Home Forums Hunting & Shooting Ask The Gunwriters Run-Out: what is allowable given different circumstances?

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.