Wildcat Neck Thickness-How much is too much?
- Thread starter JerryK
- Start date
B
Baron Graham
Guest
I am running a .30 Cal w/ .012" necks and a 6mm w/ .0105" necks and the shot quite well. Turn them until you get 100% clean necks!
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6.5fan
Guest
.015 is just right the necks don't dent too easy and when you you aneal them they are consitant.at .016-.0165 they are harder to aneal.
JerrySharrett
Senile Member
Before you start turning, figure out what your chamber neck diameter is, then turn your brass to where you will have about 0.002"-0.003" TOTAL diameter difference measuring the brass neck over a seated bullet.
Most all benchrest shooters set up for 0.00015"-0.003" total clearance in a given set of brass. (Not some on that lot at 0.0015" and some at 0.003" but pick a diameter and turn your brass to where is is all the same diameter within 0.0001-0.00015")
For example, a shooter. lets call him Tony B wants his 6mm chamber neck to be 0.263" diameter so he turns his brass to 0.2615" over a seated bullet. Another shooter, lets call him Jack N wants his 6mm chamber neck diameter to be 0.262" and his brass all turned to 0.259". Which is the best? On a given day either one could and often do win.
Most all benchrest shooters set up for 0.00015"-0.003" total clearance in a given set of brass. (Not some on that lot at 0.0015" and some at 0.003" but pick a diameter and turn your brass to where is is all the same diameter within 0.0001-0.00015")
For example, a shooter. lets call him Tony B wants his 6mm chamber neck to be 0.263" diameter so he turns his brass to 0.2615" over a seated bullet. Another shooter, lets call him Jack N wants his 6mm chamber neck diameter to be 0.262" and his brass all turned to 0.259". Which is the best? On a given day either one could and often do win.
Sounds like WSSM to me..
I hope you're making brass -before ordering the reamer.
Very thick brass has more springback variance, all else equal. This produces tension variance, and higher ES.
Also, stress relieving brass so thick(with a torch) could be tricky and actually increase variance if not done just right. That is, somewhere between inconsistant springback & annealed(ruined).
If you can set the desired chamber neck, I'd go .291, and turn to .013 thickness or less for loaded necks of ~.290.
If it's not YOUR chamber, well then I guess your choices are pretty darn few.
I hope you're making brass -before ordering the reamer.
Very thick brass has more springback variance, all else equal. This produces tension variance, and higher ES.
Also, stress relieving brass so thick(with a torch) could be tricky and actually increase variance if not done just right. That is, somewhere between inconsistant springback & annealed(ruined).
If you can set the desired chamber neck, I'd go .291, and turn to .013 thickness or less for loaded necks of ~.290.
If it's not YOUR chamber, well then I guess your choices are pretty darn few.
I'm making a short 6.5x284, about 48mm high. After improving it, it will be close to 57 water grains. At this stage it's 54.5 grains with a 25 degree shoulder and .300 long neck. I'm getting the brass close enough so I can order the reamer. I hadn't considered uneven tension variance with thick necks, that makes .013 sound right. I will probably run .0025 to .003 clearance, however, to be safe.
Shorty 6.5 X .284
Jerry -
Howdy !
Hey... you can try-out your wildcat idea, by runnin' a 6.5 X .284 case up-into a stock
.264 Win Mag FL die.
You can make a " perch " out of a standard.308 shellholder, a machine screw w/ a head of .less than 470"; and two jam nuts. Screw thread diam is chosen so that it fits through the central primer ram hole in the shellholder. One jam nut above and one jam nut below the shellholder, secure the machine screw in-place.
Brass to be formed is set atop the perch, and run up-into the case forming die.
I ran a similar wildcatting exercise, to come up w/ a new wildcat that would hold a nominal 44gr of powder. Use of just one die to verify case parameters and ease-of-froming... is one way to go.
Best of luck in your endeavors !
Regards,
357Mag
Jerry -
Howdy !
Hey... you can try-out your wildcat idea, by runnin' a 6.5 X .284 case up-into a stock
.264 Win Mag FL die.
You can make a " perch " out of a standard.308 shellholder, a machine screw w/ a head of .less than 470"; and two jam nuts. Screw thread diam is chosen so that it fits through the central primer ram hole in the shellholder. One jam nut above and one jam nut below the shellholder, secure the machine screw in-place.
Brass to be formed is set atop the perch, and run up-into the case forming die.
I ran a similar wildcatting exercise, to come up w/ a new wildcat that would hold a nominal 44gr of powder. Use of just one die to verify case parameters and ease-of-froming... is one way to go.
Best of luck in your endeavors !
Regards,
357Mag
357-- It was an old post of yours that explained your method that finally got me going. I had the short 284 idea for about 6 months, I even considered having a special forming die made to neck the brass down. When I saw your post, I took the plunge. It works perfect, but because the Lapua brass is so thick at the neck, I found it works better to use a 300 Winchester Mag full-length die so you don't squeeze the neck to much. There is serious resistance about halfway down, (when you hit the end of the factory annealing) so I had to anneal the shoulder and then neck down some more.
Thanks for your idea.
Jerry
Thanks for your idea.
Jerry
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4Mesh
Guest
Back in my early days of "Reamer design", I made a cartridge that began with a 416 Rigby and made a neck and shoulder out of the body brass. There were issues with the brass causing accuracy problems with necks that were .012 thick (30 cal cartridge) and the thing I found was that the shoulder was causing too many irregularities due to it's variations in thickness. The only solution I found to work on that was to make tooling and fixture the cases in a CNC, then internally back-bore the shoulder and shoulder to neck radius, along with turning the outside to match. This way, the shoulder brass was equal in thickness all the way around. It acted more predictable when run in a FL die. While the thickness wasn't perfect, it was so close it didn't matter, and the neck was centered up better and stayed much closer to perfect as the brass aged. That brass was fired a gazillion times (60+), and is still loaded today. It's also very straight. That cartridge, while superior to the WSM in many ways was a serious pain in the ass to keep shooting.
I don't know of a way to do an operation like that by hand, but, I think the process is important. Thick shoulder brass is problematic. Uneven shoulder brass is even worse. How to cut the inside of a shoulder to dimension without a CNC lathe I do not know. Case forming is an art, and takes many mistakes to learn. My toughest lesson to learn, use a factory cartridge...
.015 necks will be very tough to keep competitive.
I don't know of a way to do an operation like that by hand, but, I think the process is important. Thick shoulder brass is problematic. Uneven shoulder brass is even worse. How to cut the inside of a shoulder to dimension without a CNC lathe I do not know. Case forming is an art, and takes many mistakes to learn. My toughest lesson to learn, use a factory cartridge...
.015 necks will be very tough to keep competitive.
Just Ho'ley kuh'RAP!
That's perty extreme right there.... I like it. As was said in an earlier thread, "life's too short to do it the easy way!"
Although most often doing it the hard way LEADS to finding the easy way!
LOL
al
I've had similar experiences to Phil. Different solutions, but an equal PITA. (die, hardened pilot bushing, chucking reamer to perfect fit w the bushing, etc, etc.
See my remark on muzzleloaders in the 6BRX thread -- i.e., get the bullet centered, seal the chamber the same way with each shot, make sure the ignition system is as good as you can get it, and forget about the rest. As always, bullets, barrels (and a bit of luck) win matches.
See my remark on muzzleloaders in the 6BRX thread -- i.e., get the bullet centered, seal the chamber the same way with each shot, make sure the ignition system is as good as you can get it, and forget about the rest. As always, bullets, barrels (and a bit of luck) win matches.
Depends which one gives you .002 clearance in your neck. Other than the clearance issue the thickness ISN'T an issue IMO.
al
4
4Mesh
Guest
I have a couple of those too Charles. Early on, I also tried doing some neck work on the inside. I ran my case up in the die and left it there. Then I took a piece of tubing, about the right length for my reamer and put a plug in one end. That plug became the bushing the reamer used to stay centered. Then, I bored the other end of the tubing for a slip fit on the die, and of course used a drill on the reamer. The guide kept the reamer straight while I did the internal ream. Never did like it really and I think they lay on a shelf somewhere now.
Al, if you think thats' something, that 416 case was cut off at around 2.300 or so. Then before any forming was done, I internally profiled the case head and body so as to have perfect volumes and weights. Then went on to shoulder forming in a staged die set. I made several of those sets of form dies for guys with 30-404's back in those days. My dies were notorious for never loosigng a case by crushing them as happened with most peoples neck down operations. My necks on the 416 case were >.030 when the rough forming was done. The case went down from .550 to .350 to make a neck and shoulder. I Also made a set of dies for another cartridge based on a 416 and one based on a 50cal that was worked on by Ken Markle of K&M fame. His 416 brass was actually sent and re-drawn so the bodies were of a much thinner material. From there he formed a shoulder and that set was I think 6 stages.
In all those cases, keeping the shoulder brass pretty consistent was a major goal. Working with necks is easy.
And to the OP, I think in LR BR, you'll find most guys with 30 cals shooting necks in the range or .011 to 012. As you go down in bullet size, usually those numbers decrease. I've seen some guys with 6's shoot necks as thin as .007 or .008.
Al, if you think thats' something, that 416 case was cut off at around 2.300 or so. Then before any forming was done, I internally profiled the case head and body so as to have perfect volumes and weights. Then went on to shoulder forming in a staged die set. I made several of those sets of form dies for guys with 30-404's back in those days. My dies were notorious for never loosigng a case by crushing them as happened with most peoples neck down operations. My necks on the 416 case were >.030 when the rough forming was done. The case went down from .550 to .350 to make a neck and shoulder. I Also made a set of dies for another cartridge based on a 416 and one based on a 50cal that was worked on by Ken Markle of K&M fame. His 416 brass was actually sent and re-drawn so the bodies were of a much thinner material. From there he formed a shoulder and that set was I think 6 stages.
In all those cases, keeping the shoulder brass pretty consistent was a major goal. Working with necks is easy.
And to the OP, I think in LR BR, you'll find most guys with 30 cals shooting necks in the range or .011 to 012. As you go down in bullet size, usually those numbers decrease. I've seen some guys with 6's shoot necks as thin as .007 or .008.
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Phil, my situation was a little more complex than just neck turning on the inside. I pushed the neck/shoulder way back on a 8X68 case in making a ,30. Nice long neck. Since it is similar to Tooley's BooBoo, I call it Sort-of-Boo -- SOB for short.. At least it is well-named. Shoots fine, but no better than any other well-chambered 88-grains-of-water-capacity case like the ,308 Norma or Tooley's Boo. Lots more work, though.
The seam of the old neck/shoulder junction was a problem; no way to fix it by outside turning. So I rough-formed the cases in a die, fireformed without a bullet, reamed undersize with the die described above, fireformed again, then neck turned. About half the cases came out so there was no runout -- or little enough that a .001 dial indicator didn't flicker. By "runout" don't mean neck wall thickness, but runout of the entire case supported at the case web and mouth, measured at the neck.
I did a batch of 10 cases where I then lapped the inside of the neck, to get a better finish. "Why?" you say. Good question.
The seam of the old neck/shoulder junction was a problem; no way to fix it by outside turning. So I rough-formed the cases in a die, fireformed without a bullet, reamed undersize with the die described above, fireformed again, then neck turned. About half the cases came out so there was no runout -- or little enough that a .001 dial indicator didn't flicker. By "runout" don't mean neck wall thickness, but runout of the entire case supported at the case web and mouth, measured at the neck.
I did a batch of 10 cases where I then lapped the inside of the neck, to get a better finish. "Why?" you say. Good question.
M
mks
Guest
The use of thinner necks tends to increase the consistency of the chamber pressure at which bullets are released. As necks are work hardened by sizing and shooting, the yield stress of the brass gradually increases by up to about a factor of three over soft annealed. For typical sizing and seating conditions, the hoop tension in the neck is proportional to this yield stress and to the thickness of the neck and the seating depth. The chamber pressure at which the bullet releases is proportional to the hoop tension and the friction coefficient between the bullet and the neck. Thus, if the yield stress varies from one case to another due to material differences, number of firings, etc., then the thicker neck will vary more in chamber pressure at bullet release. For instance, a 0.015 neck would have 50% more variation than a 0.010 neck, all else being equal. Higher chamber pressure at bullet release tends to increase peak chamber pressure and muzzle velocity, so variations should be avoided for best accuracy.
I made up an Excel file that calculates these parameters. If anyone is interested, let me know. Sorry, no test results for validation yet. If I ever find the time...
Cheers,
Keith
M
mks
Guest
Al,
Me, too.
From previous posts, I think you have found that neck tension has an insignificant effect on muzzle velocity. I can't say that I disagree with you. But if you google "chamber pressure neck tension" you find a number of discussions, most of which support my simple-minded notion that anything that impedes the bullet increases combustion rate and pressure. Other effects, such as acoustic wave travel and static versus dynamic friction if the bullet is momentarily stopped as it begins to engrave notwithstanding, the speculation makes some physical sense, but says nothing about whether the effect is large enough to be of concern. My calculations show that a 0.308" bullet seated 0.2" into a clean dead soft neck would release at 1282 psi chamber pressure, while the same bullet in a work-hardened neck would release at about three times this pressure. This difference is probably large enough (maybe just barely) to see with a PressureTrace system, and if one were measuring muzzle velocity at the same time, conclusions about peak pressure and muzzle velocity could be drawn.
Cheers,
Keith