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Author Topic: Socom functioning issues  (Read 8060 times)

JohnOD

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Socom functioning issues
« on: March 27, 2011, 03:53:47 PM »

20" 6.5 Grendel on top, my new 16 1/2" 458 Socom below

Fired 13 rounds of Corbon 405 JSP factory loads from my new upper today. The first four rounds I loaded from the magazine (aluminum 20 round mags, I tried two different mags), none of them would fully seat in the chamber... I had to mortar the gun hard to get the bolt back each time. I started dropping a round manually into the chamber then dropping the bolt on the loaded round. Those fired fine but didn't fully eject. I went back to loading from the mag and the rounds started hanging up on the feed ramp.
Out of the 13 rounds fired today only one actually ejected from the rifle... the other 11 ended up like this

and one like this

The gun is clean and well lubed. Before shooting it today I completely tore down the bolt and all parts seem to be functioning normally. I did notice that the bolt is very tight in the carrier.
The bolt is not moving all the way to the rear as if it’s under gassed.
Any suggestions/input is appreciated
Thanks, John
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458MADNESS

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Re: Socom functioning issues
« Reply #1 on: March 27, 2011, 04:27:04 PM »

using a heavy buffer??? what kind of spring?

JohnOD

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Re: Socom functioning issues
« Reply #2 on: March 27, 2011, 04:33:23 PM »

Standard RRA rifle buffer spring with ~2000 rounds on it. Enidine hydraulic buffer.
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Big Bore

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Re: Socom functioning issues
« Reply #3 on: March 27, 2011, 04:34:10 PM »

What length gas?  It looks longer than CAR length to me.  If it's a middy that is quite possibly your problem.  
As to your chambering problem it sounds like either the chamber is not cut correctly or most likely, the Cor-Bon ammo is a bit out of spec.  If by some chance your chamber is short throated then it could be jamming the bullet into the lands.  Blacken the bullet and case with a Sharpie and chamber it and see where the binding is happening.  That will tell you if the bullet is too long and being jammed into the rifling or if the case is too large and being wedged into the chamber.
« Last Edit: March 27, 2011, 04:39:45 PM by Big Bore »
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JohnOD

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Re: Socom functioning issues
« Reply #4 on: March 27, 2011, 04:38:15 PM »

Mid length. I found the post re 405 Rem bullets hanging up on the feed ramp & will tweak the feed lips a mag to get the bullet nose to ride higher.
Thanks
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Big Bore

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Re: Socom functioning issues
« Reply #5 on: March 27, 2011, 04:42:46 PM »

I bet that is your problem.  Those Cor-Bonds are loaded for the standard CAR length gas since it is only recently that the middy craze has hit.  The 458S does not really like midlength gas systems and you must take care with your powder selections.  My CAR and handgun length gas rifles run fine with H110 powder but my 20 inch rifle which is middy gassed will not run worth a hoot, doing exactly what yours does.  I switched to Re #7 for that rifle and it runs fine.  The powder in the Cor-Bon ammo could be too fast and its pressure peak is not compatible with the middy length gas system.  While the middy is the craze right now with the 5.56 it does not work as well with the .458 SOCOM and you are not the first to be finding this out.
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capn jack

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Re: Socom functioning issues
« Reply #6 on: March 27, 2011, 04:48:54 PM »

JohnOD,
Lets start with the rounds not fully chambering....
Is you chamber bright and shiny? No sign of anodizing?
Have you tried any other ammunition other than Corbon?
Seems to me, a while back Corbon put out some out of spec.
ammunition.
Is there anyone near you that has one of Marty's chambering
Dies to check the ammunition?

If you can't easily chamber and eject a loaded round, your rifle
isn't going to function properly. If all of that works, then it's time
to check buffer springs and gas blocks.

Basics first....Jack... ;)
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Marty

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Re: Socom functioning issues
« Reply #7 on: March 27, 2011, 06:03:01 PM »

OK, this is one of my builds and actually one that has been fired by myself and about 20 rounds for an article.  It was also on display at the SHOT Show in January.  So no need to explore short/tight chambers or parkerizing left behind.

It is an 16" carbine gas length and it may indeed not like the 405 gr load from CorBon - I will admit that I never fire the 405 gr load as it has the worst perceived recoil to me.  With the 300 gr loads it runs fine and has been shot with SBR loads as well.  I cannot say if the CorBon loads are perhaps a little long, but I have not seen issues with this upper during test cycling here.

I would try removing the Enidine buffer and using a standard buffer and spring to see if that helps remedy some of the issues - it may be affecting the cycling.  If the bolt remains tight, let me know and we will send out another one to see if that resolves the ejection issues (the extractor is acting like it is not wanting to release the rim)
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JohnOD

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Re: Socom functioning issues
« Reply #8 on: March 27, 2011, 06:19:05 PM »

Marty I came up with the mid length from your add on AR15COM. I just did a visual comparison on all four of my AR uppers and the Socom chamber looks great. The Corbon ammo I fired today is the first time I've fired it & I don't have any other ammo on hand. FWIW the 405 Corbon load averaged 1518 FPS @ 12' from the muzzle, 35 degrees fahrenheit. Once the cartridge gauge shows up I'll start on some reloads. I'm holding some of the Corbon loads back to check them in the gauge.

Big Bore I do have some Re7 on hand and will start with that.

I was pleasantly surprised at how mild the recoil was with my Socom upper. Cant wait to get a load dialed in and get some fur in the cross hairs ;D.

Thanks for all the help gentleman.

John
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Marty

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Re: Socom functioning issues
« Reply #9 on: March 27, 2011, 08:36:11 PM »

I will be honest and say that I cannot be sure on the gas length, my original notes said carbine, but the customer may have changed that into the project.

Your gage leaves here next day or so, should make life easier.  I suspect the CorBon ammo to be a hair tight, we have spoken with them and we are actually sending them a gage, too!

Re7 should work well, that is what we use almost exclusively for our T&E ammo.
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458MADNESS

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Re: Socom functioning issues
« Reply #10 on: March 27, 2011, 10:24:15 PM »

if it's truly a mid that may be part of the problem, but first do what marty said about the buffer. corbon did have some brass that was off, but that was '07 and before (i think). you should be able to call them up with the lot number and they can tell you.

Forester

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Re: Socom functioning issues
« Reply #11 on: March 28, 2011, 09:15:54 AM »

I will be honest and say that I cannot be sure on the gas length, my original notes said carbine, but the customer may have changed that into the project.

Your gage leaves here next day or so, should make life easier.  I suspect the CorBon ammo to be a hair tight, we have spoken with them and we are actually sending them a gage, too!

Re7 should work well, that is what we use almost exclusively for our T&E ammo.

I have some more recent Corbon ammo from maybe late '09 to early '10, and yes, it is a little tight. It takes a light "mortar" effect to extract - I always thought it was a problem with my chamber until I tried the SBR ammo. Problem solved!
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458MADNESS

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Re: Socom functioning issues
« Reply #12 on: March 28, 2011, 10:29:13 AM »

so it's corbon ammo? wonder if corbon will swap it for you. not sure why they would be tight unless their brass was thicker...i believe they use starline as well.

JohnOD

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Re: Socom functioning issues
« Reply #13 on: March 28, 2011, 05:16:01 PM »

I'm going to check some unfired rounds in the gauge before I contact Corbon.

I checked this afternoon it is a mid length gas system .

John
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Big Bore

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Re: Socom functioning issues
« Reply #14 on: March 29, 2011, 06:34:29 AM »

Did you black sharpie the case and bullet to see where it was binding yet?  I have had a bad lot of Cor-Bon ammo (.32 NAA, not in .458S since I have never bought a factory loaded round for this caliber) but I am certain I have heard of bad cases and loads.  In the .32 NAA the crimp was so heavy that it actually loosened the bullet and you could spin the bullet in the case.  If a crimp is too heavy it can cause the neck to bulge away from the bullet actually decreasing neck tension and it can cause the base of the shoulder to bulge outwards.  Look at your crimp on the Cor-Bon.  If it is obviously a heavy crimp then the base of the shoulder could be bulged and that is what is causing the hang up.
I ran into this quite often when I was first starting loading and regardless of what the manuals said, if a little crimp is good, maybe a lot is better?  You can't tell a 12 year old anything.  Well, 42 years later I have seen misadjusted crimp dies cause all kinds of problems from chambering to erratic loads with very wide ES.  Crimp can tighten up ES but if over done it cause wide ES also, and loose bullets to cases that will not chamber can all be attributed to too much crimp.
Blacken up the case and chamber and do not be surprised when you mortar it out you see a bright brass ring in the black field of the sharpie all around the base of the shoulder. 
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