Concave Bases on Recovered Boolits ?

[41mag]

I did a bit of shooting this weekend, and I used my new boolits trap to recover the boolits. Nothing fancy just some 6 gal buckets with screw on tops. I fill them with some sandy loam soil and as I fill them I break it up and pack it in so that there is little to no space left. They work really well and are about as cheap as you can get.

Anyway I recovered the 15 rounds I put into the one bucket. Most had blown off the HP, which wasn't a big deal. The thing I found odd was that about half of them had a concave base.

The boolits were poured from straight Iso core alloy. They were the MP-258 and were loaded over 15grs of AA-9, with Wolf LP primers.

I was just wondering if this might be somewhat a tell tale sign of the load being to much for he alloy?

Could this simply be from the impact into the bucket lid and soil?

The only reason I ask is this is the first time I have noticed this on anything I have recovered. As far as leading int eh barrel none what so ever, and the accuracy was great. I'm still learning about the different alloys and load pressure, so if this is something I need to watch for in my loads I will keep an eye out for it.

Thanks.

[GP100man]

I`ll take a shot !

As the nose opens & the forces push on the outer layer of the boolit pushin the outside back ,at the same time as the nose is openin or peelin off it draws alloy from the center thus aiding the concave affect ya see. the softer alloy will show this good ,ya iso alloy is runnin around 12 bhn?

I use wet sand or news paper soaked to a pulp to simulate soft targets .
& I reaize you were just catchin ya lead.

[.22-10-45]

Hello, 41mag. Nearly all of my fired cast bullets..from .22 Hornet up thru the heavy .40's I use in my single shots..gas checked, or plain-based, show this concave base. If you think about it, your forcing a groove dia or greater piece of lead thru a bore with splines from .003" to ? deep...that metal has to go somewheres.

[303Guy]

It happens right in the throat. It could cause accuracy problems because of uneven 'cupping'. There is drag on the outer surface of the boolit as it enters the bore plus pressure is concentrated toward the centre (I think). I think it important to reduce that effect and this might require harder alloys or a rebate at the base of the boolit. Again - I think.

http://i388.photobucket.com/albums/oo327/303Guy/22gr2205214IMP006-1.jpg
http://i388.photobucket.com/albums/oo327/303Guy/Baseedgefeatheringandcupping.jpg

It's the unevenly 'feathered' edge of the second one that concerns me. I've had more cupping than this but couldn't find a pic in a hurry. That first one is the solution I found with a small rebate. Those white bits are bits of paper patch. Both examples were paper patched.

[runfiverun]

your right about the pressure being higher in the center than it is on the outside edges.

[41mag]

GP100man,
Well that was my initial thought as well, just the bullet evolving into that form from the expansion occurring as it rolled back. That would explain why the solids don't show it. Yep the BHN is right in that area. These were simply some preliminary loads using up a last bit of that can of powder. They were also the first HP's I have shot form this mold. Everything else has been the solid version.


303Guy,
The second picture just about nails it. Since this was only some preliminary load testing I will be keeping an eye on things in the future. Like i mention above, I just had a bit of powder that needed to be finished off and this was a good excuse.

I hate to harden it up much, but if further testing proves it needs it I can gradually work it up. I have poured both a 44 and 45 caliber in similar design and not noticed this, which was what concerned me. I just didn't want to be pushing the things overly fast for that particular allow.

Like I said, I'm still learning the cast boolits, and when something unusual pops up, you can bet I am going to ask about it.

Thanks.

[SciFiJim]

41mag,
Search the terms "trailing edge failure" using the forum search feature. There are some very interesting (and very in depth) discussion.

[popper]

Pressure is NOT higher in the middle, you are just extruding the lead into the bore. Push through sizer does almost the same thing. That is why you want a small channel above the GC, else it might get pushed off. What do the grooves look like? If not V'd, iso is probably hard enough.

[geargnasher]

Pascal's law dictates the pressure will be even on the base. The drag in the throat during engraving does it, and more may happen when passing through the bucket lids.

Gear

[runfiverun]

you guy's are correct i said that wrong, completely wrong.
gas pressure IS even in all directions,other forces are dragging on the lead while it is still being forced forward.
this is one of the things that a gas check covers up/fights.

[popper]

What did that old ventriliquist say -soall right, soOK. Center is in compression, sides are in shear. Shear strength is only 50-75% of compression strength.

[geargnasher]

you guy's are correct i said that wrong, completely wrong.
gas pressure IS even in all directions,other forces are dragging on the lead while it is still being forced forward.
this is one of the things that a gas check covers up/fights.

I'm sure, like me, you've even seen concaved gas checks if the launch pressure is high enough. There's definitely a lot of drag shearing back the sides.

There can be pressure waves or fronts within a closed system, such as what causes detonation in internal combustion engines and also chamber ringing with fillers tamped against a powder column, but the force is equal across the area of the moving front. Moving gas columns have a lot of inertia in and of themselves which is why "velocity stacks" were used on some carbureted race engines with huge camshaft overlap, and also why retarding exhaust valve timing will "scavenge" exhaust gas from a cylinder and help "suck" fresh air in.

Gear

[41mag]

Well here are a couple which show the bases. The one at the top right and in the middle for comparrison, are actually flat.

http://i49.photobucket.com/albums/f285/41nag/Shooting/Cast%20Boolit%20Loading%20and%20Shooting/P6040048.jpg

Like I mentioned, I am simply looking to get a handle on what to look for when I evaluate the recovered boolits.

I'm sure hoping to try one out on a hog in the not so distant future. Just looking at the recovered pieces, it looks like this alloy would do a number on one for sure. Once I go through these I might try blending in a bit more tin to see if that might help them stay in one piece a bit better. Just going by what I have read on the Iso core alloy it could use a touch.

[9.3X62AL]

Heck of a thread, folks. Lots of interesting thoughts, esp. the engine tech by GearGnasher. Cast Boolits at its best.

[olafhardt]

I'm sure, like me, you've even seen concaved gas checks if the launch pressure is high enough. There's definitely a lot of drag shearing back the sides.

There can be pressure waves or fronts within a closed system, such as what causes detonation in internal combustion engines and also chamber ringing with fillers tamped against a powder column, but the force is equal across the area of the moving front. Moving gas columns have a lot of inertia in and of themselves which is why "velocity stacks" were used on some carbureted race engines with huge camshaft overlap, and also why retarding exhaust valve timing will "scavenge" exhaust gas from a cylinder and help "suck" fresh air in.

Gear

Damn, Gear, I love it when you show how smart you really are!!!

[runfiverun]

those are pretty close to what a 22 bullet looks like when fired.
the heel on those pretty much swages up and fills the bore with a very concave base.
but you can see rifling marks all the way to the base.

[popper]

And those dragster engine rockers look like 2x4s. Gee, I just found out that the gas going by a 500 fps CB is > 100,000 fps ( what's that, Mach 3?). No wonder we get gas cutting (hammering).

[geargnasher]

Just a little hotrod 101, I used to be the left cylinder head builder on an IHRA drag team, among other things. I used the analogy to show an example of different pressures within a dynamic system, but that unless there's some complex turbulence, the pressure wave will act uniformly upon a wall, such as the boolit base.

I think the boolits in that pic deformed on impact. Notice the one with the flat base didn't mushroom as much. As the cross-section of the boolit expands, it's trying to turn inside-out like half an orange rind.

[edit] I just remembered I had a pic of something similar, just concaved bases. These were fired very hot from a .45 Colt NEF, water-dropped 50/50 alloy, and were sized .457" to fit the throat and fired through a .4525" groove at 1320 FPS. Yeah, there's a little dishing on the bases!

http://castboolits.gunloads.com/imagehosting/thum_89094ec09d2ee72fc.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=2693)

Gear

[runfiverun]

303 guy has a pic [of a copper alloy airc] that is completely rolled over itself at low velocity
i wonder how it's base looks.

[303Guy]

http://i388.photobucket.com/albums/oo327/303Guy/MVC-452F.jpghttp://i388.photobucket.com/albums/oo327/303Guy/MVC-458F.jpghttp://i388.photobucket.com/albums/oo327/303Guy/MVC-451F.jpghttp://i388.photobucket.com/albums/oo327/303Guy/MVC-618F.jpg

Those middle ones take the term 'mushroom' to it the extreme!

The bottom one shows the rim left over from base cupping or trailing edge drag.

Those were fired into sand. Not bad for hold together. They were quite hard after firing.

41mag
Those bases don't look like they'r a problem. The trailing edge looks pretty good. The rifling impression doesn't quite cut the trailing edge. Were those chamfered? If not them there's been a bit of bump up.

Ok, I've thought about it. I speculate that the pressure acts evenly when the boolit is moving slowly (or is stationary) but once it gets to an appreciable speed, the same drag acting on its perimeter is also acting on the gasses following behind it so there will be a higher pressure in the centre region possibly by only a small margin since the gas molecules are moving relatively fast, and then mostly toward the end of the bore where the pressure has dropped of. It's the drag on the outer surface probably mostly as the boolit swages down to bore diameter that causes metal displacement to the rear at the trailing edge. In a bottleneck case there may be jetting focusing the gasses toward the centre of bore for a distance.

[runfiverun]

funny you mention the exhaust valve timing.
i have a 3 valve 4.6 in my mustang,and that is exactly where the power comes from is in the exhaust timing and duration.
when i was shopping cams that is the question i asked most of the speed shops i dealt with and it fluxomed their countermen every time.
they wanted to talk valve lift,and cam duration and i wanted to know exhaust valve timing and duration.
the two intake valves moved enough air, especially with the other modifications i had allready done.
i wanted the exhaust to do the extra work without losing the efficiency of the engine.

well that was off topic.

back to the topic.
so is the base concaved in the bbl or on impact?

[popper]

In the bbl! Pb compression strength is 2x shear value( Comp = 2K-6k;%Sb 1-5) Fast pressure rise work softens the center and edges are in shear. Result is slightly concave. I think that is 1 reason GC work; Cu is work hardened by pressure and resist HV gases better (BHN goes from ~35 to ~60). Faster the pressure rise the faster the phase transitions occur (hardening or softening). Phase transition causes very fast temp rise - not by conducted heat. Once the CB starts moving, the pressure still rises (6k psi to 30-50K psi) but the energy is now in the CB and forces on the CB decrease rapidly.

[popper]

You need the 2 intakes to get charge in (low pressure diff) and 1 for exhaust (high press diff) for wedge chamber. Hemi seems to work better with 2+2. Exhaust scavenging is getting a low press zone between exhaust pulses to increase press diff in exhaust. Did Ford, Chev and Hemi a Loong time ago.

[303Guy]

I thought the modern idea is a larger exhaust valve area? Mind you, two smaller inlets give a higher velocity for dynamic charging. Oops - off topic (just slightly).[smilie=1:

[DRNurse1]

Any thought on the effect of similar/ different substances on their friction/ interface? Water slides on water better than it does on river bottoms so the center of a stream/river moves faster than the bottom/ edges. do the expanding gasses and boolit create similar effects in their interface and those with the bore and gas propellant? that might explain some of the higher force in the center of the base in addition to the shear on its edges.Sorry this is off the engine topic a little but I wuz just thinkin....

[303Guy]

That's pretty much what I was thinking.

[geargnasher]

Part of the 3-valve concept for the 4.6/5.4L engines has to do with EGR and quench. Mess with it too much and the camshaft phasers will go nuts trying to correct the overlap and duration. You'll get an eternal SES light with multiple camshaft phaser trouble codes at which point the ECM says "F-it" and defaults to reduced-power mode. That is, unless you can find a pair of camshafts that come with a new timing and fuel map for the ECM, install phaser limiters to keep the pistons from hitting the valves at WOT, and you'll probably need a set of valve springs with more juevos as well.

This has to set a new forum record for thread drift, sorry fellas!

Gear

[runfiverun]

yeah a set of cams comes with phaesars to trick the cam sensors.
you don't wanna change the timing too much as the cam timing is variable.
and the little extra bit of exhaust to tie into the first intake valve opening really gets the air moving.

i am really trying to work a tye in here.
but the downsizing of an oversized boolit in the throat has to contribute to this too.

[41mag]

Well I had a 69 Coronet with a stock 383 in it that ran pretty well, and a close friend around the corner built up several smoking engines in a 67 Cuda. I never got the chance to play with mine much, as starting a family when I was 18 severely hampered any thoughts of building hot rods. Besides the 383 ran good enough for me, and I probably didn't need to find out exactly how fast she would go anyway. I know that the needle would easily slap the dash once it passed 120, hard enough to bounce back to around 85 or 90. She wasn't much in the quarter, but loved the longer runs.


I think the boolits in that pic deformed on impact. Notice the one with the flat base didn't mushroom as much. As the cross-section of the boolit expands, it's trying to turn inside-out like half an orange rind.

Well the truth be told, the on the top right with the flat base, smacked into some VERY seasoned hickory at 50yds, but so did the one on the top left. The others, bottom left and bottom right, wee all recovered from the bucket of sand. I threw in the mix as these were the cleanest ones I had in the bag.

That's what had me a bit confused. Granted there were two different loads shot, the one listed above, and one which used a 258 in a solid which was 13.5grs of AA-9. I can easily tell the solids as the noses simply blow off and leave a somewhat short wad cutter type base, with very little expansion. The HP's all show extensive expansion similar to what was posted.



Those bases don't look like they'r a problem. The trailing edge looks pretty good. The rifling impression doesn't quite cut the trailing edge. Were those chamfered? If not them there's been a bit of bump up.

The rifling impressions DO go all the way to the bases on everything I have, it's just the high dollar Olympic D380 Ebay special that I have as a camera, that makes getting everything nice and focused a pain. It took me around 10 shots to get the nice one I posted.

I could upgrade the camera, but since I have three of them and use them for my fishing and hunting pic's I don't sweat the small stuff, usually. They were initially going to be hacked into game cams, but I lost interest in that after the first one got snatched.

So anyway, I have upgraded through the years from the 383 to the Hemi we had in our 03 Ram 4x4, to the 06 Cummins we now host in our Ram 3500. Don't think by looking at the list here I am stuck on Dodge, but I DO have to say, I think that most of the trash talk is simply jealousy. :lol: My main reason for goin with them has been price for what I got. I simply couldn't see paying extra for a long bed in a standard dual cab truck, which was the case on both of the last ones we looked at getting in Ford or Chevy, and also the lowest either of them would come down was still 5-8K over what I paid for the Dodges.

I DO know that the engine I have under the hood of the wife's little 3500 trumps anything we have had in the past by a good margin. I started to hop it up a bit when we first got it, but after a few runs to the country in it, I decided it was fine just the way it is. Sure is nice to ease down on the peddle at 75 and feel the seat start to roll in around your back, as you start to easily surpass the slower car ahead. To move a truck as heavy as that in that fashion so easily is really something.

So as to the alloy, these were straight Iso core, if one takes a core at 32# and adds in a half pound of tin, according to the spreadsheet calculator this should bring the alloy up to around a 2.5/2.9/94.5 blend. Would this be better suited for keeping the HP's together? I see where most recommend to keep the tin at 2% or so, but would adding a touch more, plus to 1# and 15# of pure lead bringing it up to around a 2.75/ 2/ 95.3 be better, worse, or simply be a waste of material? Granted the calculator spreadsheet is only an approximate, but it's all I have to run with the materials I have on hand.

Thanks

[popper]

DRNurse1 nailed it! H2O has tremendous compression strength but ALMOST no shear strength. 41mag - Per Bumpo's calc, iso core and ingot have the same BHN. 180 gr 98/1/1 dents when you drop on the floor(4'), 95/2.5/2.5 doesn't. I think R5r or gear said commercial hardcast is core. Ingot should give better HT performance.

[runfiverun]

if you have the small containers they are the 2.5/2.5/95
if you have the big ones they come in at 1/3/96
adding tin to an alloy will cause a longer SbSn chain within the alloy making the alloy tougher.
tin likes lead but it loves antimony so adding more tin than antimony causes problems with the sbsn chain where the extra tin becomes detatched and causes hard spots on the alloys surface.
the hard spots of tin do not have time to re=bond with the lead and the hard spots are surrounded by soft spots of pure lead.

the 2.5/2,9 you show sounds reasonable.
and you can add soft lead to that mix to get the results you want without changing the matrix of the alloy.
cutting that alloy 1/3 would be a pretty good alloy with a bhn of about 9-10 [off the top of my head]
with some good malleability and toughness.

[popper]

I'm using 2.5/2.5/95 for full house 30-30 and 308 loads. 1/3/96 is shotgun like @ same load. 1/1/98 is working for 40SW full house load. Both are ~180 gr CB. Pretty much like R5R says. Pressure data I got for the 30-30 show fps increase for last 1/2 of the bbl is almost nil.

[41mag]

Runfiverun, and popper,

Thanks for the heads up on the alloy, that is great information. I have been using the Lg core as alloy, and it does VERY well for most boolits. The HP's however not so well. That was why I was looking to soften it up so to speak.

I also have some of the Iso ingots form Muddy as well as some mixed hardness range lead, and straight WW ingots form "The Capitan". It was so much more simple when I was pouring just the Lee 300gr RF for the 454 from straight WW or a blend of the Iso ingots, and some of the Antimony lead from another member here. Those two mixed 50/50 were spot on with my original WW alloy as far as hardness went, and being the RF GC'ed type boolit, they were awesome performers in the Raging Bull.

I'll do a little bit of blending where I can easily triple or more the weights, and see how things go form there. Hopefully it will work out where I get somewhat the best of both worlds and get a HP which will stay together long enough to penetrate, and if the nose blows, so be it. I really just need to test these out on a real critter to really see how they are going to work.

Again thanks a ton, and any other alloy info you feel like sharing on the Iso cores please feel free to shoot me a PM, or post it up here.