Bullet Blow Ups

[fyrewall]

243winxb's response was what I was looking for in another thread - this appears to be annealing of bullets. Just keep on asking sometimes helps, at the risk of appearing to be slow - I sure did not find what I was looking for in that thread. My attached link gives more info on annealing bullets.

I also was curious as to where lead was produced in Missouri, a region with large galena deposits. A subsequent search showed a huge lead recycling facility near Bixby Missouri complete with rail access and large capacity electrical power lines leading directly into the plant. Apparently, this plant recycles lead batteries instead of smelting operations using galena. Hopefully, lead production might be done by some wet chemical process that would reduce pollutants to acceptable levels - thus keeping the entire operation within the USA (jobs). A view of that plant's operations showed ingot forming from melted lead and mentioned mixing other metals that I would guess might be antimony.

My thoughts are that during the bullet forming operation the bullet jackets might be excessively work hardened. I am also guessing that real long pointy bullets might have more yaw than stubby bullets and a combination of yaw, huge rpms caused by fast twists, high velocities and brittle jackets might result in bullet disintegration a short distance from the muzzle. My 53 grain Hornady hp fb bullets as best as I remember were longer than the 52 Sierra bullets and were not stabilized adequately as shown by bullet profile holes at 100 when shot from a 1-14 .22-250 - that is the bullets that did not blow up.

Taking a look at 10X magnification of various sectioned pointy hollow point Berger bullets shows shallow grooves on the outside of the bullet leading to and converging at the point. Looking at the inside of a Sierra 107 grain 6.5 bullet (large void in front of core) shows a series of shallow flattened areas separated by grooves leading to the point, same for the Berger bullets. My guess is that the grooves might be deeper than seen (expansion cracks?) and could indicate areas where the jacket might fail. All this is from my casual observations as an amateur having no insider info.

The OP of the original thread apparently was shooting 142 Sierra MK's from a 6.5-.284. Another member observed a problem with 162 Amax's from a 7 RUM. Another indicated problems with 90 grain .224's. All long pointy bullets.

I think the very short transit time a bullet spends inside the barrel would prevent lead core melting. Various bullets having lead exposed at the base like the 100 grain .257 Nosler partitions I fired from .257 AI and .25-06 did not show melting when the bullets were recovered from various dead animals. I quit the .25's and now shoot 6.5's.

How dirty is dirty? Would extreme jacket fouling result in jacket failure considering the contact area of bullet and barrel is the shank of the bullet, the area having the least work hardening.

 

[dkhunt14]

It isn't all the barel time that melts the lead in the bullets. It is the spin rate and friction from the air. Usually bullets dont blow up close in. I also dont believe its not the length of the bullet, but the spin rate. Longer bullets need faster twists to stabilize them. That in turn spins them faster. I shoot 1000 yard BR and see bullets hit the bank from the pits. If the bank is wet, they lay there and sizzle.

Almost everytime I saw a bullet blowup in 18 years of competition, It was a rough barrel from high round count. Rough barrels damage the jackets. We use plenty of long bullets in different calibers and some are pushed pretty good. Very few bullets blow up. Also a 5R rifled barrel doesn't damage the bullet as much.

Years ago, the ones blowing up were 6.5 and most times, the barrels had high round counts. They also were fast twists and pushed hard. Berger had changed their jacket material when they were bought out. They also used reclaimed lead, both because it was cheaper. When they stopped that and went back to the original stuff the blowups stopped. Even though they came out with a target version with thicker jackets to help. The guys went back to the hunting version, which was the original bullet and the blowups stopped. Matt

 

[fyrewall]

Here is a pic of a 154 7mm SST sectioned bullet after being toasted for 20 seconds in the lower part of a candle flame. Looks like nothing happened. Will this bullet perform differently than an untoasted (not annealed) bullet? Not having ballistic jello (gelatin) or pig carcasses. I plan to round up some big city telephone books, tear off the shiny pages, soak them in water, put them in cardboard boxes and shoot both, toasted and not toasted, at the boxes with my .280 with 154 SST's having a MV of about 2875 fps at 300 yards.

Note no melted lead or signs of melting. No destruction of plastic tip. What appears to be some black stuff that might be burned lube is near the plastic tip. This SST has a much thicker jacket than I expected. Shooting some big deer with broadside strikes using the standard interlock 139 boat tail gave almost complete penetration at ranges of 350 - 400 yards. I won't shoot at unwounded game over 400. The NZ guys who originated my first link mention 1000 yards or so - not me!

Would this low temp treatment on target bullets have any application in preventing blow ups of long pointy target bullets?

Toasting brass cases with a candle might get into the Arrherinus stuff being crystal formation/change rates being dependent on time. Would toasting a brass case for hours effect crystal change? This sort of brings back my struggles as a student.

Bullets sure get hot fast, add penetrating air at high speeds to bore friction and short flight time would make for a real hot bullet. The last time I picked up a freshly fired bullet it was a 123 grain ball (stubby and slow) from a 7.62X39 and it was so hot I dropped it. Taking another look at the bullet showed no heat damage to the exposed lead core at the base of the bullet.

 

[243winxb]

lower part of a candle flame

Correction ...

I deleted my above post , because i was wrong , using the upper part of the flame.

The same bullet started melting in 53 seconds, when held lower.

Bullet used was my home cast 357, 158 gr lswc.

 

[fyrewall]

Naked bullets melt quick

 

[Drop Port]

It isn't all the barel time that melts the lead in the bullets. It is the spin rate and friction from the air. Usually bullets dont blow up close in. I also dont believe its not the length of the bullet, but the spin rate. Longer bullets need faster twists to stabilize them. That in turn spins them faster. I shoot 1000 yard BR and see bullets hit the bank from the pits. If the bank is wet, they lay there and sizzle.

Almost everytime I saw a bullet blowup in 18 years of competition, It was a rough barrel from high round count. Rough barrels damage the jackets. We use plenty of long bullets in different calibers and some are pushed pretty good. Very few bullets blow up. Also a 5R rifled barrel doesn't damage the bullet as much.

Years ago, the ones blowing up were 6.5 and most times, the barrels had high round counts. They also were fast twists and pushed hard. Berger had changed their jacket material when they were bought out. They also used reclaimed lead, both because it was cheaper. When they stopped that and went back to the original stuff the blowups stopped. Even though they came out with a target version with thicker jackets to help. The guys went back to the hunting version, which was the original bullet and the blowups stopped. Matt

This was my personal past experience I had with a 6.5x284. The rifle was fed a steady diet of Berger 140's and I started to lose a few when the round count was high and the throat was rough. A switch to 142 SMk's gave me 200 rounds of acceptable varmint accuracy before pulling the barrel.

The only other observation was a friends 6x284 undressing a light bullet at warp speed, but don't remember the bullet, a switch to Nosler solid base cured that.

 

[raptor1ronin]

It isn't all the barel time that melts the lead in the bullets. It is the spin rate and friction from the air. Usually bullets dont blow up close in. I also dont believe its not the length of the bullet, but the spin rate. Longer bullets need faster twists to stabilize them. That in turn spins them faster. I shoot 1000 yard BR and see bullets hit the bank from the pits. If the bank is wet, they lay there and sizzle.

Almost everytime I saw a bullet blowup in 18 years of competition, It was a rough barrel from high round count. Rough barrels damage the jackets. We use plenty of long bullets in different calibers and some are pushed pretty good. Very few bullets blow up. Also a 5R rifled barrel doesn't damage the bullet as much.

Years ago, the ones blowing up were 6.5 and most times, the barrels had high round counts. They also were fast twists and pushed hard. Berger had changed their jacket material when they were bought out. They also used reclaimed lead, both because it was cheaper. When they stopped that and went back to the original stuff the blowups stopped. Even though they came out with a target version with thicker jackets to help. The guys went back to the hunting version, which was the original bullet and the blowups stopped. Matt

So all the 90vld that went pop were from a 32" Bartlein 5R 6.7 Twist. Sent it back to Frank and he looked at the barrel and deemed it good. I have tried different lots with no success. I went to a 7 twist thinking that it would solve the problem it dint. 4 groove / 5 it didn't matter they would still go pop. i tried to slow them down to 2700 nothing still popped. Had a buddy who never had one pop in a 7 twist had several pop. Berger replaced the bullets we went to test them and bingo popped. What was strange is the bullets prior to popping would hit low from previous shot. I spoke with many people on this with same results. I come to think that its definitely RPM's and heat.

Going forward i shoot the 90SMK which shoot just as good. and NOW the 95's which shoot great and no blow ups.

 

[geo.ulrich]

Matt, you are right material changed from c21000 which is true 95-5 to c 22000 which is 90-10 plus or minus 1% on both with traces of lead less than .05 % for both..

 

[dcali]

Matt, you are right material changed from c21000 which is true 95-5 to c 22000 which is 90-10 plus or minus 1% on both with traces of lead less than .05 % for both..

Why the change? Do you know what drove that decision?

 

[geo.ulrich]

Fyrewall, I am alittle confused are you referring to bullet blow ups in air or upon impact with game? The 20 seconds with a candle is not enough to change grain. this is because of two reasons, first there is to much mass it will absorb the the heat before grain will change. If my memory is correct sierra runs empty jackets at 1200* for 30-45 seconds on a conveyor. on a long 6 mm jacket would only weigh 35 or so grains.. The ogive still is not work hardening, the creases you are seeing are either lube lines or material gathering which with bullet you showed is not the issue as it is full of lead. If you wish I will send you samples of jackets, cores, seated cores and bullets in different depths of point up with excessive lube or dry. then you can see how the material moves in process....remember core is held by a certain amount of spring back applying heat afterwards ,,,, well

 

[geo.ulrich]

Why the change? Do you know what drove that decision?

$$$$$$$$ they saved if I figured correctly maybe 8 $ per bucket. just by adding trash

 

[Webster]

Some time ago I was seeing posts in the gunsmith section about barrel quality causing inflight bullet blow ups.

My thoughts are the inflight bullets blow ups or jacket failures are not caused by barrels but by bullet jacket defects or excessively thin jackets, combined with high velocities.

I have found references to annealing of bullets over candle flames in the 1000 to 1200 degree F range. Has anybody done this? I see that the molten salt annealing process uses temperatures of 700 degrees C or 1292 degrees F to accomplish annealing on brass cases consisting of about 25 percent zinc and 75 percent copper; would a brief exposure to temperatures (with a candle) at this range anneal bullets that are about 10% zinc and 90% copper without melting cores or damaging the tiny little plastic tips?

I have also seen in the forum references to 6.5 147 Hornady ELDM bullets having some type of failure.

I hope to try this annealing stuff out with 154 .284 Hornady SST bullets at impact velocities in the 2300 fps range on wet news papers at 300 yards.

Hope to have some pics of this event.

I would E-mail the bullet manufacturer and ask about max fps and RPM. I wouldn't expect annealing to solve anything. Just pick a different bullet. Are you really having bullets blow up or are you asking about it? MV around 2850 should be acceptable and not cause blow ups. I usually hear about blow ups with super high velocity varmint bullets. All bullets sold should not fail in the expected MV for any cartridge. The manufacturers must test their product.

 

[fyrewall]

In response to Webster's and other's reasonable questions:

I am not having any of my bullets blow up but I am curious about this phenomena. I am only a casual shooter using nominal weight for caliber bullets.

I am thinking that there is a link between long and heavy for caliber bullets and blow ups, some examples would be 90 grain .224 boat tails, .243 bullets weighing more than 107 grains, 140 grain or more .264's displaying extremely high G7 BC's, and .284 caliber bullets weighing more than 175 grains. All of these bullets are designed for extreme range, velocity retention, and wind resistance. As expected, these bullets are pushed at maximum velocities using fast twist barrels. I would expect the velocities obtained are somewhat over 2850 fps with the exception of 90 grain .224's shot from .223's. Complaints about bullet blow ups have been from Hornady, Sierra, and Berger bullets.

I commonly use normal or nominal length varmint bullets like the .204 40 VMax, .224 53 VMax, .243 VMax, and .264 95 VMax. I try to get these bullets going as fast as possible without destroying my brass and with near optimum accuracy. Velocities range from a high of 3800 to a low of 3300. None of these bullets has blown up. Accuracy is acceptable for my field shooting needs.

Taking a look for the heavy and long for caliber match type bullets, like mentioned above, there appears to be a link between that bullet type and blow ups at velocities at about 3,000 fps. At this time I need to do more "home work" on what happens just after the bullet has emerged from the barrel - stuff like yaw and precession. Possibly there is a link. I am talking of bullet blow ups just feet from the muzzle. Possibly excessive wobbling combined with huge rotational forces.

I am not a metallurgist but I think during the bullet forming process excessive work hardening occurs in the ogive portion of the bullet. In an earlier post a link was included of a test by Berger where 100's of .264 bullets were rapidly fired until they started blowing up; another lot of bullets was tested, these having heavier jackets, and the blowups stopped. The argument was presented that the thinner jacketed bullets, first tested, blew up because of some fault in the jacket and that some previous used bullets, not tested, having similar dimension jackets but of a superior material whether it be alloy composition or degree of hardness did not blow up. A suggestion that Berger hunting type bullets had superior jackets was made at this point. My suggestion is that annealing the formed bullet might fix the problem. Again, this phenomena, seems to be associated with long, heavy for caliber bullets that require fast twists to stabilize.

With the exclusion of some thin jacket "explosive type" bullets these stubby varmint bullets can be driven real fast, some over 4,000 fps without blowing up. From my bullet sectioning, the jackets or the speedy stubby varmint bullets are very similar appearing to the jackets of the long, heavy for caliber match bullets.

I have viewed some match type bullets at 10X magnification and have seen what appears to be very shallow, faint, striations originating just at the base of the ogive and terminating at the bullet point. Taking a look at the innards of the sectioned bullet a series of alternating flat ridges and grooves can be observed - the squashed jacket material has to go somewhere. My former studies of compression of various materials showed that features described as "tension fractures" could originate at right angles to the force applied to the material. I hope to acquire access to more stuff including brain power to further check this out.

On the annealing, I included a link from Ballistic Studies, a New Zealand company, that suggested that annealing SST bullets would soften the ogive portion to prevent disintegration at close ranges allowing for increased penetration and that the softer ogive portion would allow more expansion at longer ranges. The link showed a bullet held in channel locks being rotated over a candle flame for about 10 seconds. I duplicated the test for 20 seconds and saw no visible change. I did not test these bullets for expansion performance. My thoughts are, if in fact, the ogive portion was annealed bullet blowups on match bullets might be fixed. Are the Ballistic Studies group on solid ground (valid)?

Another link concerning a patent for bullet annealing for "bonded bullets" appeared. A very quick read of the process was that bullet cores were copper plated (electroplated?), inserted in jackets, then the entire works annealed with ogive forming either before or after the annealing. This would be essentially annealing a formed or partially formed bullet. Would one of these "bonded" bullets blow up, even if it was long and heavy for caliber. Who needs a $100 per box of 100 bullets.

Thank-you for your interest & suggestions. What we have here is "bullet necropsy"

 

[geo.ulrich]

Fyrewall, the way you are sectioning bullets your not seeing all. try cutting down one side then down the opposite side and leave base peel like a banana and see how well core is seated. look for inclusions or pock marks on core also wipe inside of jacket with a q tip and check for oil residue. core should look fairly shiny

 

[Dusty Stevens]

At what temp does copper anneal at? At what temp does lead melt? If the lead inside expands from the heat does it compromise the seating of the core to the jacket or does it kinda lose shape if it gets to the semi solid state before melting?

 

[Ned Ludd]

The melting point of lead is approximately one third that of copper. Even the upper range of the useful annealing temperatures for copper is above the melting point of lead. I think it very unlikely that you can ever realistically "anneal" any portion of a copper jacket bonded to a lead core.

With regard to the 90 VLDs, the conditions leading to jacket failures generally correspond to twist rates combined with velocities that generate bullet spin rates in excess of 300K RPM. The propensity for jacket failures drop dramatically at RPMs lower than that. Although one solution to this issue is to switch to different bullet(s), that is not necessarily a satisfactory solution either. In the two cases described, you're talking about a bullet of comparable weight, but with a significantly lower BC than the 90 VLD, or a bullet with an identical BC to the 90 VLD, but with greater weight, so that it can realistically only be pushed to velocities in the neighborhood of 100 fps slower than the 90 VLD. Either way, the performance will not be the same.

In fairness, it must be stated that a bullet that fails to reach the target certainly has a more devastating consequence to your score than the occasional point lost merely to missed wind calls. Nonetheless, the ideal solution would be to use the bullet with the combination of the best BC and tuned velocity range, which is clearly the 90 VLD. Further, it is unclear whether there is actually any issue with the 90 VLD jackets; it may be far more likely that we have simply been exceeding the design characteristics. Either way, it doesn't appear as though any changes to the 90 VLD jackets are forthcoming. Thus, the only realistic way to achieve the ideal solution currently is to use the 90 VLDs with no faster than a 7.0-twist barrel, and at velocities that don't exceed about 2850 fps from a 30" barrel. Otherwise, the faster the barrel twist rate beyond 7.0 and/or the greater the velocity beyond 2850 fps, the greater the risk of jacket failure. As noted by others, the best alternative choice is to use a different bullet and accept that the performance may not be quite what you could have gotten with the 90s if there were no concerns about jacket failure. Otherwise, you're taking your chances with possible jacket failure if you try to get the most out of the 90s and exceed the parameters outlined above.

 

[geo.ulrich]

This is why they are drawn back in hardness before the core seating operation

 

[geo.ulrich]

At what temp does copper anneal at? At what temp does lead melt? If the lead inside expands from the heat does it compromise the seating of the core to the jacket or does it kinda lose shape if it gets to the semi solid state before melting?

At that high at temp. and already swaged either the core will start to soften or jacket will lose its tension on the core, unless there is some tin in the core

 

[DaveTooley]

At that high at temp. and already swaged either the core will start to soften or jacket will lose its tension on the core, unless there is some tin in the core

George what do think of this?
Have you ever eaten directly out of a container of ice cream. The outer layer melts. During the core seating process the jacket is expanded thus a mechanical bond between core and jacket. Melt the lead and it's going to flow somewhere. The cause, the jacket returning to its original drawn diameter.
I tend to think that would have a detrimental effect on performance.

 

[243winxb]

The lead core and copper jacket will rotate at different speeds if the bullet is not formed correctly.
Bonding of the 2 are by pressure, solder or bead blasting the inside of the jacket. Some custom bullet makes use vinegar to etch the inside of jacket , so it grips better.


A loose core + spinning friction may make the core liquid. No a good thing for accuracy.

Berger - Failures have several causes. The most common is produced by the core melting. The core melts because it gets too hot. The core gets too hot because of the FRICTION between the rifling and bearing surface. This has been proven to be the hottest part of the bullet as it moves through the barrel. This area has been shown in high speed, infared images reaching tempuratures at the melting point of lead.

Cast bullets are heated in an oven, then placed in cold water . They increases in hardness , as long as 2% or more antimony is present in the alloy.
A cast bullet shrinks in the mold as it cools. The % of antimony content has a direct effect on diameter. The higher % of antimony, the larger the bullets diameter.

So, if you heat a copper alloy jacketed lead core bullet to the correct temperature, long enough and cool in water, the lead core will harden and the jacket will soften.

The final process would be sizing of the bullets in a die.. If the bullet is sized down more than .005" the lead core may become loose inside the jacket. Brass springs back more then lead.