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Posted: 4/18/2015 1:44:46 PM EDT
This pic is all of the information I have on the breakage. Older DPMS, my brother's rifle. I will update this post when I know more.
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| any part no matter quality can fail...ive had sheared lugs on HP/MP tested bolts..dpms had this problem on their bolts way back when..dont know if its been cleared up but its a good reason to always keep spares on hand no matter who makes your bolt that way youll never be out of action. |
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The thin webs around the cam pin hole are under considerable stress. The bolt carrier in a normal rifle length gas system has a velocity of about 6.25 m/s when the front of the cam pin slot slams into the cam pin and starts to try and pull a stationary bolt back. If you start shortening the gas tube and increasing the piston pressure, or reducing the carrier/buffer weight, or all of these, the bolt carrier velocity goes up significantly.
Eventually, they fatigue and fail. Any surface defects, even very minor ones like surface corrosion, nicks dings, etc will accelerate failure. |
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any part no matter quality can fail...ive had sheared lugs on HP/MP tested bolts..dpms had this problem on their bolts way back when..dont know if its been cleared up but its a good reason to always keep spares on hand no matter who makes your bolt that way youll never be out of action. This. Get a new one and press on. I run Colt & BCM products and keep a spare bolt in my kit because you just never know. . |
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This. Get a new one and press on. I run Colt & BCM products and keep a spare bolt in my kit because you just never know. . Quoted:
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any part no matter quality can fail...ive had sheared lugs on HP/MP tested bolts..dpms had this problem on their bolts way back when..dont know if its been cleared up but its a good reason to always keep spares on hand no matter who makes your bolt that way youll never be out of action. This. Get a new one and press on. I run Colt & BCM products and keep a spare bolt in my kit because you just never know. . Exactly. Bolts are known to fail under some hard use. It is always a good idea to keep a spare around when you are running an AR hard. It looks like the OP's brother's DPMS has been used quite a bit and not babied at all. |
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This post overwhelmed me with technical information, backing your assertions. I'm interested to see more info/pictures. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. This post overwhelmed me with technical information, backing your assertions. I'm interested to see more info/pictures. I know right? Fucking dag, yo! OP, when bolts decide it's their time to go, there are 2 areas they snap at. 1- the lugs 2- around the cam pin hole. This is a very common breakage, and to the people that are going to talk shit about DPMS, It is a wear item. They will ALL break eventually. Could it have been improperly hardened? Yes. Is it likely this one was? Hard to say for sure, but im going to go with no. All bolts eventually break. Small fractures turn into big fractures. |
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. If it were a Colt or any other "Commando" brand, it would be the result of global warming or some other uncontrollable natural disaster. Hate to say it but if you have an AR you are going to have a broken bolt somewhere down the line. Get a new bolt and carry on. Most of us keep spares because of this. |
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Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. |
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Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. That area is not shot peened, nor does it get loaded under HPT. |
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That is soooo 2010... Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. That is soooo 2010... So are you saying they have greatly stepped up build quality of their rifles? I believe Pat Rogers often says good bolts break lugs, and shoddy bolts break around the webbing. Good bolts often go near or past 10,000 rounds. |
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I know right? Fucking dag, yo! OP, when bolts decide it's their time to go, there are 2 areas they snap at. 1- the lugs 2- around the cam pin hole. This is a very common breakage, and to the people that are going to talk shit about DPMS, It is a wear item. They will ALL break eventually. Could it have been improperly hardened? Yes. Is it likely this one was? Hard to say for sure, but im going to go with no. All bolts eventually break. Small fractures turn into big fractures. Unless there's more to the story (like a kaboom), that right there ^^^^^^^^^^^^^^^^. |
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This pic is all of the information I have on the breakage. Older DPMS, my brother's rifle. I will update this post when I know more. http://i66.photobucket.com/albums/h251/baxshep/1f3bdb683f1d19feb6eb4736205007b6_zpszojeogee.jpg Obviously didn't prepare the Fetzer valve with some 3-in-1 oil and gauze pads. Next time use about ten quarts of anti-freeze, preferably Prestone. No, no make that Quaker State. 
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8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. |
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Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. There are a few, even PSA sells one, at least they did. During the great panic, these things were popping up everywhere. |
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Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. PSA does (or did.) I have couple that I got during the Panic. Never had occasion to use them. |
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Quoted: 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. Quoted: Quoted: Quoted: Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. |
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Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. AR Stoner did during the Sandy Hook panic. PSA did as well IIRC. The AR Stoner bolts were shearing lugs with double digit round counts. |
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There are a few, even PSA sells one, at least they did. During the great panic, these things were popping up everywhere. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. There are a few, even PSA sells one, at least they did. During the great panic, these things were popping up everywhere. Years ago, there were plenty made of 8620. |
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This post overwhelmed me with technical information, backing your assertions. I'm interested to see more info/pictures. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. This post overwhelmed me with technical information, backing your assertions. I'm interested to see more info/pictures. Another case of "just as good as". 
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Obviously didn't prepare the Fetzer valve with some 3-in-1 oil and gauze pads. Next time use about ten quarts of anti-freeze, preferably Prestone. No, no make that Quaker State. Quoted:
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This pic is all of the information I have on the breakage. Older DPMS, my brother's rifle. I will update this post when I know more. http://i66.photobucket.com/albums/h251/baxshep/1f3bdb683f1d19feb6eb4736205007b6_zpszojeogee.jpg Obviously didn't prepare the Fetzer valve with some 3-in-1 oil and gauze pads. Next time use about ten quarts of anti-freeze, preferably Prestone. No, no make that Quaker State. It's all ball bearings nowadays. |
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Yea and there have also been runs of bolts that were 8620 that had many issues. Normally it is just the carrier that is 8620, but you are incorrect in that fact that there haven't been runs of 8620, because there has been. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. I didnt say there haven't been runs made. What I was saying is I would be blown away if DPMS made bolts out of 8620. In my opinion they know better. DPMS gets a bad wrap because of their old rep, but every DPMS part I've owned has been quality. |
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Can't believe I saw references to Pat Rogers here, of all places.
He also says don't buy economy grade rifles and think you got a go-to-war gun, and I believe he also doesn't believe in builds. Also, 1000 rds before you know a gun is good to go. Travis Haley recommends against builds and economy grade guns. My DPMS was jacked up from the factory due to poor assembly and could have only made it through their QC if they didn't have any QC; so no love from me. |
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AR Stoner did during the Sandy Hook panic. PSA did as well IIRC. The AR Stoner bolts were shearing lugs with double digit round counts. I would expect the lugs to fail rather quickly if you made the bolt out of 8620. The yield strength of 8620 is about 80% of 9310 or 158. Do we know these were 8620, and not a bad heat treat batch? |
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I would expect the lugs to fail rather quickly if you made the bolt out of 8620. The yield strength of 8620 is about 80% of 9310 or 158. Do we know these were 8620, and not a bad heat treat batch? Quoted:
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AR Stoner did during the Sandy Hook panic. PSA did as well IIRC. The AR Stoner bolts were shearing lugs with double digit round counts. I would expect the lugs to fail rather quickly if you made the bolt out of 8620. The yield strength of 8620 is about 80% of 9310 or 158. Do we know these were 8620, and not a bad heat treat batch? Those specific one's I mentioned, yes, we know for certain those bolts were 8620. You can search here, there were multiple threads about the AR Stoner bolt failures. I do not think OP's brother's DPMS pictured in the OP had an 8620 bolt though. |
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Those specific one's I mentioned, yes, we know for certain those bolts were 8620. You can search here, there were multiple threads about the AR Stoner bolt failures. I do not think OP's brother's DPMS pictured in the OP had an 8620 bolt though. Quoted:
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AR Stoner did during the Sandy Hook panic. PSA did as well IIRC. The AR Stoner bolts were shearing lugs with double digit round counts. I would expect the lugs to fail rather quickly if you made the bolt out of 8620. The yield strength of 8620 is about 80% of 9310 or 158. Do we know these were 8620, and not a bad heat treat batch? Those specific one's I mentioned, yes, we know for certain those bolts were 8620. You can search here, there were multiple threads about the AR Stoner bolt failures. I do not think OP's brother's DPMS pictured in the OP had an 8620 bolt though. Agreed, a few of us posted this in here, and remember the sales ads clearly. Broken bolts at the cam pin hole is not new, and definitely not new for DPMS 158 units. |
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I would expect the lugs to fail rather quickly if you made the bolt out of 8620. The yield strength of 8620 is about 80% of 9310 or 158. Do we know these were 8620, and not a bad heat treat batch? Quoted:
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AR Stoner did during the Sandy Hook panic. PSA did as well IIRC. The AR Stoner bolts were shearing lugs with double digit round counts. I would expect the lugs to fail rather quickly if you made the bolt out of 8620. The yield strength of 8620 is about 80% of 9310 or 158. Do we know these were 8620, and not a bad heat treat batch? No, we do not. This is simply a bash DPMS opportunity for most. I don't even remember reading a round count on this bolt and people are already claiming it's a cheap 8620 part. I've read from the DPMS rep on this site that they do not use 8620 for their bolts. I've got a DPMS bolt with around 5K on it through a carbine. Guess I have been lucky that so far it hasn't killed me. But no worries now, as it was relegated to backup duty when I changed barrels. |
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There are a few, even PSA sells one, at least they did. During the great panic, these things were popping up everywhere. Quoted:
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Dpms, crappy materials, crappy quality control, crappy brand. Yep. 8620 steel instead of carpenter 158. Not shot peened, not individualy hpt or mpi. 8620 is carrier steel. 9310 and C-158 are bolt steel. If you can show me something that says this bolt was made from 8620 I would be blown away. Right...never seen a bcg with a 8620 bolt. Don't think anyone makes one. There are a few, even PSA sells one, at least they did. During the great panic, these things were popping up everywhere. Yes sir the do/did. I have one... in my spare parts bin as a last resort EOTWAWKI replacement... |
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