I have several 10" SOPMOD II uppers at work that are being used on M4A1s. Recently armorers came by and gauged them (along with a bunch of other things), and tagged a couple as “shot out, need replacement.” If I turn them in we won’t get new ones as replacements, instead we’ll get 14.5" RAS equipped uppers (non SOPMOD II). As you might imagine, the guys assigned those shorties are reluctant to give them up for regular M4A1 uppers with short, non free-floated rails.
Does anyone know what criteria the armorers use for determining when a barrel is shot out, and what that actually means? I asked them and all they could say was they use a go/no-go gauge. We have shot those uppers for accuracy since the inspection, and could not tell a difference between the good ones, bad ones, or our 14.5" M4s, hence no one is really rushing to get rid of them.
Sounds like they may have some slight excessive headspace, this can lead to case head seperation. How many rounds on the barrels?
How would headspace gauges determine if the barrel is shot out?
Wouldn’t throat and muzzle erosion gauges be required?
this…
can your armorers re-barrel them?
In a perfect world they would be.
I was told the only option was a 1 for 1 swap for a 14.5" old style M4A1 upper.
how do they shoot?.. accurate? any keyholing issues?.. if not wouldnt worry yet, but keep an eye on it
I wouldn’t want to trade the SOPMOD package for a M4 MWS.
Sometimes a Bolt replacement will get them to pass those stupid guages.
The wear of the back of the bolt lugs against the inside of the barrel extension is what causes headspace to “grow”. Since the barrel extension can’t be changed, all you can try is a new bolt.
Then you are wasting a good bolt. Thats the issue, if the barrel still groups and shoots well then your wasting the remaing life of the barrel, and same for the bolt.
They should have properly checked the barrel not the headspace.
I understand that. But if they insist on going by the guages, that’d be a way to try to show that the barrels are still good.
The headspace is the more important parameter to check in my untrained opinion. I mean… the barrel will tell you when it’s shot out. But the headspace may not be as obvious, and could let to a separation in the middle of a gunfight.
They’re calling the barrels “shot out”, but regardless, they may be out of spec. At one time I had heard that Colt came out with a “Field 2” guage because barrels were being replaced too early. Not sure what ever came of that story.
Well I would rather get a new bolt than a different upper.
OP how many rounds are on the barrels?
Yeah… that’s the idea behind it. One of the military armorer procedures outlines this. I think Iraqgunz was the one who told me this. If the bolt swap won’t get it to pass, the barrel and bolt are both replaced.
You know 10.5" barrels are free market items and I’m sure the same type that is on the uppers can be bought. Consider an out of pocket expense and some garage gunsmithing…
Are the barrels marked with serial numbers to match them to a lower?
What range are you doing accuracy testing? Inside of 50…hell, 100 yards you won’t notice anything unless its shooting key holes which is a very obvious problem.
That’s exactly what I would do. Swap out the barrel myself, and have whistle dick re-guage it.
Is that an option for military types?
It’s interesting that the armorers would check only the headspace and come to the conclusion that the bore is toast. A “headspace out of spec.” tag would make more sense. No point in ditching a barrel if it still provides acceptable accuracy.
If possible, I would try to clarify with the armorers exactly what they did to classify the bores as “shot out”.
Round count is less than 10,000 but not by much.
Buying our own barrels is definitely an option, as we do have the ability to install them ourselves (sanctioned or not).
This is the correct procedure per the TO. I’m not sure it’s a real solution to just swap the bolt so much as a work around to save the replacement cost of the more expensive part, if only until it fails ‘GO’ again.
It’s certainly worth trying, especially if you are trying to extend the barrel life.
If you have the ability to purchase and install new barrels, what about buying some throat/muzzle erosion gauges? That way you would know for sure what condition the bores are in.
It seems like the armorers’ approach is to just get rid of it rather than rehab it…