Can anyone help with this "mystery load"

[gahillhunter]

Please be kind, I'm not a reloader, just a joe blow shooter. Some time ago I purchased some .308/M118 commercially loaded ammo (from a small ammo manufacturer, no major brand). I shot about 10 rounds, in total, from my Remington 700 (5R barrel). This stuff is HOT!

I was shocked at the recoil, but more shocked when I had most of the cases stick upon cycling the bolt (name brand ammo has never done this in this rifle). I thought it was odd but shot a few more as they were grouping ok at 200 meters. I shot a few more and not only did I have sticking cases, but one case rupture. The case ruptured outside of the chamber, just before the extraction ring (that was the last round I shot).

My first thought was this was a BS company simply tumbling mil-surp, but the rounds are not crimped at the neck or the primer. I disassembled one to see if the powder was pulverized, it's looks "normal" to a non-reloader. I was wondering if anyone here could help identify what might be going on.

Upon disassembly I weighted the powder (I do have reloading equipment, I just don't reload). The powder charge is 43.7gr, with a 175gr projectile. The case lists the speed as 2,645fps. Pic of powder is attached, in case that helps any.

Any insight you can offer would be helpful. I'll likely need to disassemble and re-load these (as my first go-round at reloading) but I'm very curious if you all think they just have too much powder (which means I could re-use the powder) or if there is something fundamentally wrong.

TIA

Chad

 

[Evintos]

M118LR using Alliant RL-15 at 43.5gr and 175 SMK (Alliant Techsystems Inc era M118LR). It's correct and yes, it's a spicy load.

 

[gahillhunter]

M118LR using Alliant RL-15 at 43.5gr and 175 SMK. It's correct and yes, it's a spicy load.

Any thoughts on why it would swell and rupture the case?

 

[Evintos]

Any thoughts on why it would swell and rupture the case?

It was just that hot because the powder charge was too high and caused excessive pressure especially with increases in ambient temperature.

Edit - should also add, the amount of chamber free bore also matters when it comes to pressure. I don't remember the dimensions but there is a M118LR chamber spec (longer freebore, etc).

M118LR has had several iterations due to the pressure issues causing parts breakages, which caused the powder charge to change from 43.5gr of RL15 down to 43gr of RL15. Accuracy issues of the M118LR at 43gr of RL15 eventually led to the development of M118LR MK316 MOD 0 by NSWC-Crane, which is basically 175gr FGMM using IMR4064 powder and Federal 210M primers (modern FGMM uses Alliant AR-Comp).

Your small ammo manufacturer probably just copied the recipe and didn't realize there were changes for reasons.

 

[gahillhunter]

It was just that hot because the powder charge was too high and caused excessive pressure especially with increases in ambient temperature.

Edit - should also add, the amount of chamber free bore also matters when it comes to pressure. I don't remember the dimensions but there is a M118LR chamber spec.

M118LR has had several iterations and due to the pressure issues causing parts breakages, which caused the powder charge to change from 43.5gr of RL15 down to 43gr of RL15. Accuracy issues of the M118LR at 43gr of RL15 eventually led to the development of M118LR MK316 MOD 0 by NSWC-Crane, which is basically 175gr FGMM using IMR4064 powder and Federal 210M primers (modern FGMM uses Alliant AR-Comp).

Your small ammo manufacturer probably just copied the recipe and didn't realize there were changes for reasons.

Thank you for that information, it really helps put things into perspective. I can see the load I have being ok in a gas blowback operated rifle where the same round in a bolt action may overpressure. I'll try reloading a few to 43gr and see how they perform.

Since I have about 500 rounds, I guess I may get to use this reloading gear I've 'inherited'

 

[Doom]

@gahillhunter, you ammo description leaves a lot to be determined. M118 has a long history and many mods. It would help if you would provide a detailed description as provided on the packaging. For instance M118 Mk316 Mod (0) is known as M118 7.62 MM Special Ball, Long Range. This is the round that is supposed to utilize the 175SMK and was developed by Federal for the Navy. It uses ~42 gn of IMR 4064. This was developed about 2009. The previous version of the cartridge M118 7.62 MM Special Ball, Long Range goes back to 1996 and was load for a time with RL15 but had temperature issues in the desert. I believe the load was about 43.5 gn.

 

[gahillhunter]

@gahillhunter, you ammo description leaves a lot to be determined. M118 has a long history and many mods. It would help if you would provide a detailed description as provided on the packaging. For instance M118 Mk316 Mod (0) is known as M118 7.62 MM Special Ball, Long Range. This is the round that is supposed to utilize the 175SMK and was developed by Federal for the Navy. It uses ~42 gn of IMR 4064. This was developed about 2009. The previous version of the cartridge M118 7.62 MM Special Ball, Long Range goes back to 1996 and was load for a time with RL15 but had temperature issues in the desert. I believe the load was about 43.5 gn.

Unfortunately, I provided all information available on the container (500 rounds in an ammo can with a sticker giving the info I provided). Again, this was not major manufacturer, it was a local startup company. I thought I would give them a shot for a local supplier.

 

[Doom]

Rem 700 308's have a generous chamber and if you are having heavy bolt lift do not shoot this ammunition. Unfortunately I really can't identify the powder based on the picture. The fact that you had a case head separation leads me to believe this may be what is called Remanufactured ammunition, meaning the cases have been used and resized. If not, then it is a case datum dimension issue (commonly referred to as headspace). Does this can have a unique lot number on it to identify the ammunition? You need to contact the supplier and make them aware of the issue. This is especially true of the case head separation.

Let me give you some advice based on experience:

Don't buy remanufactured ammunition. The history of the cases used is unknown.
Don't buy ammunition in ziplock bags. Even if it identifies powder and bullet. You don't know anything about the loader.
Don't buy commercial ammunition that does not have an identifiable lot number. It is untracable.

It is also not advisable to shoot handholds other than your own. Doing so may put the loader at liability if something should go wrong.

 

[308pirate]

Thank you for that information, it really helps put things into perspective. I can see the load I have being ok in a gas blowback operated rifle where the same round in a bolt action may overpressure. I'll try reloading a few to 43gr and see how they perform.

Since I have about 500 rounds, I guess I may get to use this reloading gear I've 'inherited'

Overpressure is overpressure regardless of rifle type.

 

[308pirate]

Unfortunately, I provided all information available on the container (500 rounds in an ammo can with a sticker giving the info I provided). Again, this was not major manufacturer, it was a local startup company. I thought I would give them a shot for a local supplier.

Lesson learned: don't buy reloaded/remanufactured ammo from fly by night nobodies.

 

[supercorndogs]

It was just that hot because the powder charge was too high and caused excessive pressure especially with increases in ambient temperature.

Edit - should also add, the amount of chamber free bore also matters when it comes to pressure. I don't remember the dimensions but there is a M118LR chamber spec (longer freebore, etc).

M118LR has had several iterations due to the pressure issues causing parts breakages, which caused the powder charge to change from 43.5gr of RL15 down to 43gr of RL15. Accuracy issues of the M118LR at 43gr of RL15 eventually led to the development of M118LR MK316 MOD 0 by NSWC-Crane, which is basically 175gr FGMM using IMR4064 powder and Federal 210M primers (modern FGMM uses Alliant AR-Comp).

Your small ammo manufacturer probably just copied the recipe and didn't realize there were changes for reasons.

Or they put it in a heavy case like LC or Lapua. I shoot 43.5 of RL15 in Hornady brass with 175SMK 175 Nosler CC and 178 a max. It shoots 2735 out of my 23" Kreiger barrel, and the brass is on its 9th run.