Bullet core stripping
- Thread starter Gene Beggs
- Start date
Gene Beggs
Active member
Hi Pat
That your 68 grain benchrest bullets withstand 3700 fps from a 10 twist speaks well for both the quality of jackets and your skills as a bullet maker.
Gene Beggs
Gene Beggs
Active member
Well said Dave
No one could have said it better.
Gene Beggs
I believe any stretching of the jacket is excessive. The problem with stretching the jacket isn't so much that the grip on the core is lost, but instead that the jacket wall doesn't stretch evenly. When material is displaced and and flows, the bullet becomes inbalanced and is no longer straight. Also, the material that moves work hardens, so the material hardness isn't consistant throughout the jacket. I don't think the "core stripping" theory plays into the stretched jacket scenario.
Start with good jacket and dies, keep everything as consistant as possible, make sure the jacket interiors and cores are clean, seat the cores so that the jackets are filled out but not stretched, rest the bullets for a day, point carefully and cull out any odd-feeling ones, and you'll have as good a bullet as the dies will make.
-Dave-
No one could have said it better.
Gene Beggs
Gene Beggs
Active member
Hi Don
Hope someone with more knowledge and experience than yours truly can answer your question.
E-mail me please, genebeggs@cableone.net
Later,
Gene Beggs
C
criver600
Guest
Lead build-up
Usually means your core seat punch is on the small side.
Usually means your core seat punch is on the small side.
J
J. Valentine
Guest
I agree with this , I have never liked excessive core seating pressure .
I like to seat with just enough pressure so that a proper fitted punch comes out of the jacket and the jacket stays in the die reliably.
Occasionaly a bit too much lub will cause one to stay on the punch but another swage will remove it .
Leaning on the press handle without any real idea of how much pressure is being applied does not appeal to me.
I adjust my press to go over center right at the point that the core is swaged with just enough pressure for the jacket to stay in the die.
I tried the sustained pressure and feel method and I made some good bullets with it but I just did not like it .
I cant say that one produces better bullets than the other. However I never used excessive pressure with either method.
However I can say that the over center method if adjusted properly puts less stress on the press and dies than compared to the inexperienced person just leaning on the handle with all his might.
Bullet swaging is a gentle art and if it takes too much force you are doing it wrong.
There is a risk factor with the over the center method and inexperienced swagers . If they adjust the core seating to have too much pressure before it goes over center and they expect it to go over center they may just lean on the handle to try to force it over center and lock the press up or bust something.
Again , it is a gentle art . It is a misconception that bullet swaging requires a lot of muscle on the press handle. That is brought about by the fact that bullet swaging presses are very strong and have high compound leverage.
In the big calibers and hard alloys the muscle required would increas but making 6mm bullets does not require Arny at the press.
The problem with forums is that on this thread alone their will be people using a whole range of different press and die systems but all addressing advice to the same subject.
You have reloading type presses, dedicated vertical swaging presses , dedicated horizontal presses , Hydraulic presses etc. all using slightly different types of dies and all having different capabilities as to what they can swage.
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Gary Sinclair
New member
Core stripping/core seating
Hi Guys! I've been reading this thread with a great deal if interest, since I've been making bullets for a few years NOW and have been struggling with this very issue. I'd really like to thank Gene for introducing the topic.
First let me say that what I believe Gene is referring to when he says "Bullet Stripping" is the loss of accuracy due to improperly core seated jackets, rather than bullets that completely fail. Core seating is without a doubt the most critical and subjective phase in the bullet making process. On a couple of occassions I have assembled several different combinations of bullets and then travelled to Lou Murdica's tunnel to test them. Using a rail gun in Lou's tunnel will immediately show the difference that different core seating pressures will make on accuracy! A little too much or too little pressure and the bullets just won't group!
Also, Gene is correct in his interpretation of Skip Otto's method of determining the correct core seating pressure by watching the cores initially shorten as the die is adjusted down and then reach a point where the core will begin to stretch. As the jackets begin to stretch, you have gone beyond the maximum necessary pressure and need to back off. Any more pressure will only damage the jacket. However, be aware that this technique only applys to Flat Base bullets.
When core seating Boat Tails, the first thing that will happen is that the core will immediately stretch when the die is adjusted down and will continue to stretch until it pops. Here in lies my problem, since my preference is to make Boat Tails. The point at which just the right amount of pressure is reached and when you go beyond that point is very subjective and does not lend itself to mechanical measurements as does flat base core seating.
I once asked Walt Berger about this and his responce was to purposely pop a jacket (in a carbide die) and measure the jacket, since this will be the maximum diameter that that die is capable of making. Then back the die off and start again, measuring the diameter of the jackets until you reach the original maximum diameter and then stop, since any further pressure will only result in stretching the jacket.
I've used this technique with fair success but I'm still not satified.
Now some how, Gary Ocock seems to be able to reach this ideal point as if by magic! I guess twenty plus years of experience could account for this!
I had a very unexpected and pleasent surprise during the receant Nationals at Phoenix when George Kelbly Sr. approached me and said that he had heard from Lou Murdica that I was struggling with my bullet making, (Thanks Lou!). Anyway, George offered to give me his personal instructions on core seating on my next trip to Ohio. What a sport when one of the great legends offers to share his time and information!!! Ya got to love these guys!
Anyway, just my two cents worth and again, I'd like to thank Gene Beggs for starting this thread!!!
Hi Guys! I've been reading this thread with a great deal if interest, since I've been making bullets for a few years NOW and have been struggling with this very issue. I'd really like to thank Gene for introducing the topic.
First let me say that what I believe Gene is referring to when he says "Bullet Stripping" is the loss of accuracy due to improperly core seated jackets, rather than bullets that completely fail. Core seating is without a doubt the most critical and subjective phase in the bullet making process. On a couple of occassions I have assembled several different combinations of bullets and then travelled to Lou Murdica's tunnel to test them. Using a rail gun in Lou's tunnel will immediately show the difference that different core seating pressures will make on accuracy! A little too much or too little pressure and the bullets just won't group!
Also, Gene is correct in his interpretation of Skip Otto's method of determining the correct core seating pressure by watching the cores initially shorten as the die is adjusted down and then reach a point where the core will begin to stretch. As the jackets begin to stretch, you have gone beyond the maximum necessary pressure and need to back off. Any more pressure will only damage the jacket. However, be aware that this technique only applys to Flat Base bullets.
When core seating Boat Tails, the first thing that will happen is that the core will immediately stretch when the die is adjusted down and will continue to stretch until it pops. Here in lies my problem, since my preference is to make Boat Tails. The point at which just the right amount of pressure is reached and when you go beyond that point is very subjective and does not lend itself to mechanical measurements as does flat base core seating.
I once asked Walt Berger about this and his responce was to purposely pop a jacket (in a carbide die) and measure the jacket, since this will be the maximum diameter that that die is capable of making. Then back the die off and start again, measuring the diameter of the jackets until you reach the original maximum diameter and then stop, since any further pressure will only result in stretching the jacket.
I've used this technique with fair success but I'm still not satified.
Now some how, Gary Ocock seems to be able to reach this ideal point as if by magic! I guess twenty plus years of experience could account for this!
I had a very unexpected and pleasent surprise during the receant Nationals at Phoenix when George Kelbly Sr. approached me and said that he had heard from Lou Murdica that I was struggling with my bullet making, (Thanks Lou!). Anyway, George offered to give me his personal instructions on core seating on my next trip to Ohio. What a sport when one of the great legends offers to share his time and information!!! Ya got to love these guys!
Anyway, just my two cents worth and again, I'd like to thank Gene Beggs for starting this thread!!!
Gene Beggs
Active member
Thank you Gary. It has been most interesting; hasn't it. And thanks again to everyone who has taken the time to share their expertise with us.
Gene Beggs
Gene Beggs
J
J. Valentine
Guest
I got a problem with this description above.
If I am reading this right that is.
The jacket will stretch before it pops.
So you would have to stop adjusting well before the maximum diameter that originaly poped the jacket before any stretch started .
No wonder some of my Bergers were blowing up.
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J
J. Valentine
Guest
I believe any stretching of the jacket is excessive. The problem with stretching the jacket isn't so much that the grip on the core is lost, but instead that the jacket wall doesn't stretch evenly. When material is displaced and and flows, the bullet becomes inbalanced and is no longer straight. Also, the material that moves work hardens, so the material hardness isn't consistant throughout the jacket. I don't think the "core stripping" theory plays into the stretched jacket scenario.
Start with good jacket and dies, keep everything as consistant as possible, make sure the jacket interiors and cores are clean, seat the cores so that the jackets are filled out but not stretched, rest the bullets for a day, point carefully and cull out any odd-feeling ones, and you'll have as good a bullet as the dies will make.
-Dave-
I agree 100%
Dave Short
New member
I get the distinct feeling that you're holding out on the type of incense you use.......probably just to protect an (unfair) competitive advantage. I do see though that you were specific about which bones are used from the (unfortunate) chicken ...Thanks.
-Dave-
John Kielly
Shari's fan club
Dave,
Wouldn't it be the same incense you burn when you're camping near cattle to keep biting insects away?
JOhn
I enrolled at several and attended none. Finally just gave up and "attended" Vietnam. I can't remember what I had for lunch but I'll never forget my Dad's words when my first grade report arrived. He looked at the report and then straight in my eyes and said..."Hell Fire son, you didn't even pass play period".
As I remember, lead build up on the punch comes and goes with different lots of lead. Not a minor problem at all. A bit of screen wire will get it off the sides of the punch quickly and anything that scrapes will get it off the business end. It's a real hassle. A small percentage of antimony seems to be the cure but I'm not sure about that.
definitions...
There are some things that I think need to be defined. Maybe everyone is not thinking along the same lines when they post here.
1) Does "stretching" of the jacket mean in the length wise direction or the circumferential direction?
2) Does "popping" refer to a length wise failure or a circumferential failure of the jacket?
3) Does core slippage refer to sliding between core and jacket or does it mean a shear or tension failure in one of the metals (probably the core)?
4) During core seating is radial pressure of the core out against the jacket always assumed to be same as plunger pressure against the core?
There are some things that I think need to be defined. Maybe everyone is not thinking along the same lines when they post here.
1) Does "stretching" of the jacket mean in the length wise direction or the circumferential direction?
2) Does "popping" refer to a length wise failure or a circumferential failure of the jacket?
3) Does core slippage refer to sliding between core and jacket or does it mean a shear or tension failure in one of the metals (probably the core)?
4) During core seating is radial pressure of the core out against the jacket always assumed to be same as plunger pressure against the core?
J
J. Valentine
Guest
What I have experienced is when excessive core seating pressure is applied with a neat fitting punch then the jacket is sort of pushed and extruded out of the die lengthwise making it grow longer and if enough pressure is applied then eventually the jacket breaks or the lead blows past the punch because the jacket has thinned.
I can't say if there is any radial expansion that adds to this effect or not.
Can't say what internal pressures may or may not be.
I can't say if there is any radial expansion that adds to this effect or not.
Can't say what internal pressures may or may not be.
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-As you 'load' the core during the seating process, the jacket initially expands outward to the i.d. of the core seating die. At that point, the jacket begins to stretch along it's length as more seating pressure is applied.
-This is a circumfrential failure of the jacket as a result of excessive lengthening.
-I consider the term 'core slippage' to mean that the jacket rotates around the core.
-I'm not sure how the two coorelate.
It's hard to quantify all these areas and then apply them to everyones bullet making operation. Core seating pressure is going to feel quite a bit different from setup to setup depending on the type of press used and the leverage they have. My press is going to have much more feedback compared to someone who uses a Rockchucker with an extended handle, for example.
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Jerry Dailey
Southron
Stephen,
He may talk like the rest of us hillbillies, but he must have got a good education somewhere. I have NEVER met a smarter man. Just wish I could be arround him as much as in past years. He 'splained difficult stuff to me in a way that even I could understand: but he also could use those $10 words with the best of 'em. Most important thing I learned is "dont try and make it more complicated or difficult than it really is" Thank Wilbur
Just a couple more things that I feel are important and then I'll shut up.
-It's important to know the exact dimension of your core seating die.
-It's important to have a good assortment of core seating punches in .0005 or .001 increments to fit the various lots of jackets.
-It's important to monitor lead bleed by between the jacket and the core.
-It's important to not have cores fit to tightly in the jackets.
That's more than a couple.
-It's important to know the exact dimension of your core seating die.
-It's important to have a good assortment of core seating punches in .0005 or .001 increments to fit the various lots of jackets.
-It's important to monitor lead bleed by between the jacket and the core.
-It's important to not have cores fit to tightly in the jackets.
That's more than a couple.