate all the perspectives shared.

Still not sure how I never thought to read the directions for my casemaster lol.

Enjoy your Saturday!

Question for clarity. Are we taking runout of brass only or loaded round here?

I was talking about the loaded rounds.

What is "volume loading"?

IME if your loading technique and equipment are solid < .003in is the norm. Only time that has not been the case (pardon the pun) is a 308 neck die that INDUCED .007 runout in every brass. Sent it back to the manufacturer and replaced it with a FL die since I now use LCD for most loading.

Recently my son bought a couple of boxes of Federal Premium 270 Winchester ammo loaded with 150 grain Nosler Partitions, a combo that normally groups well inside of 3/4" at 100 yards.
This stuff, though, had trouble staying inside of 2" at that distance. We thought something might be wrong with the scope so tried a group with ammo from an older lot which put 3 shots into a 1/2". So it's likely something to do with this newer lot.
When we got home I checked for bullet run out and was shocked to see it was running from 0.01 to 0.012" ( 10-12 thou!). The older lot showed run out from 0.002 - 0.003".

Federal Premium used to be very good. Anyone else experienced recent quality issues with Federal Premium ammo?

I agree. Anything over .005" TIR and guys that shoot well, will see a difference in group size. The reason I keep my loads less than .003". I always say my properly adjusted standard RCBS dies give me that. Sometimes even better. I like that more. I was checking my 22-250 loads the other day, since I switched bullets that are known to be troublesome (from some guys here) and run-out was less than .002". Checked some 6.5 CM loads and the run-out was all less than .0015 TIR. If I were a benchrest shooter, I'd strive for less than .001" TIR. A very long time ago a company called Brown Precision put out an article discussing run-out and how Chet Brown used his concentricity gauge to check and adjust run-out. He submitted his findings in that article and basically said the same thing as mathman. Anything over .005" and you could definitely see a difference in group size. One thing that I have to say in regards to concentricity: When testing for accuracy/precision, you really need to be shooting an accurate rifle to begin with. Testing with an SKS is going to get you no where. Testing with an accurate rifle (even an accurate hunting rifle), you'll see the effects of poor run-out vs. extremely small TIR readings.

Loaded rounds

I agree. That is a very good point about equipment. It is always a good idea to check your finished loads to make sure your equipment is adjusted properly to minimize run out. If equipment is not up to the task, get rid of it and replace it with something that gives good TIR's. For those that don't know, that doesn't mean you have to use benchrest seating dies or anything fancy. It just has to be consistent and produce the numbers you are looking for. With my ammo, I an not happy with anything that produces more than .003"

I think that’s where I’m headed too (.003). I was keeping things under .005 but now realize my window might have been a bit too wide.

That's what I always talk about too. Its the finished product that is important. As far as brass you use. Lapua is excellent right out of the box. If you don't know how to properly prep your brass, then it is a good idea to buy Lapua. After all is said and done any good brass will produce great accuracy/precision if you prep it right. There's always a lot of talk about how accurate guys' rifles and loads are, but with no proof. Its always, you have to use this or that and I get sub 1/2 moa out of my rifle and load. Its all talk unless you can prove it otherwise. Also guys that don't check run-out have their heads buried in the sand and are driving blind. That chidt is going to sneak up behind them and bite them in the AZZ...

OK... so what's the best tool (s) for checking runout (both case & loaded)?... Been look'in at that sexy new redding slant gauge...

I don't shoot commercial ammo much. When I do I measure concentricity of every cartridge. Some are fine, up to 0.003". Others not so much. Many years ago like Mathman, I measured and sorted cartridges to shoot groups. I did this because prior to then I never paid any attention to concentricity figuring that any shot outside of groups I was shooting I must have pulled off at trigger break.

Cartridges with little runout grouped well, more runout groups opened up. Sort a group of cartridges where 3 had little runout, add 2 that had 0.010" runout, there were the fliers.

There is a mathematical relationship between bullet tilt and group size.... up to the point where the chamber bends it straighter.
This relationship depends on random rotational orientation of the bent bullet.

As I explained on this forum 4 years ago.
https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/12563531/re-collet-dies#Post12563531

I keep runout to 0.003 or less, it's not hard to keep it less than 0.003. I'd say most of mine are 0.002 or less. I also turn the necks as well to keep everything nice and aligned. It's is a PITA but since I started keeping case necks the same thickness and keep runout to a minimum, accuracy improved.

Honest question...at what yardage does a difference of 0.002" make in accuracy or group size?

Take for example 500 yards. Same case lot for powder - primer - bullet - and brass. Same rifle - shot same day - same conditions.

Shooter has sorted his ammo. He has 10 rounds at 0.002" runout - and 10 rounds at 0.004" runout.

How much of a difference will that .002" make at 500 yards?

I too would like to know what tools are used to measure AND correct runout. I want to start doing this....

Measuring is no indication that it DOES matter. Measuring ammo won't affect accuracy. First, you need to load it correctly.

There is a reason the the big dogs quit measuring; it is because it DIDN'T matter within reason and was thus a waste of time. Hell, before I ever knew I was supposed to measure it, I was shooting cleans.

Unless your process is terrible, your components are junk, or your equipment is junk, it is hard for it to matter in the grand scheme of things. Even a novice hand loader won't load ammo >0.005". I shot some factory Hornady into .25 MOA with 0.008" runout recently. I only measured it out of curiosity.

Unless it is TERRIBLY bad, it really doesn't matter. I used to check match ammo, but I also dropped the habit and saw no difference in scores. I haven't shot matches in a few years, but still shoot/teach long range shooting and use GOOD ammo when demonstrating in class. What matters more is keeping a rifle in tune.

Measuring for runout should be reserved for setting up equipment or when making changes to process or used as a diagnostic tool. Measuring each and every round is time consuming and the effort won't show up on target.

Correcting runout involves changes in process or equipment. The idea you can use a tool to correct loaded rounds is nothing more than a gimmick.

To measure it, purchase a concentricity gauge and dial indicator.

Some will measure a fired case to determine if their chamber is true. Then some will measure the neck after sizing...but do not fall into this trap as imperfections in the neck are pushed OUTWARD from the expander mandrel or expander ball. Personally, I prefer an expander mandrel or gauge pin to an expander ball. Sizing of the case and expanding the necks should be done in separate steps.

The true test of processes is to determine bullet runout. There is a debate as to where this should be measured; ogive, near the tip, or between the tip and ogive. Believe it or not, many times the runout found here can actually be bad bullets. Many claim they are getting 0.001" runout and maybe they are...but anything reasonable is OK. If you have a problem, the tool can help you identify which step is inducing it.

Could not agree more.

I’ve got to say your posts are what I was hoping for - many benefit from different positions taken from life experiences especially when the details are being parsed in a respectful way. Cheers!

Yes but imo knowing your ammo is straight is one hell of a mental booster.

[/quote]
Yes but imo knowing your ammo is straight is one hell of a mental booster.[/quote]

Yes, and it eliminates one factor that often affects accuracy.

I might also mention that EVERY factor (including measurement) that's been discussed here is included in my GUN GACK books. They're definitely not The Revelation, because everything was learned from reading and talking with other handloaders, plus experience. And I continue to learn something just about every week or month.

But one thing I've noted before about the Campfire (and other Internet sites) is most people want some simple answer for free--especially relative newbies, many of whom have never even bothered to purchase a current loading manual, or if they have, never read anything except the data for the cartridge(s) they plan to reload.

That's a bit different than saying it doesn't matter. I don't measure every cartridge every time precisely because I know what a given batch of brass will do with a given set of dies with me as the operator.

Interesting thread.

I always strive for < 0.003 on both brass necks and bullet runout.

JB - I agree on all points - just interesting to hear of a similar opinion put into different words - for me, both resonate & make me a better shooter.

Good evenings to all!

Exactly.

Yeah, I lean to .0015.

Yesterday evening I loaded up some rounds for a custom barreled 270 Winchester that I am working up loads for. About all I can get are Hornady SST bullets right now for my hunting needs.
After loading I checked all of the rounds on my Sinclair concentricity gauge and found a couple were .008” out when measured just in front of the connelure. I had a hard time believing the necks were crooked because I used the Lee Collet die so I then reset the gauge to measure the case necks.
They were all within .002”.
I am now thinking that the bullet seating die is the problem as I was using the Lee bullet seater and it only makes contact with the tip of the bullet rather than further down closer to the ogive. I am going to pull the bullets and reseat with a RCBS seater to see if it makes a difference. If it doesn’t then it has to be the bullet jacket being thicker on one side I would think.
What I don’t understand is how can the bullet be that far off center of axis and it not showing up when measuring the case neck?

Great post. Curious myself!

Sounds as though we agree more than we disagree. But I will reiterate, unless it is TERRIBLE, it doesn't have much affect. Other factors affect precision of ammo more than runout. I've not seen 0.008" shoot noticeably worse than 0.001".

I alluded to this earlier in the thread; bullets often have runout that can be measured independent of the cartridge. Especially cheaper bullets designed for hunting. But you're definitely right to suspect seaters as a potential problem or it could be seating process. How is the chamfer and deburr? How clean are your necks? Are they too clean? Did you use lube prior to seating...this could lead you down the rabbit hole of investing in an arbor press that gives you a measure of seating force.

I see more runout after brass has been resized and shot a few times.For hunting I usually use once fired brass.The brass is soft and I see very low runout.I'll still see a few that will run over .005 and I separate those,but most run between .000-.003.Without annealing the brass,about the third or forth firing,I see more of the brass that was running .000-.003,running .005 or greater.I could be wrong,but it may be as the brass became harder,the bullet is harder to seat and may be the cause for more runout.

Couldn't agree more. A concentricity gauge can be valuable for fine tuning/troubleshooting your process but within reason, runout is not the problem in 99% of shooting.

I found that a good outside chamfer on the case mouth helps as much as a good inside chamfer. I get results I like with RCBS seating dies.
Your mileage may vary.....

Copied and pasted from JB :

But one thing I've noted before about the Campfire (and other Internet sites) is most people want some simple answer for free--especially relative newbies, many of whom have never even bothered to purchase a current loading manual, or if they have, never read anything except the data for the cartridge(s) they plan to reload.

This with reloading and long range shooting have in common. Both take time and experience. and go together,. Bad reloads will not hold up over 8 or 900yds for consistency. Neither will bad shooting form. I have thirty years into both and learn something new and important all the time......

The sizing die can induce neck runout no matter how good or expensive the brass is. The seater die can do the same thing with loaded rounds.

I know this is contrary, but I don’t measure neck wall thickness very much. Instead I size the fired cases and let the concentricity gauge tell me what brass is going to size straight. I’ve had cases measure a fair amount of neck wall variation and still size straight, and on more rare occasion have brass with tiny variation size crooked no matter what die I used.

Accuracy in smaller calibers like 6mm tend to be more sensitive to runout than larger calibers. I strive for .003 with my 243’s, .005 with my 30-06’s for example.

Factory bbls in a HUNTING rifle in say, a 243 don’t produce smaller groups at .001 vs .003, at least for me it doesn’t. Could be the shooter though. My 30 cal rifles I keep at ~.005, because lower runout generally doesn’t produce smaller groups either.

I’ve been spinning brass and loaded rounds on concentricity gauges for almost 30 years now, and unless it’s a custom bbl or full house custom rifle .003-.005 runout of a loaded round, depending on caliber, seems to be the threshold. Anything less doesn’t help. Could be my shooting though….

What in the seating process could cause mis-alignment? As I stated, the necks are, at most, .002” run-out, and that is most likely due to a slight bulge common with the Lee Collet die. (Which I said I am using) or, it is from the case neck being slightly thicker since I do not turn my case necks. There is NO lube in or on the case neck, as I said I am using the Lee Collet die.
Chamfering the case mouth? I doubt it. They were chamfered after trimming and the SST bullets are boat-tails.

I pulled one of the bullets that was .008” out and re-seated it with my RCBS seater and it brought it down to .005” of runout. I am going to re-re-pull the same bullet, dump the powder and run it through the Collet die again, the reload it and see what happens.

The seater could be shaped poorly for the type of bullet, or it could be making contact out of square. The further from the ogive, the greater the chance of misalignment. The chamfur/deburr could cause greater seating pressure which could cause inconsistency, as well. Lube in the case neck (or on the bullet) can reduce seating force and allow the seater's job to be a little easier. Lots of things can actually affect seating. I believe F-Class John, Winning in the Wind, Bolt Action Reloading, and a few others have demonstrated the effects of various phenomenon affecting seating.

When I'm loading for accuracy i check every piece of new brass on my lathe for runnout. There are bad pieces of brass in every lot. With Lapua, its typically 4 cases per box that i scrap.

Checking runout of loaded ammo just confirms that your process and components are good. I check the first couple and if they're good, i don't check any more that session.

Also, WHERE you check runout is as telling as anything

This is rising to the top as something that should be discussed further

Indeed. I humbly submit that the proper place to check bullet runout is at the beginning of the ogive of the bullet in relation to the tip because, in theory, we want the bullet to contact the rifling uniformly. Furthermore, we should roll cartridges just below the shoulder and just above the un-sized portion of the body near the case-head.

To build upon these two posts - there are two spots where, if we measure runout, will give us a complete picture of what we are working with? Should we consider averaging the two data points or just mentally compare them to gain understanding of the overall quality of an individual cartridge?

To me, it’s good to understand how different variables correlate. This is, to me, defining a particular element of an overall equation. Correct me if I’m off base.

I guess those who light this fuse can determine how far it burns.

My gauge has two 0.375 dia balls at case head, two 0.3125" dia dowl pins that shoulder index on.

Vertical dowl pin where case head indexes against. Indicator tip just forward of junction of bullet body diameter where ogive intersects. Works for me.

I have done just that to check my sizing die setup.

Pints,
The sliding sleeve seater dies will generally seat bullets the straightest.

Glad you brought up annealing and straight ammo, I too anneal around third to fifth firing because brass usually sizes straighter and bullets seat straighter.

I have started annealing every firing. Doing the same thing every time lends itself to consistency.

A few comments:

Again, the directions for the RCBS Casemaster suggest measuring runout approximately .1 inch in front of the case mount, or about where the ogive typically begins. As somebody else already stated, this is the area where the bullet typically enters the rifling.

Annealing after every shot certainly helps, especially when searching for the finest accuracy--which is why I typically anneal the 6mm PPC brass for my benchrest rifle after every firing.

With hunting rifles I typically anneal after every four firings, but keep the brass separated in Ziploc bags, with how many times they've been fired written on the bag with a Magic Marker. Have gotten fine accuracy by using only brass that's been fired the same numbers of times after the last annealing when loading a box or two of ammo. (I anneal after four firings because even with "ordinary" brass that's soon enough to prevent necks from cracking. But have found that even "premium" brass results in more consistent accuracy when annealed regularly, even if not after every firing.)

Might also mention "experiment" I made with factory ammo around 20 years ago. Had a custom rifle built in a well-known but not super-common chambering, and shortly thereafter was invited on a Coues deer hunt in Sonora. Didn't have time to work up a load, but lucked upon some factory ammo that had received great reviews--and not just in gun magazines. Since Coues deer aren't very big (in general smaller than pronghorns), I wanted all the accuracy possible.

Bought several boxes, then sorted them according to bullet run-out, measured as described above, about .1 inch in front of the case mouth. The batches were those with at most .003 run-out, .003 to .005, and over .005, which ran up to .008.

The .003 or less rounds averaged 3 shots in around .5 inch at 100 yards, the .003-005 rounds around an inch, and the over-.005 rounds about 1.5 inches. Now, even the >.005 rounds would certainly work fine on most big game at "normal" ranges, but I used the <.003 rounds. The buck I eventually got was only 220 yards away, but I was very confident at twice that range--or more.

Apparently that variation in accuracy potential would be meaningless to some here, and my field experience indicates it is--on animals considerably larger than Coues deer. But I was indeed happier and more confident with the best accuracy.

That's closer to what I've seen. The other fellow's comment that he hasn't seen runout up to .008" make any difference is in direct contradiction to the blind test shoot I did with my friend.

I can truly state that I have NEVER measured round out on any cartridge, nor do I plan to in the future. I do believe that if you are a benchrest competition shooter, that it would be a critical factor, BUT for 99% of big game hunters I believe it is a waste of time and energy. I am a hunter primarily elk and deer, and believe that one should do the best job possible in developing a hunting load, I do not believe that weighing cases, weighing bullets, or primers, will make a difference in your ability to get the job done. Load them carefully with good components and don't worry about the minutia.

For conversation, what falls under the headings of doing the best job possible and loading them carefully?

Well that's just great... .003 or less runout =1/2 inch groups, and .005 or more = 1 to 1 1/2 inch groups... now i want a slant bed concentricity gauge to check my load test ammo (before i taint the data with crooked necks)... And a teslong bore scope from that other thread (so i can be sure what my barrels look like)... You guys are kill'in me ($$$)... You know that, Right!... A bunch of Enablers for sure... lol

Both those items are nice to have but not necessarily required.

With all the discussion about cartridge run-out, has anyone ever delved into how precisely rifle chambers are aligned with barrels, and that effect on accuracy?

I hear ya - in general however with the reduced a availability of components I’ve started elevating my quality standards if only to reduce my use of materials. To me, checking runout is an easy way to make more sure that a loader isn’t just churning out substandard stuff and testing more loads than necessary chasing better accuracy. It’s nice to qualify what different die sets or combination of dies creates the best ammo or not.

So I guess, for me, this step helps me determine what my quality components indeed are then I can load more freely without worrying about every single cartridge etc.

Thanks for adding so much solid data to the thread - helps us all evolve in a more thoughtful manner

I start by case exam, i look for red fingernail polish on primer, if it's red it goes in trash, check, for cracks, then size, length, clean and chamfer. I load powder with spoon, and measure each amount ( especially on full loads), then seat bullet. Done except for running through magazine.

Sure have. -Al

Great. Can you describe the process?

Dialogue on this thread is outstanding- thank you all!

Seems like what I've learned so far is, the people who say there's no need to measure, do in fact measure, just maybe not as often. That's not the same as not measuring.


Still want to know more about fixing problems (not necessarily the rounds themselves) and what are you doing with the culls? Breaking them down and starting over? Saving them to "shoot out" for a just cleaned barrel?

After reading a lot of Mule Deer's writings on this subject, I now check my rifle rounds for runout and adjust as necessary with the Tru Angle tool. The result has been more consistent accuracy from my rifles. The extra effort is definitely worth it to me.

Could you refine your components and processes so adjustments to runout become unnecessary?

I've worked on that some but am not there yet.

I’ve done the same over the years. Starting with consistent necks (either from the factory or turned), I found that a combination of the LCD, Redding BD, and Forster BR dies is almost guaranteed to produce 0.0015” or less of TIR, indicated on the ogive. Cheap dies can give good concentricity performance, as well, but it’s not such a sure thing, IME.

Amazon will put a very serviceable Teslong borescope on your doorstep for $55.99.

Royce,

I've done some research into that as well.

One other thing my Gradient Lens bore-scope has revealed in the 20 years I've owned it is that many factory chambers aren't perfectly aligned with the bore. This is obvious when the lands and grooves one one side of the throat are longer than on the other. This has to affect accuracy at least a little bit, but some of those barrels shoot pretty accurately!

John

[/quote]
I’ve done the same over the years. Starting with consistent necks (either from the factory or turned), I found that a combination of the LCD, Redding BD, and Forster BR dies is almost guaranteed to produce 0.0015” or less of TIR, indicated on the ogive. Cheap dies can give good concentricity performance, as well, but it’s not such a sure thing, IME.[/quote]

Have mentioned this before here and there, but one thing I've noticed over decades of using all sorts of dies is that the odds of a typical basic set of expander-ball dies from Lee, Lyman, RCBS, Redding, etc. producing reasonably straight ammo are about 50/50. I'm not talking super-accurate larget ammo, but dies capable of 1-incg groups in a typical factory hunting rifle.

Another thing I've noticed while using an alignment gauge is that if you simply roll a loaded round across a smooth, flat surface (say a mirror laid flat on a table) that if the tip of the bullet "wobbles" noticeably, then run-out is more than .005. If you can't see any wobble, run-out is .005" or less.

Mule deer
Would a chamber cast be precise enough to show any misalignment between chamber/throat/bore?

I make an effort to put together ammo with minimal run-out, but some people don't. A relative in our group that travels west for Mule deer and Elk always used factory ammo in his 30-06. The day we got together to shoot rifles to sight in or make sure they are on he showed up with reloads that he put together with assorted reloading equipment he had ordered online. His groups on the target were not as good as factory ammo did for him. Oh, oh!

I told him to come over to my house and we will fix it. I got out the Sinclair gauge and the TruAngle tool and showed him how to straighten his ammo. Went back to the range and VOILA! A happy hunter.

I put a Rem 700 7mmRM take off barrel in the lathe to practice chambering a surplus mauser.

I cut off the tenon threads with a parting tool.

That left a huge burr that I did not get rid of.

The 7mmRM reamer cut the chamber 0.9" deeper.

But the reamer never stopped wobbling.

I put a test indicator in the rear of the chamber and the runout was 0.0070".

As a joke I took the rifle, with a lot of other rifles, to the range.

To my surprise, the rifle shot sub moa.... good for any of MY 7mmRM rifles.

I puzzled over how bullet tilt could cause such big groups [mathematically predicted and verified by AA Abatto , NRA, and the US Army*], but chamber tilt did not.

Then later I found out it is because bullets are inserted with random center of mass off center rotational orientation, while bent chambers throw the bullets off in the same direction into the same tiny group.

*MATHEMATICAL SOLUTION

A laterally displaced center of
gravity moves through the rifle bore
in a helical (screw) path. The pitch
of this helix is the pitch of rifling,
and its radius is the lateral displace-
ment of the center of gravity. On
leaving the muzzle, the center of
gravity continues in the direction it
had at that point. For example, if it
leaves at top of the bore and rifling
is to the right, the departure will be
to the right. The bullet travels ap-
proximately 2l.5" in a 24" barrel,
making 2.15 turns in the 10" twist
of rifling. The number of turns
shows the orientation on emergence
compared with that in the chamber
before firing. The angle of emer-
gence is that angle whose tangent is
2 pi times the lateral displacement
divided by the rifling pitch. For
.004" point displacement and I0"
rifling pitch, the tangent is 1/8(2·pi)
(.004)/l0 and the corresponding
angle is 1.1 minutes.
The displacement on target from
this cause is proportional to the
range and can be obtained without
noting the angle. For example, ,004"
point displacement gives in l0"
rifling pitch, so far as this mecha-
nism goes, a target displacement at
100 yds. (3600") indicated by the
proportion .00l· pi /10=X/3600, from
which x =1.1".

That is a pretty good experiment without intending to be an experiment Clark!

Did you happen to note if the case head face perpendicularity shifted out of alignment with the case body axis? I'm thinking that with the chamber crooked it had to be out of square to the bolt face.

In his book RIFLE ACCURACY FACTS, author Harold R. Vaughan (an actual rocket scientist) tested a bunch of factors, and found that case-heads out of square with the bolt-face didn't have any effect.

There are quite a few things that contribute to the answer of "How much matters?".

Good tooling (dies) and processes are where you want to start, as well as an understanding of what each step is actually doing. For example, a full length bushing die like the excellent Redding Type 'S' or Wilson's new stainless f.l. bushing dies (excellent product, by the way) can actually increase the T.I.R. if the necks themselves aren't of a consistent thickness. That's no knock on the dies...they're just not being used with proper case necks for that style die.

On a standard die, most neck issues can be traced to the expander style and location on the decapping rod. Redding's carbide expander ball conversion and powdered graphite for lubing the necks goes a long way to minimizing these issues. On most of my guns with standard unturned case necks, the dies have been fitted with the carbide expander balls and the neck area of the die opened up with a reamer to not excessively size the neck in the first place. A couple of days ago, I opened up a .17 Remington standard RCBS f.l die neck diameter from the factory .188 to .195 along with reducing the diameter of the expander plug to where it's .004 smaller than the I.D. of the case neck after being sized to .195 (it measures .196 after sizing). The result was the T.I.R. went from .004 to .0025. Adding an 'o' ring between the die lock ring and the top of the press dropped the T.I.R. to .0015.

Another area that's overlooked is the diameter of the neck area in the seating die. If it's not a close fit to the neck diameter and the neck is excessively small before the bullet is seated, the result can be a lot of run out. As a rule, I don't like to see any more than .004 difference in diameter between what the neck measures with a bullet seated and what the neck diameter of the die measures. Since the die mfgs. have to accommodate any neck diameters that might get shoved up in there, this area can be a real wild card for run out.

A few bucks spent for a decent micrometer that measures to the .0001 (tenth of a thou) is what you need for this....forget using a dial caliper, even a good one. On the neck area of the dies, I use gauge pins from my gauge pin sets. If you don't have these, a number or letter drill bit can give you a pretty good idea as can pushing a fired case into the seating die and measuring the case neck to see if it's been reduced. If the neck area is pretty large in your seating die, cut a strip of clear tape a bit narrower than the length of the neck and precisely wrap it around a case neck so the ends just butt up or have a little gap.....don't overlap the ends, for obvious reasons.

Seat a bullet and compare the run out to the run out of an untaped neck. If it's better, you just found a cause for some of the run out.

For standard dies, it's amazing how much the 'o' ring can sometimes help. Even a flat rubber washer can be helpful.

Good shootin' -Al

Al Nyhus; For clarity, are you saying the o-ring or rubber washer is allowing the die to float... Negating some misalignment between the die & press... Great post by the way... But i have a feeling i'm going to be bothering my "Master Machinist" friend soon...

Yes, that's exactly what it does. For that same reason, slightly sloppy press linkage and a loose-ish press rams can make straight ammo...provided the dies are straight.

Another thing to try is an 'o' ring on the shell holder to replace the metal clip.

Good shootin' -Al

Thank you Sir; I use a Bonanza Co-Ax press (also floating)... perhaps it's a part of the good luck iv'e had loading accurate ammo... anyway, I'm getting a concentricity gauge so i can know for sure what's going on...

Lee reloading dies have O rings slightly recessed underneath the die nut. Is this what you are referring to?

I found I had less flyers when i started checking runout, especially on factory ammo. The Hornady concentricity gauge is pretty to easy to use with a little practice. Plus checking helps confirm your reloading setup and process. Nice to check a tray of handloads to find almost no runout. I too starting using a oring to help the die "float".


The hornady unit allows you to correct runout, but in my experience only if there is a little. Anything over .010 which I have found in factory ammo you risk loosening up the bullet when trying to correct. But I guess that all depends on the brass and neck tension. I checked some federal fusions and they were all over the place, probably why I've never gotten better than 2in groups with them.

roundoak; I don't have Al's expertise, but i think ? that's exactly why lee dies have the o-ring... when you close the press the o-ring takes up any slight perpendicular misalignment (common) between the die & press instead of bending the cartridge case neck (the die tilts instead of the case neck)... at least that's what i think? is going on...

So we have two camps here. O-ring or no O-ring. I have a read a thread or two urging reloaders to get rid of the Lee nut/o-ring.

Worth mentioning: some bullets/chambers/rifles are very sensitive to runout. Other rifles/chambers/bullets are not very sensitive to it at all.

Not really sure why that is, but I've seen both.

Regardless, paying attention to it will help your loading practices.

A smaller O-ring can also be fitted beneath the top of the expander-ball stem in many sizing dies, which can also make a difference.

Its not a one size fits all deal. You just have to try it with your set up and see if it makes a difference or not. I have some dies where it makes no difference and some where it does.

Good shootin' -Al

Exactly!

Shell holders and case rim diameter discrepancies, often noticed over the years cases can be a little loose in the shell holder, able to push the case around from side to side in the shell holder causing the case to be offside of the centerline of the ram and die. Both seating and sizing dies can suffer this, as the case does not always self center when inserted into the die especially with loose fitting standard seating dies. Always wondered how one could be sure of having the case centered.

Have also been conscious of keeping case mouths square and true, if one side is shorter as often happens with unturned necks after a few firings, it will want to tip the bullet crooked when seating, more so with flat based bullets.

Hadn’t thought about that aspect. I’ll have to give that a try.
MD, your technique of depriming separately and moving the expander ball up in order to expand the neck while it’s still partly contained by the neck portion of the die has helped with several resizing dies. It works.

I would like to apply for a federal grant to study this.

I bought a second-hand, custom rifle built by the late Gary Stiles. It is chambered in 257 Roberts. I took it to the range with some of my hand loads. It was shooting 2.5” groups at 100 yards with the loads I tried. I was at a loss. I have loaded for about 10 years. But kept things simple. Then I remembered something I had read by Mr. Barsness on this forum about run out. I rolled a round across my bench and the wobble was pronounced. Every loaded round did the same thing. I bought a set of RCBS dies to replace the Lee dies and also bought a Hornady concentricity tool. Problem solved and I’m able to get groups <1” out of the Stiles rifle. I’m a believer in the importance of straight ammo.

A little 'straight ammo' incident:

My local police department had three Remington 700 PSS 308's that were contracted to my good pal, the late Stan Ware (SGR Custom Rifles), for rebarreling and action work due to a pretty significant accuracy fall off. Two of the SWAT team members assigned to these rifles were guys that Stan and I shot registered IBS and NBRSA Benchrest tournaments with, so they were very capable shooters. The department had used factory Federal 308 Gold Medal Match ammo (Sierra 168 Match King) for a long time and it had given 3 shot groups of right around 1" @ 100 yds for all three rifles. More importantly, the first shot from either a clean bore or a 'fouled' bore went right were it was supposed to go...an important 'must' if the rifle(s) were ever fired at a human, given the subsequent litigation and investigation that will follow.

Anyhow, the rifles were to come over one at a time for the rework along with several boxes of the Federal ammo for test firing after the rebarreling. Prior to pulling the barrel on the first one, Stan test fired it at his home range for documentation. It struggled to shoot under 2" at 100 yds. I rolled some of the supplied FGMM ammo across the workbench and the bullets wobbled around like a Saturday night drunk. We pulled bullets, dumped the powder out of each case seperately, sized the cases in a Redding f.l. die, dumped the powder back in each case, reseated the bullets with a Wilson seater and an arbor press and went to the range again where rifle now shot 5/8" 3 shot groups.

We never measured the run out on the 'before' ammo but it was likely close to .012-.015 out of the box. The 'after' ammo was .0015-.002 as measured on my home crafted concentricity gauge.

The department wisely decided to rebarrel all three guns anyway. The excessive run out FGMM ammo was returned (I think there was about 4,000 rounds remaining of that lot number) and the rebarreled rifles (with a chamber designed to better fit the dimensions of the FGMM ammo) all were capable of 1/2" FIVE shot groups with the replacement lot of FGMM ammo that had T.I.R. about .003.

M.D.'s comment about rolling ammo is spot on. If you can see the bullet tip move when you roll it across a flat surface, it's > .005.

Just a note about concentricity checkers for those considering purchasing one. I made several designs before settling on the one I have now. Anything with a base 'stop' (a pin, etc) can transfer base condition issues that may show up on the dial indicator as stuff that isn't really there. A lot of that depends on the internals of the dial indicator, as well.

My 2 cents this morning over a second cup of Sulawesi.

Good shootin' -Al

Yes, maybe on the base stop but what is FAR worse is a gauge like the Hornady concentricity gauge that holds the case face in a cone on one end and the bullet tip at the other. It showed ammo to be straight and when the same ammo was rolled in the Sinclair gauge, it showed to be considerably off AND also was noticeably visible. Any irregularity on the case face can show up on the dial indicator.
The Hornady gauge is better than nothing but it is not nearly as good as the Sinclair IMO.

Noted, SoTex. I’m always interested in upgrading equipment. 🙂

I never paid attention to case necks or cartridge runout. But after my short time of being a 24hour addict and reading how crooked ammo can effect accuracy I decided 6 weeks ago to buy a Redding Slant. Boy did I get an awakening.
I Always thought that all ammo was straight. I’ve since bought Forester sizing and seater dies for four of my bottle necked rifle calibers. And all so made my own cartridge straightener out of a piece of angled aluminum.
I haven’t had a chance to get any shooting done because of the weather, but let’s just say I’m ready to go.
Any of my loaded rounds that were way out of wack I pulled and reloaded using the Forester dies. It worked some of the times and some times it didn’t. I’m thinking it’s the brass. A lot of the brass I’m using is Winchester and Hornady. And a lot of it is new unfired. I want to get at least one firing on them before I make any final decisions. But I have enough brass that I can find the good ones to use.
From what I’ve read and if I had to do it over again I would have went with Lapua brass and the Forester dies from the beginning.
Now with all that said I’m by no means a sniper, long range hunter or shooter. But I want straight ammo.
My old dies (RCBS & Hornady) would have been good enough for what I do, but it’s a mental thing for me.
I figure I already had rifles that would out shoot me. So now I’ll have the ammo too.

Heavyload,

I used to use a bunch of "standard" factory brass from Remington and Winchester when I first got into the entire straight-ammo/accuracy thing about 30 years ago. The first thing I'd do, however, was run the necks of new cases over an expander ball, then measure neck thickness with the Casemaster gauge RCBS sent me for a a review, sorting out any cases with necks that varied more than .001 in thickness.

At the time I only rejected about 10-15%, which was a lot cheaper than buying more expensive brass. Federal was also offering their Gold Medal brass then, and it had an even lower rejection rate. But about a decade later Federal quit offering Gold Medal cases, and I noticed the rejection rate of Remington and Winchester bulk brass had gone up considerably, often 80-90%.

There have been exceptions since then, such as the bag of 100 Winchester .222 Remington cases purchased at a local store a few years ago, which were excellent. In the past few years I've also found that Hornady brass has generally improved a LOT, so use a lot more. Have also had great But am also not hesitant to buy Lapua or Peterson or other brands of high-quality brass, especially for a big game rifle where 50-100 will last a lifetime. Such consistent brass makes an immediate difference, especially dies like Forster Benchrest.

Heavy,

I'll revisit a point Al mentioned in an earlier post, namely that sizing dies may well size down the case necks more than necessary. Aside from cold working the metal, this dimensional issue can cause runout even if everything about the die is straight and the brass is uniform.

The Forster sizing dies have the rubber washer already so that’s a plus. I don’t think I’m going to be having my dies custom machined though.
I do have a question, let’s say the cartridge has .005/.006 runout (more then likely from bad brass) and you use the cartridge straightener and get it down to .002. Will that cartridge be just as good as a cartridge that has .002 runout from the beginning without straightening? And will that case always need straightened out?
And if a case neck varies more then .001 let’s say .002 or .003 will the runout of a loaded cartridge probably be double that? .004/.006 even with decent dies.

BTB, I didn’t mean to slam you or your Hornady gauge, but was just trying to point my experiences with it. On my Hornady concentricity gauge, I can move the spring loaded end that holds the bullet tip by .004” (rolling a loaded case in it) and that is just with my finger tip.
I have learned things the hard way myself. That is how I ended up with the Sinclair gauge. (Laugh)

Excellent thread! Exceeding all of my expectations. Thank you all for asking and answering such great questions. Indeed I’m
learning a ton.