Results of Bullet Testing

[Rick Teal]

I did some bullet testing a few weeks ago, which I will summarize here, and I welcome any comments you may have.

I was testing bonded .35 calibre bullets in a wet phone book medium.  My bullet weights were 200, 220 and 245 grains.  My set-up was very poor, and I wasn’t able to fire as many shots as I’d hoped.  My rifles were a .35 Remington, a .358 Winchester, a .35 Whelen and a .358 Norma.

First, a little background would be in order.  I am not a fan of narrow wound channels, retained weight or exit wounds.  I believe that the perfect bullet would provide some initial shock to the animal to stun it or put it down.  The bullet would then resist expansion long enough to penetrate into the internal organs where it would rapidly expand and then fragment causing maximum tissue damage to the internal organs.

My bullet design incorporates a hollow tip made from an inverted jacket that is covering a small core inserted into the bullet’s primary (bonded) core.  I’m using .030 main jackets and .015 tips.  The intention is for the tip to collapse on impact causing the bullet tip to open a certain amount to provide the initial shock.  The remnant tip, the small core and the bonded major core would then act to temporarily impede expansion while the bullet penetrates the body wall and possibly bone.  The bullet would then expand rapidly and then fragment, causing maximum internal damage.  I’ve shot two deer with non-bonded versions of this bullet, and in both cases, the animals dropped like rocks with their lungs shredded, and there were one-inch exit wounds (not expected). :shock:

In every case, during my recent testing, there were indications of impact shock from the collapsing tip, with cratering at the point of impact.  Several of my tests, however, resulted in the bullet tumbling shortly after impact.  :?  This seemed to happen only with the Remington and Winchester rounds, and at lower velocities.  I believe that this was the result of the violence of the initial impact and collapse of the tip.  It seems that the lower velocity rounds weren’t able to overcome the initial upset.  The higher velocity loads seemed to maintain their stability inside the expansion medium.  I have been shooting these bullets at paper for a few years, and have never had any indication of key-holing, so the upset had to happen after impact.  

A bullet that tumbles inside the animal isn’t necessarily a bad thing – after-all, that’s one of the things that initially sold the M16 to the US military.  It’s simply unexpected and not what I anticipated.  The wound channels were 2 to 3 inches for most of their length, and quite deep averaging about 19 inches.

Otherwise, the wound channels seemed to be about what I expected.  For example, my 245 grain bonded at 2825 fps gradually expanded to about one inch at a depth of 4 ½ inches, and then went quite rapidly to 4 inches in diameter at 6” of penetration.  It then held an average diameter of 6 inches for the next half-foot of penetration.  The wound channel then declined quite rapidly to where the bullet fragments stopped at 16“ from the point of impact.

I encountered one other thing that concerned me.  In two cases, when I picked up the base of the bullet with a lead remnant in it, I was able to separate the lead from the jacket with the force of my thumb.  :shock:  This indicates that the base wasn’t bonded, however, other bullet fragments (from the walls of the same bullets) still had lead bonded to the copper jacket.  It’s my assumption that the “core bond” flux wasn’t present at the base of the bullet when I melted the core inside the jacket with my propane torch.  

I’ve been using the method recommended by Corbin of inserting the core into the jacket, then putting a couple of drops of flux in on top of the core.  For a while I tried putting one drop of flux in first, but I found a couple of cores shooting out of the jackets  :oops: propelled by boiling flux, so I discontinued the practice.  Has anyone else been faced with this problem?  I’m thinking of going back and trying the “drop-in-first” method again.  Maybe it’s common for the bond to break down at the base of the bullet?

Thanks!

[contendernut]

Rick,

Dave Corbin makes a cup tipped core swage punch for jackets that are thicker at the base to prevent trapped air.  This might help get a better bond at the base.

[talon]

Thanks, Rick, for the description of bonded bullets, and especially concerning the use of a jacket within a jacket. I believe the stile you highlight is about as much as one would want in hunting thick skined, big boned game. As far as cores poping out under heat ( or for that matter when seating the cores) the core/jacket match is somewhat critical. Yes, Virginia, not all jackets and cores, or core seating punches are matched, causing no end of grief to us hobby swagers that continually experiment or otherwise have to use various lots of jackets. Take the .35 caliber. You can get strait and/or sloped walled jackets with a wall thickness of .014, .018, .020, .030, and .035"... and possibly others. To use these you should have to have core making die(s) that form a core =/- .003-.009 less in diameter than the ID of the base of the jacket. If not, the core won't fall to the heal of the jacket: it will jam on the jacket wall before reaching the bottom forming an air pocket (or steam pocket in the core bonding exercise).  This not only prevents air entrapment (poping), but  allows the maximum range of bullet weight. For instance, if your core just barely fits, all the way to the jacket bottom, of a .035 walled jacket, it would be so thin in being used in a .014 jacket that you couldn't fill up that jacket with enough lead to make a heavy bullet in that jacket (remember, seating really long cores in a jacket is a good way to make the die maker rich as he'll be selling you more punches for the ones you will probably break in this procedure). Another associated difficulty with using jackets of different wall thicknesses is the fact that you will need a different sized punch to fit each one, or take a chance of the swaged core/jacket not attaining the full caliber of the die. Remember, it is in the CS die that the full diameter, or at least 99.99% of it, is attained. The PF die only concentrates on putting the ogive on the nose. So, the bottom line: make sure your core drops all the way to the bottom of the jacket when core bonding. If it doesn't, it will pop up, melt, run over the side of the jacket, and weight control is out the window, as well as being able to easilly swage the core/jacket to proper diameter. Been there, done that. By the way, I use a shot glass with a little core bond chemical in it and a Q -tip to only swab the entire inside of the jacket before droping the cores in. Also use some of those 'bricks' Corbin Co. markets to hold the jackets while being flamed. Also, I learned that if the core doesn't drop all the way to the jacket's bottom, to give it a crank or two with one of those Corbin knurling tools. Not for huge production runs, but a neat technique for the hobbyist! ( costs less than a 2nd core die, too). There's a caution here: definately wash those bonded cores right after the bonding operation: that chemical will rust your dies, and if you use the Corbin brick, any of its powder  remaining on the jacket is very abrasive to your dies.

[Lead pot]

Rick.

Sounds like you did some extensive testing.I tryed the same testing once,with dual jackets and core bonding.
I found a better way for me that worked real well for heavy .458 bullets.I used a .35 jacket 7/8 long.then I cast cores made from Monotype that has a BHN of 28 or 29 very hard stuff about 6 points harder then linotype,I corbonded 3/8 to the bottom of the jacket.I dont use that corbond flux I dont like it and it is to expencive I use a flux used on refrigeration called Engelhard,It's a liquit flux,you dont need much just dip the jacket and drain it off, drop in the core and melt it,and let it cool,drop in the pure lead(reflux the jacket and lead)and remelt the pure lead so it bondes to the Monotype.This takes a little heat controle you dont want to remelt the Mono to much again.Let the cores cool and wash off the flux with hot soapy water.,they might turne a little dark but you can clean them in the tumbler.
Rick this is a little time consuming but it workes.I would not go through this,but in the passed you could not buy a comercial .458 bullet with controlled expancion that size.This bullet is a little nose heave but it flyes good.
One more thing on your core seperation It may have been a cold solder joint or when you get the jacket to hot the flux turnes into a oily substence and the solder just wont stick.I always stressed that to my Plumbing apprentice.I made him clean the copper pipe and touch the cleaned pipe and fitting with his dirty fingers then solder it then cut the soldered fitting in halve flaten it with a hammer and seperate the joint and you will see were the fingers touched the pipe.The same with over heating the copper and flux,It just wont run.
Lp.

[Rick Teal]

Thanks for the comments guys!

The jackets I had the problem with popping cores were tubing jackets I made myself.  These were straight walled .032 jackets (approx), producing an internal space of a little under .292, and I use a .280 core.  The set was designed by Corbin, so I tend to trust the core/jacket diameters.  I'm starting to use cores from Butch Hairfield at .030, which should provide even more space.  I believe that these are straight walled as well - at least they look to be (I'll go downstairs and check when I sign off).

I believe the problem with core bonding at the base is either lack of flux at the base of the bullet or insufficient heat at that point.

Talon:

I think I'll try that shot glass/swabbing method, and see how it goes.

Lead Pot:

Does this Engelhard flux bond the lead cores to the copper jacket?  If it does, where can I get some?  A plumbing supply place?

Rick

[Lead pot]

Rick.
You can find it in plumbing supplys. almost any soldering fluxes for copper tubing will work.
I like rosin flux but it is hard to find it is used in electronics mainly,It wont corode like the acid based flux will.When I melt my cores and after they set i wash them in soapy water so they dont corode and are easer to polish in the tumbler.I do this before I swage the bullet.Most generly I use type L copper .35 wall,but I also use M copper tubing.
Rick were people have problems with solder not flowing at the base is they have the jacket sitting on a thick steel plate and that acts as a heat sink which keeps the base of the cup cool.I use a thin alumineum plate and train the flame on it to heat it before I heat the cup.The trick is dont over heat it and burn the flux.The flux will run as soon as heat hits the jacket and cover what you wight have missed when applying the flux.Johnsom past flux is good also for this job.
Lp.

[Donna]

Hello Rick and all,

You can also find the rosin flux at electronic stores, your local Fry’s will have a very good supply of flux, and you don’t have to worry about getting any acid based flux. The paste type fluxes are easy to apply with what is called, ironically, an “acid brush” but the brush does not have any acid and you can pick up a supply of these brushes at the same time as you pick up the flux. Good swaging and shooting.

Donna