Runout Test/Hornady Concentricity Test

[jwrowland77]

Went to the range yesterday to shoot some workups. While at the range, I decided to shoot a runout test.

One group had rounds with runout >.005" (most were around .007"). The other group all had runout of .001" (corrected to .001" with the Hornady Concentricity gauge), with one being .0015". All rounds were shot round robin. Shot runout round (>.005"), then a minimal runout round (.001") then so on and so on.

All rounds were the same as far as powder, case, primer, bullet and ogive measurements. All rounds were shot off of a Caldwell lead sled. I had planned to shoot them 200yd, but since I was shooting workups as well, and had a crosswind, I decided to bring it in to 100yd.

All rounds were just picked up and put in the chamber in no particular way like your avg person might (I know some folks mark the runout and put the runout rounds in the chamber the same way).

As you can see, the rounds with runout landed in no form of a group/pattern. The rounds where runout was reduced using the Hornady tool, were all in a horizontal line (I like this much better than all over the place.). It was fairly windy out with a crosswind w/gusts.

Conclusion: the Hornady Concentricity gauge works, and it DOES help to reduce runout in match ammo, and that when you reduce runout, it does help in accuracy. I believe had this been shot at 200 yards, then the runout group of greater than .005", the pattern would have been worse than what it was at 100yd.

I just figured I'd put this out there so folks can draw their own conclusions. As for me, I'll be checking and correcting any runout I see on my match rounds.

Rounds:



Test Results:



The measurements on the calipers is with the .308 deducted from it already. Shooting .308 Win. 178gr Hornady BTHP Match.

 

[Walkalong]

I loaded some .223 ammo the other day (After some testing with various powders) with some poly tip and hollow point bullets looking for some decent accuracy (Better than FMJ plinking loads) using matching brass vs range brass. I tested two different seaters. My old Forster "benchrest" seater gave half the runout than my standard Redding seater. .0005 to .003, with most being <.002, vs .001 to .006, with most .003 or less.

Which seater(s) do you have? Are the cases straight after sizing?

 

[jwrowland77]

I'm using Hornady seater. Most all my rounds end up .004" down to .0005". I've been correcting everything that needs it down to a max of .001" though. When I take my time like I used to, runout is normally in the .001"-.002" range.

 

[Walkalong]

If your brass is straight after sizing, you need a better seater. If it is straight until you size it, you need a better sizer, etc, etc.

 

[quartermaster]

Agree with Walalong. I usually check my neck runout B4 loading and find that neck runout leads to bullet runout.

I found that turning necks have helped a bit. I know people think it is a waste of time, but it works for me, using bushing dies. New brass is what it is, but with once fired, I can usually keep my bullet runout at around .002 or less. .004 or more does happen occasionally. Those few are marked as foul shots.

Carefull case prep is the key IMO. QM

 

[jwrowland77]

Well the above rounds that had runout, I induced the runout. They had started at around .002"-.003" runout. I was mainly testing the effects of runout vs no runout in accuracy.

 

[Sni-per]

Sorry for asking, as I am new to reloading, but what is runout???

 

[jwrowland77]

The less the runout, the more concentric the bullet is compared to the case. You want as little as possible that way the bullet is dang near lined up in the center of the barrel when you chamber a round.

The more off line the bullet is, the less accurate. Those fliers in a group, more runout.

 

[Walkalong]

In a perfect world you would want your round to be perfectly straight, but they are hardly ever perfect. The straighter the better though.

 

[Sni-per]

That is what I envisioned runout being, but had to ask. Is runout something that you can 'fine-tune' in your dies?

 

[jwrowland77]

You can get dies to help reduce runout, like bushing dies, or Lee Collet neck dies. I use the Lee Collet neck dies.

In this test I posted, I used the Hornady Concentricity Gauge tool to help reduce or induce runout for the test.

 

[Walkalong]

Is runout something that you can 'fine-tune' in your dies?

Not really, if a die makes crooked ammo, buy a different one. There are tricks to setting up dies to help them be lined up with the shell holder or plate well, but if this produces crooked rounds, you need a better die. Better isn't always more expensive, but it's a good place to start.

 

[Thundercat]

Not really, if a die makes crooked ammo, buy a different one. There are tricks to setting up dies to help them be lined up with the shell holder or plate well, but if this produces crooked rounds, you need a better die. Better isn't always more expensive, but it's a good place to start.

Walkalong, will a bad die induce runout during sizing or seating? Or can a subpar die induce runout on both steps? Which step usually induces the runout? Or do you just check the concentricity after both steps?

 

[jwrowland77]

I know this was addressed to Walkalong, but from what I've read and researched is the use of an expander ball on the resizing die, can/will pull the neck offline causing it to be pulled out of concentricity.

Seating a bullet can also cause runout as well if the bullet is not exactly straight when seating. Of course, is this caused because the neck is already out of line.

Did the chicken or the egg come first?

 

[MrBorland]

As you can see, the rounds with runout landed in no form of a group/pattern. The rounds where runout was reduced using the Hornady tool, were all in a horizontal line

Thanks for doing this - there's nothing like a little actual data.

OTOH, I'll play Devil's advocate and point out that the pattern from the runout group appears to have more vertical spread because of a single round. Take that round out, and the 2 groups are very similar.

Perhaps that round is real and will appear in every 5-shot group. Perhaps not. One can't say anything definitive from such a small data group.

 

[jwrowland77]

I thought the group that had less runout showed a horizontal pattern, which I would much rather have. Horizontal patterns could much easier be fixed or reduced. Vertical patterns normally show a velocity difference, and then throw runout in the mix, and it looks like a shotgun pattern, just much smaller.

If these two groups were shot at 200, 300 yards or further (F-Class match at 600yd), the difference would really show between the two groups.

 

[MrBorland]

I thought the group that had less runout showed a horizontal pattern, which I would much rather have. Horizontal patterns could much easier be fixed or reduced. Vertical patterns normally show a velocity difference, and then throw runout in the mix, and it looks like a shotgun pattern, just much smaller.

I understand, but from your data one can't definitively conclude that low-runout groups will have less vertical spread than high-runout groups. It all hinges on a single round that might (or might not) have been a flier. You simply need more groups to say.

If you shot these groups at 200 yards, yes, the difference would be bigger, but the story would be the same - any conclusion would hinge on a (possibly fluke, possibly real) single round.

I'm all for data and experiments, but to say anything definitive between runout and accuracy, you'd need to shoot more groups.

 

[Walkalong]

Having shot a great many "aggregates" in Benchrest, I would have to agree that one or two groups might point you in the right direction, and might not. Either way, one or two groups is not definitive.

That said, I see it all the time here. Something like: I shot one group each with 4.0, 4.2, and 4.4 Grs of X powder. 4.2 shot the best. It means nothing, unless it repeats its self over and over.

I could easily shoot a .9 something as easily as a .2 something with the same gun and load back to back, all while trying to shoot the best I could. Aggregates, or multiple groups will tell the tale.

Vertical dispersion can be the shooter, just as horizontal can, although if I see continued groups with excellent vertical dispersion and bad horizontal, I would feel better about that than the other. Hmm, must be missing something in the wind. If I can fix that, my groups will tighten up. But then again, the shooter can cause side to side misses as well.

Shooting tiny groups is tough, and can be very frustrating at times. Trying to put all 25 shots where you want them in an aggregate without losing a single one can positively drive you out of your mind.

 

[jwrowland77]

Definitely learning that last part. Lol. I've gotten lucky the last couple of range trips, but I figure, if I can learn at least one thing every trip, then it was a trip well taken.

Plus all the testing and experimenting has made me a better shooter over time. Especially since I started shooting F-Class, it definitely makes me pay attention to what I'm doing when behind the trigger.

 

[MrBorland]

Getting a definitive answer to even a seemingly simple question takes a surprising amount of work, which is one reason science goes as slow as it does, and why objective and reliable reloading info is often tough to find.

Using this case as an example, to get data one could start drawing conclusions from, I'd think you'd need at least ten 5-shot groups from each of the high- and low-runout groups. And since your low-runout group introduces two variables - low runout, and correction by the Hornady jig - a 3rd group in which runout was low right from the press (i.e. wasn't corrected) needs to be included.

To get the best data, consistency of your ammo should be optimized, so prepped cases and bullets sorted, powder trickled, etc. And all the ammo loaded on the same day, then all shot on the same day.

As you can see, that's at least 150 match-grade rounds loaded on the same day, and 150 of your best shots taken on the same day. That's not an easy thing to pull off, and most of us would find the question easier to ignore than going through all that, especially if we've got a pet load or pet procedures we're already fond of.

 

[jwrowland77]

True very true. Don't forget the monetary expensive of buying and going through precise components.

 

[jwrowland77]

I may have to test it anyway. Lol. I'll hopefully soon have time on my hands with not much else to do.

 

[murf]

jw,

you didn't mention how you select your cases. same headstamp? all fired the same amount of times?

suggest you measure case neck thickness and only use those with a variance of .001" or less. there is an old Handloader article that tests case neck thickness variance. the conclusion was that a .002" variance affected accuracy significantly.

you can measure the variance using calipers. the actual thickness won't be accurate, but the variance will be.

i think it is important to remove this variable from your test. it is common to find quite a few cases with neck thickness variance greater than two thousandths.

great test and write up, by the way.

murf

 

[jwrowland77]

Murf,

All cases came from the same lot that I use for my match ammo (same headstamp)

All cases fired the same number of times with same everything. All had same case capacity within .3gr of each other.

All necks were turned to .0125".

All bullets same weight and length from base to ogive.

I attempted to take out as many variables as possible, much like I would for my match ammo.

Thanks murf, I've never really written up a report in findings. It was rather fun. I'll be testing more on this, as soon as time allows, which will hopefully be soon.

 

[murf]

jw,

glad to hear you "match prepped" your cases. that needed to be said for others that want to duplicate your test.

murf