Questions using expanding mandrel

[Sheldon N]

My approach is to size the case and bump the shoulder with a full length Forster sizing die with the expander ball removed. I had Forster custom hone the neck of the FL die so that it is 0.0035 smaller than the OD of a loaded round, only costs $12 extra when you order the die. Then I run the brass over a Sinclair Gen II expander die with a carbide mandrel that is 0.002 under bullet diameter. I get very consistent sizing dimensions, very low runout ammo, and have been happy with the process. I'm using unturned brass so I prefer to have any inconsistency in the neck pushed to the OD by a mandrel.

 

[ImBIllT]

My approach is to size the case and bump the shoulder with a full length Forster sizing die with the expander ball removed. I had Forster custom hone the neck of the FL die so that it is 0.0035 smaller than the OD of a loaded round, only costs $12 extra when you order the die. Then I run the brass over a Sinclair Gen II expander die with a carbide mandrel that is 0.002 under bullet diameter. I get very consistent sizing dimensions, very low runout ammo, and have been happy with the process. I'm using unturned brass so I prefer to have any inconsistency in the neck pushed to the OD by a mandrel.

I definitely like this approach with un-turned brass. I do however wonder if the result would be equal, or if it would be inferior, if you simply used an expander ball .002" under bullet diameter in the Forster sizer. If the same result coul be obtaine with one step less, then it only makes sense. I turn necks on match guns, so the only thing I run over an expander is hunting guns, but I've not identified any noticeable accuracy issues from condensing the steps. I can't determine that with my match guns because my necks are turned.

 

[Josh11]

I am shooting a 6.5x47 Lapua. 130 Norma GT, and 37.2 Varget. I'm shooting in PRS style matches. Some matches go out to 1400 yards.

 

[Bart B.]

Whatever the case, .5 MOA ammo through a test gun in a machine rest under what are probably good conditions is NOT the ammo I want to shoot in a match. If the best the ammo can do is .5 MOA, then because I am an imperfect operator shooting in adverse conditions, then I will be shooting larger than .5 MOA groups.

Well, that's what the NBRSA multi range 150-shot aggregate (average) shows being .3355 MOA as some of the fifteen 10-shot groups were .5000 MOA or bigger. Others were in the zeros and ones. They were shot in the best of conditions.

The best (smallest) 10-shot groups Sierra's shot in both their California 100 yard and Missouri 200 yard ranges are in the ones and zeros.

 

[Sheldon N]

I definitely like this approach with un-turned brass. I do however wonder if the result would be equal, or if it would be inferior, if you simply used an expander ball .002" under bullet diameter in the Forster sizer. If the same result coul be obtaine with one step less, then it only makes sense. I turn necks on match guns, so the only thing I run over an expander is hunting guns, but I've not identified any noticeable accuracy issues from condensing the steps. I can't determine that with my match guns because my necks are turned.

That certainly would be an option and probably a good one. I've heard some people say that the downward force of a mandrel die is less likely to induce runout than the upward pulling force of a expander ball. Probably not an issue if you've got the correct size neck on the FL die and the expander ball isn't doing much work. As far as ease of use and multiple steps, I'm doing mine on a Dillon 550 with floating dies. Deprime station 1, FL size station 2, carbide mandrel station 3. It goes very fast, ~ 8 minutes to run through 100 cases.

 

[Bart B.]

Internal and external ballistics are too complex to be calculated exactly.

I think most people would be amazed at how precisely a bullet's exit can be calculated for where in the muzzle axis 360 degree swing cycle they leave at. And learning all bullets leave in just a few degree spread in that cycle.

One top quality barrel maker has a page on his web site where you enter your 308 Win barrel's profile dimensions, rifle weight and center of mass below bore/recoil axis. Then the bullets barrel time will show on the calculated muzzle axis angle where it departs at.

 

[jsthntn247]

I think most people would be amazed at how precisely a bullet's exit can be calculated for where in the muzzle axis 360 degree swing cycle they leave at. And learning all bullets leave in just a few degree spread in that cycle.

One top quality barrel maker has a page on his web site where you enter your 308 Win barrel's profile dimensions, rifle weight and center of mass below bore/recoil axis. Then the bullets barrel time will show on the calculated muzzle axis angle where it departs at.

I'd like to check that out. What barrel maker

 

[Bart B.]

Border Barrels; made in Great Britian and as good as any made any other place.

Here’s the page from Border Barrel’s Geoffery Kolbe modeling approximate barrel vibrations to determine bullet exit angle based on barrel time. Typical barrel times for 308 Win ammo is 1.1 to 1.2 milliseconds; depends on how fast the load pushes the bullet and how long the barrel is. Muzzle velocity changes about 25 fps per inch of barrel length for the 308 Win. It shows what happens in general terms but what actually happens for a given rifle, ammo and shooter will be different because different rifle and ammo's used and the shooter's hold and position with the rifle has small changes in where the muzzle points when the bullet leaves; the reason why four people shooting the same rifle and ammo will have different sight zeros for target range.

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm

This one shows how the muzzle vibrations are measured to compare against bullet exit time. It’s the means for all barrel muzzle weights moving back and forth to change the muzzle axis frequency it whips at and so changing the bullets departure angle:

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

Most interesting is Kolbe’s reference to Mr A. Mallock ("Vibrations of Rifle Barrels", Proceedings of the Royal Society, Vol. 68, page 327, 1901) book printed over a century ago explaining why the British 303 ammo’s huge muzzle velocity spread was compensated for to shoot more accurate at longer ranges than medium ranges. The good stuff can be seen at:

https://ia800701.us.archive.org/6/items/philtrans05900167/05900167.pdf

Here’s Varmint Al’s web site page listing these excellent views on barrel vibrations and bullet exit times:

http://www.varmintal.com/ashot.htm

On the left side, click on each of these screen buttons to see details of how expensive and precise mechanical engineering software calculates how barrels vibrate and when bullets exit their muzzles; along with other interesting stuff about how the whole rifle whips and wiggles as the bullet goes through the barrel:

Fluted Barrel Analysis
22LR Rifle & Tuner
Esten's Rifle & Tuner
Light Rifle & Tuner
Barrel Harmonic Movie
Barrel Tuner Analysis
6PPC Barrel Dynamics

 

[jsthntn247]

Thanks Bart. Went to the site and got this graph. No clue what it means though.

 

[Bart B.]

Went to the site and got this graph. No clue what it means though.

Here's how to use that graph.

The sine wave shows how the muzzle axis swings up and down from the barrel's straight axis before the round fired.

If the bullet takes 1.2 milliseconds to leave the barrel, look at the bottom scale to find the 1.2 millisecond mark. Go up from that mark to where the sine wave crosses very close to the - 20 MOA point. That's the angle the bullet leaves relative to the muzzle axis with the barrel at rest.

Faster bullets leave sooner; if barrel time is 1.1 millisecond, it leaves sooner on the muzzle axis down swing about 10 MOA above the barrel's at rest angle.

Does this help?

 

[ASbobcat]

Here's how to use that graph.

The sine wave shows how the muzzle axis swings up and down from the barrel's straight axis before the round fired.

If the bullet takes 1.2 milliseconds to leave the barrel, look at the bottom scale to find the 1.2 millisecond mark. Go up from that mark to where the sine wave crosses very close to the - 20 MOA point. That's the angle the bullet leaves relative to the muzzle axis with the barrel at rest.

Faster bullets leave sooner; if barrel time is 1.1 millisecond, it leaves sooner on the muzzle axis down swing about 10 MOA above the barrel's at rest angle.

Does this help?

"......four different shooters using the same rifle and ammo will have four different hold points......."

So tell me about the usefulness of all these calculations.

 

[fguffey]

The industry standard for how tight bullets are held in case mouths is release force; or sometimes called extraction force. It's the force needed to push the bullet out of the case. 20 pounds has been the arsenal standard for M118 7.62 NATO match ammo. As much as 60 pounds for service ammo.

.002 tension is fine for hunting ammo and semi-auto, but .001 generally gives much more consistent accuracy in a single shot.

While a dimensional tension (.002" is very popular), that much interference fit between bullet and case mouth diameters does not give the same neck grip force all the time. It'll be less with softer case brass.

And then then there is bullet hold, I am the fan of bullet hold, I want all the bullet hold I can get; because? I do not have a tension gage that measures tension, all of my tension gages measure in pounds. And yes, the term 'interference fit' finally gets mentioned. And then there is crush fit, I have used crush fit, there were times I used tons of crush fit, if I wanted to know how many tensions I was using I would look up and read the gage on the press, and then? As the two pieces came together the gage would slowly drop.

002 tension is fine

Again, I do not have a tension gage that measures tensions because all of my tension gages measure in pounds so? How much bullet hold does the neck have with 2 tensions. And then? There was grip, bullet grip, how many tensions are in 4 bullet grips.

F. Guffey

 

[Bart B.]

And then then there is bullet hold, I am the fan of bullet hold, I want all the bullet hold I can get;

I want the least amount that allows handling and loading to not change bullet position in the case neck. Extraction force will have the smallest spread and that contributes to uniform muzzle velocity spread.

 

[Bart B.]

"......four different shooters using the same rifle and ammo will have four different hold points......."

So tell me about the usefulness of all these calculations.

My original statement is: “... the shooter's hold and position with the rifle has small changes in where the muzzle points when the bullet leaves; the reason why four people shooting the same rifle and ammo will have different sight zeros for target range.” I don’t know what your “hold points” are referring to, except if it’s the way they hold the rifle, then that’s OK.

First off my bat, these finite element software programs (used by mechanical engineers figuring out how things vibrate at different frequencies) helps some people understand how barrel tuners sliding near the barrel muzzle change the frequency the muzzle axis whips vertically at so compensation for muzzle velocities makes slower bullets strike the same place as faster ones. Their difference in bullet drop at target range is minimized. The Browning BOSS system, for example.

Second, it helps some people understand that their use of the term “harmonics” actually involves the fundamental low resonant frequency (a few dozen cycles per second) a given barrel shape has plus its several harmonic frequencies (8 or more up to several thousand cycles per second). The muzzle axis frequency mostly effecting bullet departure angle is about 3 to 4 times that of the barrel’s resonant frequency of 80 to 100 cycles per second or thereabouts

Third, people can see how different holds on the rifle change the center of mass offset from the recoil axis causes the bullets to depart at different angles to the original line of sight. The barrel is wiggling while the bullet goes through it.

Fourth, it helps folks learn why their zeros for a shouldered rifle and ammo obtained from a benched rifle atop bags is 1 to 2 MOA to the side compared to zeros for field positions such as standing, kneeling, sitting or prone.

Then there’s the group who believe the barrel is motionless and does not move at all until the bullet exits. All this harmonics stuff doesn’t matter because they think the bullet is gone before the barrel moves in any way.

 

[fguffey]

I want the least amount that allows handling and loading to not change bullet position in the case neck. Extraction force will have the smallest spread and that contributes to uniform muzzle velocity spread.

I can control the amount of clearance between the chamber neck and case neck, there is one factor I have trouble with, when the hot high pressure metal cutting gas expands the case expands and fills the chamber, that includes the neck meaning the neck expands before the bullet leaves. I would have to say that could be violent and centering the bullet could be complicated when all that hot high pressure escaping gas passed the bullet. I know at one time reloaders did not know some of the gas escapes past the bullet, there are a few that have know that for many years. A photographer took a picture of a bullet leaving the barrel, the picture won a prize for art sake and then someone from an arsenal saw the picture years later and had to rethink the sequence of events after the trigger is pulled.

F. Guffey

 

[dmoran]

And then then there is bullet hold, I am the fan of bullet hold, I want all the bullet hold I can get; because? I do not have a tension gage that measures tension, all of my tension gages measure in pounds. And yes, the term 'interference fit' finally gets mentioned. And then there is crush fit, I have used crush fit, there were times I used tons of crush fit, if I wanted to know how many tensions I was using I would look up and read the gage on the press, and then? As the two pieces came together the gage would slowly drop.

Again, I do not have a tension gage that measures tensions because all of my tension gages measure in pounds so? How much bullet hold does the neck have with 2 tensions. And then? There was grip, bullet grip, how many tensions are in 4 bullet grips.

F. Guffey

F. Guffey - again Thanks for the link you have often given to LE Wilson !.!.!
On a note and high-lighted below from that link you leave, LE Wilson does not use "hold" as you you do to describe neck tension. Like reloaders, they understand neck tension also.

 

[Bart B.]

I think "neck tension" with dimensional units is a poor descriptor for how tight case necks grip bullets. Here's why.

Turn 11 case necks also their thickness ranges from .007" to .017".
Size them so all their mouth diameter is .002" smaller than bullet diameter.
Which case neck wall thickness grips bullets the tightest?

Will soft brass case necks grip bullets with the same force as hard brass; all other things equal?

Do expander balls size case mouths to their exact diameter?

Military small arms ammo has a release (extraction) force spec for so many pounds is required to push or pull the bullet out of case necks. No such specification in SAAMI specs.

Machine shop term for pushing something into a space a tiny bit smaller than it is called an "interference (or press) fit." A couple thousandth inch interference fit will have a big range of extraction force needed to separate them; a lot for a bullet in a hole of hardened steel, very little for a hole in a marshmallow.

 

[spife7980]

And yet changing the diameter is still the easiest way to change your tension. And I agree that its not "tension" proper because its not the force transmitted by a sting but it is the vernacular used, connotative vs denotative.

Sure its not a linear change with all of the variables involved but it does allow you to at least keep that one parameter constant. Sure they get harder each firing and the force exerted will vary but thats also why we anneal, to deal with that additional particular change. While we may not know exactly what the hardness or elasticity actually is empirically but we can at least return it to a consistent state and thats all that is really necessary- consistency.

If using dimensional units is a poor choice then I propose you offer up a better one short of equipping an industrial level lab measuring each individual pieces brass hardness and then using a different properly calculated bushing for each individual piece. Seems a bit foolish to go to those steps when you could just select a bushing .002 under loaded diameter that pretty much every one seems to be a good choice, no?

And does the military have those requirements for the sake of accuracy or is it because they dont want their bulk ammo all arriving with the bullets pressed back into the cases?

 

[fguffey]

I think "neck tension" with dimensional units is a poor descriptor for how tight case necks grip bullets. Here's why.

I agree, one more time, I have tension gages, none of my tension gages are marked off in tensions. All of my tension gages are marked off in pounds, and then there is the one that measures deflection in thousandths and in pounds.

I have a stack of conversion graphs and charts, I do not have one that will get me from tensions to pounds.

F. Guffey

 

[Jay Christopherson]

I agree, one more time, I have tension gages, none of my tension gages are marked off in tensions. All of my tension gages are marked off in pounds, and then there is the one that measures deflection in thousandths and in pounds.

I have a stack of conversion graphs and charts, I do not have one that will get me from tensions to pounds.

F. Guffey

oh, FFS. Get over it. If you *really* need it, I can give you a Google search that will provide thousands of examples of nomenclature that is not "technically correct", yet somehow, people still manage to communicate their meaning. Out of all your 1500+ posts, at least half are some variation of this stupid post. Just stop it already.