Problems with my new Rock River Arms 458 SOCOM.

[marksman13]

I took my new Rock River 458 SOCOM upper to the range this morning. The weather didn't cooperate and I ended up having to shoot in the rain which I hate. The rain was just the beginning of my troubles.

To start with, the recoil was fairly stiff and I attributed some of my shooting woes to an adjustment period at first. To sum it up, I was shooting all over the place. High, low, left, right and everything you can imagine. I'll be honest, I was a little startled with the recoil. It wasn't punishing by any means, but it was just heavier than I was accustomed to from an AR15.

I shot a few more after I settled in and it was better, but it was still inconsistent. At this point I was pissed off at the rain and my shooting, not to mention the $3.00 I was burning every time I squeezed the trigger, so I started picking up my brass to head home. What I saw caught me by surprise.

Of the 19 rounds I fired, 15 had split cases!!! Most of them also had damage to the rim of the case, some of it severely gouged. I tried to take pictures of all the damaged cases.

The ammo was factory loaded Corbon Hunter 300gr rounds. The upper is a Rock River Arms CAR A4 upper. The lower is a Spike's Tactical with a RRA two-stage match trigger.

I think it's either some hot-loaded factory ammo or a poor head spacing job by RRA. I'm going to give them a call first thing in the morning to see what they say. I'm pretty sure if the issue is on Rock River's end they will make it right. Here's the pictures.

 

[Trent]

That's bad headspacing. (It's not getting a good mate on the shoulder of the chamber, to the shoulder of the brass).

Defective.

Send it back, they built it wrong.

 

[Trent]

(Just to be SURE, measure the CORBON ammo to make sure THEY did it to spec; I suppose it's possible they had a bad batch of brass with a shoulder that was set back too far.)

 

[Grumulkin]

I don't see significant scuff marks on the body of the case so I'm thinking the load isn't too hot. It could be a bad chamber but I think bad brass is more likely.

 

[marksman13]

That's my thoughts. Wouldn't be as bad if I hadn't burned $60.00 in ammo.

 

[marksman13]

Grumulkin, does it not look like the headspace is too short because of the way the bolt is digging into the rim of the case. That coupled with the split cases makes me think it's headspace. I've never had an issue with Corbon ammunition before.

 

[Trent]

PS I hot loading ammo wouldn't cause that; the split would be at the other end of things and the damage tends to be more on the "catastrophic" end of things.

There's too much space between the shoulder of that ammo and the shoulder of the chamber. If the ammo measures to spec, then the barrel+barrel extension with the locking lugs was not done to spec; rifle needs to be rebarreled.

 

[dprice3844444]

contact the maker

 

[Trent]

Also, assuming a set-back shoulder during ammo manufacturing isn't the cause, if that barrel is THAT far out of spec - it'd take a LOT to give it room to split the case - I'd be more than a little upset. Something that far out should have NEVER made it out of the factory.

Assuming the ammo is in spec, it'd take a chamber that's out of whack by a good .015 or more (gut feeling) to give it room to split that far.

Can you post up a side-by-side view of the Unfired ammo vs. the Fired ammo (assuming you have any unfired left?)

*Really* curious to see how far the shoulder got pushed out.

 

[Trent]

One last thing. The reason the back of the cases are getting battered;

When the firing pin strikes it'll "shove" the case forward until the shoulder makes contact. (You SHOULD also get a fair amount of "FTF" on the first pull, if it's bad enough)

Then when ignition happens the case is blown BACKward until it makes contact with the bolt head. (Not good on the bolt, by the way!).

THEN the case GROWS forward again, due to the pressure, which is when the case splits. (Not good on the chamber, or the rest of the gun, by the way, as now you have uncontained gas getting OUT of the casing and trying to get along the sides of the case; not to mention now you have a little high-powered 20,000 psi jet of gas burning the living hell out of your chamber.)

So you end up with battered brass on the back side, split shoulder, a severely beaten bolt head, and a hell-a-fouled chamber.

Bad news all around.

 

[jmorris]

I've loaded hot enough with mine to flaten the primers and mess up the rim but have never had a case split like that.

 

[JPG19]

I'd send it back and pickup a matching Spike's Tactical upper, but that's just me

 

[Trent]

With a properly supported chamber, a hot load won't cause a blowout on the front.

It'll blow out where the round is not supported by the chamber.

(E.g. around the circumference of the webbing of the case - case head separation, or from the primer pocket out.)

Both are highly dangerous.

What his cases show aren't especially *dangerous*, but not good for accuracy, cleanliness (chamber fouling) OR from a reloading standpoint. Losing 75% of your brass to structural failure due to bad chambering is certaily not trivial, considering the cost of brass.

 

[redneck2]

If I split that many cases I'd be all kinds of pissed

If you want to send me some of the split brass, I'll try to check it with my reloading dies to see how much the shoulder gets set back when it's run thru a sizer die. I can also compare it to my fired brass

As for recoil, better get used to it. In the world of recoil, the SOCOM's not all that bad. I've got an 870 that shoots 3" Copper Solid sabots. The SOCOM is a pussycat after that.

Of course, that's the reason I'm selling the 870 and using the SOCOM for deer.

 

[marksman13]

I'm not recoil sensitive. I've just shot ARs in 5.56 for a long time and I guess I have a certain muscle memory for the way I shoot them from a bench and if I were to shoot this rifle the way I shoot those I would have had a nasty scope ring. It's not bad at all on the shoulder. It's my jaw that seems to take the worst of the recoil.

 

[marksman13]

Also, assuming a set-back shoulder during ammo manufacturing isn't the cause, if that barrel is THAT far out of spec - it'd take a LOT to give it room to split the case - I'd be more than a little upset. Something that far out should have NEVER made it out of the factory.

Assuming the ammo is in spec, it'd take a chamber that's out of whack by a good .015 or more (gut feeling) to give it room to split that far.

Can you post up a side-by-side view of the Unfired ammo vs. the Fired ammo (assuming you have any unfired left?)

*Really* curious to see how far the shoulder got pushed out.

The round looks to be in spec to the naked eye. At least the bullet doesn't appear to recessed back into the case. It doesn't look like the shoulder has been pushed out very far either, though if I spin the case it looks as though the shoulder is no longer concentric to the rest of the case. I guess what I'm saying is that it looks as though the shoulder has been blown out on one side but not the other.

 

[marksman13]

JPG19, gonna be kind of hard to get a Spike's upper considering they don't make a 458 SOCOM.....

 

[JPG19]

Excellent point. Whoops!

 

[marksman13]

JPG19, haha. I looked at every manufacturer I could think of for a 458 SOCOM. Rock River seemed like the best balance of quality and cost. I feel confident that Rock River will resolve this issue quickly and professionally. I'll keep everything updated as the process plays out.

 

[Trent]

That's a bad chambering job with incorrect headspacing. The "one side pushes more than the other" is due to the case expanding inconsistently until it splits. Once it ruptures, then gas pressure equalizes inside and outside the case, and it STOPS expanding further.

Assuming the CORBON ammo is in spec, that is a bad barrel assembly. Needs to go back.

 

[marksman13]

Update 6/11/2012:

Talked to BJ at Rock River Arms this morning, very professional guy by the way. I described the issues I have had with my upper. Long story short, they are sending me a shipping label and scheduling a UPS pick-up of my upper on their dime. This is the first sign of good customer service to me. I am sending the upper and spent casings along with empty Corbon ammo box to them. I believe they will resolve the issue quickly. We shall see.

 

[repmurcs]

That's good news --- I got my RRA 458 about 2 weeks ago - Haven't sent a single shot down the barrel yet. You had me scared with this story. Now I gotta go make time to do so, to make sure it's not a common issue. I LOVE THIS WEBSITE ..

 

[Tex4426]

Redneck2 what accuracy are u getting out of your 458...im getting ready to build one for deer hunting and would like to be able to stretch it out to 250 yards if possible....do u guys think the recoil on this will beat up an eotech 512 or should it handle it

 

[repmurcs]

After having many months to research add on's for my 458 - EoTech 512 seems to be the Optic of choice --- that and ACOG but ...
For a cheaper version (yet to be proven) Mueller Quick-Shot is something I've been toying with I've even contacted Mueller - they stated that these are sold to Turkey hunters and handles the recoil of a 12 Ga. Turkey Load just fine. All speculation though

 

[redneck2]

Redneck2 what accuracy are u getting out of your 458...I'm getting ready to build one for deer hunting and would like to be able to stretch it out to 250 yards if possible...

Maybe 1.5" at the very best. Not a tack driver, but adequate. I consider it a 150, maybe 175 yard gun at the very best.

If you hand load and you're looking for something Indiana deer legal, get ahold of D-Tech in Bemidji, Mn. I got an upper based on a .25 WSSM necked up to .358. It's a true 250+ yard gun. Mike's got the dies, brass, loads, everything. Builds the upper with a Shilen match grade barrel. Cost is maybe $900.