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Posted: 10/29/2017 1:15:29 PM EDT
Hit the range yesterday, had a couple stuck cases that were easily removed via a very light morter. Then suddenly it stopped working all together. Took a look and found the extractor had broke. I've never seen one fail like this. Does the channel the extractor sits in look sloppily machined? Was one of the complete BCA 16" SS uppers.
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Posted: 10/29/2017 1:36:52 PM EDT
[#1]
TBH I’ve seen a half-dozen or so BCA BCG’s and the bolts all looked a little rough as far as finish machining.
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Posted: 10/29/2017 3:15:04 PM EDT
[#2]
Oddly, their have been a number of Extractor failures lately on Grendel bolts, even the ones with the stronger .136 recess.. I've seen a few reported AA "hard use" bolt failures and even a JP failure with a 3 gunner. Could be a bad slew of extractors made it out the door..
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Posted: 10/29/2017 5:24:46 PM EDT
[#3]
Sorry cant determine anything about the machining from the photos. However, if you contact BCA they will take care of you.
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Posted: 10/29/2017 5:26:54 PM EDT
[#4]
Also please tell us what kind of ammo you were using and why the cases were getting stuck. Approximate round count?
This info will be helpful for all those interested in a BCA 6.5G upper. BTW, I sell lots of those uppers at my shop so the info will be very helpful for me, as well. |
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Posted: 10/29/2017 6:04:35 PM EDT
[#5]
Quote HistoryQuoted:
Also please tell us what kind of ammo you were using and why the cases were getting stuck. Approximate round count? This info will be helpful for all those interested in a BCA 6.5G upper. BTW, I sell lots of those uppers at my shop so the info will be very helpful for me, as well. I did send BCA an email about it. For what its worth, I've been pretty happy with the upper, decent accuracy and the fit and finish was good especially at that price point. |
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Posted: 10/29/2017 7:09:50 PM EDT
[#6]
I have also noticed that the brass after extraction on mine are kind of roughed up with burrs on either side of where the extractor was over the case rim. Has anyone else noticed this?
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Posted: 10/30/2017 10:27:25 AM EDT
[#7]
Looks like a poorly heat-treated extractor.
AA had a run of them like that too about a year ago. |
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Posted: 10/30/2017 6:30:04 PM EDT
[#8]
BCA impressed me, they have already shipped me a new one. Solid customer service.
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Posted: 11/1/2017 10:26:27 AM EDT
[#9]
Quote HistoryQuoted:
BCA impressed me, they have already shipped me a new one. Solid customer service. another thread Involving BCA with multiple rusted chambers and bores with their X39mm uppers/Barrels... Glad that BCA did the right thing and responded quickly and properly to a customer service or factory defect part replacement... Good luck. |
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Posted: 11/13/2017 11:13:09 AM EDT
[#10]
It happened to me too with a JP bolt.....3 extractors and then finally a bolt.
It appears to be common with the Grendel with the extra machining to the bolt and extractors. |
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Posted: 11/13/2017 12:16:40 PM EDT
[#11]
Quote HistoryQuoted:
It happened to me too with a JP bolt.....3 extractors and then finally a bolt. It appears to be common with the Grendel with the extra machining to the bolt and extractors. |
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Posted: 11/13/2017 4:56:23 PM EDT
[#12]
Quote HistoryQuoted:
Some people may try to deny the issues with the Grendel, but the reason it has issues with feeding and extraction due to case dimensions. The design of the case limits bolt strength and feeding/extraction reliability, especially in accelerated fire. I wonder if the case was sticking, which put additional pressures on the extractor. What specifically would make you speculate on the case sticking? Which dimensions are problematic and why? Not to sound trite, here. Just wondering how you came to those conclusions. |
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Posted: 11/13/2017 5:08:27 PM EDT
[#13]
I've heard from a good source that broken extractors is a reason the round will most likely never be adopted by the U.S. Armed Forces. That and the reliability in semi and full auto high round count tests.
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Posted: 11/13/2017 6:11:59 PM EDT
[#14]
Quote HistoryQuoted:
I've heard from a good source that broken extractors is a reason the round will most likely never be adopted by the U.S. Armed Forces. That and the reliability in semi and full auto high round count tests. Not aware of any serious look at it from the US Army outside of AMU. Maybe your "good source" is more reliable than all of mine. |
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Posted: 11/13/2017 6:43:31 PM EDT
[#15]
Quote HistoryQuoted:
That would have been simple to determine by examining the case rim for signs of extractor pull. What specifically would make you speculate on the case sticking? Which dimensions are problematic and why? Not to sound trite, here. Just wondering how you came to those conclusions. http://www.65grendel.com/forum/showthread.php?979-Broken-excractor |
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Posted: 11/13/2017 6:58:35 PM EDT
[#16]
Quote HistoryQuoted:
It is my understanding that to be seriously considered for full auto use, a case needs to have more taper so it can extract easier. When the case is more parallel, it is more prone to sticking, which causes the case to be more prone to sticking, which then causes types of extraction issues. It is not that rare of an issue with the 6.5 Grendel. http://www.65grendel.com/forum/showthread.php?979-Broken-excractor ETA: Found this: "Actually, the Grendel has more taper then a 7.62 NATO and the 5.56 NATO.. " https://www.ar15.com/forums/ar-15/6-5-Grendel-FAQ/121-271627/ |
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Posted: 11/13/2017 7:03:50 PM EDT
[#17]
Quote HistoryQuoted:
I was not asking about full auto usage. Why would the case taper be problematic here, but not elsewhere? |
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Posted: 11/13/2017 7:24:25 PM EDT
[#18]
Quote HistoryQuoted:
Sorry for being too vague. The issue prevents consideration for full auto. The issue however is also seen on guns that are not full auto. The 6.5's case is known to have extraction issues, and under rapid fire people don't have time to clear malfunctions....however, these issues happen without rapid fire as well although heat supposedly makes it worse...the malfunctions just aren't as critical since you are not in a hurry to get another round down range (such as in combat). Quote HistoryQuoted:
Quoted:
I was not asking about full auto usage. Why would the case taper be problematic here, but not elsewhere? There are no inherent extraction issues to 6.5 Grendel, and a case with that thick of a rim has extraction advantages, like the 7.62x39. Grendel rims are thicker than .308 rims if you measure them, which means less chance of the extractor tearing a rim off in a gun that is improperly timed. Extractor failures have been very rare until recently, with some lots of extractors. Any extractor design in a self-loader is going to be subject to metallurgy, regardless of the cartridge it's chambered for. You either get the metallurgy right, or not. If it's wrong, then 5.56, 7.62 NATO, and any other cartridge chambering will see failures. To make the claim that it is particular to one type of cartridge is just incorrect. 6.5 Grendel actually had full auto testing as a standard with AA at one time, not that soldiers or Marines are taught to use full auto fire from their service rifles or carbines. You get an idea of who you're dealing with when people start talking about full auto fire from carbines and service rifles. As to case taper, if someone is telling you that 6.5 Grendel has less case taper, ask them, "Why then does it require a curved 15rd magazine to feed reliably, when 5.56 feeds from straight 20rd magazines reliably?" One of these statements is true: "6.5 Grendel can't feed reliably for full auto use because it doesn't have enough case taper." "6.5 Grendel has more taper, so it needs curved magazines for capacities larger than 10 rounds." If someone told you 6.5 Grendel has particular extraction issues, you can write that source off as either misinformed or biased. If biased, why?  6.5 Grendel Full Auto Mag Dump  King Ordnance 6.5 Grendel Suppressed Full Auto- Chase |
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Posted: 11/13/2017 7:33:24 PM EDT
[#19]
Really any variant isn't going to be as reliable as the 5.56. Even the 300 blk has much higher failure rate than the 5.56/
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Posted: 11/13/2017 7:39:20 PM EDT
[#20]
Quote HistoryQuoted:
Really any variant isn't going to be as reliable as the 5.56. Even the 300 blk has much higher failure rate than the 5.56/ It's the same thing that I think contributes to less reliability with the AR10 in 7.62 NATO as well. 5.56 NATO and the 6mm wildcats especially do not exhibit this behavior. |
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Posted: 11/13/2017 7:40:16 PM EDT
[#21]
Quote HistoryQuoted:
Sorry for being too vague. The issue prevents consideration for full auto. The issue however is also seen on guns that are not full auto. The 6.5's case is known to have extraction issues, and under rapid fire people don't have time to clear malfunctions....however, these issues happen without rapid fire as well although heat supposedly makes it worse...the malfunctions just aren't as critical since you are not in a hurry to get another round down range (such as in combat). Any variant cartridge that has not been thoroughly tested can deveolpe issues. Some manufacturers/vendors put a product on the market without significant testing. The problems with the original M-16 in the late 1960’s when the switch was made to a different powder is an indication of how testing should be conducted. Any mass produced parts will have failures and improper heat treat or poor quality steel/materials are not unheard of in the firearms industry. I’m not trying to make excuses for the 6.5 Grendel but most 6.5 Grendels have been sold to the consumer are used for hunting, target or pleasure. I’m not aware of any Military or LE use. I have only read of a few instances where the 6.5 Grendel has been used in action shooting competition. I know Serbia was testing an AK style rifle in 6.5 Grendel. The AR-15’s in 7.62X39 have seen improvements in the design of bolts and don’t seem to get as much negative feed back in forums as the 6.5 Grendel even though both cartridages have roots in the 220 Russian. |
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Posted: 11/13/2017 7:52:55 PM EDT
[#22]
Look that extractor over carefully before installing it. With it out of the bolt, hold it into the groove on a Grendel shell and then slowly rotate the shell as if it's getting pushed out by the ejector while keeping the shell firmly against the extractor. If the shell reaches a point where it "locks up" in the groove, that extractor will forever be the root cause of FTEs. The fix is to take a needle file or stone to the extractor and round off the two "points" on it which cause the case to lock up. With the larger diameter 7.62 and Grendel shells this issue shows up when it's not a problem with smaller 5.56/.223 shells.
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Posted: 11/13/2017 8:06:37 PM EDT
[#23]
Quote HistoryQuoted:
This has not been my experience as any extraction issues can be traced to a root cause. An example for some failure to extract or extractor failures can be traced to over size gas ports or out of spec chambers. I’m curious how much first hand experience AmericanSentinelK9 has with the 6.5 Grendel cartridge and AR-15’s. Any variant cartridge that has not been thoroughly tested can deveolpe issues. Some manufacturers/vendors put a product on the market without significant testing. The problems with the original M-16 in the late 1960’s when the switch was made to a different powder is an indication of how testing should be conducted. Any mass produced parts will have failures and improper heat treat or poor quality steel/materials are not unheard of in the firearms industry. I’m not trying to make excuses for the 6.5 Grendel but most 6.5 Grendels have been sold to the consumer are used for hunting, target or pleasure. I’m not aware of any Military or LE use. I have only read of a few instances where the 6.5 Grendel has been used in action shooting competition. I know Serbia was testing an AK style rifle in 6.5 Grendel. The AR-15’s in 7.62X39 have seen improvements in the design of bolts and don’t seem to get as much negative feed back in forums as the 6.5 Grendel even though both cartridages have roots in the 220 Russian. Quote HistoryQuoted:
Quoted:
Sorry for being too vague. The issue prevents consideration for full auto. The issue however is also seen on guns that are not full auto. The 6.5's case is known to have extraction issues, and under rapid fire people don't have time to clear malfunctions....however, these issues happen without rapid fire as well although heat supposedly makes it worse...the malfunctions just aren't as critical since you are not in a hurry to get another round down range (such as in combat). Any variant cartridge that has not been thoroughly tested can deveolpe issues. Some manufacturers/vendors put a product on the market without significant testing. The problems with the original M-16 in the late 1960’s when the switch was made to a different powder is an indication of how testing should be conducted. Any mass produced parts will have failures and improper heat treat or poor quality steel/materials are not unheard of in the firearms industry. I’m not trying to make excuses for the 6.5 Grendel but most 6.5 Grendels have been sold to the consumer are used for hunting, target or pleasure. I’m not aware of any Military or LE use. I have only read of a few instances where the 6.5 Grendel has been used in action shooting competition. I know Serbia was testing an AK style rifle in 6.5 Grendel. The AR-15’s in 7.62X39 have seen improvements in the design of bolts and don’t seem to get as much negative feed back in forums as the 6.5 Grendel even though both cartridages have roots in the 220 Russian. Still waiting. We're talking multiple day and night courses where we go through hundreds of rounds daily, and this goes back to at least 2010 shooting Grendels. I've been shooting 5.56 since the 1980s, and have seen plenty of broken bolts with it, usually after 10k rounds. You know what I did when I broke 5.56 bolts? It was pretty crazy. I.....replaced them with another one. Like I said, still waiting for a Grendel bolt from my armory full of Grendels, some of which I even use as loaners for when attendee rifles break, but I'm sure I'll see one anytime now. I did have one attendee and fellow forum member report to me at least 2 extractors failing in a row, so there was definitely a bad batch that one manufacturer put out, but that hasn't been the norm since Grendel's introduction. No matter who the company is, they can have a bad day or even a bad lot if they let their guard down on standards. Recall the lots of 5.56 bolts post-Sandy Hook, or the recent recall of SCAR-17 bolts. So when someone tells you it's a specific problem with 6.5 Grendel, I'm very skeptical of those claims. |
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Posted: 11/13/2017 8:10:15 PM EDT
[#24]
Quote HistoryQuoted:
Look that extractor over carefully before installing it. With it out of the bolt, hold it into the groove on a Grendel shell and then slowly rotate the shell as if it's getting pushed out by the ejector while keeping the shell firmly against the extractor. If the shell reaches a point where it "locks up" in the groove, that extractor will forever be the root cause of FTEs. The fix is to take a needle file or stone to the extractor and round off the two "points" on it which cause the case to lock up. With the larger diameter 7.62 and Grendel shells this issue shows up when it's not a problem with smaller 5.56/.223 shells. That was something added to the TDP along the way as well with the continual development of the AR15/M16/M4, which still has not ceased to be refined from continual ODT&E. If you pull out an extractor, there are relief cuts along the sides of the underside of it corresponding to the lip, and that process will take the lip off. Some don't even have them, and would fail a current Mil-Std inspection process. 
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Posted: 11/13/2017 9:46:15 PM EDT
[#25]
Why the curved mags? You don't think that it is because they have a very slight taper, just not as much as others...
The 5.56 NATO has about 0.030" of taper, The 6.8 SPC-II has about 0.020" of taper, The 6.5 Grendel has about 0.010" of taper. or perhaps because the steep shoulder and large ratio between neck and case diameter...or to prevent tilt with that steep shoulder? You can say what you want, but taper is much reduced on the 6.5, well...what do you think of Latency's post on 5/17/16...in the topic "6.5 Grendel or 6.8 SPC Automatic Rifle?" I didn't see you challenge his comment even though you posted many replies to the 6.8 fans there. Quote HistoryQuoted:
Just about any cartridge can be made to function in an automatic weapon. With that being said there a certain design characteristics that are more common to target rounds and certain design characteristics that are more common to rounds ‘white boarded’ for automatic weapons. The 6.8 SPC has some case body taper, a shallow shoulder angle and a favorable ratio of neck diameter to case diameter (leading to a comparatively low shoulder area). These factors combine to make a cartridge that makes the feed / extraction systems job easy i.e. somewhat optimized for automatic fire. The 6.5 Grendel has comparatively little case body taper, a steeper shoulder and a larger ratio between neck and case diameter (leading to significantly more shoulder area). These factors combine to make a cartridge that makes the feed / extraction systems job comparatively harder i.e. somewhat optimized for target use / maximized case capacity. There are other issues associated with bolt thrust and case body / shoulder angle, but those are more obtuse. Both cartridges are within reasonable bolt thrust limits in the ar platform. With that being said. Given the choice of magazine fed ar based squad auto type weapons in the proposed calibers? I would pick a Six8 platform based 6.8 SPC automatic rifle every time. 30 round dedicated magazines + optimized cartridge + a piston to keep excess heat, from sustained firing, out of the bolt carrier assembly = a win in this instance. |
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Posted: 11/13/2017 11:02:12 PM EDT
[#26]
Taper between 6.5 Grendel, 5.56 NATO, and 7.62 NATO is so close, you need a really good eye to see any difference.
6.5 Grendel definitely has less taper than 7.62x39, that's for sure, which helps reduce bolt thrust and increase capacity. Neither Grendel nor 6.8 were intended for automatic rifle use in a light support weapon. Grendel drops into RPD links if you want to make a belt-fed Grendel in the RPD, whereas some guys have invested in 6.8-specific links for the SAW. 6.8 is a marginal cartridge at best for a LSW even if you unrestricted the COL because of the projectile weight you would need to move up to in order to get decent performance for the 500m + engagement distances. Before any civilians decide to pipe-in on Automatic Rifles and LSWs, just keep in mind that these were my duties and responsibilities in several of the Light Infantry and Airborne units I was in, filling duty positions from SAW gunner to Fire Team Leader, Machinegunner, and Weapons Squad Leader. Squad-level belt-fed machineguns serve certain roles in the infantry, most of which are fundamentally misunderstood to outsiders, even within the military. What does any of this have to do with the OP and his Grendel extractor failure? |
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Posted: 11/14/2017 12:09:13 AM EDT
[#27]
Does anyone else think LRRPF52 and AmericanSentinelK9 sit around and pray for an argument over 6.5 and 6.8 to start up so they can try to defeat one another? Lol its every damn time anyone mentions either caliber. It's an apples and oranges argument, you don't have to defend your choice to shoot one caliber over the other at every turn! That said I enjoy the child like arguing, at least it keeps me entertained!
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Posted: 11/14/2017 12:19:36 AM EDT
[#28]
This thread reminds me, I need to get some extra bolts. Maxim has done me well for alost 1k so I expect it to fail any day now.
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Posted: 11/14/2017 1:18:22 AM EDT
[#29]
Quote HistoryQuoted:
Taper between 6.5 Grendel, 5.56 NATO, and 7.62 NATO is so close, you need a really good eye to see any difference. 6.5 Grendel definitely has less taper than 7.62x39, that's for sure, which helps reduce bolt thrust and increase capacity. Neither Grendel nor 6.8 were intended for automatic rifle use in a light support weapon. Grendel drops into RPD links if you want to make a belt-fed Grendel in the RPD, whereas some guys have invested in 6.8-specific links for the SAW. 6.8 is a marginal cartridge at best for a LSW even if you unrestricted the COL because of the projectile weight you would need to move up to in order to get decent performance for the 500m + engagement distances. Before any civilians decide to pipe-in on Automatic Rifles and LSWs, just keep in mind that these were my duties and responsibilities in several of the Light Infantry and Airborne units I was in, filling duty positions from SAW gunner to Fire Team Leader, Machinegunner, and Weapons Squad Leader. Squad-level belt-fed machineguns serve certain roles in the infantry, most of which are fundamentally misunderstood to outsiders, even within the military. What does any of this have to do with the OP and his Grendel extractor failure? Actually the 6.8 in a SAW does better than the 5.56 to 800 meters. With 115 grain projectiles. I've fired them, I have worked with them. With just a lengthened feed tray and a slightly modified top cover the SAW can fire 6.8 ammo at 2.3 OAL. This accommodates a 130 grain projectile at 2550 fps with a .475 G1 BC. Do the math in that scenario sir. From a 16in barrel as well. Who do you think I work with at MGA? Civilians? The Saudi's, Kuwaiti's, US Army, CAG and more present at the live fires, in the last 2 years. I work with members of fire teams from 3 branches and a former CIA. My company XO is a former Marine fire team leader. Some guys haven't invested in 6.8 links, one company holds the patent. They also run x39 in the SAW, as well as .260 Rem and 300 BO. The x39 runs in slightly modified 6.8 links. The 6.8 absolutely was intended as a military cartridge. The Grendel was designed as a sporting cartridge. I have belted 6.8 ammo on my workbench. |
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Posted: 11/14/2017 1:33:45 AM EDT
[#30]
Needs more 6.8 workbench pictures.
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Posted: 11/14/2017 1:29:49 PM EDT
[#31]
Forgot to add Yama_Raja to the list of overzelous arguers! Mines better, no mines, better! (Guys they're basically the same thing)
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Posted: 11/14/2017 1:39:03 PM EDT
[#32]
Quote HistoryQuoted:
USMC hasn't looked at Grendel since mid 2000s, outside of Sniping Community. Not aware of any serious look at it from the US Army outside of AMU. Maybe your "good source" is more reliable than all of mine. |
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Posted: 11/14/2017 1:52:08 PM EDT
[#33]
The Grendel was originally marketed by Bill Alexander as a Police/ Military cartridge superior to the 5.56x45 in the AR-15 platform.
Everything else happened later. |
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Posted: 11/14/2017 1:55:42 PM EDT
[#34]
Quote HistoryQuoted:
Forgot to add Yama_Raja to the list of overzelous arguers! Mines better, no mines, better! (Guys they're basically the same thing)
LRRPF52 seems to present pure math and facts. Very helpful guy with the 6.5 Grendel. He is definitely appreciated around here. I personally know AmericanSentinelK9 and he is one of the most intelligent persons I have ever known. With that said, it's most likely is a bad extractor and nothing to do with the case's design. I have had extractors break for other popular rounds on different type of bolt designs. There's good stuff and cheap stuff and sometimes it's a matter of a bad batch. |
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Posted: 11/14/2017 1:59:50 PM EDT
[#35]
Quote HistoryQuoted:
Indeed my source is more reliable and recent. |
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Posted: 11/14/2017 2:08:10 PM EDT
[#36]
Quote HistoryQuoted:
Forgot to add Yama_Raja to the list of overzelous arguers! Mines better, no mines, better! (Guys they're basically the same thing) I hate misinformation. I own a Grendel, I shoot a Grendel, I build argueably one of the best hunting bullets for the Grendel. Expansion 2x caliber to 450 yards, 99% weight retention and sub .7 MOA to 1000 yards. I agree they basically can do the same thing. The 6.8 has more reliable operation but either are a fine choice. |
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Posted: 11/14/2017 4:54:05 PM EDT
[#37]
Quote HistoryQuoted:
Not really. I hate misinformation. I own a Grendel, I shoot a Grendel, I build argueably one of the best hunting bullets for the Grendel. Expansion 2x caliber to 450 yards, 99% weight retention and sub .7 MOA to 1000 yards. I agree they basically can do the same thing. The 6.8 has more reliable operation but either are a fine choice. |
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Posted: 11/14/2017 5:14:49 PM EDT
[#38]
Quote HistoryQuoted:
How fast is your bullet from a 16" Grendel? From a 16in realistically, 75 fps less perhaps 100 fps less. I have not tested a 16in. Nor do I have reports from a 16in. One reported AR Comp load is .35 MOA @ 2520 fps, 18 in barrel. It expands down to 1600fps with a confirmed .505 G1 BC. Confirmed by the man who does the 1000 yards milk jug challenge with the Grendel. He is who took them to .7 MOA at 1000 yards He's a friend of mine now. He hunted with them this year. I am not going to say the name or point anyone at them. Forest told me talking about performance is ok. I have no intention to shill here. |
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Posted: 11/14/2017 6:12:03 PM EDT
[#39]
Quote HistoryQuoted:
I personally know AmericanSentinelK9 and he is one of the most intelligent persons I have ever known. For the record, I don't want to come off claiming to be an expert of the 6.5 or the 6.8 or any other ballistic stuff. Instead, I just believe in knowing both rounds are good rounds and both excel in different areas...but it is irritating a bit when I see some people very subjectively deny facts on the subject concerning the 6.8 SPC-II's superior performance from short barreled guns at ranges less than 300 yards, because for those of us that are ONLY interested in this applications...such as for hunting...the 6.8 makes a great choice. Why some people will work so hard to try to misrepresent that is beyond me. I am not talking about the SAAMI 6.8...but the 6.8 SPC-II. If someone likes the 6.5 Grendel better for their goals, great. If they like it because they don't want to reload to SPC-II specs...and want factory ammo...and don't want to wait for the SPC-II factory ammo to come back around...great...but those people shouldn't lie about the performance of the rounds...and they shouldn't lie about the differences in bolt strength or feeding reliability. With their short comings, they are still both two awesome rounds...and the .224 Valkyrie will just add more spice to the 6.8's future. |
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Posted: 11/14/2017 9:24:53 PM EDT
[#40]
Of all the high volume shooting I've done with ARs dating back to the 1980s, the only extractor I've broken was on a DPMS LR-308, which is pretty common with that rifle, and why DPMS sought out a different material for the extractor on the GII.
I've broken 5.56 bolts at high round counts, cracked at the cam pin hole. Any time a new manufacturer gets into a new cartridge, there are going to be growing pains, especially if the technical data and processes aren't nailed down and adhered to. Even a company that had it nailed down will see departures from the acceptable range if they allow their tooling, processes, and inspections to deviate. No matter what cartridge it is I'm chambered for, I'm a stickler for sourcing quality parts, starting with the barrel and bolt. I also keep spares and deployed with spares, which saved my subordinates on at least one occasion. |
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Posted: 11/14/2017 11:10:34 PM EDT
[#41]
Quote HistoryQuoted:
and they shouldn't lie about the differences in bolt strength or feeding reliability. 
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Posted: 11/14/2017 11:30:04 PM EDT
[#42]
Simply put...regardless of who says what, when you have less material left after milling, the weaker the product will be. The larger case head on the 6.5 means less material on the bolt of the 6.5. This is why it has a lower pressure rating. What is it...52K for the 6.5 Grendel vs 58K for the 6.8 SPC-II? I know some go over 60K with the 6.8 SPC-II, but my understanding is 58K should be considered max loads, but even that is a result of their being over 10% more bolt strength on the 6.8.
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Posted: 11/15/2017 1:19:09 AM EDT
[#43]
Quote HistoryQuoted:
Simply put...regardless of who says what, when you have less material left after milling, the weaker the product will be. The larger case head on the 6.5 means less material on the bolt of the 6.5. This is why it has a lower pressure rating. What is it...52K for the 6.5 Grendel vs 58K for the 6.8 SPC-II? I know some go over 60K with the 6.8 SPC-II, but my understanding is 58K should be considered max loads, but even that is a result of their being over 10% more bolt strength on the 6.8. 55ksi for 6.8 55ksi for .223 Remington 62ksi for 5.56 NATO with very specific brass alloy, specific chamber, specific bolt alloy and testing protocols, and very specific barrel alloy per Mil-Std You need longer bolt lugs to increase the working pressure after you've dealt with chamber wall thickness. Chamber wall thickness, bolt thrust, and its demands on lug length and extension tooth length all factor in together for the working pressure rating of the containment system. If you increase working pressure, you have to increase wall thickness or move the thread relief forward, increase the bolt strength, increase the brass alloy strength, and increase the barrel strength once you start pushing towards 60,000psi or more, otherwise you will reduce component life and fatigue the system early. For those that doubt this, explain the .30 RAR SAAMI MAP of 55ksi and the SCAR-17 bolt at 7.62 NATO working pressure. The .30 Remington AR bolt is almost like an AR10 bolt when you look at the front of it. But lug length is the same as an AR15, as is the barrel extension teeth length. 
The SCAR-17 bolt is nowhere near as massive on the head as the .30 RAR bolt, yet it is rated for 7.62 NATO pressures in extensive volume sufficient for SOCOM requirements. How is that possible? The alloy it is made from is much stronger and the lugs are longer. The chamber wall thickness is also typical of a 7.62 NATO rifle, and specific alloy is used on the barrel by FN. FN's engineers are well-versed in systems design, testing, and establishing of testing parameters. 
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Posted: 11/15/2017 5:09:56 AM EDT
[#44]
Quote HistoryQuoted:
50ksi for Grendel 55ksi for 6.8 55ksi for .223 Remington 62ksi for 5.56 NATO with very specific brass alloy, specific chamber, specific bolt alloy and testing protocols, and very specific barrel alloy per Mil-Std You need longer bolt lugs to increase the working pressure after you've dealt with chamber wall thickness. Chamber wall thickness, bolt thrust, and its demands on lug length and extension tooth length all factor in together for the working pressure rating of the containment system. If you increase working pressure, you have to increase wall thickness or move the thread relief forward, increase the bolt strength, increase the brass alloy strength, and increase the barrel strength once you start pushing towards 60,000psi or more, otherwise you will reduce component life and fatigue the system early. For those that doubt this, explain the .30 RAR SAAMI MAP of 55ksi and the SCAR-17 bolt at 7.62 NATO working pressure. The .30 Remington AR bolt is almost like an AR10 bolt when you look at the front of it. But lug length is the same as an AR15, as is the barrel extension teeth length. http://i1085.photobucket.com/albums/j422/LRRPF52/Tech/st_r15andthe30rar_200905-d_zpscfge0ucx.jpg The SCAR-17 bolt is nowhere near as massive on the head as the .30 RAR bolt, yet it is rated for 7.62 NATO pressures in extensive volume sufficient for SOCOM requirements. How is that possible? The alloy it is made from is much stronger and the lugs are longer. The chamber wall thickness is also typical of a 7.62 NATO rifle, and specific alloy is used on the barrel by FN. FN's engineers are well-versed in systems design, testing, and establishing of testing parameters. https://i0.wp.com/4.bp.blogspot.com/-aYOWixYlHLU/ThDapLM5XzI/AAAAAAAABT8/1kCICWFAyoE/s1600/P7030007.JPG If I pressure tested some from the Grendel forum, or your manual, what may I find? Thru all your preaching you still ignore Western Powder certifying loads to 58500 PSI as safe in the SPCII chambers. In fact they have stated to me the 6.8 is fine chamber wise to 60,000 PSI. Where they pull it back is the bolt and unsupported part of the case. Yet you do refer to Western Powder in your arguments. So which is it? They are reputable or not? I will say this to you yet again. They 6.8 community has been running loads to 58,500 PSI for TEN years, that's 10, T-E-N. You know 5+5, 9+1 TEN. With NO egged chambers, NO broken bolts, NO failed over stressed Hoops, NO failed barrel extensions, nothing. From Maine to Commiefornia and Montana to Texas. Hot rapid fire 100+ degree temps on hogs. You completely ignore 10 years of field testing, 10 years sir. Again my issue is not with the Grendel, it with the quintessential Grendel salesman constantly attacking, demeaning and belittling the 6.8. For his own gains. Guess whats gonna happen if the 224 Valkyrie starts cutting into the Grendel pie? Lets wait and see shall we. |
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Posted: 11/15/2017 9:16:09 AM EDT
[#45]
Quote HistoryQuoted:
Interesting to see you post the Grendel at 50K PSI. Make sure you don't exceed that with your recommended loads now. If I pressure tested some from the Grendel forum, or your manual, what may I find? Thru all your preaching you still ignore Western Powder certifying loads to 58500 PSI as safe in the SPCII chambers. In fact they have stated to me the 6.8 is fine chamber wise to 60,000 PSI. Where they pull it back is the bolt and unsupported part of the case. Yet you do refer to Western Powder in your arguments. So which is it? They are reputable or not? I will say this to you yet again. They 6.8 community has been running loads to 58,500 PSI for TEN years, that's 10, T-E-N. You know 5+5, 9+1 TEN. With NO egged chambers, NO broken bolts, NO failed over stressed Hoops, NO failed barrel extensions, nothing. From Maine to Commiefornia and Montana to Texas. Hot rapid fire 100+ degree temps on hogs. You completely ignore 10 years of field testing, 10 years sir. Again my issue is not with the Grendel, it with the quintessential Grendel salesman constantly attacking, demeaning and belittling the 6.8. For his own gains. Guess whats gonna happen if the 224 Valkyrie starts cutting into the Grendel pie? Lets wait and see shall we. |
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Posted: 11/15/2017 10:24:25 AM EDT
[#46]
I'm beginning to wonder if the 6.8 people actually shoot their rifles or carbines enough to have a bolt failure? That being said I've broken both 5.56 and Grendel bolts. And witnessed some AR 10 bolt failures. So is insecurity the reason they don't post a wore out piece of equipment or is the 6.8 mystical?
I wish someone would post up some broken 6.8 bolts and send them in to be tested along side some other bolts. I am willing to bet that tests would reveal same metal fatigue... |
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Posted: 11/15/2017 10:57:09 AM EDT
[#47]
I don't even get why this is worth talking about, OP you broke a 5 dollar part, buy a new one. Buy two and have a spare, boom thread completed. How do you people get into this argument every time lol. Children.
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Posted: 11/15/2017 11:34:36 AM EDT
[#48]
Quote HistoryQuoted:
Thru all your preaching you still ignore Western Powder certifying loads to 58500 PSI as safe in the SPCII chambers. In fact they have stated to me the 6.8 is fine chamber wise to 60,000 PSI. Where they pull it back is the bolt and unsupported part of the case. Yet you do refer to Western Powder in your arguments. So which is it? They are reputable or not? I see that isn't good enough because he is reporting 55K. Really? SMH...he is clearly up to more cherry picking again. |
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Posted: 11/15/2017 11:36:38 AM EDT
[#49]
Quote HistoryQuoted:
This has nothing to do with a broken grendel extractor. I'm sure the OP is glad you guys are taking a dump in his thread. Are 6.5 extractors thinner where the claw is reamed, as is the bolt head edge? |
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Posted: 11/15/2017 12:27:30 PM EDT
[#50]
Quote HistoryQuoted:
The extractor has to fit within the dimensions of the bolt head right? And then it has to take the pressures. Are 6.5 extractors thinner where the claw is reamed, as is the bolt head edge? Quote HistoryQuoted:
Quoted:
This has nothing to do with a broken grendel extractor. I'm sure the OP is glad you guys are taking a dump in his thread. Are 6.5 extractors thinner where the claw is reamed, as is the bolt head edge? This is why the bolt face is recessed to .136". The extractor pin location is also different, as is the extractor shelf depth in the bolt. 
Colt did most of the engineering on this with the 7.62x39 in the 1980s. For those that might be scratching their heads wondering what is going on in this thread, you basically have forum members who are acting as surrogates for a formerly banned vendor who has a major bone to pick with 6.5 Grendel because it out-performs his pet cartridge, the 6.8 SPC. He was banned for posting customer personal data, to include their name, address, and phone number here on AR15.com. This was over some issue with 7.62x39 bolts he made at the time, and his stated intent was to "punish" the customer for whatever dispute it was that they had. Of course, he was banned immediately, then came back with another account, and was banned again. He then opened another account and went low-key until it was discovered and banned again. Since he can't post here, other 6.8 fanatics with very little knowledge of how AR15s and pressure containment systems work have taken it upon themselves to pipe in to lash out at 6.5 Grendel because of their insecurity, hence the endless uninformed posts in this thread from members who swallow the train of thought by the banned retread x3 vendor, who also openly called for 6.8f___m members to come here and shill for his products, "first one gets a free muzzle brake." |
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