Bullet run out how much matters?

[cw308]

That's a big difference at 100 yards from .003 to just about perfect . One of my best groups were when I didn't even know what runout was and Im sure it wasn't .0005 dead center on the bull one hole . How was your rifle set up for the test . Was that the only difference , runout .

 

[Idaho-Lefty]

Well Guys,..I did NOT mean, to start an "online Battle" over this, subject as, I do NOT have, a $7,000 "Target" Rifle !
I have an old, T3 Tikka .243 Win., in SS lite, that is, pretty accurate, already. I do see "both sides" between, Uncle Ed and Dusty S. and BOTH are probably, RIGHT,.. for me and my informal,.. Target, Coyote, Deer Huntin' type of, shootin'! Thanks Guys ! This subject, does get pretty DEEP if, you HAVE a serious,.. Target Rifle as others, have explained !
But, .002 Max. TIR, "gets it done" for ME and for MOST of, the "informal Target" shooters & Hunters! I DO want, as close, to "Perfection" as my, Sub $1,200 Rifles with, 4.4-14X Scopes, can produce, tho ! I will start, by "TOSSING' the Expander Ball and using my existing RCBS Die as, it "Mirrors" my Chamber, really well. Every load (even the "Bad", ones !) shoot, Sub MOA but as, I am a bit spoiled NOW and HAVE shot, several Sub 1/2 MOA groups with, the Tikka .243 ! I think that, this is, what, I "need", NOW,.. LOL ! IF, I cannot get, the .002 or less, TIR out of MY current Dies, repeatably,.. I might "spring" for the Forster FL Die/ Match Seater set for, $82.00 or so, as they ARE, highly Rated, Dies, UNLESS, you have, a $4,000 - $7,000+ Target Rifle !
THANKS AGAIN, Guys as, I learned a bit more from, this "Thread" and hope others have, too !

 

[Idaho-Lefty]

I also, want to THANK, K-22,.. as his recommendation of, 42 grains of IMR 4350 with, the 80 gr Sierra Blitz, #1515, "shoots" AWESOME in My Tikka !
I found great groups from, 42.1 to 42.7 grains of this, "Pixie Dust",.. easily, SUB, 1/2 MOA at, 100 ! Thanks, K-22 !

 

[oley55]

YUP and I'm piszzed oft about it, BUT am getting, .280 ( 3 shots ) to sub, 1/2 MOA ( 5 shots ) groups from my Tikka T3 .243 win. loaded with, the 80 grain, Sierra #1515 Blitz's @ 100. I believe the problem lies with the Expanding Ball pulling thru the "Neck" after FL sizing, I lube the necks lightly and have polished the Exp Ball. I have also, polished/ lapped, the Seat Plug to "fit" my Bullets, so I don't think it's a Bullet seating issue. NOT all the loads are that, "BAD" but more than, I'd like !!

Idaho, any chance at some time in the past, you broke the depriming pin? If so, there is a good chance the expanding ball stem was bent at the point where the ball screws onto the stem. So now the ball is cocked and inducing runout. Not an expert here, but been there and done that. So just a thought.

A real good way to see if the problem is the expander ball is to size a couple cases with the ball/stem removed. With expander removed, my RCBS FL dies easily produces cases with less than .002" runout. That's not to say I don't find some with more, but those seem to be from necks that are excessively thin on one side. So I set them aside thinking I may eventually want to turn my necks further down and they may become usable. I also quarter turn the brass and always resize, but not with the expander ball.

 

[mrjdasr]

Would a FL Redding Sizer Die, do the "trick" for descent, Neck "runout" as, thier expander ball sits in a different position than, all the rest of,. the die manufacturers? Anyone using the Redding FL Die the one,.. w/o the Bushings?

redding full length bushing dies are a little pricey
forster makes a very good full length non bushing die and they will hone the neck diameter to your specs so you don't need the neck expander I have one for a 6.5x47lapua, I works mighty fine
Whidden dies are also very good

 

[Idaho-Lefty]

Idaho, any chance at some time in the past, you broke the depriming pin? If so, there is a good chance the expanding ball stem was bent at the point where the ball screws onto the stem. So now the ball is cocked and inducing runout. Not an expert here, but been there and done that. So just a thought.

A real good way to see if the problem is the expander ball is to size a couple cases with the ball/stem removed. With expander removed, my RCBS FL dies easily produces cases with less than .002" runout. That's not to say I don't find some with more, but those seem to be from necks that are excessively thin on one side. So I set them aside thinking I may eventually want to turn my necks further down and they may become usable. I also quarter turn the brass and always resize, but not with the expander ball.

Yes, i was real careful setting, the expander / spindle straight when starting, to load. THEN, i later removed it, that's when, the ugly "run-out" appeared as I did NOT realign expander, carefully. No, I didn't break/ bend, the pin. I took the Exp Ball, OUT of the sizer and now have, less than, .002 TIR "run-out" with, about .005/ .006 Neck Tension. I will try these New loads, as soon as the WIND dies down, a bit! Cold and Windy here !!

 

[Damon555]

.....this isn't to prove anything one way or another but I have experienced some odd things when it comes to bullet run out. Mainly while shooting AR15 and the like.

There have been several occasions when a round becomes jammed while being chambered in one of my AR15's. It'll chew the bullet up good but it's still ok to fire......I'll fire my next group and include that buggered up round in the group just to see what'll happen. Of the handful of times that I've had that happen the buggered up round has shot well within the group....(whether the group was good or not)....if I shot a 3/4" group the buggered up bullet never spoiled the group....Common sense would tell me that the darn bullet with .05" (ha) of run out would be well off the mark......Doesn't make any sense to my simple mind.

 

[Bart B.]

With due respect to all owners of cartridge runout measuring tools, I'm convinced a given cartridge will have different numbers across all makes, models and their set ups.

Therefore, a.001" reading on tool/setup A can show .003" reading on tool/setup B. It might read zero on a third.

 

[One Shot One Thrill]

I used to be obsessed with runout. I used to measure it on every round I loaded.

View attachment 1080493

Then one day I decided to build a 260AI, you can read my experience with fire forming and runout issues in this old post: http://forum.accurateshooter.com/threads/my-new-260-ai-build.3909184/


The bottom line is that I consider low runout a byproduct of good brass prep and reloading process. Runout is not a goal. However many people inadvertently cause rounout by manipulating their brass necks by trimming or chamfering after resizing the brass. Once the brass is resized you want to protect your necks.

Some of us know that, of the 3 components of the Holy Trinity of precision ammo are 1. Powder, 2. Seating depth and 3. Neck tension. Runout is not mentioned there.

Regards,

Joe

P.S. The best place for an expander ball is in the box that it came in, just in case you decide to sell the die somewhere down the road.

Very Well said!!

 

[Bart B.]

Too many guys using imprecise/cheap tools.

And none use the case shoulder mid point as the front rest like it is in the chamber when fired. I'm amazed that nobody makes runout thing-of-a-bobs that does that. Maybe they're ignorant of what really happens.

Regarding bullet ogive uniformity, people who have used 50X optical comparitors comparing shapes across a production lot see excellent uniformity. Except one lot of Lapua 30 caliber 185 grain FMJRB Match bullets that had 4 different ogive shapes. Proof they came from 4 different pointing dies.

 

[michaeljp65]

Admittedly unscientific sample size. 10 shots each, .308, 100 yards with a stock FN SPR

I continue to “feel” that run out is important, and the less there is the better. Of course, it could just be more reloading witchcraft.

Thats a good experiment Nature Boy showing a difference. Now, im not doubting anything you've done here, intact i commend you for taking the time to do it. But, what if you did the same experiment and shoot the .003 group first? Im thinking that the .001" group im assuming you shot first. Cold barrel, clean barrel. You may well have let the barrel cool right down for the other two groups as well. But it would be interesting to see if you get the same results if shot in a different order.
Cheers

 

[SWRichmond]

Mass produced sizing dies dont know how thick the case neck of "your" case will be, so they have internal dimensions guaranteed to smash down the neck of the thinnest case that might exist and still produce several thousandths of neck tension.

So if you're using thicker-necked brass, the case mouth is many thousandths of neck tension, and in my experience lots of neck tension causes lots of run out.

 

[Alex Wheeler]

And none use the case shoulder mid point as the front rest like it is in the chamber when fired. I'm amazed that nobody makes runout thing-of-a-bobs that does that. Maybe they're ignorant of what really happens.

Regarding bullet ogive uniformity, people who have used 50X optical comparitors comparing shapes across a production lot see excellent uniformity. Except one lot of Lapua 30 caliber 185 grain FMJRB Match bullets that had 4 different ogive shapes. Proof they came from 4 different pointing dies.

What really happens is the cartridge is supported by it's two tightest diameters, the bullet in its freebore diameter at the front and the case base at the rear. I think this may be why I believe runout has little effect. Theres only a couple ten thousandths that a bullet can "runout" from the freebore, because that is all the clearance it has. If I was loading short oal for magazines and the bullet was not supported in it's freebore then I would expect to possibly see effect of runout because at that point, the case shoulder would be doing some "aligning".

 

[Scott Harris]

What really happens is the cartridge is supported by it's two tightest diameters, the bullet in its freebore diameter at the front and the case base at the rear. I think this may be why I believe runout has little effect. Theres only a couple ten thousandths that a bullet can "runout" from the freebore, because that is all the clearance it has. If I was loading short oal for magazines and the bullet was not supported in it's freebore then I would expect to possibly see effect of runout because at that point, the case shoulder would be doing some "aligning".

And this is also why having "tight-neck" chambers doesn't improve alignment, but sure can cause other problems.

 

[Bart B.]

What really happens is the cartridge is supported by it's two tightest diameters, the bullet in its freebore diameter at the front and the case base at the rear. I think this may be why I believe runout has little effect. Theres only a couple ten thousandths that a bullet can "runout" from the freebore, because that is all the clearance it has. If I was loading short oal for magazines and the bullet was not supported in it's freebore then I would expect to possibly see effect of runout because at that point, the case shoulder would be doing the back of the case body some "aligning".

What this tells me is bullets are a couple tenths smaller than throats and the back of the case body the same amount smaller than the chamber.

What prevents the firing pin from driving the case shoulder hard into the chamber shoulder for consistent primer firing?

First time I've heard of this scenario.

Are clearances this small in all rifle barrels?

 

[Uncle Ed]

"a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway.

In conclusion, I believe that allowing the bullet to find a relatively stress-free alignment in the throat by full length sizing (including the neck) and turning necks to enhance concentricity gives the bullet the best probability of a well-aligned start into the rifling."

The Rifleman's Journal
Germán A. Salazar

 

[Alex Wheeler]

What this tells me is bullets are a couple tenths smaller than throats and the back of the case body the same amount smaller than the chamber.

What prevents the firing pin from driving the case shoulder hard into the chamber shoulder for consistent primer firing?

First time I've heard of this scenario.

Are clearances this small in all rifle barrels?

The firing pin can and will drive the case forward but the bullets in the freebore in most cases and its not changing that. Many saami spec reamers dimensions do not go much over .001" nominal bullet diameter. I would expect very precise bullet alignment to improve accuracy. However, in practice, even loosening the freebore diameter specs has not harmed accuracy, in fact I believe its improved it. I also believe that the neck opens to release the bullet mostly. I do not believe the bullet slips out of the neck in the same fashion its seated. If that was the case, we would see necks that are not fully expanded as pressure could equalize on the out side of the neck. That said, if thats true, which I believe it is, then all of the concentrity goes right out the window at the instant pressure builds and the necks starts to release the bullet. There are many scenarios, but in this case I am speaking in terms of a rifle built for accuracy. In the case of a sloppy factory chamber, I have no interest or opinions.

 

[Scott Harris]

The firing pin can and will drive the case forward but the bullets in the freebore in most cases and its not changing that. Many saami spec reamers dimensions do not go much over .001" nominal bullet diameter. I would expect very precise bullet alignment to improve accuracy. However, in practice, even loosening the freebore diameter specs has not harmed accuracy, in fact I believe its improved it. I also believe that the neck opens to release the bullet mostly. I do not believe the bullet slips out of the neck in the same fashion its seated. If that was the case, we would see necks that are not fully expanded as pressure could equalize on the out side of the neck. That said, if thats true, which I believe it is, then all of the concentrity goes right out the window at the instant pressure builds and the necks starts to release the bullet. There are many scenarios, but in this case I am speaking in terms of a rifle built for accuracy. In the case of a sloppy factory chamber, I have no interest or opinions.

why do you think a larger freebore vs bullet diameter increases accuracy?

 

[Bart B.]

German Salazar sez:

Barring a seriously out of square case head, I don't think the bolt can have a negativeeffect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber.

He forgot to mention the extractor can push the case body rear end against the chamber wall. And inline ejector's can push cases full forward in chambers like firing pins do.

Case droop?

 

[Bart B.]

I do not believe the bullet slips out of the neck in the same fashion its seated.

Why not? Especially if it's been seated for only an hour or two. Ever measured?

If a 30 caliber bullet needs about 2 pounds of force to seat it, it will start moving out of the case neck when pressure in the case is about 27 psi. A 22 caliber bullet the same, it'll start moving out at about 51 psi. They slow down as they get engraved, then speed right up.

I don't think case necks will expand much forward of their heels. And very little behind the heel.