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Posted: 1/19/2011 9:09:27 PM EDT
I had about 100 rounds TOTAL through the lower.... about 5 that day....when I noticed the bolt locked back about halfway with the shell casing just sitting on top of the full magazine.... I cleared the malfunction, charged the weapon.. and it happened again... I cleared again, made safe, and was wondering WHY it was happening..... then I noticed the buffer tube was extremely loose...
Well... I found out why.. very quickly.. 
EDIT: Talked to Russ, who called from SHOT... Very easy guy to deal with, pointed out some things that make me believe I have issues with my upper, either weak buffer spring or overgassing or both.... You can see the carrier key impact on the lower, which he nailed right away..... He will be replacing it, even though it appears to be an issue with the upper.... I think this will be my lightweight 5.56 build, as he explained that people are using them for all calibre builds without issue, but it was designed with 5.56 in mind... A+ for customer service. OK, well after 2 weeks, I have a replacement lower in my hands... One problem.... It's completely stripped.... I sent them a completed lower minus the buttstock, and in exchange I get a completely stripped lower.. W T F.... Where's the QC? Lets see how they handle this... :( |
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Posted: 1/19/2011 9:20:05 PM EDT
[#1]
Awesome.
I am sure they will fix it. |
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Posted: 1/20/2011 1:36:17 AM EDT
[#2]
That's why I don't buy plastic lower receivers.
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Posted: 1/20/2011 1:46:49 AM EDT
[#3]
Why is the area around the crack "blueish"? it looks like having a different colour, maybe purple to it.
And it looks shinier than the rest of the piece. |
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Posted: 1/20/2011 1:55:48 AM EDT
[#4]
Quoted:
That's why I don't buy plastic lower receivers. Never seen a cavarms do that. |
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Posted: 1/20/2011 1:56:02 AM EDT
[#5]
Quoted:
Why is the area around the crack "blueish"? it looks like having a different colour, maybe purple to it. And it looks shinier than the rest of the piece. I assume the stress that caused the fracture would change the molecular structure of the surrounding polymer chains. |
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Posted: 1/20/2011 2:58:09 AM EDT
[#6]
Quoted:
That's why I don't buy plastic lower receivers. +1 |
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Posted: 1/20/2011 3:38:20 AM EDT
[#7]
Quoted:
Quoted:
That's why I don't buy plastic lower receivers. +1 +2 Manufacturing firearms out of plastic is just plum crazy!!! 
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Posted: 1/20/2011 4:09:09 AM EDT
[#8]
Quoted: Quoted: Quoted: That's why I don't buy plastic lower receivers. +1 +2 Manufacturing firearms out of plastic is just plum crazy!!! That's just crazy talk.  |
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Posted: 1/20/2011 4:17:22 AM EDT
[#9]
Been waiting for this post, I'll stick with aluminum.
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Posted: 1/20/2011 4:43:16 AM EDT
[#10]
PVC welder?
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Posted: 1/20/2011 4:46:17 AM EDT
[#11]
Quoted: Been waiting for this post, I'll stick with aluminum. Me too, it was inevitable. Change the material without changing the design and you get failure... |
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Posted: 1/20/2011 4:48:27 AM EDT
[#12]
Wait...a plastic rifle lower broke?
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Posted: 1/20/2011 4:54:47 AM EDT
[#13]
Quoted: Wait...a plastic rifle lower broke? I know, right? Un-possible... |
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Posted: 1/20/2011 5:11:57 AM EDT
[#14]
Was this the RE installed by the manufacturer or one you installed? If it was theirs, did you ever remove and remount it?
I'm thinking something was overtorqued... |
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Posted: 1/20/2011 5:14:00 AM EDT
[#15]
Quoted:
Wait...a plastic rifle lower broke? ...and water is wet, 
7mm |
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Posted: 1/20/2011 5:33:54 AM EDT
[#16]
Quoted:
Was this the RE installed by the manufacturer or one you installed? If it was theirs, did you ever remove and remount it? I'm thinking something was overtorqued... Buffer tube was installed by myself - to spec. only other difference was an XP hammer spring.. NONE of which should cause a catastrophic failure like that, |
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Posted: 1/20/2011 5:41:44 AM EDT
[#17]
Quoted: Quoted: That's why I don't buy plastic lower receivers. Never seen a cavarms do that. That's because the buffer tube is built in to avoid that weak spot |
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Posted: 1/20/2011 6:06:52 AM EDT
[#18]
Quoted:
Quoted:
Quoted:
That's why I don't buy plastic lower receivers. Never seen a cavarms do that. That's because the buffer tube is built in to avoid that weak spot +1 I have NO problem with someone wasting their money on this as a range toy. but it's a range toy, and nothing more. |
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Posted: 1/20/2011 10:15:04 AM EDT
[#19]
Quoted:
Why is the area around the crack "blueish"? it looks like having a different colour, maybe purple to it. And it looks shinier than the rest of the piece. Looks like it is melted like someone put model glue on it. |
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Posted: 1/20/2011 11:50:35 AM EDT
[#20]
Quoted:
Been waiting for this post, I'll stick with aluminum. I know, right? I see tables at gunshows covered with these complete lowers usually selling for $99. Usually if something is too good to be true it generally is. |
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Posted: 1/20/2011 2:33:34 PM EDT
[#21]
Quoted:
Quoted:
That's why I don't buy plastic lower receivers. Never seen a cavarms do that. That is because they split at the mag well. |
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Posted: 1/20/2011 11:22:38 PM EDT
[#22]
Best test to see if a plastic lower is better than a metal lower is to use them to beat down doors.
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Posted: 1/21/2011 6:27:29 AM EDT
[#23]
Quoted:
Quoted:
Been waiting for this post, I'll stick with aluminum. I know, right? I see tables at gunshows covered with these complete lowers usually selling for $99. Usually if something is too good to be true it generally is. Especially when you can get quality aluminum lowers for $99 
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Posted: 1/21/2011 6:30:48 AM EDT
[#24]
You can see where the carrier key impacted.
Are you running a carbine buffer in a rifle tube? Key contact can split an AL lower there too. |
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Posted: 1/21/2011 6:38:15 AM EDT
[#25]
Quoted:
Quoted:
Quoted:
That's why I don't buy plastic lower receivers. Never seen a cavarms do that. That is because they split at the mag well. one of mine did that....... AFTER I USED A FILE TO SMOOTH OUT THE MAGWELL. I'll venture the majority of these rare cases are similar. remember the cavaid lowers came with alot of flash on them in a semi-finished state. |
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Posted: 1/21/2011 11:57:27 AM EDT
[#26]
Quoted:
Quoted:
Was this the RE installed by the manufacturer or one you installed? If it was theirs, did you ever remove and remount it? I'm thinking something was overtorqued... Buffer tube was installed by myself - to spec. only other difference was an XP hammer spring.. NONE of which should cause a catastrophic failure like that, To spec for an aluminum lower or to spec for a composite lower? I'm wondering if you inadvertently overtightened the castle nut (if carbine) or RE (if rifle). Composite can be flaky in compression. ETA: Glad to see they're taking care of you! |
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Posted: 1/21/2011 11:56:43 PM EDT
[#27]
Oh come on man, two words... Super Glue! :D
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Posted: 1/22/2011 12:00:22 AM EDT
[#28]
Quoted:
I had about 100 rounds TOTAL through the lower.... about 5 that day....when I noticed the bolt locked back about halfway with the shell casing just sitting on top of the full magazine.... I cleared the malfunction, charged the weapon.. and it happened again... I cleared again, made safe, and was wondering WHY it was happening..... then I noticed the buffer tube was extremely loose... Well... I found out why.. very quickly.. http://i91.photobucket.com/albums/k294/technoweenie/pcbuild/pclfailure2.jpg http://i91.photobucket.com/albums/k294/technoweenie/pcbuild/pclfailure1.jpg EDIT: Talked to Russ, who called from SHOT... Very easy guy to deal with, pointed out some things that make me believe I have issues with my upper, either weak buffer spring or overgassing or both.... You can see the carrier key impact on the lower, which he nailed right away..... He will be replacing it, even though it appears to be an issue with the upper.... I think this will be my lightweight 5.56 build, as he explained that people are using them for all calibre builds without issue, but it was designed with 5.56 in mind... A+ for customer service. Looks like a knit line failure. |
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Posted: 1/22/2011 5:03:00 AM EDT
[#29]
Quoted:
You can see where the carrier key impacted. Are you running a carbine buffer in a rifle tube? Key contact can split an AL lower there too. XP Hammer Spring is lifting the BCG EITHER WAY PLASTIC IS FOR TOYS. |
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Posted: 1/22/2011 5:34:52 AM EDT
[#30]
Quoted: XP Hammer Spring is lifting the BCG EITHER WAY PLASTIC IS FOR TOYS. Shouldn't matter, since the key should never reach the lower to begin with. Mostly agree |
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Posted: 1/22/2011 6:54:56 AM EDT
[#31]
Given the mark left where the gas key contacted the receiver extension thread area, are you sure this gun wasn't fired (even once) accidentally without the buffer installed?
It would be embarrassing to admit, but it could explain what weakened that point prior to failure. ????  ???? |
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Posted: 1/22/2011 10:21:14 AM EDT
[#32]
good to hear about the customer service
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Posted: 1/22/2011 2:16:24 PM EDT
[#33]
Quoted:
Given the mark left where the gas key contacted the receiver extension thread area, are you sure this gun wasn't fired (even once) accidentally without the buffer installed? It would be embarrassing to admit, but it could explain what weakened that point prior to failure. ???? http://i1011.photobucket.com/albums/af237/14point5/Hardware/gaskeycontact.jpg ???? Russ, their support guy, immediately keyed onto the fact that the upper was suspect, and immediately acknowledged that even thought it looked like an upper malfunction (and I agree with him ) he's still gonna replace the lower.. So A+ in the CS department. I was running the carbine buffer spring/buffer in a ace pistol buffer tube... Now, the impacts happened while I was using a spikes STT2 buffer (4.13 oz), that was the only difference between these 4 rounds and the other rounds I shot through it.... I'm going to intentionally misalign the gas port a microfraction of an inch to see if it still cycles reliably....if it does, then I know it was an overgas situation. |
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Posted: 1/22/2011 3:42:44 PM EDT
[#34]
Quoted:
Quoted:
Quoted:
Quoted:
That's why I don't buy plastic lower receivers. Never seen a cavarms do that. That is because they split at the mag well. one of mine did that....... AFTER I USED A FILE TO SMOOTH OUT THE MAGWELL. I'll venture the majority of these rare cases are similar. remember the cavaid lowers came with alot of flash on them in a semi-finished state. I have only seen two bust at the mag well. The green one and the yellow one. Isnt yours the green one? I have seen only one Plum Crazy break. So that isnt a high amount for either brand. |
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Posted: 1/22/2011 3:54:27 PM EDT
[#35]
FWIW, I have 4 cavarms lowers in service with no failures. (One yellow, one blue, and two blacks.)
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Posted: 1/22/2011 6:41:15 PM EDT
[#36]
Quoted: Quoted: Given the mark left where the gas key contacted the receiver extension thread area, are you sure this gun wasn't fired (even once) accidentally without the buffer installed? It would be embarrassing to admit, but it could explain what weakened that point prior to failure. ???? http://i1011.photobucket.com/albums/af237/14point5/Hardware/gaskeycontact.jpg ???? Russ, their support guy, immediately keyed onto the fact that the upper was suspect, and immediately acknowledged that even thought it looked like an upper malfunction (and I agree with him ) he's still gonna replace the lower.. So A+ in the CS department. I was running the carbine buffer spring/buffer in a ace pistol buffer tube... Now, the impacts happened while I was using a spikes STT2 buffer (4.13 oz), that was the only difference between these 4 rounds and the other rounds I shot through it.... I'm going to intentionally misalign the gas port a microfraction of an inch to see if it still cycles reliably....if it does, then I know it was an overgas situation. Overgassed or not, the carrier key should not have impacted the lower. |
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Posted: 1/22/2011 8:05:18 PM EDT
[#37]
Quoted: Overgassed or not, the carrier key should not have impacted the lower. +1 That is why I suspect it was fired without the buffer installed. |
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Posted: 1/22/2011 8:39:42 PM EDT
[#38]
Quoted:
Quoted:
Overgassed or not, the carrier key should not have impacted the lower. +1 That is why I suspect it was fired without the buffer installed. Spikes buffer and standard carbine spring was installed. I did replace the buffer spring and the new one is about a half an inch longer. the key is still impacting the lower, although barely.. You can see a light impact mark on the aluminum lower. I ran bout 100 rounds through it on my aluminum lower, and there's an ever so slight shadow (?) where you can tell the key impacted the lower.... |
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Posted: 1/22/2011 8:44:21 PM EDT
[#39]
whose upper are you running?
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Posted: 1/23/2011 3:24:55 AM EDT
[#40]
Quoted: Of course he did...Quoted: Given the mark left where the gas key contacted the receiver extension thread area, are you sure this gun wasn't fired (even once) accidentally without the buffer installed? It would be embarrassing to admit, but it could explain what weakened that point prior to failure. ???? http://i1011.photobucket.com/albums/af237/14point5/Hardware/gaskeycontact.jpg ???? Russ, their support guy, immediately keyed onto the fact that the upper was suspect, and immediately acknowledged that even thought it looked like an upper malfunction (and I agree with him ) he's still gonna replace the lower.. So A+ in the CS department. I was running the carbine buffer spring/buffer in a ace pistol buffer tube... Now, the impacts happened while I was using a spikes STT2 buffer (4.13 oz), that was the only difference between these 4 rounds and the other rounds I shot through it.... I'm going to intentionally misalign the gas port a microfraction of an inch to see if it still cycles reliably....if it does, then I know it was an overgas situation. He's not gonna admit his plastic is at fault. I wonder if this thread is just a indicator of things to come with these lowers? |
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Posted: 1/23/2011 4:23:10 AM EDT
[#41]
Quoted:
Quoted:
I had about 100 rounds TOTAL through the lower.... about 5 that day....when I noticed the bolt locked back about halfway with the shell casing just sitting on top of the full magazine.... I cleared the malfunction, charged the weapon.. and it happened again... I cleared again, made safe, and was wondering WHY it was happening..... then I noticed the buffer tube was extremely loose... Well... I found out why.. very quickly.. http://i91.photobucket.com/albums/k294/technoweenie/pcbuild/pclfailure2.jpg http://i91.photobucket.com/albums/k294/technoweenie/pcbuild/pclfailure1.jpg EDIT: Talked to Russ, who called from SHOT... Very easy guy to deal with, pointed out some things that make me believe I have issues with my upper, either weak buffer spring or overgassing or both.... You can see the carrier key impact on the lower, which he nailed right away..... He will be replacing it, even though it appears to be an issue with the upper.... I think this will be my lightweight 5.56 build, as he explained that people are using them for all calibre builds without issue, but it was designed with 5.56 in mind... A+ for customer service. Looks like a knit line failure. Yup my first thought as well. ETA there's a lot not adding up here. The bolt should bottom out prior to making contact with the lower receiver. In addition, you said you were using a longer buffer spring which would make the carrier bottom out sooner making a carrier strike even more impossible unless: 1. If you weren't using a carbine buffer in a rifle tube then, 2. you shot it without the buffer spring/buffer in place or 3. the area cracked first (knit line failure as stated above) and the carrier strike occured as a result of the knit line failure. |
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Posted: 1/23/2011 5:13:40 AM EDT
[#42]
Quoted: This. The buffer should be hitting the back of the receiver extension before the gas key hits the lower. Quoted: Overgassed or not, the carrier key should not have impacted the lower. +1 That is why I suspect it was fired without the buffer installed. |
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Posted: 1/23/2011 9:05:41 AM EDT
[#43]
Quoted:
Quoted:
This. The buffer should be hitting the back of the receiver extension before the gas key hits the lower.
Quoted:
Overgassed or not, the carrier key should not have impacted the lower. +1 That is why I suspect it was fired without the buffer installed. I just tried pushing the carrier into the buffer tube by hand/...Carrier goes back fully into the buffer tube, striking the carrier key, does NOT bottom out before striking the key... Buffer tube is about even with the lower, so it is screwed in far enough. |
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Posted: 1/23/2011 9:35:29 AM EDT
[#44]
Quoted:
Quoted:
Quoted:
This. The buffer should be hitting the back of the receiver extension before the gas key hits the lower.
Quoted:
Overgassed or not, the carrier key should not have impacted the lower. +1 That is why I suspect it was fired without the buffer installed. I just tried pushing the carrier into the buffer tube by hand/...Carrier goes back fully into the buffer tube, striking the carrier key, does NOT bottom out before striking the key... Buffer tube is about even with the lower, so it is screwed in far enough. I just grabbed my known good carbine that was lying next to me and did the same - the BCG bottoms out in the carbine RE with 5/16" to spare between the back of the gas key and the lower receiver ring. |
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Posted: 1/23/2011 9:42:22 AM EDT
[#45]
Quoted: I just tried pushing the carrier into the buffer tube by hand/...Carrier goes back fully into the buffer tube, striking the carrier key, does NOT bottom out before striking the key... Buffer tube is about even with the lower, so it is screwed in far enough. You need to replace your buffer tube with one that's in spec. |
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Posted: 1/23/2011 12:32:18 PM EDT
[#46]
Quoted: AaaaHa! That is your problem!Quoted: Quoted: This. The buffer should be hitting the back of the receiver extension before the gas key hits the lower. Quoted: Overgassed or not, the carrier key should not have impacted the lower. +1 That is why I suspect it was fired without the buffer installed. I just tried pushing the carrier into the buffer tube by hand/...Carrier goes back fully into the buffer tube, striking the carrier key, does NOT bottom out before striking the key... Buffer tube is about even with the lower, so it is screwed in far enough. |
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Posted: 1/23/2011 2:41:44 PM EDT
[#47]
Quoted:
PVC welder? Hose clamp.
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Posted: 1/23/2011 2:57:59 PM EDT
[#48]
It has to have a gap between the rear of the key and the lower reciever bridge when done by hand because when being fired, the urethane bumper on the buffer has a bit of compression in it and it will go a bit further.
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Posted: 1/23/2011 6:54:07 PM EDT
[#49]
Quoted:
Quoted:
I just tried pushing the carrier into the buffer tube by hand/...Carrier goes back fully into the buffer tube, striking the carrier key, does NOT bottom out before striking the key... Buffer tube is about even with the lower, so it is screwed in far enough. You need to replace your buffer tube with one that's in spec. I think it's the spikes buffer..... Spikes = hits key 'standard' = minute fraction of an inch clearance Hmmm... maybe the combination of both being out of spec a hair? stacking tolerances? |
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Posted: 1/23/2011 6:56:18 PM EDT
[#50]
Quoted: Quoted: Quoted: I just tried pushing the carrier into the buffer tube by hand/...Carrier goes back fully into the buffer tube, striking the carrier key, does NOT bottom out before striking the key... Buffer tube is about even with the lower, so it is screwed in far enough. You need to replace your buffer tube with one that's in spec. I think it's the spikes buffer..... Spikes = hits key 'standard' = minute fraction of an inch clearance Hmmm... maybe the combination of both being out of spec a hair? stacking tolerances? There should be more than a "minute fraction" of an inch... Sounds like the buffer tube is too long. You said it was a pistol tube, who made it? Some brands have a screw-on cap on the back. If that has backed off some, then it would let the bolt overtravel... |
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