Blown case base...looking for feedback

[Tusker6N]

OK everyone. Looking for some feedback on this one. I've never seen a case do this. Here is the run down on what happened.

Rifle is a new Remington 700 action with Preferred Barrel's 20" heavy barrel chambered in 375 Raptor. Headspace was set using Go/No Go gauges.

All brass used was once fired Lake City that was collected on a civilian shooting range and fired from an AR-10 or bolt action 308, no machine gun brass. Brass was sized and fire formed for 375 Raptor. This is the 3rd firing for the brass.

The load data for the round is proven and was loaded at the same time as all other rounds fired during the firing session. This was the 8th round to be fired through the rifle. Rounds 1 thru 7 were inspected for any pressure signs and none were present. The brass split perfectly into 3 segments at the base and the splits only extended to the top of the webbing. The bolt opened easily after firing. The primer was not punctured by the firing pin.

I have 2 AR-10s and the Rem 700 in 375 Raptor. I've fired hundreds of rounds through the AR-10s, all using LC brass and have multiple reloads on brass. This is the 1st catastrophic failure I've ever had with this chambering.

So...is this just a bad brass?
Do I need to check if the angle cut on the chamber face is too deep and leaving too much of the base unsupported?

I'm trying to decide if I need to scrap all the Lake City brass and go to new commercial brass.

Thanks for the input.

 

[gunsandgunsmithing]

Bad brass or massive over pressure..one way or another. Can't see the critical area regarding too much unsupported case but with the way that one ruptured, it doesn't look like the cause.

 

[M-61]

Certainly looks like massive over pressure, but I’ve never used brass that was ‘picked up’ at any place or range. No one has a clue what it was really fired in nor how it was reloaded.
Plenty of people pick up brass off the ground and are really successful doing so.
I will not do that.

 

[jackieschmidt]

Certainly looks like massive over pressure, but I’ve never used brass that was ‘picked up’ at any place or range. No one has a clue what it was really fired in nor how it was reloaded.
Plenty of people pick up brass off the ground and are really successful doing so.
I will not do that.

^^^^^^[[

 

[markm87]

Another vote for over-pressure. I'll scoop up 5.56 and straight walled pistol brass. Sizing and seating the primer will tell me if it's destined for the scrap bucket.

 

[K22]

Never seen a case failure like that before.

I stopped using range brass a very long time ago after a bad experience with 308 cases, presumably fired out of a semi. As M61, the uncertainly of prior use of the cases renders the case as the number suspect since you claim the load is a "proven" load, presumably meaning it is safe pressure wise and assuming you got the powder charge correct with the correct powder.

Also, since you have no prior failures with the rifle, it seems reasonable to rule the rifle out.

That leave the case possibly being subjected to severe over pressure by the prior user creating stresses that finally gave way after reaching the yield point of the metal after a few more reloads.

Of course, all of this is just speculation, but I wouldn't continue to use these cases. If this condition reoccurs with virgin cases sized and fitted to your rifle chamber, then you will have your answer.

 

[Walt Krafft]

I know a bunch of shooters who are absolute brass hounds, until they know the brass is junk. Then they leave it for someone else to pick up. You got what you paid for it.

 

[Walt Schmidlin]

What is the thickness of the neck of the ruptured case versus the neck thickness of the previous 7 cases?
I only use range pick up brass for 45ACP cartridges.

 

[SeabeeKen]

All good ideas here. Do you have a pic of the case from the side? Were the pick ups with primer crimps or not? If not then the brass was reloaded before and had the primer crimps removed and makes the brass suspect. While I do pick up LC brass, I inspect the hell out of it. First look is for a primer crimp and then pressure signs. I'd also like to know the neck thickness. Could there be a donut that bound the bullet from being released? I also agree that you might consider virgin brass and be sure neck thickness gives at least .002" under chamber dimension for a loaded round. Glad you weren't hurt.

 

[jepp2]

I had to research to find out what cartridge that even is. I don't know what powder you are using or the water capacity of the fired case. But as a minimum I would start with new Lapua or Peterson brass to form from. Any idea what pressure you are loading to?

I am a brass hound, but not for a cartridge that has as much going on as yours does.

Do I need to check if the angle cut on the chamber face is too deep and leaving too much of the base unsupported?

I would be asking this to whoever chambered the barrel and sharing the failure you experienced and ask their opinion.

 

[Bill K]

Looks like that one had a extra grain or so in reloading and had to much pressure when fired and blew the case at the base. ( Over Pressure, is my opinion) No other did this, or did you stop shooting when this occured ?

 

[Tusker6N]

I appreciate the feedback and it all supports my conclusion that I need to go with new commercial brass and stay away from military stamped.

Yes, it is once fired, I removed the crimp.

The load data i used is from the manufacturer website for the Raptor. I started 6 grains below their published loads, stopped when I got pressure signs in the primer and backed down 2 grains.

I will be cutting that brass open and measuring the wall thickness at the webbing. I will compare it to other LC 05 and other brands of 308 brass.

I seperated all brass by brand and measured water volume when I was developing the load. All the LC stamped brass had the same volume. Other brands of brass had less volume, so I figured less case capacity. Seems that could mean a thicker webbing at the base.

I will be cutting open every brand of brass in 308 that I have...find the thickest one and buy new.

Will also be looking to see how much of the case is supported by the chamber.

 

[Walt Krafft]

If you had a case support issue, it would have blown out the side, not split the head.

 

[Tusker6N]

Looks like that one had a extra grain or so in reloading and had to much pressure when fired and blew the case at the base. ( Over Pressure, is my opinion) No other did this, or did you stop shooting when this occured ?

The 7 rounds prior looked perfect after firing

 

[6.5 forever]

Range pickup brass leaves the door open for all sorts of unexplained problems.

 

[Rsadams]

I only pick up lake city 5.56 that appears new and shiny no machine guns around my range... The crimped primer let's me know it's once fired.... I don't pick up any other rifle brass because it can be a dangerous game... Pistol brass I pickup as long as it has the right color primer in it or if I see the shooter take it out of a box and fire it....

Honestly I just buy a box ( 9mm ) and reload it over and over till it starts shooting weird... Except for stuff like 10mm which I buy starline because I load it pretty hot compared to the crap you buy at academy... That academy brass or extremally nice range pick ups get loaded down to plinking/practice rounds which I shoot till they get to shooting weird , split or won't hold a primer correctly... Large rifle i buy new brass....

 

[fkimble@charter.net]

A close up side view of that brass would be nice to see!!!!!

Frank

 

[JSH]

Range brass = headaches now or later.
That is coming from an X brass hound.
For the few cents you save can cause $$$$$ in damage and issues.
The older I get the more valuable I find my time.

 

[RegionRat]

I appreciate the feedback and it all supports my conclusion that I need to go with new commercial brass and stay away from military stamped.

Yes, it is once fired, I removed the crimp.

If you are positive that you picked up once fired cases and the primers were still crimped, then something else happened and I would not blame the headstamp as the cause.

When you picked it up to prep it, you would have noticed any evidence of abuse on the first firing. Abused brass should have been evident on inspection and sizing, and you also would notice if the primer wasn't crimped if you were checking.

Most Lake City Mil-Spec 308 brass is above average quality in both material specifications and heat treat. By itself, the use of once fired LC Mil-Spec headstamp isn't a likely cause.

There can be statistical "escapes" in any and all brands of brass where material defects can sneak through the inspection process. It is just an unfortunate fact of life. The good news is it is also rare when the manufacturer is on their game.

There is nothing wrong with the idea of going with virgin commercial brass for use in a conversion where you put work into forming the brass, but pick a good one since there is more uncertainty in the quality and design of commercial 308 brass than there is in Lake City.

If it were me, I would only have used my own once fired brass where I was positive of the history.

That said, I would go double check everything else because the odds are that this was not a "common cause" issue.

I would inspect that chamber as well as my whole reloading process to double check you didn't miss something. Good Luck with the new rig and play it safe.

 

[MisterHelix]

All I use in .223 is once fired LC brass by the thousand, but it would only take one blown case for me to start ordering commercial because I’m superstitious and squirrelly and easily spooked.

I reckon you only need a couple hundred for your specialty chambering, so why not order a box of starline or lapua?