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I've read so many posts here about this, I thought I'd throw out some things we've come to observe. I say we've, because I'm only posting what I've come to learn from the forum members here. Very little of this is my knowledge.
Stick around long enough, and it'll come to be part of you, too.
First: Improper gas port size. The port size being too small, under-gasses the system causing slow or weak rearward bolt movement and the bolt doesn't lock back on the empty chamber. Too large, and it sends the bolt back early with enough force to swell cases and strip the extractor claw off the case rim. http://www.65grendel.com/forum/showt...c-18-quot-RLGS, among several others.
Second: Dirty/improperly finished chambers. This causes the case to have too much grip inside the chamber immediately after firing which has almost identical results as a too large gas port mentioned above. Evidence here would be case wall condition rather than extractor claw damage. Easily confused and frustrating when a complete tear down and rebuild to change a gas block doesn't fix it. For some reason, makers aren't properly QCing the chamber walls for polish level before shipping barrels. A necessary cleaning or polish is an easy fix. Polishing a chamber while rewarding, is more than most want to do to correct an issue on a barrel they just spent good money on. http://www.65grendel.com/forum/showt...case+scratches
Third: Improper extractor design/finish. Improper extractor design rips up the case, and can cause extraction/ejection issues. The Grendel extractor needs to have rounded corners at the claw. It should be slightly less curved in the paw, and should have springs strong enough to extract the fatter, wider case under pressure. There are several videos available, Johnny's Reloading Bench's video about it is good. https://www.youtube.com/watch?v=kMrMUyyWV0k,
Fourth: Bolt face depth. No brainer. Proper head face depth matched to the chamber type make all the difference for smooth and proper extraction and ejection.
Fifth: Proper ejector spring length. Too long, and it sends brass off the deflector with enough force to cause the all too recognizable case mouth "dent" or flat spot, and occasionally overrun the lock or throw a case back into the chamber prior to stripping the next round. There are 5 thousand pictures about it. The mouth dent doesn't hurt the cases, it all comes out in the proverbial wash. But it does cause some extra wear to the deflector, and rear of the ejection port which is unnecessary. The fix is easy, trim a coil off the ejector spring at a time until 3:30-4 o clock piles of brass are common. If it's too short, it mimics the issues above and can be hard to track down. Solution: add the oring or replace with another full strength spring - or both. I'm not aware of a specific Grendel ejector or spring. http://www.65grendel.com/forum/showt...ejector+spring
Sixth: I'm going to need help here. Gas system length. Carbine was the original design, for barrels up to the 16 inch class. Beyond that, mid-length. Rifle for 20 and beyond with some fancier +X options when you really get long. There are some suppressed builds that are using mid-length systems for shorter barrels to more properly time them under the increased suppressor pressure and induced dwell times. If my memory is correct, the carbine length system on short suppressed barrels is hard on bolt lugs and extractor claws. This is not unique to Grendel, it's been an issue on all AR platforms running more back pressure/cyclic rate. LRRPF52 would be my go to here, off the top of my head. One of many threads about this topic - http://www.65grendel.com/forum/showt...+system+length. It took me a while to find this one again, it's got a post showing many port sizes for every caliber (refer to #1) BUT grendel... go figure. Useful though nonetheless.
The links I've included are just enough to get someone started. When building/troubleshooting, research and knowledge are key. Look a bit before posting a question about an issue you don't understand. That way, when asking your question you include data that is pertinent, and concise. This is important, because with flawed data, you will get sent down a rabbit hole that may or may not fix your problem, and will lead to spending time, money, and effort for less than stellar results. This makes frustration explode... nevermind how I know.
Stick around long enough, and it'll come to be part of you, too.
First: Improper gas port size. The port size being too small, under-gasses the system causing slow or weak rearward bolt movement and the bolt doesn't lock back on the empty chamber. Too large, and it sends the bolt back early with enough force to swell cases and strip the extractor claw off the case rim. http://www.65grendel.com/forum/showt...c-18-quot-RLGS, among several others.
Second: Dirty/improperly finished chambers. This causes the case to have too much grip inside the chamber immediately after firing which has almost identical results as a too large gas port mentioned above. Evidence here would be case wall condition rather than extractor claw damage. Easily confused and frustrating when a complete tear down and rebuild to change a gas block doesn't fix it. For some reason, makers aren't properly QCing the chamber walls for polish level before shipping barrels. A necessary cleaning or polish is an easy fix. Polishing a chamber while rewarding, is more than most want to do to correct an issue on a barrel they just spent good money on. http://www.65grendel.com/forum/showt...case+scratches
Third: Improper extractor design/finish. Improper extractor design rips up the case, and can cause extraction/ejection issues. The Grendel extractor needs to have rounded corners at the claw. It should be slightly less curved in the paw, and should have springs strong enough to extract the fatter, wider case under pressure. There are several videos available, Johnny's Reloading Bench's video about it is good. https://www.youtube.com/watch?v=kMrMUyyWV0k,
Fourth: Bolt face depth. No brainer. Proper head face depth matched to the chamber type make all the difference for smooth and proper extraction and ejection.
Fifth: Proper ejector spring length. Too long, and it sends brass off the deflector with enough force to cause the all too recognizable case mouth "dent" or flat spot, and occasionally overrun the lock or throw a case back into the chamber prior to stripping the next round. There are 5 thousand pictures about it. The mouth dent doesn't hurt the cases, it all comes out in the proverbial wash. But it does cause some extra wear to the deflector, and rear of the ejection port which is unnecessary. The fix is easy, trim a coil off the ejector spring at a time until 3:30-4 o clock piles of brass are common. If it's too short, it mimics the issues above and can be hard to track down. Solution: add the oring or replace with another full strength spring - or both. I'm not aware of a specific Grendel ejector or spring. http://www.65grendel.com/forum/showt...ejector+spring
Sixth: I'm going to need help here. Gas system length. Carbine was the original design, for barrels up to the 16 inch class. Beyond that, mid-length. Rifle for 20 and beyond with some fancier +X options when you really get long. There are some suppressed builds that are using mid-length systems for shorter barrels to more properly time them under the increased suppressor pressure and induced dwell times. If my memory is correct, the carbine length system on short suppressed barrels is hard on bolt lugs and extractor claws. This is not unique to Grendel, it's been an issue on all AR platforms running more back pressure/cyclic rate. LRRPF52 would be my go to here, off the top of my head. One of many threads about this topic - http://www.65grendel.com/forum/showt...+system+length. It took me a while to find this one again, it's got a post showing many port sizes for every caliber (refer to #1) BUT grendel... go figure. Useful though nonetheless.
The links I've included are just enough to get someone started. When building/troubleshooting, research and knowledge are key. Look a bit before posting a question about an issue you don't understand. That way, when asking your question you include data that is pertinent, and concise. This is important, because with flawed data, you will get sent down a rabbit hole that may or may not fix your problem, and will lead to spending time, money, and effort for less than stellar results. This makes frustration explode... nevermind how I know.
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