Adam Arms piston kit failure

[Moose242]

Those are not that great of a rifle. They are inaccurate and heavy.

Truth. The Sig 556 is damn inaccurate, has a stamped upper, a long stroke AK-like piston and a bolt head that resembles one too, and a very shitty glock-like trigger. The real SIG 550s from Switzerland are phenomenal, but any Exeter made Sig is fucking terrible.

I have tried to sight mine in 3 or 4 times and the POI wanders so bad that I just gave up.

[dee]

m14 or m1a?

m1a

[KBScobravert]

I can't find any record of a carbine length or longer piston rod failing when installed right. I think that the piston rod is just too short to deflect any stress and directs all into the bolt carrier.

CJ you should just ask them for a carbine rod and use it on another build OR send it back for refund OR get another rod and sell it.

[CJ]

I can't find any record of a carbine length or longer piston rod failing when installed right. I think that the piston rod is just too short to deflect any stress and directs all into the bolt carrier.

CJ you should just ask them for a carbine rod and use it on another build OR send it back for refund OR get another rod and sell it.

Still no return call today. I've considered both of those options, but I'd like to salvage it if possible. Maybe Adam Arms can find a problem with something I did and help me to get it working right.

[inline 6]

Would they even make it if it wouldn't go 20 rounds? I am not really buying the whole "its too short to bend and deflect stress" theory. To keep from reading the thread again, is the gas block adjustable? Did you have it turned way up or down if it is an adjustable block? Is there there any chance that if it is turned up to max that it is just putting too much stress on the part that it destroyed? What is the material of both pieces? Also is the piston supposed to rest against that part of the BCG when is ready to fire that would "push" the BCG back or was there a gap that would allow the piston to "punch" the BCG? is that even adjustable?

[KBScobravert]

Would they even make it if it wouldn't go 20 rounds? I am not really buying the whole "its too short to bend and deflect stress" theory. To keep from reading the thread again, is the gas block adjustable? Did you have it turned way up or down if it is an adjustable block? Is there there any chance that if it is turned up to max that it is just putting too much stress on the part that it destroyed? What is the material of both pieces?

I have toyed with the 3 gas settings on my carbine and could not tell a difference between them. If you do a search on the internet for bent AA push rods you will find 99% of them are pistol kits. Carbines being the next shortest rod, runs fine.

<---- no engineering background what so ever.

[inline 6]

I agree, the proof is in the puddin with those stats. But you think they would have this figured out if they are selling this stuff to the public. Things like the gas port size and other factors could be adjusted to make this work. I know the adjustable gas block should fix that but there is no reason why the next length up as you said can be made to work perfectly and this one is a basket case. The simple answer of the piston is not long enough to bend is kinda hokey to me.

I am not an engineer either but I do deal with all types of metals from lead to exotic stuff like high grade titanium and tungsten on a daily basis and have a pretty decent understanding of what they will and will not take and what types of things happen to metals under stress. Things that the human eye can not see kinda like one of those slow motion videos of a valve train running on a car, the springs look like spaghetti in slow mo and to the eye they barely move. With that said I totally get your concept of what the problem may be and it would be stupid of me to say that the longer rods are not bending at all when in action and common sense would say that the shorter rods if made from the same diameter and type of material will hold up and deflect less than its longer counterpart is a valid point. I just do not think that's the issue. Personally I would be looking at the quality of the material on that bolt and questioning if it was heat treated or hardened properly. It also looks like the piston had a chance to get some momentum going before it impacted the bolt. I am not familiar with piston setups but that sounds like excessive wear and tear waiting to happen.

What ammo were you shooting through it CJ? was is .223 or 5.56? reloads or new stuff? Is there any chance that the ammo you were using was not allowing the bolt to seat all the way and creating space for the piston to slap it around?

[KBScobravert]

I agree, the proof is in the puddin with those stats. But you think they would have this figured out if they are selling this stuff to the public. Things like the gas port size and other factors could be adjusted to make this work. I know the adjustable gas block should fix that but there is no reason why the next length up as you said can be made to work perfectly and this one is a basket case. The simple answer of the piston is not long enough to bend is kinda hokey to me.

I am not an engineer either but I do deal with all types of metals from lead to exotic stuff like high grade titanium and tungsten on a daily basis and have a pretty decent understanding of what they will and will not take and what types of things happen to metals under stress. Things that the human eye can not see kinda like one of those slow motion videos of a valve train running on a car, the springs look like spaghetti in slow mo and to the eye they barely move. With that said I totally get your concept of what the problem may be and it would be stupid of me to say that the longer rods are not bending at all when in action and common sense would say that the shorter rods if made from the same diameter and type of material will hold up and deflect less than its longer counterpart is a valid point. I just do not think that's the issue. Personally I would be looking at the quality of the material on that bolt and questioning if it was heat treated or hardened properly. It also looks like the piston had a chance to get some momentum going before it impacted the bolt. I am not familiar with piston setups but that sounds like excessive wear and tear waiting to happen.

What ammo were you shooting through it CJ? was is .223 or 5.56? reloads or new stuff? Is there any chance that the ammo you were using was not allowing the bolt to seat all the way and creating space for the piston to slap it around?

All points understood.

I wonder if there would be a way bleed off gas before hit pumps into the op rod chamber.

Maybe you get us enough tungsten to build an Op rod and bolt carrier out of

[CJ]

I agree, the proof is in the puddin with those stats. But you think they would have this figured out if they are selling this stuff to the public. Things like the gas port size and other factors could be adjusted to make this work. I know the adjustable gas block should fix that but there is no reason why the next length up as you said can be made to work perfectly and this one is a basket case. The simple answer of the piston is not long enough to bend is kinda hokey to me.

I am not an engineer either but I do deal with all types of metals from lead to exotic stuff like high grade titanium and tungsten on a daily basis and have a pretty decent understanding of what they will and will not take and what types of things happen to metals under stress. Things that the human eye can not see kinda like one of those slow motion videos of a valve train running on a car, the springs look like spaghetti in slow mo and to the eye they barely move. With that said I totally get your concept of what the problem may be and it would be stupid of me to say that the longer rods are not bending at all when in action and common sense would say that the shorter rods if made from the same diameter and type of material will hold up and deflect less than its longer counterpart is a valid point. I just do not think that's the issue. Personally I would be looking at the quality of the material on that bolt and questioning if it was heat treated or hardened properly. It also looks like the piston had a chance to get some momentum going before it impacted the bolt. I am not familiar with piston setups but that sounds like excessive wear and tear waiting to happen.

What ammo were you shooting through it CJ? was is .223 or 5.56? reloads or new stuff? Is there any chance that the ammo you were using was not allowing the bolt to seat all the way and creating space for the piston to slap it around?

It was M193 spec 5.56mm ammo 2.26" OAL, 25.0gr WC844, 55gr M193 projectile. The ammo was case gauged, trimmed, and perfectly 100% verifiable correct. I also shot all 19 of these rounds through a chronograph, 2218fps average - perfectly normal for spec M193 in a 7.5" barrel. The gun showed no signs of overpressure with ejection, and the primers look fine. The same ammo cycled perfectly fine in another rifle. As far as the gas settings - no mention anywhere in the guide, or when I bought the pistol rod and spoke with Matt up at Adam Arms that it might need to run on a lower gas setting. If it did, then the entire kit is pointless for me and I would have never installed it. I will need a lower gas setting for my can, so it must operate correctly on the standard setting.

[inline 6]

It sounds like you have that ammo question fully covered. What about any gap or clearance between the bolt and piston when the bolt is closed? Also is there any chance that the piston over travels and smashes the bolt when it is fully retracted?

[CJ]

It sounds like you have that ammo question fully covered. What about any gap or clearance between the bolt and piston when the bolt is closed?

You're suppose to have 0.020" of clearance, which I gauged with a feeler. The barrel had 52ftlbs of torque on it to get the clearance for the op rod. The gas block was in exactly the same place after shooting as before - so I don't think the gap changed when firing. You know.. I was just sitting here brainstorming and I just remembered something I had dismissed when it happened. When I was firing through the chrono, I do remember looking at the op rod and the spring was fully compressed and stuck that way, when I turned my rifle up to look at it better it popped back out and reset the rod and I laughed at phaux and disregarded it. I wonder if my spring retainer bound up and let the rod smash around? I wonder if it was like that for several rounds? It's possible it smashed the bolt and with metal fatigue it turned it into playdough.

[inline 6]

It's a good chance. If thats the only abnormality you have found it makes sense to me. My coworker has been warning me to stay away from these kits as I have mentioned several times that I was Interested in them. If something that simple can get in a bind and cause that kind of failure I am really not interested in them any more

[Brandon-k]

I'll be sure to keep a little CLP sprayed on my op rod spring/retainer from now on. Just in case.

[svauto-erotic855]

An M14 is not inaccurate in the slightest, it's probably the most accurate semi auto rifle there is. The US military uses M14's to this day as the designated marksman rifles. I agree with the AK and G3. I'd rather have an accurate rifle that needs regular cleaning than a gun that will get me killed at moderate ranges. And I'll never change that mindset.

The term "accurate" is subjective. I love my M1As and they are my go to rifle but they are tough to keep it in top shape. Accuracy drops noticeably after a few thousand rounds and then it is time to tweak on them to get it back.

[CJ]

It's a good chance. If thats the only abnormality you have found it makes sense to me. My coworker has been warning me to stay away from these kits as I have mentioned several times that I was Interested in them. If something that simple can get in a bind and cause that kind of failure I am really not interested in them any more

I've never had any issues with any of my other AA piston kits, but this is my first pistol length. Keith has like 10 AA kits and has never had an issue.


I decided to just send Adams Arms an e-mail explaining what happened, and I linked this thread.