ACR tiny pin fell out

mikethebike

mikethebike

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Guys, this tiny little pin right under the hole where the puston rod goes through fell out when I took my barrel out of my upper today for cleaning.
I put it back in there, with some difficulty, but is it suppose to come loose? sounds weird that this would come loose.
Anyways what I am asking is:
1 Did i put it back in the right spot?
2 Is this little pin supposed to be loose?
3 Is it important, becausr I think eventually I will lose it?
4 What is the pins purpose?

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Please post a picture of your barrel because that looks like the index pin. If your barrel extension is missing it, you will need to get it repaired.
 
There is a small little hole on the barrel right under the rod. Is that where the pin goes? Do I just push the pin in there? Or was it welded in there and it came loose? This barrel is brand new, so the previous owner said, I put about 300 rounds through it so far.

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Yes it is the index pin. I am unfamiliar with how they install those but it needs to be in place with the barrel to prevent it from spinning inside the trunnion of the receiver.
 
Ok so do I just punch it in the hole? Or is it welded in there?
If i just punch it in there, there is a side that is shiny to the pin and a side that is black, does it matter which end goes in the barrel and which end sticks out?

if I put it back in the hole this is what it looks like, is this normal now?

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mikethebike said:
Ok so do I just punch it in the hole? Or is it welded in there?
If i just punch it in there, there is a side that is shiny to the pin and a side that is black, does it matter which end goes in the barrel and which end sticks out?

if I put it back in the hole this is what it looks like, is this normal now?

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Yeah, that part isn't supposed to come out. They are press fit in place, so they should never come out under normal circumstances.

I would be on the phone to Dlask to see if they can fix it, DO NOT shoot it like that.
 
Ok yah thats what I thought. Good thing dlask is 3 minutes walk from my work.
Now how do I know if I havent shot it with the pin loose and not in place? This is a brand new barrel so Its not through wear that this pin came loose.
Could I have done damage to the piston rod?
Its pretty damn ####ty since this barreled was done by dlask on February 25th!
 
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mikethebike said:
Ok yah thats what I thought. Good thing dlask is 3 minutes walk from my work.
Now how do I know if I havent shot it with the pin loose and not in place? This is a brand new barrel so Its not through wear that this pin came loose.
Could I have done damage to the piston rod?
Its pretty damn ####ty since this barreled was done by dlask on February 25th!
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Realistically, I don't think much would've happened except some excessive wear on the bolt lugs, if the barrel was locked up tight.

Now if that barrel was manufactured right, they should be able to just press fit a new pin in place and it should be okay, the one you have may be worn out so that it's no longer wanting to stay in. The barrel extension is torqued on very tight, and normal handling couldn't ever work it loose.
 
Once the barrel is in the upper receiver the pin is held captive in any case, and won't come out. But I would still send it back.
 
I've been following your threads and you've had the worst luck with expensive firearms. Hopefully this is the only issue you will have with the ACR
 
This sucks Mike, I hope they sort it out in a hurry.
My best guess is that the pin itself is out of spec by a tiny margin. Should be a 5 min job. I'm glad you're close as it took me 2.5 hrs driving there/back.
 
drifter dave said:
This sucks Mike, I hope they sort it out in a hurry.
My best guess is that the pin itself is out of spec by a tiny margin. Should be a 5 min job. I'm glad you're close as it took me 2.5 hrs driving there/back.
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Yah they're just down the road for me, about 1 minute drive really.
Hopefully they can do it right then and there when I bring it in.

its supposed to be a 0.125 diameter x .25 but i dont have such precise tools to measure it to see if its out of spec.
 
Redblack said:
I've been following your threads and you've had the worst luck with expensive firearms. Hopefully this is the only issue you will have with the ACR
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Extractor is very very weak, but I can replace that very easily with e beefed up bcm spring and a rock river arms extractor.
yah its becoming discouraging...
 
That's very weird but I wouldn't worry too much. Luckily it's easy for you to take it in for a fix.
If the barrel had twisted in the receiver the bolt wouldn't have been able to engage the receiver. As long as there is no weird wear on the op rod it probably stayed where is was suppsed to be. Once the barrel is installed the pin isn't really doing anything anyway. It's just to line it up during install.

Good luck and don't let it worry you, it's an easy fix.


If the rifle isn't having problems extracting I wouldn't worry about it.
 
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