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AR cycling problems with piston kit

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supertool73 View Drop Down
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    Posted: August/31/2011 at 11:24
So for a while I have been wanting to try a Adams arms piston kit for an AR.  So I finally bought one to try out.

I installed it per the instructions and am pretty certain that is done correctly.  I have fired 120 rounds out of it and only had 9 or 10 rounds that have cycled properly.  All the others seemed to be short stroked.  Many times it did not even open far enough to eject the spent case, other times it ejected but did not catch a new round to put in the chamber, or the action got stuck open because it did not quite go far enough to eject the spent round and it got stuck.

It is a mid length upper, and I am using a A2 length stock with a rifle spring and buffer in it.  I am wondering if I have to much weight in the buffer spring combo.

I know there are weights inside the buffer.  Can I take one of more of these weights out?  Or will that mess up the dynamics of the buffer?  Should I switch over to a carbine length system so I can get different weight buffers?  I would like to stay with the stock I have, but am open to other options to get this working.


Edited by supertool73 - August/31/2011 at 11:25
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVT_Tactical Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 11:40
I"ve never messed with one but are you sure you have the gas block lined up with the port correctly?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 11:43
Yeah, that was the first thing I checked.  I took it off and I could see by the carbon marks that I had it perfectly centered over the gas port.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVT_Tactical Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 11:46
have you called adams about it, they have a good record of helping with their kits from what I can find on the net about them
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shooter07 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 11:47
Definitely sounds like it's not getting enough pressure to fully push the BCG back which to me is either what G said or a spring problem in the buffer. Just off the top of my head.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lumberjack149 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 11:48
Originally posted by SVT_Tactical SVT_Tactical wrote:

I"ve never messed with one but are you sure you have the gas block lined up with the port correctly?
+1 on what SVT said, from everything you described that would be my first step is to take it back apart and verify they line up since youre not getting enough gas. 
Did it cycle fine with the original gas system before you swapped? That would eliminate the buffer weight and receiver extension variable.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thundey Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 11:59
When you say you have a "mid-length" upper, what exactly do you mean.  Are you going off of Adam's measurements of 16-18" for that spec.  Also I'm sure you've already measured the shoulder, so that shouldn't be an issue.

Maybe watch this???
 http://www.youtube.com/watch?v=spOZqpMLldQ&feature=related

And you might call their CS and see if they can walk you through it?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:09
Thanks guys.  I do have an email into them.  Just asking for other opinions as well.  I am sure it is just a configuration issue.

When I say mid length I mean it has a midlength gas system. 

Yes my shoulder is the correct size.  I have watched the video six or seven time while I was assembling it.  I am not an expert to ARs by any means, but I have built, tore apart and rebuilt quite a few of them so the basics I understand okay.

I am pretty certain gas getting to the piston is not the issue.  I know I have the gas block on correctly. and the rod and gas block get mighty hot.  The carrier just does not appear to be getting pushed back far enough.

So it seems to me it is the buffer or spring.  So the questions I asked before about them are really what I am curious about.  I have never had a cycling problem with a DI AR before no matter what buffer setup I have had so I am just curious as to what options I may have with it.


Edited by supertool73 - August/31/2011 at 12:11
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BeltFed Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:17
Sorry, I'm not a fan of piston conversions for ARs. To much to go wrong. If you want a piston AR then either buy a complete rifle or an upper. That said; is your barrel a 20" or a 16"? Gas port size and location, as well as carbine or rifle buffer don't mix well between rifles and carbines.
It sounds like you need a carbine buffer, spring, and buffer tube (unless it's a dissapator and 18" barrel); which means you also need a carbine stock. Whatever you do don't take the buffer apart unless you just want to toss it.
At first it sounded like you were not getting enough gas and needed a larger gas port, but I'm thinking you might have the wrong buffer assembly for your barrel length. Throw in the piston system and you have to start from scratch.
Then you could go bact to direct impengment and have a reliable rifle, more accurate too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thundey Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:19
Does it look like the piston is hitting off-centered on the bolt?  It might be binding/torquing the bolt.  But I'm about the same as you as far as qualifications go.  I wouldn't think that the buffer or spring was causing this.  But I could be mistaken.  And just out of curiosity what make is the upper? 

Hope you get it all worked out!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:37
Its a Sundevil Billet upper.  Looking at the bolt it looks to be hitting just right on the extension thingy.  I don't see and unusual rubbing marks on the bolt or upper. 

I have read all the goods and bads about the piston systems.  But I still had to try one. Big Grin I love messing with ARs and figuring out and learning how they tick, it is a very fun hobby for me.  So I still wanted one even though I new there was a possibility it wouldn't work.

Thanks Lynn, about the buffer.  That is the info I was curious about.  I got a Car stock with lighter buffer in it, I will give it a try.  Its a 16" barrel.  That is why I was wondering if my stock and buffer were wrong for this setup.  It functioned prefectly with the DI, but I was not sure how this would work with the piston. 

I am not a fan of collapsible stocks, so I may have to get a spacer to put in my rifle tube to make it shorter if this is indeed the issue. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVT_Tactical Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:39

I wasn't a fan of collapsable either until i tried out the ACS i bought from Paul a few weeks ago.  It is actually longer when fully extended than my ACE skeletonized one was.  And it locks tight.  Have you tried one of those ST?  I can let you borrow it if you wanna try it for a few weeks.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:44
My biggest dislike of collapsible is my facial hair gets stuck in the spot where the tubes come together and it rips them out when I move my head.  Hurts like a beeotch.  Bucky 

My cousin has a couple of the ACS stocks.  I do like them as well except for a fore mentioned problem.  Thansk for the offer SVT. 


Edited by supertool73 - August/31/2011 at 12:46
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shooter07 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:46
Originally posted by SVT_Tactical SVT_Tactical wrote:

I wasn't a fan of collapsable either until i tried out the ACS i bought from Paul a few weeks ago.  It is actually longer when fully extended than my ACE skeletonized one was.  And it locks tight.  Have you tried one of those ST?  I can let you borrow it if you wanna try it for a few weeks.

 
+1 on the ACS. It was an extra laying (was using a ctr stock) around and wasn't sold because i didn't like it. That's the best collapsable stock out there imo. Great cheek weld, and it has a locking system to avoid any wobble.
 
For around $100 new, you can't beat it imo.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shooter07 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:47
Originally posted by supertool73 supertool73 wrote:

My biggest dislike of collapsible is my facial hair gets stuck in the spot where the tubes come together and it rips them out when I move my head.  Hurts like a beeotchBucky 

My cousin has a couple of the ACS stocks.  I do like them as well except for a fore mentioned problem.  Thansk for the offer SVT. 
 
Sporting a beard myself for most of the year, i will lose a few of them to the same spot. I just let loose a few choice words and get on with my day. Big Grin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:52
On the topic of buffers.  HEre is a cool pic explanation I found.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/31/2011 at 12:58
I have enough spare parts laying around that I think I will just take this kit off the rifle it is on and assemble another complete rifle to dedicate to it.  That way my primary AR won't be a work in progress. 

I appreciate everyone's help
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: September/01/2011 at 08:50
Well I went out and tried it with the Car stock this morn.  Still did not work.

Now I am wondering if it is because the barrel nut it to thick.  I have a free float and it has the spring on the piston really compressed, might not be letting the piston travel enough.  Guess I will try the delta ring hanguards and see if they solve the problem. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BeltFed Quote  Post ReplyReply Direct Link To This Post Posted: September/01/2011 at 09:45
Originally posted by supertool73 supertool73 wrote:

Well I went out and tried it with the Car stock this morn.  Still did not work.

Now I am wondering if it is because the barrel nut it to thick.  I have a free float and it has the spring on the piston really compressed, might not be letting the piston travel enough.  Guess I will try the delta ring hanguards and see if they solve the problem. 
Sounds like you found your problem; now how to solve it. I don't think it's the barrel nut thickness, I think it might be where the recoil spring is seated. It shouldn't be overly compressed with the bolt closed, but I know very little about piston guns.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: September/01/2011 at 09:56
On the piston rod there is a bushing that is between the hole in the barrel nut and the spring, and on the other side of the spring the piston rod has a increase shoulder so the spring is bound between the bushing and the shoulder on the rod. 

So what I am thinking is because that barrel nut is quite a bit thicker than a traditional barrel nut it is compressing the spring to much and not allowing the piston to travel back the distance it needs to go to force the carrier into the stock.

If this is indeed the case, it is kind of frustrating because Adams Arms lists on their site that the MI hand guard I have is compatible.

I had to order a delta ring assembly, probably will not be here til next week.  But hoping this is the problem.  If that is the problem, then I guess another option would to have someone machine the shoulder on the rod back just a hair more so the spring can be the length it needs to be.  If I wanted to use the freefloat that is.


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