Bullets going poof! Causes besides speed

[js2013]

Thin jacketed bullets are more prone to going poof, but besides speed, what other factors can contribute to a bullet going poof? Would chamber characteristics, jump, barrel length, or powder burn rate have an effect?

 

[L.Sherm]

RPM'S, speed doesn't have much to do with it.

 

[SSL]

Perhaps you meant to include twist rate when you mention speed, but the faster the twist rate the more likely bullet destruction (assuming same velocity) with certain thin jacketed bullets. One that comes to mind in my experience is 50-grain Hornady .224" SX bullets working fine in 1-12" twist at 3,400 fps, but turning into puffs of smoke when fired from a 1-8" barrel.

 

[jelenko]

Berger did a study several years ago on the causes of bullets 'poofing'.

As I remember, the key was heat transferred to the lead core followed by RPM of the bullet. Enough heat and the lead core gets soft/melts.

Heat was transferred to the lead core from heat generated by friction with the bore. The thinner the jacket, the faster heat was transferred. Enough RPM's and the softened lead core comes out through the jacket.

Contributing factors were condition of the throat and the tightness of the bore. A ragged throat removes copper from the jacket - essentially thinning it. A tighter bore increases heat from friction.

 

[js2013]

Berger did a study several years ago on the causes of bullets 'poofing'.

As I remember, the key was heat transferred to the lead core followed by RPM of the bullet. Enough heat and the lead core gets soft/melts.

Heat was transferred to the lead core from heat generated by friction with the bore. The thinner the jacket, the faster heat was transferred. Enough RPM's and the softened lead core comes out through the jacket.

Contributing factors were condition of the throat and the tightness of the bore. A ragged throat removes copper from the jacket - essentially thinning it. A tighter bore increases heat from friction.

Great info! Just read some stuff at Berger’s site that barrel length is a factor due to more heat just like you posted. Thanks again.

 

[L.Sherm]

Contributing factors were condition of the throat

Alot of people don't take this into consideration when picking a barrel twist, its why I dont believe in spinning a bullet any faster than necessary.

 

[ronemus]

Rate of fire also comes into play - a hotter barrel heats the bullet core more.

The lead alloy used for the core is also a factor - as tensile strength decreases a greater load is placed on the jacket.

 

[Ned Ludd]

Bullet jacket failure is all about friction, so yes, velocity absolutely does come into play. Velocity dictates bullet RPM in a given twist rate barrel. Other contributing factors to jacket failure include barrel length, land/groove configuration (i.e. bore/groove diameter), barrel land/groove shape/geometry, barrel twist rate, and bullet bearing surface length, to name a few.

 

[wkdickinson]

Cut rifling can also contribute to thin jacket failure.

 

[jk80]

Perhaps you meant to include twist rate when you mention speed, but the faster the twist rate the more likely bullet destruction (assuming same velocity) with certain thin jacketed bullets. One that comes to mind in my experience is 50-grain Hornady .224" SX bullets working fine in 1-12" twist at 3,400 fps, but turning into puffs of smoke when fired from a 1-8" barrel.

Had great accuracy and performance with the 50 sx in a788 in 222. Thought they'd be great out of a 220 swift. Ummm, not so much!! They left what looked like pepper size holes in the target. Wondered what was going on, couldn't see bullet holes in the target through the spotting scope. Lol

 

[1shot]

Had a guy at our club shooting a 7mm mag. He shoot 3x1k at least once a month. Suddenly he starts blowing up bullets. He said he didn't change anything in regards to his re-loading. He was told to get some J-B bore paste and some Kroil and was given instructions on how to use it. He was back the following weekend and no more blow ups. The culprit, a badly fouled bore.
I hope this helps,

Lloyd

 

[Walt Krafft]

Poor reloading techniques that damage the jacket when seating the bullet can cause blowups. Poor chamfer, nicks in the mouth, excessive neck tension, and I am sure other things can damage the bullet. Then speed, twist, heat, and bore condition finish the job.

 

[mikecr]

In general, bullet failures can be predicted with RPMs generated -at the correct twist rate for the bullet.
The overall energy applied to get there, can be from multiple things.

For instance, if your jacketed 22cal bullet requires 7tw to stabilize, you'll start seeing failures at ~310Krpm.
290Krpm in 30cal. And of course it takes huge energies to get there.

You have to go out of your way to cause it.
Like pushing a 90VLD at 7tw, wide open from a 220swift.
This, also causing an accurate barrel life of around 400 shots..

 

[butchlambert]

In the olden days I had that problem with my 22-284. Went to a slower twist barrel and the problem went away.

 

[Alexander-M]

HEAT!

Video of Bullet Blow Up (was: The things one sees at a match)

One of our shooters here was vaporizing bullets in his fast twist 22dasher late in the strings as things heated up. We were getting the "mark target #( )" call in the pits before someone spotted the gray cloud and strange noise about 25 yards out. We now know what to look for when you get the no...

forum.accurateshooter.com

Alex

 

[urbanrifleman]

Do the math.

If you are up over 300k that's bad. Mkay?

Bullet RPM Calculator

Bullet RPM Calculator; Calculate Spin of a Bullet in RPM

www.findnchoose.net

Although truth be told that the RPM equations and blowing up a bullets seem to equate more to VLD type bullets and not so much to blunt nose varmint bullets.

 

[STOMP442]

I have found bullets with Hornady written on the side of the box a contributing factor. I have had way more Hornady bullets blow up on me than anything else.

 

[K22]

I am not ballistics expert or even trained in the discipline but why not just avoid the entire issue by following the bullet manufacturers guidelines on their bullets. I mean who knows more about their bullets than they do, they designed and tested them.

I never had an issue with bullets "vaporizing" even with the 22 250. Back in the day, I was a huge fan of Sierra bullets using them in a variety of calibers. I used the 50 grain Blitz bullets extensively in the 222 and 223 with outstanding results. I followed Sierra's guidance about velocity limitations and twist rates for their bullets thus never had a problem. For the 22 250, I used the 55 BTHP and Spitzers which were designed for the 22 250 and Swift velocities thus I avoided problems.

Today, with the preponderance of rifles being made with fast twist rifling and high RPM, following the bullet mfg.'s recommendation seems like a sane approach to me.

It seems like there is a never-ending effort to complicate this sport.

 

[wkdickinson]

I have an old Colt AR (CAR) w/a Colt 24", 9 twist barrel. It shoot Hornady 50gr VMAX bullets lights out. If I use that same load in my AR Match Rifle, 26" Krieger, 7.7 twist, only about a third of the bullets ever get to the target. Hornady told me the the jackets on VMAX bullets are thin and likely the twist is right on the edge of being too fast for them and that the cut rifled "match" barrel is likely contributed to the failure, since the rifling is so aggressive.

 

[gunsandgunsmithing]

In a nutshell, heat is the cause but the heat comes from several sources already mentioned. RPM is also a biggie, Bullets spin at CRAZY rpm. It's hard to imagine any bullet making it to the target when you think about it. Can be upwards of 300,000 rpm. I've been told being shot burns like hell. I'd say so!