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Posted: 7/24/2016 10:58:57 PM EDT
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Long story short: I broke my extractor on the Grendel last Sunday practicing before a match this weekend. The gun had just under 1000 rounds on it. Frustrating but I figured shit happens. Contacted JP and had replacements by Wednesday and was able to get the gun up and going for the match. Day 1 at match went well, Day 2 my extractor sheared again with about 250 rounds total this time. Lost a few points on stage and was able to use a back up gun and finish the match.
I have sent JP an email letting them know what happened again and am waiting to hear back. So I am unsure why my gun is killing extractors. It is a Rainier Arms Shillen 18 inch w/ intermediate gas, tuned gas block (SLR Sentry 7), JP bolt, running factory Hornady 123 amax. I am a bit frustrated and I am not sure if it is my build or the extractors. Besides killing extractors, the gun will shoot. Any ideas? |
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How long has it been since you tried firing one round to see if the bolt locks back on an empty chamber. I could see where the extractor could fail if the rifle is under or over gassed. I had an extractor failure on my 16" 6.5 Grendel. I had some problems trying to shoot some reloads with to light a charge of CFE 223 with 123 grain bullets. I added a stronger extractor spring with O ring. I also had a few issues not getting the shoulder set back properly and running a few bullets to long. I ended up having to mortar my rifle a few times. All part of my learning curve but I'm sure it all was hard on the extractor. I really think I should not have added the extra heavy extractor spring and O ring. I ended up ordering two extractors from AA so I'd have spare since I have two 6.5 Grendels. I have since been using the standard extractor spring without issue.
A Friend also had an extractor failure on his Brownell's 18" 6.5 Grendel which has a short chamber and is over gassed. He usually shoots handloads and added an adjustable gas block. Since adding his adjustable gas block and watches his COAL length he's had no further problem. Another potential problem could be a rough chamber, if it were my barrel I'd consider polishing the chamber with Flitz on a barrel mop attached to a short cleaning rod using a hand drill. |
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If the correct tool steel is not used, and the heat treat is done poorly, the extractor will break on any of these rifles, including 5.56.
After 7 years of shooting several different 6.5 Grendels, I have not had these problems. All my bolt purchases will be from AA, as I've not had issues with them, and I know there is a rigid series of tests and call-outs AA uses for extractors. Everybody has a bad day. It just comes down to how often and how they deal with it. |
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Thanks for the replies, right now I am waiting to hear the reply from JP and see what they suggest. I was planning on changing a few items on this build but now I think I will tear it down completely and start over looking for tiny issues along the way. Should be a better rifle in the end regardless.
The potential is there, refinement is needed. I will keep you all posted on the response and my actions. ETA: Edited first post to specify gas block (SLR Sentry 7) |
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What LRRPF52 said
I do not blame the platform. I blame the MFG of the extractor. The company I purchased my bolt from made good on their product. That is what I look for in a company to do business with. Why did I have 3 break?? Because they got a big batch in and dumped bad ones in with good ones. Once they figured out they had a problem they could not tell which ones were bad and which ones were good. Also the bolts had already been made and sent out or replacements had gone out. Not only did they send out the replacement but they also sent one spare and I had them in hand 2 days later. Helps that they are only about 65 miles away but still good customer service. |
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Quoted:
What LRRPF52 said I do not blame the platform. I blame the MFG of the extractor. The company I purchased my bolt from made good on their product. That is what I look for in a company to do business with. Why did I have 3 break?? Because they got a big batch in and dumped bad ones in with good ones. Once they figured out they had a problem they could not tell which ones were bad and which ones were good. Also the bolts had already been made and sent out or replacements had gone out. Not only did they send out the replacement but they also sent one spare and I had them in hand 2 days later. Helps that they are only about 65 miles away but still good customer service. Let me be clear.....JP did make good on the extractor and sent me one free and very timely, and I paid for 2 extra ones. The 3 replacements have the same lot number but it is different from the first one. |
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I am not trying to bash JP or any company, just identifying the manufacturer so there is some record should another person have this issue.
My belief is that these parts need to be perfect to survive. I feel the Grendel is a slightly compromised design ( in this area only) since it was designed off the 556 bolt. There is just physically less material. I could be wrong but this is my opinion and I am not a metallurgist, gunsmith, or engineer. None of this is stopping me from loving this cartridge in the AR-15 platform. |
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Quoted:
If the correct tool steel is not used, and the heat treat is done poorly, the extractor will break on any of these rifles, including 5.56. After 7 years of shooting several different 6.5 Grendels, I have not had these problems. All my bolt purchases will be from AA, as I've not had issues with them, and I know there is a rigid series of tests and call-outs AA uses for extractors. Everybody has a bad day. It just comes down to how often and how they deal with it. I appreciate your insight. My AA hard use bolt is shipping after a 2 month B/O. |
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Quoted:
Long story short: I broke my extractor on the Grendel last Sunday practicing before a match this weekend. The gun had just under 1000 rounds on it. Frustrating but I figured shit happens. Contacted JP and had replacements by Wednesday and was able to get the gun up and going for the match. Day 1 at match went well, Day 2 my extractor sheared again with about 250 rounds total this time. Lost a few points on stage and was able to use a back up gun and finish the match. I have sent JP an email letting them know what happened again and am waiting to hear back. So I am unsure why my gun is killing extractors. It is a Rainier Arms Shillen 18 inch w/ intermediate gas, tuned gas block (SLR Sentry 7), JP bolt, running factory Hornady 123 amax. I am a bit frustrated and I am not sure if it is my build or the extractors. Besides killing extractors, the gun will shoot. Any ideas? Can you tell is what your gas port diameter is by any chance? I would also consider what Tony said, in that the chamber may need some polishing. |
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I will measure the gas port when I strip it down in about a week. Also, I am going to check out the barrel with a bore scope prior to polishing.
I will up date this post in 10-14 days. Work and vacation are getting in the way of this mystery. Thanks for all the advice and suggestions. |
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I have not measured the gas port or borescoped the barrel yet but it will happen.
I was able to pick up a JP LMOS carrier and SCS at a great price so in they went and a new scope was mounted. I re tuned the gas system and zeroed the weapon this weekend. All 30(ish) rounds went well and my buddy and I were able to take out some groundhogs. So that's the update, no real progress but I am still having fun. |
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Quoted:
The friction of the rings in the carrier feels less than others, there is friction which would lead me to believe there is an appropriate gas seal. Just something I noticed. I do not see erratic cycling, brass is thrown in the same place, functions perfect. Without a cam pin in the BCG, extend the bolt and stand the BCG on the bolt face. Does it stay or collapse? |
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I have been shooting the gun some and it was working great until today.
Bolt lug sheared off. Extractor seems ok though 
At a loss here, I will call JP tomorrow. Any suggestions would be great because this damn gun will shoot. Should I buy another JP bolt or try another? |
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I'd really be inclined to think you just have terrible luck. I've helped quite a few people set up their Grendels, as well as going shooting with LRRPF52 and a group of Grendel shooters. Never saw a single problem until last week when an extractor from AA broke with about 200 rounds of steel on it.
It still seems like a higher failure rate than comparable 5.56 stuff, but still pretty small. |
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