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Old June 22, 2014, 07:12 PM   #1
Moloch
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168 BTHP bullet wobble

So today when letting my reloaded rounds roll on a perfectly flat surface I discovered that about 70% of them wobble their projectiles. The bullet I'm talking about is the Speer Sierra Matchking BTHP 168 grain.

The wobble is not extreme but noticeable, other reloads with a different (cheaper) bullets didn't wobble at all (same reloading procedure), so it must be the bullet and not my seating or resizing dies.

Accuracy? I'm still testing but right now its so-so, a tad better than MOA but I'm shooting with a 7x scope and a thin hunting profile barrel.

Does it affect accuracy? Its a target bullet with great reputation after all. I wonder if thats why I haven't found a more accurate load yet.
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Old June 22, 2014, 07:56 PM   #2
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Hornady concentricity tool takes the bullet wobble out to some degree. For me, I don't need one as I just plink at paper and figure the 200K-300K revolutions as the bullet exits the barrel will shake it out enough for my use. I don't have that special finis/eye sight to make a perfect marksman anyway. Lets say you make a round that is for 400 yards. It may wobble and smooth out prior to the target but using the same bullet for 100 yards may reveal it wobbled into the target. Different bullet weights, powders, etc as you know for different twist and distance plays in it a lot. Because of component availability/cost, I have to settle for so-so or I don't get to shoot.
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Old June 22, 2014, 08:40 PM   #3
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Speer and sierra are 2 different companies. Either one makes good bullets, I use sierra match king 168 as well and they are great bullets. What your describing is run out. It's not the bullet it's the case neck. Depending on the distance and how much run out you have it may not affect your accuracy. If you have less the .003 of run out you should be ok. You'd have to measure it. Likewise if you are only shooting at 100 you likely won't notice it.
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Old June 23, 2014, 04:26 AM   #4
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It can't be the case neck, other rounds made with the same dies and procedures don't have any ''runout''. The only difference is an other bullet.

Quote:
Hornady concentricity tool takes the bullet wobble out to some degree.
Thats is one heck of a great tool but boy, is it expensive.
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Old June 23, 2014, 04:29 AM   #5
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It's not the bullets. Roll the bullets on a surface before seating and see if they wobble. If they wobble you got a bad batch. The concentricity gauge is about $95. If you use it to adjust runout you run the risk of also adjusting neck tension. Which means you will have inconsistent neck tension between cartridges. It's used to measure run out. There are better gauges for it, and that comes from someone who has one. Do a search for causes of run out. Sierra match kings are the gold standard for bullets I'd be very surprised if it was the bullets.

Last edited by 1stmar; June 23, 2014 at 04:41 AM.
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Old June 23, 2014, 07:17 AM   #6
Bart B.
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It's the neck that's bent. Something is different about the process between batches of ammo. Without knowing the details of each, it's hard to say what caused it. Possibilities are:

Straight bullets are smaller diameter than crooked ones. They seat with less force so the necks don't bend as much.

Different die setup.

Different technique using them.

Different case treatment.

Pull a wobbling bullet out then roll it on a flat surface. Watch it spin true.

Most common cause of bent case necks is the die sizes them too small then the expander ball coming back up through thick walled necks bends them. Roll some empty sized cases on a flat surface to see how much wobble their necks have. Bullet seaters don't straighten them up much.

Bullets entering the bore quite crooked don't straighten up much. They exit the muzzle off the bore axis then strike some distance away from the aiming point.

Pressing a crooked bullet to straighten it changes the gripping force by the case neck. 30 caliber bullets can be straightened very well by gently gripping the rounds neck in a .338 caliber bullet puller then pressing on the case head to straighten the case body on its neck. I've done this with great success.

Last edited by Bart B.; June 23, 2014 at 07:45 AM.
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Old June 23, 2014, 07:39 AM   #7
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What dies, press are you using?

The seating punch could be the cause of the problem.
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Old June 23, 2014, 07:53 AM   #8
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Make sure the seating stem contacts the bullet on the ogive. The nose/tip should not be contacting the seating stem. Another reason may be the bullet is not seated into the case neck deep enough. The full diameter of the shank should be at the neck shoulder junction.
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Old June 23, 2014, 09:27 AM   #9
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As Bart says, this is the neck. Watch this video to see what the difference between having an expander and not having an expander results in.

Tilted bullets will cause inaccuracy that varies with how long the bearing surface is and how far the center of gravity is from the center of the bearing surface and how much mass the bullet has and the velocity and barrel twist. So it's a collection of factors from bullet spin rpm and time of flight to the amount of mass offset causing eccentric spin. Tilt affects the bullet up to a point, beyond which the bore will straighten further tilt. In typical match bullet shapes this is somewhere around 0.2° of in-bore tilt.

The mechanism by which this opens groups up is that when the bullet is in the bore it is constrained to spin around the bore axis. When it exits the muzzle it starts to spin around its center of gravity. If the center of gravity and the bore axis are not coincident, the bullet jumps to the side as it exits the muzzle to begin spinning around the offset center of gravity. That jump may be small, but it has momentum that serves as drift in the direction of the jump that stays with the bullet all the way to the target. The amount of error it introduces is just the velocity of that drift multiplied by the time of flight.

Because the tilt can be measured and located with a gauge, if you orient the cartridge so the high side of the tilt is always pointing the same way, the lateral jump at the muzzle is always in the same direction, so the group error is reduced by half. If the amount of tilt is identical in all rounds and you orient them the same way in the chamber, there is no group enlargement at all, but rather just a POI offset.

Harold Vaughn did that exact experiment with a 6 PPC in a highly accurate integral machine rest rifle, indexing the high side of the tilt 90° for each shot, so each 90° point around the clock had two cartridges fired with that orientation. The result is the group on the left in the first illustration, below.

In the 1960's, A. A. Abbatiello measured runout on 829 rounds sampled from 42 lots of .30-06 National Match ammunition and ran firing experiments showing tilt with the 173 grain boattail FMJ (not too different in shape from the Sierra 175 grain .308 MatchKing, but with shorter bearing surface and longer boattail), and got up to an m.o.a. of dispersion, with additional tilt not adding to the dispersion. From his data, had he been in possession of a machine rest rifle with the accuracy of Mr. Vaughn's gun, the group he got from the indexing test would look like the one on the right in the illustration.



The different tools give you different runout numbers depending on how the cartridge is supported in the measuring tool. If it is supported at the nose and tip, as with the Forster and Hornady gauges, you get a smaller reading for the same amount of tilt as you do measuring at the same point with one that supports the case wall in two places, like the Sinclair and Holland and RCBS Case Master do. The NECO gauge can be configured either way when you have two v-plates for it.

Because the different gauge setups read with different sensitivity, you can't compare readings off two gauges directly. You can, however, calculate the bullet tilt angle from readings with any of them, and that angle can be compared. If you are strictly looking at your own numbers on a comparative basis, though, then any gauge type will provide relative readings and you just have to track them.

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Old June 23, 2014, 05:31 PM   #10
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Resized bottleneck cases with the straightest necks are made so with one-piece full length sizing dies whose neck diameter is a couple thousandths smaller than a loaded rounds neck diameter. No other die holds the case body concentric with the case neck during the sizing process on fired cases. As such ca cases that headspace on their shoulders center perfectly in chamber shoulders when fired, it behooves the reloader to size the fired case neck all the way to the case shoulder then a thousandth or two more to ensure the case neck and shoulder are concentric and have the same axis.

When chambered, such cases are pressed against the chamber body close to the extractor groove. The case body right behind the shoulder doesn't touch the chamber at all; that point is smaller in diameter than the chamber. As very few case bodies and chambers are perfectly round, it's good to have some clearance between case and chamber near the shoulders else the case shoulder would be pushed off center there taking a bullet with it. That causes extra and non-repeatable vibrations in the barrel before the bullet exits. Those bullets leave at an undesired direction.

Full length bushing dies are almost as good. Forster hones out their dies for ten dollars each. I suggest decapping fired cases first then cleaning them before resizing them in a honed out die tha doesn't have the decapping stem nor expander ball in it.

Unclenick's cartridge runout pictures the best I've seen anywhere. I prefer to have the front rest point on the case shoulder. Then the cartridge is held closest to how it is in the rifle. That front rest can be a V block or a round hole. I prefer a nylon washer with a 3/8" hole for 30 caliber rounds and a V block about 3/10" from the case head where it touches the chamber wall. A .001" out of round condition there causes about .0005" error on the bullet about 1/4" back from its tip where I put the dial indicator.

30 caliber bullet runout can be as much as .003" and still shoot 1/2 MOA at 600 yards if bullets are seated to touch the lands when fired. They'll shoot 3/4 MOA at 600 with a few thousandths jump to the lands (freebore). This assumes the rest of the cartridges are up to snuff along with the rifle and shooter.

Last edited by Bart B.; June 23, 2014 at 05:52 PM.
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Old June 23, 2014, 05:57 PM   #11
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So to get improvements you will need to buy things like a concentricity gage and a ball micrometer and start measuring things that influence runout and make corrections in your process.

A good place to start is measuring neck wall thickness on your cases and sorting them in batches according to variation. If you have non-uniformities here it translaes directly to runout or wobble in the loaded round. It also give you the rationale to buy a neck turn tool to uniform the cases.

The next thing you might do is examine the effect of a standard FL sizing die with a conventional neck sizing button and how the upstroke (pulling the button through the neck) contributes to displacing the neck off the centerline of the case. More rationale for buying more expensive sizing dies like the Redding Bushing Dies that eliminate the expander button.

Then you will want to buy a sliding sleeve seat die from Forster or Redding to ensure axial alignment of the bullet to the case during bullet seating.

... and the fun never ends.
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Old June 23, 2014, 07:23 PM   #12
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The OP said
Quote:
, other rounds made with the same dies and procedures don't have any ''runout''. The only difference is another bullet .
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Old June 23, 2014, 07:29 PM   #13
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The OP does not have a gage to check bullet run out. He is checking only by eye and his loads that don't "look" bad could be canted/bent too.

The best way to insure straight bullet/case alignment is to use a Forester/Bonanza die, or a Vickerman bullet seater die.
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Old June 23, 2014, 07:54 PM   #14
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Video-bogus test. IMO.

In the video, the lube is not wiped off the brass sized in the Hornady die. Sizing should remove it, but did it? It there a glob in the die from sizing many cases before? Did the glob of lube inside the neck get trapped between the expander and case wall? Hydraulics at work? I know Lee wax lube when applyed with a Qtip will remain after the expander is pulled thru the necks. Some more than other. As far as seeing bulllet runout, if he can see one, he should see the other, if its that bad. Same necks, different bullet.
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Old June 23, 2014, 08:06 PM   #15
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Quality seating dies do little to straighten crooked bullets in crooked necks. I've tried Vickerman, Wilson, Bonanza and several others. With straight necks sized correctly, a ball peen hammer seats very straight bullets.

http://www.redding-reloading.com/tec...icity-problems
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Old June 24, 2014, 10:21 AM   #16
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I got the Sinclair concentricity gauge that came with a fortune cookie little piece of paper in the box that said ~~" you will probably find that the expander ball is the problem."

I have gone through my reloading process many times to see where run out increases and where it decreases.

Runout decreases when the case is fire formed [shot] in a chamber made with a reamer.

1) Then sizing adds a lot of run out.
2) Neck thickness runout adds some.
3) Seating with the worst seater in the worst way adds very little runout, but it can be measured.

Runout in the chamber [chamber wall to the bore, not like we measure ammo shoulder to the neck] can be measured at the time of chambering, and it is big, but because it is rotationally consistent [unlike randomly oriented ammo], it does not affect accuracy much.

The worst runout in ammo will get limited by the straightening the chamber does to it.... as calculated and verified in the article by A. A. ABBATIELLO , "Gauging Bullet Tilt" in American Rifleman a half century ago.
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Old June 26, 2014, 09:03 PM   #17
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In my experience, presses have always been the biggest factor in bullet runout.
I have two RockChuckers, 3 Reddings, and a Crusher. One of the Rock Chuckers prepares almost immeasurable run out. The other Chucker turns out dogs. The two Reddings and the Crusher are good, but nowhere close to the good Chucker. When I first got the good Chucker press, I thought my dial indicator was sticking. I save it for 6ppc and .284 Winchester in my competition rifles. Despite popular misconception, presses do wear and the more they wear, the worse they get.
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Old June 27, 2014, 05:25 AM   #18
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All with the same seating die?

I've used the same seater die in sloppy and tight fit presses all with the same results; seated bullets align with case neck axis regardless of press quality. Same for different seater dies.

Quote:
Another reason may be the bullet is not seated into the case neck deep enough. The full diameter of the shank should be at the neck shoulder junction.
Why?

Doing that means cartridge length and bullet jump to the rifling will vary with bullet weight and base shape.

--------

Never heard of these two reasons before.

Last edited by Bart B.; June 27, 2014 at 05:47 AM.
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Old June 27, 2014, 10:55 AM   #19
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After reading this thread I went and rolled a bunch of my loaded rounds as well as some sized cases . All I can say is I love this forum . Not one wobble , they track perfect as far as my eye can tell anyways . I looked at the tip of the cartridges straight on and the tip of my 175gr loaded smk don't move at all . You guys here have helped me out a lot and I thank you . I'm pretty new at this . It's been almost a year since I started reloading and I'm sure glad I had this forum to help me along . Of course the forum only helps if you listen Thank goodness I knew nothing so I had nothing to cloud my thinking . There's a guy at the range I go to that I try to help but he just won't listen or try anything knew . Yet there he is every time complaining about the same thing . I ask did you try what I said ? No I thought I'd try something that has nothing to do with the problem

I should add that these cases were once fired WCC 06 NATO brass fired most likely from a machine gun . I have now loaded them 6 times and annealed them once after the 5th . I've been told the best I'll get from this brass is 1/2 moa and that's about the best I get . One of these days I'll get some Lapua brass and see if my rifle and I do any better .

I use the redding FL bushing die and measure the thickness of the neck walls . If they are not under .002 all the way around they get put aside . I then use the bushing that gives me about .002 tension . That is after some serious case prep . I do decap only clean primer pockets and inside necks then tumble before anything else .

What I did for my seating die was buy the micrometer tip separate http://www.midwayusa.com/product/760...ProductFinding for the standard Redding seating die . I love having the micrometer because I load at least 6 different bullets for 2 different 308's and I just make a note as to where the micrometer was set for each load . I can just go back and dial it in for each load and it's comes out perfect every time .

As for the collet die . I've had one in my Midway USA cart for about 2 months now . After that video I'm thinking I should just get the darn thing . Will that help with those cases I have that the neck walls are not the same thickness all the way around ? I was going to buy something to turn the necks down but If the collet die will do the job I'll go with it . Does that die support the case and keep the neck in line with the rest of the case ? The video shows the guy using Lapua brass . I have to assume those neck walls are perfect-ish .

The other thing is that I assume I use my FL bushing die with NO bushing as a body die then use the collet die for the neck ??
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Old June 27, 2014, 11:02 AM   #20
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Bart. Some new reloaders think they have to have the bullet as close to the rifling as possilbe. This may leave very little shank of the bullet in the neck. A feeding ramp may crook the bullets on loading. Make sure the seating stem contacts the bullet on the ogive. The nose/tip should not be contacting the seating stem.

Last edited by 243winxb; June 27, 2014 at 11:11 AM.
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Old June 27, 2014, 11:29 AM   #21
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Also, if you roll the loaded ammo across a mirror it "amplifies" any wobble that may be present making it easier to see than just rolling them across a flat surface.
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Old June 28, 2014, 02:41 PM   #22
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Metal god,

A number of folks have reported the collets gradually moving the brass over the mandrel over a number of reloadings, but if you want good symmetry faster, outside neck turning is the only currently available option.
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