Does the bullet slide out of the neck or does the neck open to release it?

[Albany Mountain]

Doesn't matter what the acceleration of the pressure is!!! The areas, and the ratios don't change!!! The bullet will always see 25 times more force on the base of the bullet than the gap (primary example) and 60 times more force in the 2nd! Doesn't matter if it is a 100 grain bullet or a 200 grain bullet, as long as the caliber stays the same, ie 264 caliber for my example. It doesn't matter if it is a boat tail or flat base, they still have the same exposed area to the pressure!!

The formula is a linear, meaning it has a straight line with the slope angle being the base area and the intersection will be at 0,0!!! The graft will have the force on the y-axis, and pressure on the x-axis!! Therefore, the force will change proportionally to the change of pressure by the factor of the area!!!!

INERTIA (MOMENTUM) comes into play with a change in motion of a body with MASS! Mass is not in the equation!!! Pounds is a measure of force, not mass!! Weight is a force!!! F = W = mg = ma = pressure x area!! I could calculate the felt recoil by knowing the mass and caliber of the bullet, the peak pressure, the weight of the gun, and the area of the butt plate!! The Recoil is also a Force derived from Newton's law of Inertia and ACTION/REACTION!!! But, almost all in the forum doesn't understands that!! All I ever see is Tension being misused and abused!! Tension is a force and doesn't exist unless there is an equal, but opposing force acting on Tension!! That opposing force, when talking about bullet/neck forces, is COMPRESSION OF THE BULLET!!! Tension and compression are the vary bases of Engineering class fit!!!!

And THIS is why I don’t drink with engineers.

 

[AlNyhus]

Look at it this way. . .

If the neck does not expand before the bullet leaves the case, then why do we need "sufficient neck clearance" to achieve very good accuracy?

If the bullet left the case before the neck expanded we could get away with minimal to zero neck clearance, providing the case could freely chamber.

I'll point to our .30 WolfPup as an example. With a neck length of .085 and the base of the bullet .150 below the neck/shoulder junction....we were able to run z-e-r-o (measured) neck clearance with no pressure issues.

Clearly, the neck  length is what allowed this to be workable. But even though there was zero neck clearance and the base of the bullet had to move .235 to 'clear' the neck...there was always a powder residue ring around the neck. Just like a 'normal' case neck.

As Rod Serling would say: "Submitted for your approval...."

Good shootin' -Al

 

[Wild Bill IV]

And THIS is why I don’t drink with engineers.

I'm still going buying the 1st round when we finally meet up in Wyoming dude!!!

 

[dgeesaman]

And THIS is why I don’t drink with engineers.

I’m an engineer and I checked out a while ago.

 

[jelenko]

I’m an engineer and I checked out a while ago.

Same here.

 

[Bottom Fodder]

Last night in a dream I was watching a VCR tape that showed in slow motion of a cartage being fired and the results of what happens as the bullet moves forward. So now I have proof and will use that knowledge to not change anything in my loading and testing

 

[dellet]

When considering neck tension, case clearance in the chamber, whether the bullet, moves in the neck or completely clears the neck before it expands, you need to keep in mind what actually happens and when, vs what sends the bullet into the bore in the most repeatable, and efficient manner.

Example a zero clearance neck chamber, or .005” clearance. Both can be used, neither seems as efficient as .002-3”. The biggest argument for not using zero clearance is more safety and room for what if the tolerances are off. That +.001” case neck or bullet gets real interesting. Safety over effiency.

Everyone talking about soot on the case neck as an indicator of the neck not sealing before the gasses leaving the case, need to consider why recovered bullets have no similar carbon ahead of the bore diameter of the bullet. If gas gets out before the bullet seals the bore, they will be ahead of the bullet. Video seemingly defies evidence held in your hand.

If the neck was not expanded and sealing the chamber, why was the case clean below the shoulder which had clearly expanded and sealed?
Does this mean the case stretches and shoulder blows out before the neck expands?


Why can you fire form with no bullet?

Why do subsonic, low pressure loads, that bullets are a slip fit after firing, seating pressure in the sub ounce range, still blow the shoulder forward?
Why does the shoulder stretch at a different, greater rate than the neck expands?

If you have zero headsapce will the neck open sooner?

If you seat the bullet with “0” bearing surface in the case neck, do you reach peak pressure sooner or later?

What about if you seat the bullet and use a roll crimp to set the case mouth into a crimp groove with only enough crimp to hold the bullet in place, the bullet spins freely, but can’t move for and aft?
Why does accuracy improve over a full crimp or interference fit?

A whole lot more to think about when considering which moves first, the bullet or the neck an how far.

 

[46and2]

I've watched many ultra high speed videos where gas is coming out of the barrel before the bullet.

 

[Straightshooter1]

View attachment 1647705I've watched many ultra high speed videos where gas is coming out of the barrel before the bullet.

Me too. And from what I've observed it seems the further back from the lands, before the bullet is fully engraved, the greater the amount of gas comes out ahead of the bullet (e.g. Blow-by). The minimum amount is when the bullet is seated where jammed into the lands, which does makes a lot of sense to me.

 

[ebb]

"Does the bullet slide out of the neck, or does the neck open to release it?" YES! I think it all happens simultaneously.

 

[Wild Bill IV]

I’m an engineer and I checked out a while ago.

DIDO!!!

 

[Wild Bill IV]

I'm going to build a pneumatics tester for seeing how much pressure it takes to break the static friction holding the bullet in the neck! I'VE BEEN WANTING TO KNOW FOR 40 YRS!!! I'm predicting, around 150+/-15 psi!!! And I'm not going to worry about the necks expanding with that pressure range! I will seat bullets in formed cases without the primer and powder which will allow controlled, conditioned, compressed air into through the flash hole!!! The bullet will be directed into a 1/2 water filled 55 gallon barrel!! The case will set inside a 1-1/2 Schedule 40 black pipe direct toward the water!! I'll design the simple pneumatics plumbing (napkin drawing, 30 yrs of cadd is enough) with fine filler, dehydrator, dry isolation tank, sensitive regulator, back check valves, needle valve for really slow flow control, and a peak pressure gauge!!! If this works, I'll test all cases and set back case that fall out of a spec from the initial testing!!! Plus, I will have a tool to play with for testing class interference fit!!! Could save a lot of time at home testing, than range testing and save money in powder and primers, offsetting the investment costs!! But the range testing (targets) will determine what works, and what fails!!!

This could be a fun project using my robotic machine design knowledge from my previous life as a industrial Physist and Process Engineer!!! Reminds me of the $750,000 4 headed acid fillers that evacuated the air out of the battery cells, checking for pinhole leaks, before dumping the chilled acid and performing 3 vacuum purging cycles to totally saturate the cell packs!!! That was one fun project in designing, testing, installing, qualifying, and certifying!! And, operating it on 1 shift, out produced 3 other 2 headed hand loaded acid filler running on 2 shifts!! Plus, the leak checkers required on the 3 other production lines required 12 man hours!!! One operator running that one computer controlled (Allen Bradley) filler (8 man hours), was out producing 3 other acid filler and 3 leaker checkers (60 man hours)!!!! Yeah, around 2,500 batteries daily on one shift!!! Around 40 second cycle time with 4 batteries per cycle if there was no major hiccups further up the production line!!

 

[Longrange57]

As mentioned in post #67, it probably makes sense to assume a simultaneous event due to everything happening so fast. Folks who perform SAAMI specs all mention super high peak pressures in the brass before the bullet leaves. The brass would have to seal off in order for this first peak to occur. However, does it seal off before the bullet is gone? You would certainly think that the bullet would move forward and start engraving with such pressures. Many claim the second peak as bullet travels down the barrel can be actually less than first peak. Regardless of case mouth, midcase, or conformal configuration, this high peak pressure occurs. We would have to concur that with a really short neck (WolfPup) and bullet jammed, things would be different than another situation where bullet is jumped over 100 thou and very little bullet is in case. See slide 13 of Metz conformal paper. It states, Pmax is reached before projectile leaves the case. Some crazy things are happening from one rifle throat, neck clearance, and bearing surface contact, to the next. I still don't know the answer, and if I did, it probably would not change anything I'm doing. If you could accurately measure or capture with slo-mo.... these nanosecond events....., does it matter? I don't know the answer to that either!

 

[jackieschmidt]

Look at it this way. . .

If the neck does not expand before the bullet leaves the case, then why do we need "sufficient neck clearance" to achieve very good accuracy?

If the bullet left the case before the neck expanded we could get away with minimal to zero neck clearance, providing the case could freely chamber.

As much as I hate to bring it up, Virgil in the Houston Warehouse obtained phenomenal accuracy with virtually zero neck clearance and zero neck tension.

View attachment 1647705I've watched many ultra high speed videos where gas is coming out of the barrel before the bullet.

the interesting thing in the video is the cloud of gas leaving the barrel ahead of the bullet, and seemingly surrounding the bullet for about 4 inches out.

 

[X Count]

As much as I hate to bring it up, Virgil in the Houston Warehouse obtained phenomenal accuracy with virtually zero neck clearance and zero neck tension.

the interesting thing in the video is the cloud of gas leaving the barrel ahead of the bullet, and seemingly surrounding the bullet for about 4 inches out.

Yes I have read that as well. Tuned neck tension by rotating the case in sandpaper from memory? But is that no neck clearance or very little clearance?