acceptable case/ loaded round run out?

BATattack · Post by **BATattack** » Thu Aug 30, 2012 10:32 am

for the people that measure case and loaded round run out what tolerance have you found will actually start to degrade accuracy?

do you set up your run out gauge supporting the case under the web and at the shoulder and then take a reading at the bullet tip and/ or at the neck?

for people forming wildcat cases do you find that initial run out is minimised after initial firing? opinions seem to vary from what I've seen!!

Post by **AlanF** » Sun Sep 02, 2012 10:28 am

Hmmm - not many replies :-k

.

Here's my current thoughts. I have a very crude runout indicator. It has a good quality (metric) dial gauge, but the rest of it is just bolted wood and plastic. It cradles the cases at each end of the main body and runout can be measured on the neck to most of the way out the projectile. I only use it as an occasional check, and am really only looking for anything worse than about 0.05 mm (0.002") in bullet runout. Opinions vary on what is acceptable - I read once where a BR expert did some extensive testing and concluded that accuracy is not affected until runout gets to about 0.007"!

I notice a definite improvement in neck runout after the first firing of Lapua 6.5-284 brass, both in its 6.5 form and when expanded/fire-formed to 7 Shehane. This usually improves further on the second firing.

I've also noticed that FL sizing can substantially worsen neck runout. So you need to look at this carefully when deciding on a sizing strategy (many reloaders FL size every time). You may find that your particular press/die/case combination are good in this respect, but I had a situation once where FL sizing was causing about 0.003" runout every time.

Hope this helps.

Alan

aaronraad · Post by **aaronraad** » Sun Sep 02, 2012 11:59 am

BATattack you might have to consider chamber dimensions with the run-out tolerances on loaded ammunition. Particlarly freebore and neck section dimensions. Essentially the tighter the chamber dimensions the tighter you will have to hold the run-out. Have a read of the Clymer Tools Wildcat/Specials webpage:

http://www.clymertool.com/wildcat/index.html

Remeber too that wildcats are sometimes set-up with a crush fit on the shoulder datum point to ensure good support under fireforming. After reading the article you can start to understand why a gunsmith might request details and samples of the brass you intend to use.

Just out off interest have you compared an unchambered parent loaded round to a chambered but unfired parent loaded round to a first reload fireformed loaded round?

AlanF wrote:I've also noticed that FL sizing can substantially worsen neck runout. So you need to look at this carefully when deciding on a sizing strategy (many reloaders FL size every time). You may find that your particular press/die/case combination are good in this respect, but I had a situation once where FL sizing was causing about 0.003" runout every time.

From what I've read the serious reloaders get the gunsmith chamberring the barrel to use the roughing reamer to cut the FL die or body die; and the finishing reamer to do the bullet seating die. I assume this minimises reloading issues with extremely tight chamber dimensions?

Post by **AlanF** » Sun Sep 02, 2012 2:10 pm

aaronraad wrote:
AlanF wrote:I've also noticed that FL sizing can substantially worsen neck runout. So you need to look at this carefully when deciding on a sizing strategy (many reloaders FL size every time). You may find that your particular press/die/case combination are good in this respect, but I had a situation once where FL sizing was causing about 0.003" runout every time.

From what I've read the serious reloaders get the gunsmith chamberring the barrel to use the roughing reamer to cut the FL die or body die; and the finishing reamer to do the bullet seating die. I assume this minimises reloading issues with extremely tight chamber dimensions?

I have had a FL/Finishing reamer set, but still got some runout caused by the FL sizing process. It could have been something to do with uneven brass thickness on the shoulder "oozing" out onto the neck - not sure.

Alan

aaronraad · Post by **aaronraad** » Sun Sep 02, 2012 4:17 pm

I understand that the majority of BR shooters use a body die for neck turned cases to avoid over working by using a FL sizing die.

You might have to join the forum link below to see the discussion.
http://www.longrangehunting.com/forums/f28/body-die-full-length-die-shoulder-bump-14182/
Quite a good forum as far as long range shooting goes.

Same old story, no hard and fast rules just whatever works. How much the body die/FL die has to do with concentricity/run-out, I'm not sure? AlanF seems to have identified an issue with his FL die. Makes sense though if the first stage goes wrong its always harder to make-up the error with the next process.

bruce moulds · Post by **bruce moulds** » Sun Sep 02, 2012 5:14 pm

bat,
what alan says has also been my experience.
i have had up to 0.008 runout measured on an rcbs device with new 6.5/284 lapua brass, the case supported at the shoulder and the web, and the dial indicator reading the front end of the bearing surface of the bullet.
once fired, these cases went to 0.0015 to 0.000 reading.
firing lots of these cases against each other, i could tell no difference in vert from 300 to 800 metres.
i have come to the conclusion that worrying about runout up to 0.008 is a load of crock.
even so, it feels better to have minimal runout. it can't hurt!
full length sizing in a min fls bushing die, and bumping each sizing never gives over 0.0015 runout, and allows absolute firearm/ammunition reliability.
set your calipre on 0.0015 and see how much it is!
how much does jamming bullets into the throat counteract runout?
does a little jump allow bullet runout to be overcome as the bullet starts to move?
i think a lot of people read about runout and jump to conclusions before doing tests, forming opinions cast in concrete that might or might not be factual.
one group will neither prove nor disprove theories on this.
a lot of comparitive testing is required.
i have seen some pretty fancy shooting done fireforming new brass, by people who knew it was impossible before they did it. then they still don't believe it, even after they have repeated it several times.
even neck annealing assists in minimizing runout.
it is not a bad idea to run 0.004 chamber neck clearance on neckturned cases for our job. out in the elements and sometimes not being able to clean, 0.004 allows both a safety and a reliability buffer. this is 0.002 per side, which is very little, and will not cause cases to age prematurely.
if you are pulling bent cases out of your chamber, two of the causes can be: banana brass, which correct partial annealing might help, or a crooked chamber, which will need to bu cut off in entirety, before the new gunsmith rechambers.
trying to solve runout problems when seating is a waste of time. you need to get sizing right, then seating will virtually take care of itself.
i could be wrong on this, but i believe straightening loaded ammo is self defeating. this is because forcing a bullet straight in the neck can alter neck tension, another thing that requires consistency for good vert.
keep safe,
bruce moulds.

Barry Davies · Post by **Barry Davies** » Sun Sep 02, 2012 7:17 pm

Correct on every count Bruce. People worry too much about the little things in life and not enough about those aspects of reloading that really matter.

bruce moulds · Post by **bruce moulds** » Sun Sep 02, 2012 9:46 pm

forgot to include in previous post.
the biggest thing to do to minimise runout is setting dies up properly.
the coarseness of threads can allow things to be locked down out of alignment.
get this right and it costs no money for a big gain.
keep safe,
bruce.

KHGS · Post by **KHGS** » Mon Sep 03, 2012 12:13 am

Very well said Bruce, you have covered the things that matter very well, there is little to add. I agree that die setup is all important & as in all these matters, use good tools & set them up correctly.
Keith H.

DannyS · Post by **DannyS** » Mon Sep 03, 2012 8:10 am

Bruce, the Lee collet dies use a rubber O ring between the die and the press to help alleviate this issue of coarse threads and subsequent run out. I have noticed in the past that mention has been made on the 6br website of also using a O ring on other brands of dies.

Cheers
Danny

aaronraad · Post by **aaronraad** » Mon Sep 03, 2012 10:07 am

DannyS wrote:alleviate this issue of coarse threads and subsequent run out.

When were talk about 'course' threads here, I take we are talkinng about the UNF 7/8"-14 tpi engaging in the press head? :?:

I have noticed the 7/8"-14 threads sometimes misaligned when only a few threads are engaged, but never when fully threaded through a press head and a locking ring engaged.

My reloading press is a Hornday L'N'L with the quick twist adapter and o-ring providing back pressure, so I've never noticed any misalignment. I have noticed the misalignment in my swaging presses though when pushing the limits of their length capacity.

The post from bruce molds is a keeper, I'm printing that one off.

BATattack · Post by **BATattack** » Mon Sep 03, 2012 2:34 pm

thanks for all the replys everyone!

bruces post is very interesting and i apreciate the time it would have taken to share with everyone

we spend hours and hours weighing powder to within impossible limits . . . . . ensuring neck tensions is EXACTLY the same for every shot. . . . . . BUT something that is seated into one of the most precice parts of the shooting system, the neck and throat, and it doesnt matter if we have .008" runout!! its pritty crazy to think what else we could be over doing!

my reloading is very basic compared to the lengths a lot of people go to to achieve the ultimate accuracy. so far the accuracy has been beta that i can shoot so it hasnt bothered me too much.

the reson i started the thread was because i have a sneaking suspicion that im getting a large amout of run out on some new cases that ive run through the F/L die. to the point where i could actually see it when i was prepping cases . im waiting on a concentricity guage to test a few cases and see how good my "micrometer eye" actually is! :lol:

i managed to get out to the range on the week end (early in fact) to pull targets for another guy testing different impact points with when using his new magnito chronograph at 800yds. i set up my 7 saum at the same time and told him to give it a try while i was still pulling targets. considering he shoots a .223 i thought this could be interesting! so he shot it like a normal match 2 and 10. with the suspect ammo his score was 60.7 at 800yds with x ring elivation. later in the day i shot a 57.2 in a finiky fishtail and after the wind made up its mind what side it wanted to come from i finished the day with another 60.7.

so all in all i think your spot on the money bruce and once i get the concentricity guage ill be able to tell you exactly how much run out DOESNT matter! :lol:

bruce moulds · Post by **bruce moulds** » Mon Sep 03, 2012 4:58 pm

bat,
i think we buy concentricity gauges a bit like we buy borescopes.
that is we buy them to get in a position where we don't need them.
don't take my ideas as gospel.
they are only opinions, and should be treated as such.
a thing i have battled with for many years is vert caused by too much or too little cleaning. it seems that every barrel is a law unto itself in this area.
possibly the discovery of a magic way of running in might help here.
ultimately, if you can get all your shots to have less vert than the x ring, all you have to do is read the wind.
good luck,
bruce.

ecomeat · Post by **ecomeat** » Mon Sep 03, 2012 7:15 pm

I have just been buggering around in my reloading room, prepping a couple of hundred brand new 6.5 x 47 Lap cases , as well as 200 brand new 284 Win cases (Lapua 6.5 x 284 cases, expanded up to .284) hoping to be ready with both for Sydney Queens.

Using a Sinclair Concentricity guage i noted
1) Fresh out of the blue box, the 6.5 x47 lap cases had 0.0005 to 0.001 runout, which I presume should be regarded as pretty bloody good for new cases, even for Lapua.
2) Lubing them, then through a Forster FLS die, in a Forster Co-ax press and the runout blew out to 0.004/005. I was gob smacked......thought it was meant to work thye other way !
3)Replaced the Forster Die with a Redding Type S Bushing FLS die (with a 289 TN bushing......runout back to 0.001 to 0.0015

As I came in just minutes ago, I removed the decapping pin and and expander button and ran another couple of cases thru the Forster Co-Ax press. Runout out of the box was 0.0005 to 0.001 as per all the others.
Through the Forster FLS die,.................runout a neat 0.002 on both cases ?
Have I got lucky and scored a faulty Forster FLS die ? How does one define a "faulty FLS die" ?? It is second hand ......came with the rifle....and perhaps two or three years old.
I did try the Forster die in my RCBS Rockchucker press on just two cases, and with the decapper/expanding button in place, runout was same as the Forster press (ie 0.004/005)
Die is set to 1/16th of a turn off the shell holder, and has a very, very minimal effect on the new brass.

The 6.5 x 284 Lapua brass expanded up to .284 with a K&M expander, then neck turned to 0.013 avg, then run through a Custom made minimal bump FLS die made by Phil Jones of RPE who just chambered my first 7mm barrel, has a runout average of 0.0015 to 0.002 so presumably it will be just fine after fireforming.

What defines a Die as being faulty ??
Tony Berry

Post by **AlanF** » Mon Sep 03, 2012 8:02 pm

Tony.

As I mentioned earlier, I have seen the FL sizing process actually cause runout. In fact ALL of the 4 FL dies I have for the 6.5/284 or 284 Shehane, introduce some degree of neck runout to a fired case with negligible runout. I think the causes are various, with one of the main culprits being the shoulder bump, not the body squeeze. When you bump the shoulder, the excess length actually gets extruded out the neck - hence the need to length trim after FL sizing. Its a big ask to expect this extrusion to act evenly right around the base of the neck - I think its this unevenness that can cause the neck to tilt. And while I believe neck bushings limit the extent of the tilt, I don't think they prevent it fully.

What may be of more interest is that there is a workaround which can drastically reduce this FL die caused runout : do the FL size 3 times, rotating the case in the shellholder one third of a turn between each size. Don't do half or quarter turns - they aren't as good - do thirds! It won't eliminate the runout but it will noticeably reduce it.

Hope this helps.

Alan