case neck length - myth?

[indyeyedoc]

I know we've all read that for good case design a cartridge should have a neck length of approximately one caliber but I am wondering if this is just a myth or if there is any solid science behind it.  I've heard reasons given such as more uniform tension on the bullet and helping with proper bullet seating depth (ie. keeping the base of the bullet in front of the shoulder neck junction).  But then I see cartridges, even benchrest cartidges, with minimal necks.  The 30 cal Wolfpup has a neck of .080,  300 Win Mag and 300 Savage are short,  357-44 Bain and Davis has a neck of just .150 and I believe was chambered in revolvers so bullet tension must have been adequate.  I have also read that some benchrest shooters use "stepped necks"  which creates a shoulder for the base of the bullet to rest on and the bullet is seated with finger pressure only and little or no neck tension. (which kind of shoots down the idea of the need for long necks to create uniform bullet "pull" during powder ignition.)  Does anyone have any opinions or better yet real world experience with these short necked cases?  I would especially like to hear from anyone who has used the 357 B&D.  I am wanting to make sure such a short neck could adequately hold a 357 caliber bullet in place in the magazine during recoil of the rifle, if one were to make a wildcat for a bolt action with the same neck length/caliber combo.

[briannmilewis]

If I was to research this a little, I would take a look at as many bench rest cases you can find diagrams for and see if you can come up with anything consistent. These are the folks that refine their cases over and over again, and they care about things like just how much bullet grip is optimal. FWIW...just a thought.

[Win 1917]

Admittedly I don't have a lot of experience with short necked cases but I was talking to a guy I know who's a long time benchrest shooter about this a while back and he seemed to be of the opinion that short necks tend to be more difficult to keep everything concentric. Not that they don't work just that they're less forgiving. Assuming the concentricity issue is true, I could see how the 357 B&D could get away with an exceptionally short neck because the pistol bullets it's intended to use are short also. It's not like you're trying to hold a 300gr RN with it. Accuracy expectations are also somewhat less than a standard rifle round as well.

If you're looking at shortening the neck to increase powder space for the "358 short" project maybe look at the Cooper and JDJ rounds and see what neck lengths they're using. They really push standard rounds for max case volume and are also known for dependability and accuracy.     

[Darrell Davis]

Well, I will probably get shot full of holes on this, but us Ol'Coots have opinions and aren' likely to be changed a lot, or so it seems.

For most of us, for the level of shooting we do, and what our expections are in most cases, the years of myth about short necks has been just that, myth.

Now, if as has been suggested, we talk to those who spend their time shooting those tiny, very very tiny groups which are slightly over the dia. of one bullet, it may likely be a different story.

But over the years, and with having owned or loaded for a number of "short Neck" rounds. including at least 3 - 300win. mag. rifles, having loaded for the 300 Savage and owned and loaded for a 30 Gibbs with a very short neck, that neck length has been a non-issue.

I have never had a problem with bullet movement or slipage and feel, considering the results seen with 100yd. groups, the neck length had little to no negative effect.

Keep em coming!

CDOC

[Win 1917]

It depends on what you consider to be a "short necked" round. The 300 Win Mag and 300 Savage have short necks when compared to other standard rifle rounds but very long necks when compared to the 357 B&D, 30 Wolfpup, etc.

[briannmilewis]

Since the last post, I have researched BR cases and have found there are 4 common attributes, and one of them is NOT neck length.

BR cartridges have:

30 deg shoulders (universal)
.010" or .011" case taper
The start of the shoulder measured from the base of the case is close to case length x .7072
Case length is close to 1.52".

Neck length appears to be unimportant.
Case diameter appears to be unimportant.
Shoulder length appears to be unimportant.

Here (more or less) is what a 357/44 Mag with BR attributes would look like:



In reality the taper would be .009" if the taper is adjusted for case length.

[wookie76]

...The start of the shoulder measured from the base of the case is close to case length x .7072...

Can you expound on this please?  I'm having a hard time grasping the concept.

edit: Do'h; did you mean case length times .7072?  Brain skipped right over the X.

[briannmilewis]

Happens to me all the time.

After I put these factors together, Larry T shared this with me (I am sure he won't mind):

"I think it is interesting that .7071 is also the root mean square of a sign
wave.  Used in calculating the voltage of alternating current.  The 120 volt
power we all use is refered to as 120 volts RMS which is .707 times the peak
value of the sign wave.  Just a chance happening?"

The only mainstream cartridge I could find that exhibited that ratio, that was not a BR, was....wait for it....the 30-30 Winchester!

Sorry, forgot, the 17 Ackley Hornet is almost perfect with its .011 taper and its 30 degree shoulder starting (1.109" from base) further up the case than the BR starting point would be at 0.992" from the base.

What I am wondering is what any cartridge can do with a BR makeover, so to speak. If a case longer than 2.1 or there about has BR attributes applied, the neck can get silly long. So I am going to explore some cartridges with cases less than 2" and see what pops up. Also, Winchester WSSMs are close to BR in spec, just a little out, not too much, so that has me thinking about moderate WSSM loads, to reduce barrel burning, if there is such a thing.

Have fun.

[chipsoles]

Hello,
 Brian, your .7071 ratio, is also 50% of the square root of the number 2. Aliens?? I believe that the longer neck to bore ratio, is not an absolute law that dooms those with a short neck to failure, but that the longer neck, with a bullet seated nearly to the bottom, will make "better" accuracy, easier to achieve. If the bullet is seated in the case, and good axial alignment is achieved, we are headed toward success. What happens to a bullet's alignment, from the time of seating, until it is fired, do to outside forces, caused by feeding from a magazine, and transportation of the ammo(point up/point down, boxes dropped, thrown into a bag) are all factors to consider. A longer neck will help to overcome any of these things, that may, or may not happen to your ammo.
 The point was made that "acceptable accuracy", should be determined by the individual, based upon his/her application. Absolutely!
 The 22PPC, has a neck length of .286", while the 222Rem., has a neck length over .3" I would not consider neck length/bore dia., a myth, as I think that it helps to achieve any level of accuracy. One of the most important pieces to the puzzle, is to use your equipment, often enough to know the trigger, and to control the breathing, and jitters, that are magnified by a scope.
Regards,
Bob

[briannmilewis]

Excellent Bob, that is what I love about this forum. Cheers.

[helotaxi]

Brian, your .7071 ratio, is also 50% of the square root of the number 2. Aliens??

The RMS ratio works out to the inverse of the square root of 2 which simplifies to (sqrt 2)/2.  Not aliens, just higher level math.

[Xcalibre]

For many years I tried to find out why necks tended to be so short. The only legitimate reason I was given was to save on brass in manufacture. Less brass one end meant more cases per cost of material during wartime. Sounded fair enough. My first wildcat case was a Rem.243 shortened in body length and steep shoulder angle that left a neck of .480". My reason being the .243 eroded the chamber after minimal rounds fired much like a 6.5-284 does. Another reason to my thinking was to parallel the gas flow with little disturbance as possible at the back of the bullet. The long neck would help reduce erosion at the most vulnerable area of the chamber by acting as a heat sink, partially reducing  high temperature when the case itself becomes part of the barrel. Then the testing: Does it work? YES. Where I was changing out barrels at 2,200 rounds I am now up to 3700 still going very strong without any indication as yet in loss of performance. I have since built another four wildcats using the same principle and lead in F Open out to 1100m. here in Central Queensland. For wildcatters I do recommend longer necks.

[briannmilewis]

Trust another Aussie to be involved in some outstanding testing...you put your money where your mouth is. Great work and gives me a factual basis for giving any cartridge around 2" a BR makeover. Thanks for the insight. Always thought you Queenslander's were a smart bunch (quite the compliment from a former Victorian).

[briannmilewis]

After we finish the 223 Short, we will probably be doing a 6x45 (.223 Rem necked up to .243), but using the 222 .313 neck length, much longer than the regular 6x45 .225" neck, a 30 degree shoulder and .011" taper. With almost identical powder charge, small rifle primer, and 6mm bullet, we are going to try and give the 6mm PPC a run for its money, but with a poor man's parent case, and no special case prep. We have found out that with the 223 Short there are some amazing results to be had when experimenting with different powders. We have a working name of 6x45 BR. Oh what fun it is, and I will have a decent budget for this one.