What is causing this strange bullet deformation?

[TwoTone]

These are nominally 147 grain bevel base 9mm bullets from a Lyman mold. They drop at 157gn naked. I've used these before in a gun I no longer have and they seemed fine from what I can remember. Back then they were lubed in a lube-sizer, not powder coated. This is the first time I've tried powder coating them and also the first time using them in this gun (a new CZ Shadow Line - the gun performs great with other bullets). The load was a light one at 3.1gn Tite Group. *Edit - I've since found out that this is not at all a light load for a cast 157gn bullet in 9mm* The bullets were sized to .355 in a lube-sizer with no lube.

I noticed they were key-holing on the target and that some of the holes looked improbably long.
Upon cleaning the gun I found the bore to be moderately leaded, something I don't normally experience with powder coated bullets.

I fired some into a snow bank out of curiosity and yesterday finally recovered some.

Here's what I found to my surprise! (The .45 bullet on the right was fired into the same snow bank, has the same powder coating and was cast from the same alloy. I've fired thousands of those in IPSC with good results and no weirdness). I've also fired quite a few other bullets cast from this alloy (mostly 45/70 and 30-30) with great results. This alloy is lead from a sailboat keel with some tin added. It supposedly has good antimony content and I estimate that it's slightly harder than typical wheel weight alloy.

Also in the pic is a loaded 9mm round with the same bullet.
No wonder they were tumbling! Can anybody tell me what's going on here?

The rifling visible on the elongated section of the bullet suggests that it was in contact with the bore for at least part of it's passage through the barrel.

138666

138667

Here's what they looked like ready to load:

138673

[44man]

WOW, never seen boolits get longer! Looks like you had a taffy pull.
You might be running near pure lead. Boolit diameter? Gas getting past the bevel base?

[mongoose33]

No particular idea but here is the clue I'm looking at:

The rifling is engraved on the narrow part of the boolit, but i see no rifling engraved at the base of the boolit. I'm trying to figure how you can have that engraving on the middle but not the base of the boolit.

[Mk42gunner]

Strange looking fired boolit, all right.

I would try sectioning both an as coated and one of the recovered boolits. I have no idea what you will find, but the recovered boolit doesn't make any sense to me.

Robert

[243winxb]

Plastic deformation



High pressure went past the base of the bullet because it was undersize. When pressure reached the empty lube groove, plastic deformation happened. The lands had already engraved the bullet, as the photo shows. The pressure pushed in at the bullets lube groove, making the bullet longer and smaller in diameter as it flowed forward. When plastic deformation happens, the bullet will not return to its normal shape. Plastic deformation-This whole relationship centers around the elastic limit for the alloy you are using and what the elastic limit is. The elastic limit is the point at which stresses can occur to an object and it will return to it's relative shape. Once you have reached the deformation stage it no longer returns to relative shape. this is a very simplified version of this topic as it pertains to engineering mechanics of materials.
This is meant to be a guide and to keep you within safe/acceptable limits for pressure and alloy for your purposes. Obturated bullets do not mean that the shape has went through plastic deformation, just that it has expanded and stayed within the elastic limits of the alloy.
The formula does not take into account other factors that aide in reducing friction and thus combined forces on the cast slug. As stated above, one member is getting very good accuracy with soft (by most peoples standards) alloys in high velocity loads (for cast anyway).
Another factor not talked aobut is the pressure curve of the powder/cartridge combination. Does it spike quickly (fast pistol powder in rifle size case) or is it a gradual increase (full case of slower powder). Protection of the bullet base can also be a factor, we routinely do this by gas-checking, using lube wads, or fillers.

[TwoTone]

The sailboat keel lead supposedly has a decent antimony content and this alloy is definitely harder than pure soft lead.
I don't have any hardness testing gear so this is subjective.

They were sized to .355 and the sizer contacted both the base area and the shank area. I too noticed the lack of engraving at the base area.

Is this extreme gas cutting? I've never seen anything like this.

I'll pull some bullets this evening and do some measuring.

[44man]

Most nines will function with .357". Might try some without sizing.
I do not own a nine so might be a sad source.

[Yodogsandman]

My WAG would be that your alloy is near pure lead and once fired, the back half of the boolit is held back by the bore friction from the PC and the front half is wanting to go faster. 44man's description seems right on, a taffy pull!

[mongoose33]

My WAG would be that your alloy is near pure lead and once fired, the back half of the boolit is held back by the bore friction from the PC and the front half is wanting to go faster. 44man's description seems right on, a taffy pull!

<this is not arguing, it's searching for an answer>. If that would be the case, wouldn't you expect to find engraving on the bearing surface toward the base?

I'd also ask how one could accelerate the front half of the boolit w/o it being pushed by the back half of the boolit.

[Boolit_Head]

You would think the pressure would push the bullet from the base and rule out the taffy pull theory within the barrel. Must be happening once it hits the snowbank.

[44man]

<this is not arguing, it's searching for an answer>. If that would be the case, wouldn't you expect to find engraving on the bearing surface toward the base?

I'd also ask how one could accelerate the front half of the boolit w/o it being pushed by the back half of the boolit.
Exactly. gas release to the front or bad skid. Nine is a high pressure round.

[Dusty Bannister]

You may find that this is a result of a few errors. First would be the possibility of an undersized cast bullet. Second would be to check the data with Lyman Cast Bullet Handbook, 4th edition and also Lyman 49th edition. The OP stated this was a light load that shot well in another gun, but this load is more than the max recommended load for a 147 grain cast bullet. I tried to check the Hodgdon 2014 reloading manual, and Titegroup is not even listed for a bullet like this. Not much to be done until he slugs the barrel, puts a mic on the finished bullets, and verifies his data is either a "typo or an Oh-oh". Dusty

[DougGuy]

I'd suggest shooting some into a swimming pool or a 55 gallon drum of water then look at the recovered boolits.

[mongoose33]

Exactly. gas release to the front or bad skid. Nine is a high pressure round.

OK, two things upon reflection.

First, I wonder if the base, being beveled, is preventing or at least not promoting obturation.

The "gas release to the front" would appear to account for some of this. Look at the original pics of the boolits--all of the deformation, stretching etc. takes place ahead of the lube groove. Further, unless there is some sort of optical illusion going on, the area on the boolit forward of the groove appears smaller in diameter than the base.

So what it appears might happen is gas finding its way into the lube groove and then pushing the forward part of the boolit more than the back part is being pushed.

That seems to account for the evidence EXCEPT I'm still not sure why no engraving on the boolit by the base.

[MrWolf]

I'd suggest shooting some into a swimming pool or a 55 gallon drum of water then look at the recovered boolits.

Just a suggestion but don't shoot through the sides :kidding:

I also think it is undersized and gas is causing the effect. Hard to say since the pc were not fired from the same gun. Try lubing vs pc a few and see if you have the same issue but I tend to lean to undersized.

[DougGuy]

Well, it's a no brainer to figure out -why- there is no engraving on the base, the base is smaller than the rifling. When the stretching started, it probably reduced the diameter of the base. I have seen some weirdness done by boolits over the years but tbh, this one takes the cake!

First off, I would suggest pulling some loaded rounds and seeing if the base is swaged smaller by being shoved into the thickening part of the case web, OR by the crimp die, this would allow burning gases access to the lube groove and to the area in front of the lube groove if it is really swaged badly. This would explain how the base of the boolit got smaller, or it may be 2 things that made the base smaller, 1. being swaged in the case as described, 2. as the center of the boolit was squeezed and shoved rearward by gas pressure, it could be stretching the alloy like 44 man's suggested "taffy pull" but either way could be a viable explanation.

[cs86]

Could it be that the barrel could be real tight at the muzzle? Once the bullet hits the end of the barrel the last half could be trying to squeeze out and the front half is trying to continue moving forward causing it to stretch? Maybe slug the barrel and see if it gets real tight at the muzzle. Just a thought.

[bstone5]

What cs86 indicates is a very good point.

Look at the crown of the barrel also any small burr could cause the barrel to be tight at the crown.

It appears something is holding the base of the bullet once the bullet has come up to high velocity at the end of the barrel.

Traveling the length of the barrel with the pressure at the base of the barrel would keep the bullet from stretching one would think.

A little harder alloy might help also.

[Yodogsandman]

Could it be that the barrel could be real tight at the muzzle? Once the bullet hits the end of the barrel the last half could be trying to squeeze out and the front half is trying to continue moving forward causing it to stretch? Maybe slug the barrel and see if it gets real tight at the muzzle. Just a thought.

To me, it looks like there is some engraving on the base. The boolit looks to be moving forward at a high speed until the base meets friction and the front continues and the base slows down. The above post seems viable.

[Maximumbob54]

This may be a brainless stupid theory but looking at those pics is almost mind altering so here it goes...

Could there be an air void inside that is being inflated by the high pressure gas? Then upon exiting the bore it maybe snaps back under the force of the rotation caused by the bore's twist rate? The OP did say they hit the target like that so this has to be happening from the bore to the target.

My somewhat rational thought process on this is we all know if you load a HBWC too hot you risk blowing the skirt off the back end. So what happens if you have a casting where you don't have quite enough puddle for the sprue as the core is cooling and drawing lead into the cavity? You sometimes see that pin hole and maybe that high pressure is causing the balloon upon exiting the bore. I dunno. Those pics are still twisting my brain.

[bhn22]

I've seen this happen before, and we had a long, difficult discussion on the issue on the CBA forum, the last I knew, nobody could figure it out. I did notice that you are sizing bullets at .355, and that is likely too small, most 9mms favor sizing in the .357-.358 area. I'm fully aware that the "nominal" groove diameter for 9mm is .355-.356, but most gun manufacturers apparently have never read that book. You might want to verify this. Also, are you using a LEE "Factory Crimp" die on your 9mm? The main reason I ask is that you show no signs of rifling on the bullet bases, this is an extreme sign of undersized bullets, and is likely the cause of the tumbling. You may need to deal with your issues one at a time, until the situation resolves itself.

[Boolit_Head]

I am suspicious that sizing to .355, the Lee FCD sizing it down more, along with the soft lead may be causing a extreme gas cutting or blow by action. Would not hurt to slug the barrel and get a good starting point to size to.

[Artful]

Wow, New one on me - I'd also suggest try taking a fired case and see what the largest diameter boolit it will take then size just under that.

[TwoTone]

Lots of good input here. Thanks guys.

Some facts:
-This is not caused by impact with snow. The keyholed targets match the profile of the deformed bullets shown.
-This is not 'soft' lead. To the best of my estimation it is slightly harder than wheel weights.
-There was no Lee Factory Crimp Die used, just a Dillon SDB taper crimp die.
-As Dusty has pointed out (thanks!), while 3.1gn Titegroup is a light load for a 147gn jacketed bullet, it is beyond max for a 147 cast lead bullet, and of course this bullet is 157gn so it's even worse. I'm guilty of just looking at the Hodgdon data for a 147 jacketed and using the starting load for that minus .1 gn.
-The PC on the base area of the bullet shank is eroded and little or no rifling marks are visible. It's possible that the shank is undersized or maybe it's been gas cut badly enough to remove the rifling marks.
-There seems to be a consensus that .355 is too small to size a 9mm. This could indeed be playing a part. There's also the possibility that the base of the shank is being swaged down upon seating.
-Also, I mentioned that I used these bullets before, but it was a different load and they were lubed conventionally, not PC'd.

I will pull some bullets and do some measuring.
I will slug the bore and do some measuring.
If the bore size seems compatible to the bullet size, which now seems unlikely, I'll reload some at a minimum charge of Titegroup and test fire them.
If the bullets are undersized for the bore (likely) I'll use a bigger sizer (I think I have either a .357 or .358) and remelt the batch. If the bullets have been swaged by the case...well I'm not sure what to do there.

Keep the ideas coming. I'll report back as soon as I've done my measuring.

Thanks!

[Blackwater]

Frankly, I'm stumped. But if I may, let me ask a dumb question: Is that the recovered bullets that look like a small caliber, elongated Maxi Ball??? If so, I'd almost believe voo doo was involved! Just kidding.

However, if it was me, I'd have to agree with the guys who recommended going to a larger sizing die, like .357", and maybe change powders to something like Unique or something in that general burning rate range. See what that'll do, and keep us posted on the matter. We reloaders just love to be stumped. It makes us think, and work stuff out. That keeps us humble and even more interested and fascinated with some of the possibilities.

[smokeywolf]

This is what came to mind first. Titegroup burns quite a bit hotter than other powders of similar burn rate. Bevel base and hotter gas, may be working in concert to produce gas cutting around the PC.

[cs86]

Could it be that the barrel could be real tight at the muzzle? Once the bullet hits the end of the barrel the last half could be trying to squeeze out and the front half is trying to continue moving forward causing it to stretch? Maybe slug the barrel and see if it gets real tight at the muzzle. Just a thought.

Along with my thoughts. As others have said the boolit seems to be small for the 9mm. From what I see it looks like it is gas cutting all around the boolit. With the theory above there could be enough gas escape that by the time it reaches the end of the barrel with a tight crown that you don't have much pressure left pushing the boolit to push it out the barrel. Then it wedges and stretches. By using a larger boolit like .357 it might completely go away. I'd slug it and see how the slug slides down the barrel for any high spots. Also just slug at the throat and see what the diameter is.

[M-Tecs]

The only way this could happen is if the front of the bullet is providing the only gas seal so the front of the bullet is pulling the base and stretching. Pull some of the loaded bullets and see how much the brass has sized the base of the bullet undersize. Pressure at the base of the bullet tends to make the bullet shorter and fatter.

I would not believe to possible to have the front of the bullet start moving before the base but the bullet is clearly stretching for some odd reason. If you figure out why the bullet is stretching you will have your answer.

[bhn22]

To expand on my original post a bit, I mentioned seeing pics like this before, but didn't give any specifics. The last time, the bullets were fired from a 38-55 rifle, and they were fired with fast burning powder (for caliber & bullet) too. Those bullets weren't powdercoated, so we could see what appeared to be gas cutting in a reverse direction to bullet travel. Yes, it was pretty strange. Anyway, the bullet condition was similar, no rifling (that I remember) on the base of the bullet, but the reduced area of the bullet showed strong rifling, just the the OPs pics. However it would have been impossible for that area to have contacted the rifling because of the reduced diameter. I realize this isn't helping, but the two situations are so similar that I had to mention it. The reduced area of the bullet showing rifling that couldn't have possible contacted such an undersized area led me to believe that the bullet became deformed after leaving the barrel, and that the condition of the bullets are likely caused by two or more different causes.

[Blackwater]

Well, I just had another thought. This situation and phenomena is so strange, I just HAD to go back and read it again. I really don't think a restriction at the muzzle could be responsible. That would ordinarily size the whole length of the bullet, and thus, NOT produce your results. I'm starting to theorize that possibly, at least, the combination of the beveled base and a slightly undersized bullet MIGHT (???) allow gas to run around the base, but IF (???) the gas was stopped by the forward part of the bullet, this COULD (??? again) expand, and the softest, most readily yielding thing involved would be the lead of the bullet itself, and thusly, it COULD (??? yet again?) press against the sides of the bullet and thus elongate it. Just exactly how this would happen would, I think, be a very, very rare combination of factors within a VERY miniscule window of conditions, which thus, would make it exceedingly rare. Anomalies like this almost always depend on rare sets of combinations of factors, and this is the best idea or possibility I can come up with. Strange! No doubt about THAT! But it's also intriguing, too, as are all anomalies wherever and whenever encountered. Please keep us posted.

Oh yeah, and I also came up with a theory that IF the front cooled quicker, it might (???) become just hard enough to stop the flow of gasses, vs. the rear end. That's a stretch, to be sure, but the idea came to me and I just thought I'd pass it on. Thanks for posting a real poser!

[ohland]

shooting some into a swimming pool

Hope nobody you like is in the pool...

Captain Obvious, a.k.a. The Bad Humor Man, signing off...

[popper]

Small boolit, small case dia, large chamber, fast powder = gas cutting. Case expands, boolit in bore pushed by gas at the lube groove.

[M-Tecs]

What can we tell from the pics?

1. We can see that the bullet "stretched" and we have clues as to why. To stretch the bullet has to be pulled from the front or the back has to slow down quicker than the front.

2. Since there is no rifling engraving at the base of the bullet the base has to be under the bore size of .350? Same for lack of any signs of that might retard the forward movement of the base.

3. We do have engraving on the front of the bullet that at one time provide full contact and a gas seal.

4. Gas cutting at the base indicates gas flowed to the front of the bullet that was providing the seal and "stretched" the bullet. The front of the bullet started moving before the base. doesn't seem possible but the pic's don't lie.

[Blackwater]

MTec, I think you're on it like white on rice. Here's my version, after some thought. The primer goes off and ignites the powder. The bullet starts to move and engages the rifling. However, the chamber and throat are a bit generous, and there's run-around of the expanding gasses, and before the bullet can move enough, the side pressure of the bullet on the sides of the bullet press inward, causing the lead to yield and "stretch. The gasses also size down the base enough that it doesn't now reach the rifling, so it's unengraved by it. That's unlikely timing, but anomalies CAN sometimes depend on such combinations of factors. Do you think we're getting warm yet???

[gwpercle]

Advice from my Daddy " Don't believe nothing you read and only believe half of what you see"
I read, I see the photo's, but I'm not believing it. That stretched boolit just don't look right, and if things don't look right then something else is going on.
You worked real hard to get those boolits to look like that ...What's the rest of this story ?

[303Guy]

Interesting. The way I see it the forward section of the bullet is engaging the rifling just fine. The compressed (by the case) rear section does not engage the rifling too well and that combined with the bevelled boolit base and likely canting in the bore, leads to an unstable boolit that goes into a propeller like spin which stretches it by centrifugal force on its way to the target. It will be travelling full on sideways, I should imagine. As it elongates it would slow its spin rate which may limit the elongation.

I'd suggest setting up paper targets at different ranges to see when the 'propelloring' starts and how the elongation progresses with range.

[GoodOlBoy]

Warp speed.....

In Star Trek the next generation the Enterprise looked kinda like that as it took off into warp speed....

Seriously I have no idea I have never seen a bullet do anything remotely like that.....

GoodOlBoy

[cstrickland]

wow those are really weird. couple of thought and questions

1- how long and at what temp did you powder coat ?? You say the lead was hard but could it have been annealed during powder coating ?
2- did you weigh the slugs and measure the length ?? if it is stretch and not gas erosion then they should retain most of their weight and be considerable longer, they sure do look longer but that could be picture perspective.
3- are you sure that it is actually true rifling you see versus the flow of gas in conjunction with the rifling directing the flow, which could leave a faux rifling pattern? Just does not look like solid rifling to me.

[Forrest r]

A couple of things come to mind when I saw your pictures:

The pc on the 9mm's has either been scraped off or has failed. The 45acp slug is correct, the pc is intact. The 9mm shows bare lead and a bare lead line where you seated/crimped the bullet.

When you pc a bullet it makes the alloy extremely soft, I've cast wd bullets (358156 hp's) and had no problem putting gc's on them. But after pc'ing them they would compress/bend/fold/distort/compress when I was simply running them thru a .358 sizer while trying to install a gc on them. I also use the same toaster oven/temp/settings/cook time to anneal lead cores (range scrap) to swage jacketed bullets with.

After seeing all the pc gone to the crimp line along with the round lube that is undisturbed and still fully intact. It would seem you have a couple of different things going on.

Your swaging the bullet down too small when seating them. Probably a combo of extremely soft (annealed pc'd lead) bullets and a dillon expander designed to be used with jacketed bullets (too small for lead/leaving the case after springback .354 for neck tension). TG has a high short start pressure along with a fast burn that reaches max pressure quickly coupled with the maxed max load. The bullet from the crimp back shows no sign of pressure/rifling's/distortion (still has a perfectly round undisturbed lube groove). That shows that all the pressure was exerted on a small band/length of body of the bullet towards the nose of the bullet that was still large enough to make contact with bbl/riflings. As the bullet moved down the bbl the extreme pressure from the maxed max load worked it's way up the bullet from that small band that was the only place on that bullet that had resistance to that max pressure. The soft alloy failed stretching/pushing/balling the alloy as the pressure went down the bbl. Hence, the llloooonnnnggggg bullet body from just after the undersized bullet/crimp line with the rifling marks. The ball of lead on the tip of the nose of the bullet was formed from the pressure wave that was pushing/stretching/deforming the bullet as it went down the length of the bullet pushing alloy in front of it and deposited it there as the bullet left the bbl. No more pressure, no more stretch/distortion/push and the lead ball on the nose of the bullet is all's that is left from the over pressured alloy that failed.

I'm just glad to see the soft annealed alloy acted like a safety net, there could of easily been a different outcome with hardball or #2 alloy.

Anyway, just another 2 cents in the cookie jar.

[rondog]

I am suspicious that sizing to .355, the Lee FCD sizing it down more, along with the soft lead may be causing a extreme gas cutting or blow by action. Would not hurt to slug the barrel and get a good starting point to size to.
The Lee FCD won't take an already small bullet and make it smaller! Jeeze.....

[TwoTone]

I think Forrest r and several others above pretty much have it figured out.

I pulled 5 last night. They have indeed been swaged down by the case. They measure .350 on the portion that was within the case and .355 on the rest of the shank:

138721

You can also see that the bullet was indeed driven from the larger diameter band created when the base portion of the bullet was swaged down by the case. This resulted in the rear portion of the bullet being pulled along for the ride. The shank of the bullet stretched as the bullet accelerated down the bore. You can see that the point of elongation coincides with the mark left by the case rim on the pulled bullet. Here's a photo of a pulled bullet along with the longest and the shortest of the recovered bullets:

138722

You can see gas cutting and I guess 'PC-cutting' on the recovered bullets. Interestingly, all five recovered bullets weighed between 157.0 and 156.5gn so not a whole lot of lead was removed.

So I made several mistakes here and I also have some questions:

-Obviously the over max powder charge of fast powder. Rookie mistake by an experienced reloader. Complacency is dangerous.

-Inadequate expanding of the case: Maybe I can substitute the expander for .38/.357 in my Dillon SDB to correct this?

-Soft lead: I did not even consider the annealing of the lead during the PC process as mentioned above by Forrest r and others. Will quenching them in water upon removal from the oven harden them up?

-Undersized bullets: .355 seems to have been too small which is likely why the gas cutting occurred. Or perhaps the gas cutting only occurred after the bullet stretched and reduced in diameter. If they had been sized larger, perhaps the case would not have swaged them down as much. Or perhaps it would have. I have no experience with this. Comments welcome.

There was at least one doubter in the responses. I can assure you all that this was real and that I was just as surprised by it as you folks.

Also, again, there was no Lee Factory Crimp Die involved in this.

It looks like we have it figured out now though. Thanks for the help. Lots of knowledge here.

[popper]

I've used H.T.'d 2% Sb alloy and HiTek/W231 in my 9mm for a 130 gr. No problems. I tried WST (tad slower than TG) and got major leading after 5 shots. Dropped down 0.3 gr, AC and an extra coat of HiTek - problem solved and now I don't have to H.T. No smoke, reduced flash, easy managed recoil for a pocket pistol. :D You do need to size/expand/boolit size properly. Check out the 9mm loading sticky.

[44man]

Bake powder coating sure will soften lead. Why not drop into water to see what happens?

[rsrocket1]

I searched this thread and may have missed it because I didn't find your answer. You said you were going to slug your barrel. Did you do that?

.355" is very likely 1-3 mils too small for your barrel. My M&P FS and Shield barrels are tight at 0.3545" and I still size them to 0.356" because that's the maximum I can size them and get them to fit into the tight throats of the barrel.

Depending on the setup of your expander, you might be able to use a 38/357 expander plug in your die. With Lee dies, you either need a 38 S&W expander plug in the 9mm powder through expander die or make a spacer for the 38/357 plug to reach down low enough for 9mm cases. You can see that the Lee 9mm PTX plug is woefully short for 9mm lead boolits.

138731

[JonB_in_Glencoe]

OR...
maybe there is some Flubber in the alloy ?

http://en.wikipedia.org/wiki/Flubber_(material)

[Maximumbob54]

I searched this thread and may have missed it because I didn't find your answer. You said you were going to slug your barrel. Did you do that?

.355" is very likely 1-3 mils too small for your barrel. My M&P FS and Shield barrels are tight at 0.3545" and I still size them to 0.356" because that's the maximum I can size them and get them to fit into the tight throats of the barrel.

Depending on the setup of your expander, you might be able to use a 38/357 expander plug in your die. With Lee dies, you either need a 38 S&W expander plug in the 9mm powder through expander die or make a spacer for the 38/357 plug to reach down low enough for 9mm cases. You can see that the Lee 9mm PTX plug is woefully short for 9mm lead boolits.

138731

Check out the NOE Lee PTX inserts as well.

[sigep1764]

Lathesmith on this forum can turn you a new powder through expander for your sdb. With the sdb, you can only use dillon dies. They are proprietary to that model of press. I tried the 38 special and 38 s&w expanders, but they are to short to activate the powder throw. Lathesmith made me one with a plug that was .300in deep and .358 wide. This let's me seat deep into the 9mm case to deal with short throats in my barrels and will let me seat the heavy for caliber boolit designs as well. Seating that deep and expanding that wide does cause the expander to stick a little in the case. I take a patch and rub a very small amount of gun oil on the expander plug every twenty cases or so. Has worked perfectly for about 5000 rounds now.

[ericc]

Perhaps gunpowder is getting entrained in the lube grove and producing high pressures there. Basically the bullet leaves the case and the burning powder flows forward and gets into the lube groove as the bullet swages into the barrel.

The base of the bullet is still pressurized and the pressure is increasing in the lube groove due to trapped burning powder. This would cause the bullet to extrude forward like we see in the photo as the lead yields to the pressure in the groove area.

If the issue is repeatable, try putting some lube/wax in the bullet groove and see if the problem goes away.

[leadman]

Water Quenching right out of the oven powder coated or Hi-Tek coated will harden them depending on what is in the alloy. I do this to almost all of my coated boolits now.

Let the labs try to match the rifling marks on those boolits!

[303Guy]

Perhaps gunpowder is getting entrained in the lube grove and producing high pressures there.That's a thought.

Do PC'd boolits anneal evenly? could those boolits be somewhat harder in the base?

[milrifle]

I don't know that I buy the theory of gas getting past the base and pushing the nose out forward. Force is Pressure X Area. Even if the bullet were undersized a bit, the base is still the overwhelming majority of the surface area and is still getting pushed on by the gas pressure.

I really don't know what is going on with it, but a thought that crossed my mind was if the charge was really too heavy and bullet really too soft, the bullet obturated tightly against the barrel wall tightly. Since the bullet was undersized, it may have even been barrel shaped (Whisky barrel, not gun barrel) and that center portion got really hot from friction. Then, when the force was suddenly removed as it exited the barrel, the bullet tried to snap back toward it's original shape, but was so soft due to it being soft to start with plus heat from friction, that it kept going past it's original shape and actually tried to pull itself apart.

Hey, it's just a thought.

[243winxb]

Plastic deformation-This whole relationship centers around the elastic limit for the alloy you are using and what the elastic limit is. The elastic limit is the point at which stresses can occur to an object and it will return to it's relative shape. Once you have reached the deformation stage it no longer returns to relative shape. this is a very simplified version of this topic as it pertains to engineering mechanics of materials.
This is meant to be a guide and to keep you within safe/acceptable limits for pressure and alloy for your purposes. Obturated bullets do not mean that the shape has went through plastic deformation, just that it has expanded and stayed within the elastic limits of the alloy.
The formula does not take into account other factors that aide in reducing friction and thus combined forces on the cast slug. As stated above, one member is getting very good accuracy with soft (by most peoples standards) alloys in high velocity loads (for cast anyway).
Another factor not talked aobut is the pressure curve of the powder/cartridge combination. Does it spike quickly (fast pistol powder in rifle size case) or is it a gradual increase (full case of slower powder). Protection of the bullet base can also be a factor, we routinely do this by gas-checking, using lube wads, or fillers.


http://castboolits.gunloads.com/showthread.php?p=35425#post35425

[303Guy]

I don't know that I buy the theory of gas getting past the base and pushing the nose out forward. Force is Pressure X Area. Even if the bullet were undersized a bit, the base is still the overwhelming majority of the surface area and is still getting pushed on by the gas pressure.Not only that but the front section is actually smaller than the base. The pressure would have escaped and stopped pushing on it. The same with squeezing it.

We know that the boolits are hitting the target full on sideways so they must be spinning sideways. We know that the centre of gravity is toward the base and we know they spin pretty fast. The nose will have higher centrifugal forces acting on it than the base because it's further out from the CG.

[mjwcaster]

Nothing to add, but this is about the coolest/weirdest thing I have ever seen posted on here.

[wv109323]

The Brand of pistol says a lot. I have a CZ B75 that I can not get to shoot a cast boolit. Bore is .3558. I have tried RCBS 124 TC, Lee 125 RNFP, and Lee 120 TC. All these keyhole and lead the barrel. Mine were sized .3577 and .3570. No PC.
The chamber has no leed and the dies do not expand the neck enough to eliminate bullet deformation. With a boolit that large it is seated very deep in the case. I am looking for a solution also.

[1johnlb]

Pressure swagging down the bullet. I bet your shooting light loads in all your cases and because of the smaller 9mm case you ended up with more pressure than all the rest. Put that together with sailboat keel which can vary from hard to soft and is most probably softer than you realize, you end up with swagger boolits. Go pick you up some real ww and cast them to see what happens. Just my .02

[220]

The Brand of pistol says a lot. I have a CZ B75 that I can not get to shoot a cast boolit. Bore is .3558. I have tried RCBS 124 TC, Lee 125 RNFP, and Lee 120 TC. All these keyhole and lead the barrel. Mine were sized .3577 and .3570. No PC.
The chamber has no leed and the dies do not expand the neck enough to eliminate bullet deformation. With a boolit that large it is seated very deep in the case. I am looking for a solution also.

This was discussed in the HiTek thread recently, I have a norinco 9mm that leads badly and shows tumbling in as few as 10 shots.
Barrel slugs .3555 but in reality is closer to .357, it is much tighter for the inch in front of the chamber than the rest of the barrel. Regardless of what I size them to they are swaged down to .355 in the barrel and then need to bump back up to .357. Result is gas cutting starting about 1/3rd of the way down the barrel.
Another member reported the same thing with a different brand of 9mm, he stated when slugging with the boolit part way down the barrel and holding it up to a bright light source he could see light around the boolit, barrel produced similar leading to my own.
A RCBS GC mould was my solution, his was a new barrel.
Playing with Hitek, alloys and powders I have developed a plain base load that gives me 60+ shots with reasonably accuracy but heavy leading is still evident. The GC boolits will go 200+ rounds without tumbling but leading is still evident.

[243winxb]

High pressure went past the base of the bullet because it was undersize. When pressure reached the empty lube groove, plastic deformation happened. The lands had already engraved the bullet, as the photo shows. The pressure pushed in at the bullets lube groove, making the bullet longer and smaller in diameter as it flowed forward. When plastic deformation happens, the bullet will not return to its normal shape. http://i338.photobucket.com/albums/n420/joe1944usa/2015%20Reloading/Plastic%20deformation_zpsvhpk86pg.jpg

[gloob]

My guess is that the main problem is the undersized bullet and swaging of the base causing copious gas blowby that overheats the bullet. Secondarily, I bet your sailboat keel is higher in tin than typical bullet alloys. The more tin, the lower the melting point of the alloy (reason why electrical solder is up to 62% tin. At 62% tin and 38% lead, the alloy has the lowest melting point). I think your alloy might have as much as 6% tin and possibly other atypical elements, having seen auctions for that kind of alloy, before, versus typical bullet alloy of 1-2% tin. Finally, your bullet is so badly stabilized due to the undersized and asymmetrical base, it starts spinning end-over-end, shortly after leaving the muzzle, and the centrifugal force is stretching the heat-softened alloy.

I wouldn't start out at .355. I preferentially start out at w/e is the largest size that will easily chamber in the gun, and if that is as cast, then that is where I start. Then I might work down from there if I have a particular reason, such as wanting to shoot the same bullets in multiple guns. And very importantly use an expander that is within a mil or two, max, of the bullet size and which reaches to where the base of the bullet is going to sit. There's a snowball's chance in hell that you will be able to seat a long 147 gr bullet in a 9mm case without damaging the base, unless you are using a custom expander.

The alloy is the last thing I would worry about. Without the blowby, the bullet won't melt. But it would be interesting to see if your alloy might work particularly well in a hollowpoint?

Other note: I would be concerned about possible throat and bore erosion with that much gas blowy.

[303Guy]

... causing copious gas blow by that overheats the bullet.Powder coating melts at around 200°C (my temperature scale converter isn't on at the moment). Do those samples appears to have melted PC? They do look like it to me and the melting or PC cutting appears to be on the flame direction side of the lube groove and the distorted nose. Good point there gloob. Then again, can there be sufficient heat transfer in the barrel duration time?


... it starts spinning end-over-end, shortly after leaving the muzzle,Would they spin end-over-end fast enough to stretch the alloy? I'm thinking it spins sideways like a propeller, i.e. with a 90° yaw. Weren't all the hits side on? If it were tumbling end over end then one would expect some to be side on and some not.

Come to think of it, do any bullets tumble end-over-end if they are spinning up fully, i.e. have not stripped the rifling? Is there any information out there on how bullets behave when unstable to the point of 'tumbling' in flight or just yawing severely?

[GooseGestapo]

1. Your alloy is VERY soft! Evidently the heat from oven during curing of PC is softening the lead.
2. The 9mm case is tapered; the portion behind the lube groove is exposed to the flame and pressure of the powder at ignition. The high pressure from the powder charge is squeezing down the base rearward of the lube groove. The heavy bullet you're using is seated quite deeply in the short 9mm case. The "un-tapered" neck of the case is quite short, so only some of the portion foward of the lube groove is in contact with the case. The "erosion" of the PC is actually where the bullet is stretched out from under the PC.
3. When the forward portion hits the sharp throat, it "drags" or "holds" the bullet momentarily and the already accelerated bullet is held and the soft lead portion of the nose stretches forward until it "pulls" the rest of the bullet along with it.

Try quenching the bullets out of the oven to heat treat. May help. Try another powder too. Could be related to high pressure load and very fast burning powder.

I've suspected something along this line when using Lee Tumble lube bullet in .40 and 9mm with faster burning powders. After I went to a signficantly harder alloy (adding 95-5 tin/antimony lead-free solder to air-cooled wheel-weights) and using slower powders (LongShot), I got dramatically better accuracy from 9mm. But, I still prefer conventional style bullets w/o the short driving bands of T/L style bullets, even when using tumble lube. I only use tumble lube on bullets shot at less than ~1,000fps, better yet less than 800fps (.38 wadcutters).

You can also have your barrel re-throated.