Bullet Blow Ups

[fyrewall]

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.

 

[dcali]

I don’t know how you’d get the jackets that hot without melting the cores given how thin they are and how good a conductor copper is. Nor do I know what impact annealing a jacket after it’s been swaged would have. Someone must have done it.

There are a lot of theories on what causes blow ups. The most convincing one I’ve heard is that it’s due to heat transfer through the jacket, probably in the region just ahead of the boat tail that melts a layer of the core, allowing the spin to rip the jacket away. And that thicker jackets are simply a way to delay that heat from hitting the core just a tiny bit longer. But I don’t know much about it in any detail. I believe Berger looked into this in some depth a while ago.

 

[M-61]

My thoughts: Thin enough jacket, high enough velocity AND a tight enough twist. The result is that white puff down range.
My knowledge of annealing bullets is zero. (actually never heard nor thought about it at all)

 

[geo.ulrich]

Here we go again, I suppose the answers in the other thread didn't fit what you wanted.. It has been done see other thread. Geez some are hard learners.....

 

[SSL]

Considering lead has a melting point of 621.4 degrees Fahrenheit, it doesn't seem that any of the annealing plans would be of any value if one wishes to retain the core...not to mention what that kind of heat would do to poly tips.

 

[1shot]

I have personally been involved with two bullet blow up scenarios, and both were barrel related. One was a tear in the rifling that didn't get caught in the QC from the factory. (6mm)
The second was a very dirty barrel. (7mm)
I have been running fast twist bbls. for some time now without any issues.
I hope this helps,

Lloyd

 

[243winxb]

annealing of bullets

Bonded bullets using heat , or chemicals patent.https://patents.google.com/patent/US6613165

Embodiments of the described method include (a) forming a core comprising a lead alloy, (b) applying copper or a copper alloy to at least a portion of an exterior surface of the core to form a jacketed bullet, (c) heating the jacketed bullet at a pre-selected temperature for a period of time sufficient to simultaneously harden the core and stress-relieve the copper jacket, and, optionally, (d) reworking a selected portion of the heat-treated bullet by mechanical r

More at link.

Lead alloys containing antimony can be oven heat treated, then water quenched to harden them.

Sierra uses 4 different lead alloys in there cores. Some harder then others. No heating.

 

[243winxb]

Berger bullet blow up testing. http://benchrest.com/showthread.php?49336-Berger-bullet-failure-test

 

[dcali]

The other part of this problem is that only a few bullets routinely blow up, and occasionally you see a barrel that shreds bullets like it's a job. If it's the barrel, it's the barrel. Get a new one.

In fact, I'd wager that these days, there are only a handful of competition bullets out there - .224 90's, for example - that have issues that are bullet related, and they're pushing the limits of rpm and structural integrity with high spin rates. So even thinking about mitigating this "problem" in the vast majority of bullets is a waste of time and resources.

For those few bullets living on the edge, there are probably some improvements to design that can be done to help a little. I don't know what they are, specifically, but I believe George when he says that this has all been done, and logic would tell us that annealing the jacket after it has been swaged would be difficult at best, and I'm not sure I see why it would help and not hurt even if you could do it. In my opinion it would be better to address the bullet design in other ways, and just to acknowledge that there are limits to copper jacketed lead bullets. A 4" twist 120 grain .224 just isn't going to work out (for this and other reasons). If they did we wouldn't need larger calibers.

 

[Shaggy357]

Temperature, velocity, jacket thickness, and barrel twist will all be factors in causing bullets to come apart in flight. I have a 6BR that I was shooting in competition. Went thru sighters and the first five timed shots just fine. The first shot in the second round I was on target and did a slow squeeze. Nothing on the target! Next four shots were dead center. Asked the match director to check the target. Nothing! Went thru the next five shots, all center hits. Moved to the next bank of targets. Hit the first three dead center. Nothing on the last two. My spotter said they did not see anything!! Switched to a different box of ammo and cleaned the next 40 targets. Doing some later testing we found out the bullets I was using on the first few banks of targets had a much thinner jacket than the others. The fast twist 1:7 barrel was taking the jacket right off of those 105gr bullets. My buddy was shooting the same bullets in a 6TCU and never had a problem. The only difference was my 6BR was pushing them about 300fps faster. About a month later, same range, similar conditions but about 10 degrees warmer, my buddies 6TCU did the same thing. We figure the temperature probably increased the pressure in his load a little and between hotter load and hotter temperature he hit that breaking point of jacket failure. I have never had one of those bullets fail in my .243 Win or .243 WSSM. They are both 1:10 twist.

Lots of factors add up reach that point of failure.

 

[ebb]

Back when the 300RUM first came out I had a sendero that had the factory barrel and tried to shoot 210 bergers. Some would not make it to the target. The Berger tech said too much twist, too much speed and too rough of a barrel. It would not blow up a Barnes.

 

[DaveTooley]

Too many important parts to this equation to point to any one thing. We can all agree that velocity, twist rate and barrels can contribute to bullet failure. Bullet jackets can also play a role in this.
Real world example.
6.5 140 gr. FB bullets. First lot was absolutely amazing. Next lot of jackets and we immediately had bullet failures. For me 9 out of 10 blew up. I shot through angled plywood and finally got a bullet to go sideways through cardboard. It showed a lead spray emanating from the junction of the ogive and body.
Also some bullet companies anneal their jackets for specific applications.

For anyone having bullet failure shoot through a target at 15 yds. Might surprise you.

 

[geo.ulrich]

Dave you are right sierra and hornady get jacket material from here in town Olin corp Sierra as you know from visiting there plant anneals all long jackets it takes to many draws for them not to. J4 on the other does not anneal they just figure deep draw quality is good enough even though it's apparent it isn't or they wouldn't have had the problems they did. I have had to many conversations with Eric when he was in charge at Berger and answer was always the same " we are not going to change material or suppliers" Hope your doing well...

 

[ebb]

Dave my 7 RUM would not get 162 Amaxes to the target 20% of the time. After about a year off and on of messing with it I held my head away from the rifle pulled the trigger and saw the firing pin fall and the cartridge went off at least a second or more later. A trip to Gertan later and firing pin protrusion set and it seemed to work OK. Was I seeing a hangfire like I thought? Was this the reason for the blow ups? I am convinced it was but am not sure. I was told a hang fire makes way more pressure and this was the reason for the blow ups.

 

[dcali]

Dave my 7 RUM would not get 162 Amaxes to the target 20% of the time. After about a year off and on of messing with it I held my head away from the rifle pulled the trigger and saw the firing pin fall and the cartridge went off at least a second or more later. A trip to Gertan later and firing pin protrusion set and it seemed to work OK. Was I seeing a hangfire like I thought? Was this the reason for the blow ups? I am convinced it was but am not sure. I was told a hang fire makes way more pressure and this was the reason for the blow ups.

I have only ever had a few hang fires (all from the same tray of primers), but I never saw pressure signs with what was already a hot load. Just one data point but that’s my experience.

 

[mongo chicago]

I always thought too tight a twist and too light a bullet would do that

 

[SSL]

That can happen too. My .223 Ruger with 1-12" twist shoots Hornady 50-grain SX bullets into small groups. My nephew's Savage with 1-9" twist turns the identical load into interesting smoke clouds about 60 yards out.

 

[ebb]

I read some where on the net that hang fires can cause way over pressure. A change to 175 SMK was better but not the solution.

 

[fyrewall]

I have only experienced bullet blow ups from a 1-14 twist .22-.250 shooting 53 grain Hornady flat based hollow point bullets at about 3800 fps. Gray smoke with some and bullet profile holes (side ways) in paper with others.

I am no bullet expert and have no inside knowledge concerning the bullet manufacturing process.

I did find this link:

https://www.ballisticstudies.com/Knowledgebase/SST+and+Interbond+annealing+tutorial.html

In this link it shows a SST bullet being exposed to the lower part of a candle flame what might be at of 1000 degrees F. Lead melts at temperatures much less than that. The bullet appears to be exposed to the flame for an interval of about 10 seconds.

Would a ten second exposure (plus or minus) be enough to melt or damage the lead core? Would the tiny little plastic tip get droopy despite no being directly exposed but real close? Would any lubricant applied during the manufacturing process turn into "black goo"?

The originators of the above link claim bullet performance in regard to "blow ups" on game animals are reduced by the bullet annealing.

It would be no big deal to try this out, up to the point of shooting some big beast or a pig carcass (Sierra Game Changer Ad) with both non-annealed and annealed bullets. Hopefully, sectioning bullets prior and after annealing will answer the lead core melting, lubricant change and plastic tip deformation question. Not having access to pig carcasses or 500 pound rodents I will shoot at cardboard boxes stuffed with wet news papers.

In a previous post the term "arrherinus" was used to imply that heating a bullet with a low temperature flame would not supply enough heat for annealing, crystal growth to take place. Candle flames produce 1,000 degrees F and the question is - would exposure to that 1000 degrees for 10 or so seconds anneal the ogive portion of the bullet without damaging the core or plastic tip if the bullet had a tip. Apparently, the Arrherinus equation is applicable to crystal changes in metals. As mentioned immersion in some molten salt bath at 700 degrees C or 1292 degrees F for a short time can anneal brass cases.

It would really be PO'ed if I spent from $35 - $50 for a box of bullets to only see them disintegrate when shot from my nice slick, well known, high reputation, manufacture's barrel.

Longer bullets appear to have more of the bullet blow up problem than short stubby ones.

 

[raptor1ronin]

90grn Berger VLD’s seem to pop way to easy now a days. Had several not make it to the target.