What could cause a jacket separation for a mid powered load?

[jb1023]

Today during a load workup I had a jacket separate on me today and actually embed in my cardboard target at 224 yds. I've never seen anything like this before. This is a Hornady A-Max 178 fired from a Howa 308 w/20" 1:10 barrel. It was loaded with 42.5g of IMR 4064. This was the first shot of this particular load and at this target, I was done with the workup and just had a few rounds left over and some time to kill. Through the scope it looked like I hit the paper and assumed the reason for the odd shaped hole was just paper rip. I then fired off 3 more shots and all 3 went who knows where. No impacts at all. Once I discovered what the situation was I pulled the bolt and checked the barrel. Looks great. If you can't see from the pic, the lead core is missing and there is no hole in the cardboard at all. I decided to not fire anymore rounds till I took the gun home and thoroughly cleaned it.

Jacket 2_cleaned by jlb1023, on Flickr

 

[red dawg]

Did the jacket have any lead in it?

 

[J E Custom]

Do you have a muzzle brake on the rifle ?

Is it a 3grove barrel ?

Last but not least, it could be a bad batch of bullets that were sized wrong at the factory.

Strange !!!

J E CUSTOM

 

[jb1023]

No, the jacket is completely hollow.

 

[jb1023]

Do you have a muzzle brake on the rifle ?

Is it a 3grove barrel ?

Last but not least, it could be a bad batch of bullets that were sized wrong at the factory.

Strange !!!

J E CUSTOM

No, I don't have a muzzle break.

I suppose that some of the bullets in the box could be sized wrong but the last 4 fired were from the same box as the first 20 and none of those had any issues, other than a bit higher number than expected number of fliers. I still flinch sometimes so I expect some fliers.

I have no idea if it is a 3 grove barrel or not. How would I tell? It is a stock Howa barrel if that makes a difference.

 

[Mikecr]

How could a hollow/lead shedding bullet jacket hit a target at 224yds?
Pretty hard to believe, as unstable bullets are lucky to hit a target beyond 25yds.

 

[jb1023]

How could a hollow/lead shedding bullet jacket hit a target at 224yds?
Pretty hard to believe, as unstable bullets are lucky to hit a target beyond 25yds.

I agree. If it were not an oddity I would not have inquired about it. I would think it had to have separated fairly close to the target rather than right out of the barrel.

 

[Barrelnut]

Might have been barrel heat. You said it was at the end of the shooting session. I have read of A-Max bullets coming apart in hot barrels before. This is why Berger went to the thicker jacket on their target bullets. The hot barrel can separate the jacket from the lead and the bullet comes apart. The fact that it hit the target like that is amazing.

 

[J E Custom]

No, I don't have a muzzle break.

I suppose that some of the bullets in the box could be sized wrong but the last 4 fired were from the same box as the first 20 and none of those had any issues, other than a bit higher number than expected number of fliers. I still flinch sometimes so I expect some fliers.

I have no idea if it is a 3 grove barrel or not. How would I tell? It is a stock Howa barrel if that makes a difference.

The reason I ask about the brake was, if it was not installed correctly you could have a bullet strike condition that could rip the jacket off.

When sizing bullet jackets with a lead core, the jacket can spring back and be loose on the core
if over sized or the jacket materials are not soft enough.

To see how many groves you have just look at the jacket you have and it will tell you grove and land count. the reason I ask about the 3 grove barrel, they can be hard on the jackets of some bullets.

Bonded bullets would probably prevent this, but it is rare to lose a jacket at that distance.

J E CUSTOM

 

[Mikecr]

I agree. If it were not an oddity I would not have inquired about it. I would think it had to have separated fairly close to the target rather than right out of the barrel.

Like it hit a berm or a branch, flinging apart, losing all energy, just before whacking the target. I'm talkin just before, otherwise the shrapnel remaining would never have hit the target.

 

[Laelkhunter]

Is it possible that the bullets were striking low enough that they hit the ground somewhere in front of the target? The bullet could have struck the ground, the jacket separated from the core, and just the jacket bounced up and hit the target?
I would try shooting at a closer distance (50 yards) then move out progressively further until you see the bullets start to tumble or react in an abnormal way.

 

[Mikecr]

Is this your neighbor?

 

[jb1023]

Might have been barrel heat. You said it was at the end of the shooting session. I have read of A-Max bullets coming apart in hot barrels before. This is why Berger went to the thicker jacket on their target bullets. The hot barrel can separate the jacket from the lead and the bullet comes apart. The fact that it hit the target like that is amazing.

I was not aware this was a possibility. While I don't think my barrel was too hot, I waited a timed 2 min between rounds and touched it periodically, the ammo was rather warm to the touch. This particular loading was not as protected from the sun as the previous fired rounds as these were just extras and not a part of my workup. I actually passed on one of the rounds in this box as it was rather hot to the touch. This particular round was just warm. Whether that was the cause or not I am going to be more careful about keeping my rounds out of the SoCO sun.

 

[jb1023]

Like it hit a berm or a branch, flinging apart, losing all energy, just before whacking the target. I'm talkin just before, otherwise the shrapnel remaining would never have hit the target.

Is it possible that the bullets were striking low enough that they hit the ground somewhere in front of the target? The bullet could have struck the ground, the jacket separated from the core, and just the jacket bounced up and hit the target?
I would try shooting at a closer distance (50 yards) then move out progressively further until you see the bullets start to tumble or react in an abnormal way.

I suppose hitting low would be possible although that would be WAY low from POA. My target was the black diamond on a 8x11 piece of paper. The bottom of that paper was about 20" above the ground and attached to the cardboard backing. This was my first shot at this target. All 20 of the previous rounds were fired at a target at 110yds, and POI was about 2" below POA. One difference between the two that I guess could make a difference, I'm still learning, is the 224 yd target was about 15-20' above the bench whereas the 110yd target is level.

Every shot fired was over a chrono, Caldwell and not my Magneto. Having said that the numbers were fairly consistent except the final group, which included the bullet in question, was a tad slower than I expected.

Not listed in order as the 42.5 was a left over lot I chose not to go with.
42.1g = 2587
42.4g = 2644 but that had one really hot round which if I remove it the average is 2624
*42.5g = 2613
42.7g = 2677

The bullet in question had a reading of 2617. I guess with that speed I would not expect it to hit that low and I know I did not fudge the shot that badly. When i do flinch it tends to be to the right, not down I suppose anything is possible though. A low POI ricochet could explain the condition of the jacket though.