Bullet run out how much matters?

[Bart B.]

A ship has seven sides.
1. Top side
2. Bottom side
3. Port side
4. Starboard side
5. Inside
6. Outside
7 And Come along side

P.S. My dad was a retired Navy Chief, a Airedale, and always said if your stripes are not green your a nobody.

Does he or you know what side was renamed a few centuries ago.? "Come alongside" is what ships do with another, not a side of one by itself.

"Outside" has been called "topside" and "inside" has been called "below decks" for centuries. Those in and out versions are land lubber words as I learned in boot camp.

You forgot a couple sides that are always there and two more that are sometimes there.

If your Dad knows what they are, he's as good as the black shoes that help make brown shoe sailors their equal.

 

[Uncle Ed]

Does he or you know what side was renamed a few centuries ago.? "Come alongside" is what ships do with another, not a side of one by itself.

You forgot a couple sides that are always there and two more that are sometimes there.

If your Dad knows what they are, he's as good as the black shoes that help make brown shoe sailors their equal.

I was hoping you fell overboard and were eaten by sharks.

 

[Bart B.]

I was hoping you fell overboard and were eaten by sharks.

Don't feel bad about coming in second place in this ship based chat between the two of us. I finished next to last.

I spent 2.5 years aboard USS Constellation CVA-64 starting in 1960 with the nucleus crew at the Brooklyn Navy Yard during the final year of construction through 2 months of her first deployment in 1963. I was part of her main battery weapon system. I know brown shoe sailors. Wore them several times 2 years later at a training command then on a destroyer leader, DLG-29.

 

[bigstick6017555]

personally, i wish they would take their differences else where, i come here to hear opinions on guns and accuracy. not their petty differences of what they were or were not at some point in time.

 

[snakepit]

P.S. My dad was a retired Navy Chief, a Airedale, and always said if your stripes are not green your a nobody.

The green stripes are for Aviation Enlisted E-1 to E-3. From E-4 to E-9 they are red for all ratings unless you have 12 straight years of good service and then they are gold. Like your dad I also was a Airedale/Airdale.

 

[SG4247]

I’m learnin alot about the Navy, but not very much about how much bullet run out matters in my custom BAT bolt action.

 

[Uncle Ed]

I’m learnin alot about the Navy, but not very much about how much bullet run out matters in my custom BAT bolt action.

Below German Salazar answers a question about "Partial Neck Sizing". And he answers that full length resizing reduces the amount the case body and neck have on bullet misalignment in the bore. Meaning a full length resized case is more forgiving with bullet runout because the case body and neck have less guiding influence on the bullet.

"The cartridge should fit the chamber like a rat turd in a violin case" Jim Hull Sierra ballistic test lab and competitive shooter.

Now if we can keep the Navy out of this posting the world will be better off.

Reloading: Partial Neck Sizing

Good Morning Germán ,

I really enjoy reading your journal, It's very informative.

I have a question for you, but first some information about shooting down here for your interest.

I shoot F Class Standard in South Australia, at the Murray Bridge rifle Club, with a Barnard Model P action, heavy palma Kreiger in .308 1:13" twist, with a stock similar to a Kelbly M1.

A bit of information about Australian F Class. It is in 2 divisions :

Standard - restricted to .308 with 155 gn projectiles, or .223 with 80 gn projectiles (as it is in Full Bore - our equivalent of your Palma), an 8 kg weight limit, 1 kg trigger pull, and restrictions on exactly what powder ( only ADI ) and projectile ( about 4 specified ) you can use. This to a large degree causes the contest to be won by marksmanship and wind reading without too much technology.

Open - calibre 8mm and under, any projectile, any case, 'safe trigger', 10 kg rifle weight limit. This is favored by the more technological types who like to run at the leading edge high BC using the 'best' bullets, powders, cases, barrels etc etc, obviously these blokes have to be able to read the wind as well.

We shoot from 300 meters to 1000 yards, on a modified ICFRA target. With 2 optional sighters and 10 shots to count. We score out of 60, and have just introduced a 'super V' in the centre for countouts etc

I have this quote from your Oct 2009 article on neck tension :

"In the Redding Competition Neck Die with the micrometer top, the bushing can be allowed to move upward, thus limiting how far down the neck it sizes, but there is no practical reason for a Highpower shooter to do this. The Type S dies, like the one shown here, don't have that level of adjustment - and that's no loss."

When I size my .308 Lapua Brass with my Redding Type S Bushing Die, I adjust it so only half the neck is sized with the belief that the unsized portion of the neck is fire formed to my chamber and this ensures that the bullet is centered perfectly in the bore.

Now for my question,

Do you think that this is a valid expectation, and do you think that there are any reasons not to do this?

Thanks a lot,

Regards , John C.


Hello John,


Thanks for writing! Your question is a good one. You're correct that the Type S die can be adjusted to provide partial neck sizing. Unlike the competition neck die which has a spring-loaded collar, the Type S will just let the bushing ride the case mouth up until the top of the bushing stops and then it will size to whatever degree is left.

The real question is whether using the unsized portion of the neck to center the cartridge in the chamber is practical. I think this is not an optimal solution for a few reasons. First, let's consider what we're really after - we want the bullet to get a good, well-centered start in the rifling. Now let's look at a few scenarios to get there.

A case that is only neck sized depends on the case body itself - or at least that's the theory - to center the bullet. In reality, the case is banana shaped to a greater or lesser degree, but always curved and it is highly unlikely that it will actually put the bullet into perfect, straight alignment in the throat. The fully resized neck and a bit of clearance in the throat mean that the bullet is likely pointed off center to some degree, following the curvature of the case.

A case that is full-length sized, but only partially neck sized, which is the condition you describe, depends on the unsized portion of the neck to center the bullet. The resized case body is still banana shaped, but has been sufficiently reduced in diameter at the shoulder to keep the curvature from wedging the case within the chamber. Now, we get to the unsized portion of the neck. There is approximately 0.001" diametrical clearance to the chamber neck on the unsized portion just from normal brass springiness. There is probably no more than 0.0005" diametrical clearance between the bullet and the throat and in many cases as little as 0.0002" clearance. In other words, there is one-half to one-fifth the clearance in the throat that there is in the unsized portion of the neck. Which is doing the alignment? If that were all, we could say there's no harm done by the partial neck sizing, but that isn't the whole story. Unless the bullet is perfectly concentric to the neck, there exists the possibility that the bullet's alignment in the throat is being influenced by the neck's eccentricity in relation to the bullet. If you're relying on two points to align the whole, those two points had better be perfectly concentric. The longer the unsized portion of the neck is, the greater likelihood of the neck inducing a misalignment in the throat due to imperfect neck to bullet concentricity.

Now the last scenario, 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. Additionally, I place a high value on easy bolt operation and true full length sizing helps that quite a bit. I favor easy bolt operation as a prone shooter because I keep the rifle in my shoulder for the entire string and struggling with the bolt not only can shift the buttplate (always with adverse consequences) but it is also a distraction from my attention to mirage and wind flags which ideally occupies all of the non-aiming time.

Germán

 

[Bart B.]

Nothing in post #184 mentions how a rimless bottleneck case shoulder plays the biggest part of centering its neck and bullet in the chamber. Whatever amount the bullet axis is off center from the case shoulder, it's gonna be that much off center in the front of the chamber and the bore.

No cartridge spinner uses the case shoulder as its front reference.

This is too darned easy to figure out without any explanation. I'll explain for the n'er do well's

Note the part "There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat." The closest fit is at the shoulders of correctly sized cases and chambers as they are pressed hard against each other from firing pin impact. There's zero clearance there. Sometimes the case body is pressed against the chamber wall at the pressure ring, but its typically very repeatable.

 

[Uncle Ed]

Official Naval response for Bart B.

 

[Dusty Stevens]

Official Naval response for Bart B.

Both of those are perfect!!

 

[Lucky Shooter]

Bart B

I've followed your posts concerning the firing pin driving the case shoulder
into bearing on the chamber shoulder-----a tapered object being pushed
into a matching taper makes a lot of sense.

Is there an advantage in this case shoulder movement over static shoulder-shoulder
contact via a slight crush fit-----or even a neutral fit ?

Would appreciate your thoughts on this.

A. Weldy

 

[Bart B.]

Is there an advantage in this case shoulder movement over static shoulder-shoulder contact via a slight crush fit-----or even a neutral fit ?

I don't think any crush fit is a good idea. That often ends up binding the bolt head enough to make it close into battery at slightly different places. Which leads to various barrel vibration directions and amounts. Accuracy suffers.

With case headspace about .001" less than chamber headspace (.001" head clearance), bolts will be repeatable in battery, best accuracy happens and case life is longest.

 

[Lucky Shooter]

Thanks Bart B.-----haven't thought about this consideration.

A. Weldy

 

[snakepit]

I’m learnin alot about the Navy, but not very much about how much bullet run out matters in my custom BAT bolt action.

Just use your Scroll Down function and bypass what you don't want to read.

 

[dolek]

Just use your Scroll Down function and bypass what you don't want to read.

Or maybe folks could stay on the initial subject and not troll ? Sorry to make sense...

 

[Fliers]

Would the firing pin theory only apply if using fire formed brass without a shoulder bump? Otherwise, that pin itself would not cause shoulder contact would it?

 

[JimSC]

I found this test on bullet runout yesterday. It is only .22LR but it was conducted under laboratory conditions using a shooting tunnel and a machine rest

http://www.nielsonbrothersarms.com/22 Concentricity.htm

keep in mind the article is on the website of a company that sells concentricty gages

 

[Bart B.]

Would the firing pin theory only apply if using fire formed brass without a shoulder bump? Otherwise, that pin itself would not cause shoulder contact would it?

Isn't fire formed rimless bottleneck brass about .001" less in case headspace than that of the chamber? There's a smidgen of springback from the chamber, isn't there? Measure yours to see the difference.

This firing pin fact applies to all cases headspacing on their shoulders that have less head clearance in the chamber than case rim clearance to the extractor from the bolt face.

In other words, if the fire formed case headspace (head to shoulder) is no more than about .007" less than chamber headspace, the firing pin will drive the case against the chamber shoulder.

This assumes the extractor has at least that much clearance to the bolt face from the case rim. Measure yours with feeler gauges and calipers. I don't think any extractor holds a case head against the bolt face hard enough to withstand a 25 pound firing pin spring's force, if at all. Some folks do, though.

Measure case headspace on an empty primed case before and after firing it. I see a few thousandths shoulder set back on brass 308 Win cases, twice as much on nickel plated ones.

Or Sharpie blacken the shoulder of a primed case, slide it into an opened bolt face, chamber then fire it. Eject it then look at the chamber shoulder imprint on the case shoulder.

Either is proof to me it happens. Others may not.

 

[Bart B.]

I found this test on bullet runout yesterday. It is only .22LR but it was conducted under laboratory conditions using a shooting tunnel and a machine rest

http://www.nielsonbrothersarms.com/22 Concentricity.htm

keep in mind the article is on the website of a company that sells concentricty gages

I wonder what the test group sizes would have been if a receiver mounted scope was used instead of that 20X Unertl with its front mount on the barrel; a known cause of reduced accuracy.

 

[Idaho-Lefty]

Well guys, I ordered 3 set's of, FL BR Forster Dies (.22-250 Rem., .270 WSM and .243 Win and MY Bullet, "run-out" is,.. GONE !!!
Thanks for the great "tip", Uncle Ed !