Problems at the range today, upper damaged.

[usmcm16a2]

Folks,



I went to the range today with one of my Grendel builds. 20 inch 1:9 Spinta Precision, adjustable gas block, rifle length gas system, .264 LBC. Was shooting with different loads, 123 A-Max 30.5 grains of CFE223. 120gr Barnes TTSX 30.5 grains CFE 223. 2.26 COAL, and 118gr MKZ over 30.5 CFE, COAL 2.26. The 123,and the 120 shot very well. Then trouble.
I shot the MKZ, blew the primer out, I thought it was a fluke, fizzle, had to take a mallet to my charging handle. The shell was stuck, got it out blew the primer into the bolt cam recess. The charging handle was bent. I called Robert at CBB, and he is looking into his load data library. I am not looking to get a new Upper out of him. The charge seemed on the mild side. 30.5gr of CFE 223, need your thoughts. Thanks A2

[LRRPF52]

Can you post a photo of the 118gr MKZ next to a 123gr AMAX to compare bearing surfaces please?

30.5gr of CFE is max with some of the 129gr cup and core bullets, as well as a 120gr TSX.

Is the MKZ a cup and core or a solid bullet?

[usmcm16a2]

Copper solid with 3 petals that make up the hollow point. Spoke with the owner of CBB, he has safely loaded up to 31.5 of CFE 223. A2

[Klem]

It's a hot load according to QL. While some here are suspicious of QL I use it as a ready reckoner. It estimates 55,700lbs of peak pressure, which is over the SAAMI limit of 52,000 but not by much. It shouldn't have caused that much damage by itself. It does sound like a 'blocked' barrel with the pressure taking the path of least resistance.

Maybe the tighter neck of the LBC and that 118gn copper round with the big expansion hole in the base had something to do with it. If you have any spare 118's you could measure the diameter. The .295" neck diameter of the LBC vs. the .300 of Grendel is less forgiving. If Lapua cases they are thicker than others. There needs to be enough space for the neck to expand and release the bullet. maybe the copper hole in the base started expanding too early and gripped in the neck.

I am unfamiliar with these new copper bullets but that big hole in the base caught my eye just now.

[LRRPF52]

Copper solid with 3 petals that make up the hollow point. Spoke with the owner of CBB, he has safely loaded up to 31.5 of CFE 223. A2

I wouldn't go anywhere near 31.5gr of CFE under the 120gr TSX, I can tell you that.

These copper projectiles build pressure much faster than standard cup and core bullets. They don't swage into the rifling like a cup/core, and don't like to be pushed around.

I also noticed that there are only 2 pressure relief bands on the MKZ, whereas the Barnes 120gr TSX has 3, and the bearing surface appears to be quite long on the MKZ.

With a 120gr TSX, I wouldn't load anywhere above 30.3gr of CFE in 6.5 Grendel, as it really spiked on my when I went to 30.6gr from an 18" barrel.

That 30.3gr load of CFE223 under the 120gr TSX was already giving me 24" max published speeds from AA with BL-C(2).

When you blow primers out, it's either a dropped primer or severe overpressure. One of the dead giveaways is black soot flowing through the flash hole into the pocket and around the case head. Can you take pics and post them of the case with the primer that blew or dropped please?

Klem, I never considered that possibility, but if the base of the projectile was able to harness enough of the conversion and acts like another chamber of sorts, and the copper is soft enough, it could very well bell out and not want to release. That kind of event could seriously raise pressures into primer-blowing territory for sure, or much worse.

Glad your rifle didn't turn into a frag grenade.

[Klem]

+1,

The expansion thing is just a theory. I saw that big cavity in the base and wondered what happens to any powder that's inside the cup when it goes off. Surely there is some sideways expansion along with pushing the bullet forward.

Wouldn't be the first time a new innovative bullet has been released onto the market to then do damage to enough guns that it is qualified. Le High's 78gn 30cal CQB had the occasional petal flying off inside suppressors and busting them. On their website they then suggested a twist rate/RPM maximum. Now they have ironed out the bugs and declare it 'suppressor safe'. Not the first time the general public ends up finishing off someone's Research and Development.

[CavityBackBullets]

What the op is not telling you is he did a ladder of .3 grains working up his charge.
No pressure signs what so ever at 30.2 grains and states blown primers at 30.5 grains.
The suspicion is an over charge well beyond 30.5 grains in his ladder.

To answer the questions.
All our bullets are solid copper.
The bearing surface is smaller than a 120 TSX.
The base of the bullet does not expand as the cavity is never deeper than the boattail. This is by design as the pressure stays equalized on the outside and inside of the cavity.
No projectile recovered in any caliber has ever shown any changes to the cavity and base of the bullet. With thousands of samples.
QL cannot and does not compensate for the pressure handling capabilities of our design.

Our bullets are designed to have less bearing surface than standard copper bullets.
The design inherently handles pressure better than any other solid copper bullets on the market.

This is the first time anyone has stated blown primers with our bullets. In any caliber.
The suspicion is an over charge well beyond the 30.5 grains the OP thought the charge was.

[Double Naught Spy]

If we are going to use Klem's historical precedent concept to diagnose what happened here, the most common reason for gun damage by reloaders is reloader error/QC, plain and simple, and accidental charge amounts probably being the most common of reloading errors producing gun damage.

If not a charge error, I would be asking how many times the brass has been used. Loose primer pockets are also an issue when it comes to blown primers.

Of the bullets I recovered when I used CBB MKZs, none showed any discernible changes to the base due to pressure.

[Kswhitetails]

I was skeptical of the boat tail expansion theory, but it is an easy to make argument that seemingly holds water. However physics say that the pressure would be equal inside and out of the BT; As stated above, I am inclined to take this at face value.

From the description, it sounds like the only real damage came from using the mallet to force the bolt back with the charging handle. Hard to say. No pics, no other info to prevent assumptions.

I have worked some with my own sets of CBBs, a little. I haven't gotten close to max loads yet, but so far they have performed very well without the need. I am anticipating using these at less than 200 so I don't worry too much about max speeds.

Just my two cents. No issue with anything anyone has said, this is a great discussion.

I will say one last thing, CBB has been great. Sharing information, and helping with the few questions I have had.

[usmcm16a2]

Folks,


I am not trying to trash CBB, or Robert. Robert has always been great in working with reloaders like myself. To me his product is one of the best out there. As soon as my fucked up state of California gets off its ass and approves CBB I will start to use them.
I want to state clearly, and plainly that I am completely responsible for what happened. But I feel that I need/needed the help of others. I have reloaded for the better part of 20 years, but I am not perfect, but I am totally responsible for what I put out. A2

[LRRPF52]

What the op is not telling you is he did a ladder of .3 grains working up his charge.
No pressure signs what so ever at 30.2 grains and states blown primers at 30.5 grains.
The suspicion is an over charge well beyond 30.5 grains in his ladder.

To answer the questions.
All our bullets are solid copper.
The bearing surface is smaller than a 120 TSX.
The base of the bullet does not expand as the cavity is never deeper than the boattail. This is by design as the pressure stays equalized on the outside and inside of the cavity.
No projectile recovered in any caliber has ever shown any changes to the cavity and base of the bullet. With thousands of samples.
QL cannot and does not compensate for the pressure handling capabilities of our design.

Our bullets are designed to have less bearing surface than standard copper bullets.
The design inherently handles pressure better than any other solid copper bullets on the market.

This is the first time anyone has stated blown primers with our bullets. In any caliber.
The suspicion is an over charge well beyond the 30.5 grains the OP thought the charge was.

When I look at a 120gr TSX next to the 118gr MKZ, it appears that the MKZ has more bearing surface, since there are only 2 relief bands as opposed to 3 on a TSX.

"The design handles pressure better than any other solid copper bullets on the market."

I would like to see the test instrumentation comparison to support this very bold claim. I know a lot of the engineers at Barnes, Hornady, and Federal, and the decades of institutional knowledge and testing that just one of those companies has, let alone their combined expertise, and you would have to be in the company of a team of engineers and scientists who possess some level of collective genius that exceeds that of those companies' entire design and test staff to make a bullet with better pressure relief.

If you're approaching pressure relief volumetrically for a solid by allowing more case capacity into the base of the projectile, that isn't the main challenge with solids. Alloy structure and resistance to being driven into the lands is the main challenge with solid projectiles, which is why you see totally different charge weights for them compared to cup and core bullets of the same weight.

"The suspicion is an over charge well beyond the 30.5gr the OP thought the charge was."

Did you state that 31.5gr of CFE is safe under a 118gr MKZ? "No pressure signs?"

I'm also seeing references to .5gr increments on your site, without any specific discussion of the cartridge and detailed load approach. .5gr increments with a solid in .260 Remington is too large of a charge weight increase, let alone Grendel.

Especially with a solid in 6.5 Grendel or 6.8 SPC, you should never load in .5gr increments. These are ~30gr usable case capacity cartridges, and therefore applying the 1% increment approach, leaves you with .3gr increments. For a solid, I would recommend .2gr increments because they build pressure much faster than an equivalent weight cup and core bullet.

Another major red flag I'm seeing is that you immediately blamed the customer without knowing much about the facts, which is questionable business practice at best.

The next major red flag is that there is no testing data provided about your product, other than "With thousands of samples."

Your website is full of spelling, grammar, and punctuation errors, with very broad and generalized statements with zero technical data to support those statements, but your first response is to blame the customer. Normally when we see an inability to command the English language, or a failure to ensure that a business website has been proofread, it begs the question as to what other balls have been dropped and what the education level is of the staff/owner.

I think this is the first time I've seen an owner immediately rush to judgment and blame the customer on an open forum though, rather than consider all the information and work towards determining exactly what the problem is.

It may have been just a loose primer pocket with a dropped primer. It may have been an over-pressure load. It also might be a flaw in a new design that hasn't been tested by a technically competent firm, which any half decent manufacturer is going to do. Customers don't see what goes into testing of ammunition products, whether they be primers, brass, powders, or bullets.

We're talking about a huge footprint behind each component and loaded ammunition that you can't wrap your head around in a day if they gave you a VIP tour of their facilities and opened up all their proprietary engineering and test notes to you. The layman would be buried in so much data and considerations they never thought of, that they would walk away with a new and elevated level of respect for what these companies actually do.

And then there are the amateurs. I'm seeing some major red flags that I don't like here, technically and business-wise.

For manufacturers: I know that those that are professionals already know this, but if you come on this forum and blame customers right off the bat, we're probably not a good fit for your business model.

[keystone183]

Some strong assumptions in that post.....

[LRRPF52]

If you look at usmcm16a2's loading habits, he's actually on the very low end of charge weights from what I can see with a search, and my memory of his loads over the years.

He's never come across as one of the brave ones pushing for more and more speed, as long as they bang steel for him at relatively close to intermediate range, he's happy.

This is the first time I've seen a business rush to blame the customer. The only thing I can think of that comes close is an intermediary/shill blaming customers or the forum for blown primers with a particular barrel maker, with the barrel maker never making any statements here.

Other than that, standard industry/business practice is to say that you're sorry the customer had this experience, let's investigate further to determine what the problem was so that it doesn't happen again.

[keystone183]

Rush to blame a customer? You're reading things i'm not.

[davidj]

Rush to blame a customer? You're reading things i'm not.

"This is the first time anyone has stated blown primers with our bullets. In any caliber.
The suspicion is an over charge well beyond the 30.5 grains the OP thought the charge was" ??