Loaded Round Runout
BY Herschel Smith
1 year, 9 months ago
This video is interesting for reloaders (and for me too even though I don’t reload). I suppose an interesting question might be how much deviation from exact concentricity is there in factory ammunition between ordinary bulk supply milstandard cartridges and more expensive hunting rounds? The immediate question, however, is how much deviation should you aim for if you’re a reloader?
Here is an article in Rifle Shooter Magazine that also bears on the subject.
On February 18, 2023 at 1:45 am, Georgiaboy61 said:
Cartridge run-out matters – or can matter – in certain shooting disciplines where an extreme level of accuracy and precision is sought after and to be desired, such as F-Class bench-rest shooting at long range.
In brief, having the projectile precisely centered in the bore with minimal run-out means that the bullet will be presented to the rifling centered and in the proper orientation for its most consistent flight. Namely, with the longitudinal bullet axis parallel to and in line with the barrel. Assuming that the projectile is consistently formed around its axis, then the proper presentation helps assure that the bullet leaves the barrel in the same orientation each and every shot, or that is the goal at any rate.
If, on the other hand, the bullet engages the rifling off-centered, then it will travel down the barrel so oriented and once it leaves the barrel it will be rotating around that axis – at least for a time – during its flight, throwing off its accuracy and precision relative to other shots. At longer ranges, enough to cause unwanted dispersion on the target downrange.
Bullet run-out matters in factory rifles, but not to the extent that it does in custom rifles designed with tight chambers, throats and hand-lapped bores for competition use with a specific factory cartridge or hand-load. In an off-the-shelf rifle, there are so many other variables other than run-out influencing the shot that correcting for it may not make much of a difference.
The same sort of debate surrounds whether to turn case necks for precision purposes. Opinions vary for and against, but the bottom line is that if you turn necks and test those loads against the same ones with un-turned case necks, can you shoot the difference? If a competition shooter who is an expert can’t tell the difference, Billy Bob the deer hunter with his Remington 700 probably won’t be able to tell the difference, either.
As one of my mentors -a retired military officer, ballistics expert and master reloader – put it, go ahead and correct for concentrically and run-out, or turn case necks for that matter, if it makes you feel better and more confident behind your rifle and it helps you make better shots. That’s a valid reason to do it, too.
On February 18, 2023 at 12:34 pm, Grunt said:
Thanks Georgia Boy, with your explanation I won’t go out and buy ANOTHER reloading gadget.
On February 18, 2023 at 3:22 pm, =TW= said:
The pursuit of accuracy is largely the elimination of variables in order to increase repeatability. Some platforms, Ruger Minis for instance, will require more attention than, say, bolt action or single shot rifles.
Perhaps the first item to address is to determine which ammunition the weapon prefers.
Bedding, blueprinting, custom barrel etc can follow as needed. Don’t overlook the trigger.
I imagine the law of diminishing returns will apply- the least expensive upgrades might produce the largest gains.
On February 18, 2023 at 3:42 pm, =TW= said:
Pay attention to muzzle crown- it should be square to the bore, undamaged and free of defects. Muzzle devices may adversely affect accuracy.
These are the last things the bullet encounters on its way downrange.
On February 18, 2023 at 9:35 pm, Elmo said:
That was a super interesting video. Thank you. His results, to me anyway, are really surprising yet in a way back up my experience.
I don’t shoot at 1000 yards (I wish I did). My longest range is 538 yards. I don’t get carried away with anything in loading my rounds, I’m just meticulous about my powder weights and use Fed Match primers in fired Fed cases that haven’t been weight sorted and just prepped in the usual manner. No neck turning and nothing fancy in preparation. My rifle is a Savage action with a Shilen barrel, which I think takes most of the credit for my great groups. When I get a chance to shoot at that distance with my low-zootey rounds I usually expect groups of less than 3″. My best one to date is an inch and three quarters.
Short story long is that if you’re shooting for fun at long distance don’t sweat the small stuff. Do the best you can with what you’ve got, get out there and shoot and most importantly, have fun. And you’ll probably still be able to put the hurt on a coyote (or scare the crap out of a two-legged varmint) at 400 yards with ease.
On February 18, 2023 at 10:05 pm, James said:
i’ve only handloaded ~40k rounds for 3gun/multigun and load on a cheap ass turret press; the runout on concentricity can’t be great. never had issues with hitting furthest 550yrd targets on a timer. quality barrel and projectiles make the difference.
On February 19, 2023 at 1:47 am, Georgiaboy61 said:
@ Grunt
Re: “Thanks Georgia Boy, with your explanation I won’t go out and buy ANOTHER reloading gadget.”
Hey, don’t let me rain on the parade! If you want a new gadget, then go for it. Especially if you are good-enough to shoot the difference….
On February 19, 2023 at 9:07 pm, =TW= said:
My $0.02 after watching the video-
It would be difficult to reload a bullet with .035″ runout. (Video guy had to massage them to achieve this.)
It would be nearly impossible to get more than a few thousandths runout on a short, fat bullet in a straight wall case.
The long, skinny cartridge might not feed properly.
But if it did, the chamber throat and leade would correct the runout- at least to some extent. (Video guy mentioned this.)
Compromised neck tension on the massaged cartridges may have contributed to larger groups. (I assume he used identical powder charges.)
Maybe better to have fired 5-shot groups of each lot, and presented results in a less busy manner. (A minor quibble.)