Home Forums Hunting & Shooting Ask The Gunwriters bullet seating and neck length

Posted this elsewhere on the web with no luck:
There's frequent mention of the need for a sufficiently long neck so as to keep the bullet out of the powder space, but simply pushing the shoulder back seems to leave less room, not more, than having the bullet butt into the case beyond the shoulder.
As an example, the 220gr .308 goes way into an '06 case. Now if I were to invent a 'cat with the shoulder pushed to meet the backside of the bullet, would that somehow improve the performance?
It seems at best it would be the same as the '06, and at worst I'd lose all that room when seating 150gr bullets, say.
Doc, or someone, please explain this.

[aside: just got Dr Howell's big blue book (love it), and was surprised at the omission of the 375 C-T. Are the specs for this one not easily available? As popular as it is, I truly took for granted it would be there.]

Sidearm, the description you use of setting back a shoulder to keep the bullet out of the powder is very much in line with Ken's line of cartridges. I had the prividlege of meeting ken last week and examining his cartridges, he provided me with ballistic printouts of his 220 and comparison to the Swift. I am now in the process of turning one of my Ruger #1's into a 220 Howell based on this information...and a lot more. In the true scheme of things muzzle velocity is not near as important as terminal velocity. I would love to get Ken to come in here and explane the design of his cartridge. Needless to say the 220 Howell was designed around 75 -80 grain bullet and an idea to get optimum performance from that bullet and by all intents it does just that.
the neck of the cartridge is quite long, much like the 222 Remington and PPC cartridges. The Powder capacity of the 220 Howell is greater than the Swift but it operates at lower presures.
Ken has an article that i hope he gets out to us soon it is something I had the honnor of reading as he was producing it. I am beginnig to digress.

Bullwnkl.

-- excerpt from the article that Bullwinkle mentioned --

The heavy premium bullets in each caliber are long, and long bullets need to be seated in long case necks if the case is to work well in its secondary but crucial role of alignment jig to position the bullet for accurate entry into the barrel when the cartridge is fired. I've coined the term socket engagement for the concept of how much bullet shank the case neck grips. To appreciate the importance of socket engagement as it relates to the exposed length of the bullet, consider the parallels of a fence post, a telephone pole, and a flag pole.

You can get by all right by seating a fence post no deeper than two or three feet in the ground. A telephone pole, because its exposed length is much more than the three to six above-ground feet of a fence post, has to be seated much deeper to be acceptably stable. The much taller flag pole has to be seated even deeper still, or it won't stay vertical very long. Sky-scraper buildings on Manhattan Island are seated storeys deep into bedrock. The socket engagement of the fence post would not be worth much for the telephone pole, the flag pole, or a tall building. Socket engagement that's adequate for the lightest, shortest bullets in each caliber would not be enough for the longest bullets.

Somewhat arbitrarily but with what I considered to be good reasons, I established the neck length at 0.375 inch for all twelve of the new Howell cartridges. If you look at the heaviest premium bullets in all these diameters, you'll see that they're all very nearly the same length. Therefore they all need about the same length of socket engagement.

Well, I appreciate the response guys, but I think you're somehow missing the thrust of my question.
I understand the need to give the bullet good purchase in the neck.
And sure, AEBE, a case with more capacity gives lower pressures (different subject.) My question can be rephrased thus:
Given that COL is a typical limiting factor, given that you have adequate bullet grip, what is the benefit in a longer neck simply to keep the bullet out of the powder?
IOW, it isn't the relationship of neck to shoulder, but bullet tip to case shoulder that determines whether the bullet is in the powder.
E.g., I have a .35 cal cartridge, on a 2.5" case, and consider 3.35" COL the max, and consider .35" neck length "sufficient."
Now, I know the 300gr Swift will seat into the powder cavity, but if I lengthen the neck (which is truly to say "shorten the body") then I'm not gaining any space back that I didn't have, and theoretically I've lost a bit that would come up and around the base of the bullet inside the case.
Not only that, but when I go to seat a 250gr I've certainly lost some powder capacity.
Though the idea is mentioned in Cartridges of the World and other places, since we're on Dr Howell's forum, I'll quote from his excellent, blue book.
"A shorter case neck sacrifices some of the neck's grip on the bullet. A longer neck sacrifices a little powder capacity. A short neck also sacrifices a little powder capacity when the bullet is seated deeper than the length of the neck -- when the base of the bullet extends below the bottom of the case neck, it occupies space that's no longer there for powder to occupy. (Obvious when you think about it, isn't it?)"

To us thick-heads, the answer is, "no, sorry."
The only thing I can guess is that internal ballistics are such that the powder "up and around" the base of the bullet in a shorter-necked (read: longer bodied) case is somehow less- or un- useable.

Is my confusion a little clearer?

Sidearm, your arguement is a sound one, simply put more potential energy stored in the case creates a greater energy release when ignited thus the possibility of greater velocity of the bullet. How ever the faster bullet may not be the most accurate bullet for a number of reasons. The reason discussed here is bullet allingment to the bore through the use of a longer bearing surface provided by a longer neck.
The 220 Howell case as developed by DR. Ken Howell is perhaps the optimum case for this caliber using a specific style and weight of bullet, there fore it may be unwise to use this example in an arguement about case capacity. Let me explane. The 220 Howell is similar to a long 30-06 ie: 270 case. The shoulder is set back providing a long neck thus greater beating surface. The case capacity is greater than the 220 Swift thus allowing space for more powder. When fired the swift is faster by a bit at the muzzel when utlilizing a 40 grain bullet the Howell using a long 75 grain bullet bullet has the better BC and thus ovetakes the Swift and surpasses it it retained velocity at long range and with the better BC the Howell will naturally be the more accurate of the two at distance. It appears you answered your own question, but accuracy nuts like myself and Dr. Howell ( I hope I can speak for you in this matter Ken) See a different aspect of the fired round. Velocity is fine up until accuracy suffers. Compare two very similar cartridges: the 222 and the 223, the 222 Remington was the king of the at the bench rest matches for many years it is a very accurate round , long neck less powder capacity than the 223. The 223 is faster but has proven to be a bit less accurate, not to say the 223 is not an accurate round, it is, however the 222 is more accurate at the expence of powder capacity when compared to the 223. So where does this advantage in accuracy come from...it seems obviouse it is in the neck of the round. should one be able to have a 223 with a long neck one might just have his cake and eat it too. The answer is the 22PPC powder capacity and longer neck than the 223.

Bullwnkl.

Ken I have sat here pondering you fencepost, telephone pole and flag pole analogy. there is a number of factors that need to be employed to make the comparson valid. I realize we are to assume that all poles have the same diameter. This needs to be stated to avoid confusion . I first envisioned a 8-10 in diameter fence post about 7' tall then a 12 "diameter telephome pole 25' tall and lastly a flag pole 6" diameter 40' tall. In this senerio your anology fails to work. All poles must be the same diameter. Each pole has a different overturning momentum thus requiring increasingly greater support to remain vertical.
My first thought was why not grip the pole tighter that would work but it is not comparable to a cartridge for the pole is not intended to be ejected from the hole it is planted in. Tighter soil types will allow hole depth to be less when planting poles. This is not totally true of seating bullets. The tighter the grip on the bullet, the force required to Pull the bullet increases. Pressue in the case increases to eject the bullet, recoil increases, (I presume) and accuracy suffers. With this as a base for a hypothisis there must be a optimum amount of resistance applied to a bullet by the case for best accuracy amoungst many other factors. I think that using a hypothisis such as this it would help explane why some muzzle loaders are so very accurate at one time and lousy at others when all componants are equal except the patch or sizing of the ball.

Bullwnkl.

"The only thing I can guess is that internal ballistics are such that the powder "up and around" the base of the bullet in a shorter-necked (read: longer bodied) case is somehow less- or un- useable. Is my confusion a little clearer?"

Yes, to a point. I can't imagine what manner of reasoning has led you conclude that the powder surrounding the base of a deeply seated bullet somehow becomes ineffective.

KISS -- the base of the bullet, protruding into the powder cavity, occupies space that powder can no longer occupy. In the same way, the base of a shallow-seated bullet leaves space in the lower neck open for powder to occupy. How much simpler could this be? Where the bullet is, powder can't be -- and where the bullet is not, powder can be. And the powder behaves the same, once it's lit, in one place just as it does in any other. Its expanding gas propels the bullet. Less powder produces less gas. More powder produces more gas. More gas propels the bullet faster. Less gas propels it less.

X amount of powder in Y space produces the same amount of gas as it does in a larger or smaller space. The gas from X amount of powder produces higher pressures in a space smaller than Y, lower pressures in a space larger than Y.

The grip of the neck on the shank of the bullet affects the build-up of gas pressure behind the bullet as the bullet first resists, then responds to the expansion of the gas (the build-up of the pressure). A light grip (shorter neck, shorter shank, shallower seating) lets the bullet move sooner, in response to a lower level of the a-building pressure. A tight grip (longer neck, longer shank, deeper seating) resists the thrust of the gas longer, allowing pressure to build longer and higher, which in turn increases the efficiency of the powder.

In the matter of design, the longer case with a longer neck is ballistically superior to the shorter case with a shorter neck. Once the case design is established, the deeper versus shallower seating becomes a trade-off that only instrumented trial and error can resolve -- does the reduced space for the powder increase the efficiency of the powder burn enough, so that less powder produces the same or higher pressure, or does the smaller powder charge's less gas merely propel the bullet less, even though it produces a higher peak pressure?

Well, Doc, as to the manner of reasoning, it was simply the "given" that a shorter neck reduced powder space. I couldn't for the life of me figure how that was, so I was stabbing in the dark.
The critical dimension for powder space is base to shoulder, rather than end-of-case to shoulder, right?
Sounds like I was simply misreading what you, et al, were saying. Yes, you must have a sufficiently long neck, but given a COL and bullet (3.35" and 220gr .308", say) making the neck shorter is not going to decrease powder capacity. If anything, it will increase it, given the same 2.49" case.
So the object is to find just how long that neck needs to be to align the bullet well, and no more. But this isn't about powder space, it's about bullet-holding.

Then, Doc, what you say about long vs short and effects on pressure build-up is very interesting, and makes a lot of sense now that you mention it.
Could one feasibly turn the expander button some .0001" to achecive long-neck results in a shorter neck? - still assuming long enough for "jig" action.

Has this been looked into before?

(Thanks a million for the responses, once again!)

The critical dimension for powder space is the internal volume, not the length, from the web to the farthest-forward point that the powder can extend.

Yes, reducing the inside diameter of the sized neck does a lot to increase the neck tension (called "bullet pull") on the shank of the bullet and thereby increase resistance to powder-gas expansion. So also would the use of a sealant (not a cement!) like asphaltum to goo the bullet in place. So also would seating the bullet so that it firmly contacts the lands when you chamber the round. In some chambers, it's possible that a long bullet seated into the powder cavity, but with its ogive against the lands, doesn't lose anything in performance or increase the risk.

Jim, the analogy of the posts and pole is indeed valid, because it doesn't apply to the "post being ejected from the hole" or the soil's resistance to that force but is rather a matter of the sideward forces it's exposed-to, over time. Remember, the typical loaded cartridge is exposed to any number of sideward loads on its long way from the seating die to the chamber, and the case neck must hold the bullet in the same alignment and with the same grip no matter what, over the entirety of that long way. Some rifles' feeding mechanisms put a heck of a sideward load on the bullet as the round comes up from the magazine and goes into the chamber.

From 407 Spring Street here in Stevensville to the Deep Creek range the other side of Missoula is far enough -- from here to the Serengeti plain is much longer in both time and distance. From the loading bench to the shooting bench at the Powley Center will (I hope!) be only a few feet and a few minutes or even seconds. Cartridge design can not afford to assume that the loaded round will travel only a few feet in a few seconds between the seating and the propulsion of the bullet. The case neck has to do its job every inch of that distance, every second of that time.

No aspect of good cartridge design is as easy or as uncomplicated as it first seems to a casual look.